Copyright by Laura Jean Alport 2009

The Dissertation Committee for Laura Jean Alport certifies that this is the approved version of the following dissertation:

Lingual fungiform papillae and the evolution of the primate gustatory system

Committee:

E. Christopher Kirk, Supervisor

Nathaniel J. Dominy

Deborah J. Overdorff

Liza J. Shapiro

Timothy D. Smith Lingual fungiform papillae and the evolution of the primate gustatory system

by

Laura Jean Alport, B.F.A., M.A.

Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of

Doctor of Philosophy

The University of Texas at Austin May, 2009 Acknowledgements

This dissertation was truly a collaborative effort. The generosity of people who have shared their time, efforts, and financial assistance with me has been overwhelming. The collection of tongue specimens used in this work was only possible with the help of others. Thanks to Chris Vinyard and family for hosting me at their home and feeding me, while Chris gave me access to his lab and primate collection. Several other individuals took the time to send me specimens or provided me the access that allowed me to do this work including Annie Burrows, Nate Dominy, Rich Kay, Chris Kirk, Magda Muchlinski, Liza Shapiro, Tim Smith, Suzette Tardif, Carl Terranova, Russ Tuttle, Joseph Wagner, and Steve Ward. In addition to those who helped me with lab specimens, many people were involved in enabling the collection of my field data. Many thanks to Trudy Turner who was the first person to let me join in on her field project so that I could collect data in South Africa. It was such a pleasure to get to know her and I am grateful for her friendship in addition to her academic generosity. Thanks to Ken Glander, who regularly introduces students to La Pacifica, for his work and help in Costa Rica. Work in Madagascar is never accomplished alone. I’d like to thank the many Malagasy people who help researchers to work there, including porters, cooks, guides, and the darting team, just to name a few. They make our research happen. Additional thanks to all those at ICTE and MICET, who I rarely ever met, but continue to work hard behind the scenes to facilitate our trips and research. Thanks to Toni Lyn Morelli for coordinating the darting during our trip. I’m sure I will never know about all the things she had to take care of to make sure our research all went smoothly. Much appreciation to Patricia iv Wright for working to make Ranomafana a protected National Park and one of the premier research locations in Madagascar. Thanks, also, Pat Wright, Ed Louis, and Randy Junge for help in facilitating my work in Mengavo with Andrea Baden. I cannot thank Freddy Ranaivoarisoa and Ravaka Ramanamahefa enough for their help in Ranomafana, also. Without their assistance coordinating and translating, our data collection would never have happened, and I really enjoyed their companionship in the field. Thanks to Felicia Knightly for her veterinary assistance and consistent doses of humor. It was a delight to get to know Jeff Wyatt and Andrew Winterborn, who were incredible travel companions. In addition to his enthusiasm for students’ research, Jeff goes above and beyond the call in helping to facilitate great experiences for young veterinarians and researchers. Not only did Jeff invite me to the Madagascar fundraiser at the Seneca Park Zoo, but he was such an amazing host while I was there. Jeff also arranged for me to collect data on animals at the Zoo, to which I would not have had access otherwise. It was joy to work with Andrew and, later, to meet his family. Andrew was a trooper in the field and helped me to adjust my methods to work better with the lemurs. Thanks to Andrea Baden who introduced me to Mangevo and let me jump in to do data collection during her project. I am so fortunate to have gotten to know Andrea while working with her in the field. Many thanks to my dissertation committee: Chris Kirk, Deborah Overdorff, Liza Shapiro, Tim Smith, and Nate Dominy. I am very fortunate to have a committee in which each member has made a significant contribution to my graduate career. I would especially like to thank Chris Kirk, my advisor on this dissertation. Chris was a new faculty member when I asked him to take on the responsibility of being my advisor. I am so grateful that he agreed. He has helped me to shape this research from the beginning and been my advocate through the process, even when I was the one resisting. He pushed v me to do the best dissertation I could. This document would have been sorely insufficient without him. Deborah Overdorff has been a role model for me since I became her Masters student way back when. Between my first (never completed) dissertation and the one here, Deborah has helped me with more grant proposals than an advisor should ever have to read for one graduate student. Deborah also took me on my first trip to Madagascar with her daughter, Hannah, then four years old, and introduced me to that wonderful place and the research there. I can’t thank her enough for that introduction. She also encouraged me to go for it when I wanted to change my dissertation by reflecting to me that this work with olfaction and taste is really what curls my anthropological toes. Deborah was always good at seeing the whole person and being an academic mother. She set a good example of living a life rooted in her values. Liza Shapiro has also been on my committees from the beginning. I am so thankful for her help and for the example she sets. She is a rock in our department. In addition to being fair, consistent, forthcoming, and challenging, she is fun-loving, as well. Many thanks to Tim Smith, who has been a wonderful committee member and collaborator. Our conversations between two artists-turned-scientists have been unique. Tim has been encouraging and more than generous in offering collaboration and authorship on projects, in addition to facilitating my own work. It has been a joy to bounce ideas around and to work together with him. Nate Dominy provided my first introduction to sensory ecology and was the first person with whom I discussed this dissertation idea. Without Nate’s help I never would have gotten those first primate tongues to check out. In addition to my committee, I’d like to thank Becca Lewis for her help on statistics and Sam Wilson for being an example of a great academic and leader. His integrity and authenticity has not gone unnoticed.

vi My friends and family have been my source of strength during my graduate career. Thanks to Stacey Tecot, whose enthusiasm about the animals and people with whom she works is contagious. She set a great example for me and helped me to persist in this endeavor. She never failed to gladly step up when I’ve asked for help. Dave Raichlen started this journey with me in my student cohort. He is the person I call when I need advice on academia and I always take his advice to heart. He is a person who I know believes in me unequivocally, and his enduring friendship is invaluable. Along with Stacey and Dave, Amanda Clapp, Rene Uhalde, Damon, Elizabeth, and Stella Rose Waters, all provided me much needed rest and relaxation. I am so grateful that I had them to introduce me to Paradise Island and several other reunion locals since then. Magda Muchlinski wound up being my cohort in the end. She paved the way for my dissertation writing, taught me how to knit so that I would have something to do when I needed a break, and was a resource for dissertation questions of all kinds. Sharon Cohan has been my family in Austin. Sharon has been my running, walking, and swimming partner, and the best unofficial therapist and confidant a girl could have. She has always been here for me and I am so grateful to have her in my life. It is hard to find words with which to thank David Miller; he was my source of hope when I had none. David not only believed in me but also invested in me. I am especially grateful for his talent, empathy, big heart, sense of humor, and the incredible influence he has had on my life. Chris Grassi has been like an advisor and best friend all rolled up in one. She helped me with my master’s thesis, meeting with me in the rock climbing gym to teach me statistics. I learned about dissertation writing during our regular Saturday night dinner dates. It was at those dinners when she told me so many stories about Madagascar that I finally had to go there. Chris helped me get my research approved and completed with the chimpanzees in San Antonio. Much of the data used for this dissertation would not exist were it not for her vii help. Chris always said yes when I requested that she read grant proposals or dissertation chapters, despite the fact that she already had too much on her plate. Without fail, she has been a consistent and empathetic encourager while I completed this dissertation. In the past year, I have gotten to know Deeann, Mark, Samuel, Libby, and Ruthie Regnerus. They have opened up their home and family to me, listened to me on all matters of life, and made me feel heard and loved. The Regneruses are a truly amazing family. Along with the Regneruses, the Arabies, Sleets, and Joneses have been patient, genuine, and kind, asking for regular updates on the progress of this document. Through the ups and downs of my dissertation writing, Eric Stumberg showed great patience and understanding. He was a cheerleader, comforter, problem solver, and a great listener no matter the flavor of my reports each day. Eric lovingly challenged me to grow and sometimes change my attitudes and taught me to celebrate small milestones along the way. The people to whom I owe the greatest debt of gratitude are my family. How can I thank them enough? I am so blessed to have the brothers I do. Jordan and David have played such integral roles in my life, each of them teaching me year after year. They are my constant confidants and friends. We feel each other’s triumphs and trials, perhaps a little too acutely, and I am eternally grateful for their friendship. My mother’s encouragement, empathy, support, and belief in me have been invaluable. She always knew I could do it, even when I wasn’t so sure. And finally, this dissertation would never have been completed without the support of my father. From ballet recitals to this doctorate, his pride in me has always been my greatest reward. Funding for this dissertation provided by Sigma Xi and the National Science Foundation (award number 0648884). Thanks, also, to ATC for financial support.

viii Lingual fungiform papillae and the evolution of the primate gustatory system

Publication No.______

Laura Jean Alport, Ph.D. The University of Texas at Austin, 2009

Supervisor: E. Christopher Kirk

Among humans, the density of lingual fungiform papillae (DFP) is correlated with taste sensitivity. The purpose of this dissertation was to investigate the evolution of the primate gustatory system through a comparative analysis of DFP. This investigation was conducted in three separate studies. The first study took a broad perspective incorporating data from 37 primate species to assess the relationships among DFP, body mass, taste sensitivity, and diet. Among the major findings of this first study: (1) Sucrose sensitivity was negatively correlated with DFP and positively correlated with papilla area. (2) Sucrose sensitivity was not correlated with the percent of leaves or fruit in the diet. (3) DFP and papilla area were correlated with diet. (4) The relationships between fungiform papillae and diet differed among different taxonomic groups. The second study of DFP investigated whether there are sex differences in the DFP of non-human primates, as there are in humans. In all five primate species investigated, females had higher mean DFPs than males. These sex differences were significant in Pan troglodytes and Cebus apella, and not significant in Alouatta palliata, ix Cercopithecus aethiops, or Varecia variegata. Pan, Cebus, and Homo share large relative brain sizes with associated life history parameters making each offspring very costly. Accordingly it was suggested that sex differences in DFP may be due to the particularly high risk of lacking nutrients or ingesting toxins for females of these three species. The third study was a comparison of phenylthiocarbamide (PTC) taste ability and DFP in humans and chimpanzees. The major questions addressed in this study were (1) Is DFP correlated with PTC phenotype in chimpanzees as it is in humans? (2) Are there sex differences in PTC genotype and phenotype as there are in DFP? Although females had greater DFPs than males, and significantly more females had the genotype for higher PTC taste sensitivity, there was no correlation between DFP and PTC phenotype. Several explanations for the differences between human and chimpanzee results were offered, including small sample sizes for chimpanzees and greater accuracy in determining PTC sensitivity among humans.

x Table of Contents

List of Tables ...... xvii

List of Figures...... xviii

Chapter 1: Introduction ...... 1 The five primary taste categories...... 1 Anatomy and physiology of the primate gustatory system...... 4 Anatomy of the mammalian gustatory system...... 4 Phylogenetic variation in lingual anatomy among primates...... 9 Gustatory receptors and transduction...... 10 Salty and sour taste transduction...... 10 Sweet, umami, and bitter taste transduction ...... 12 Innervation and cortical processing ...... 15 Encoding stimuli ...... 18 Genetics of taste receptors ...... 20 Genetics of sweet and umami taste receptors ...... 20 Genetics of bitter taste receptors...... 21 Evolution of sweet-umami and bitter taste receptor genes among vertebrates ...... 22 Evolution of bitter taste receptor genes among human and non-human primates...... 23 Genetics of phenylthiocarbamide (PTC) taste sensitivity...... 27 Population genetics and selection for the PTC polymorphism in humans...... 29 PTC sensitivity and genetics in non-human primates...... 30 Psychophysical taste research...... 33 PTC taste sensitivity in humans...... 33 PTC/PROP taste sensitivity and dietary intake...... 35 PTC/PROP sensitivity and density of fungiform papillae ...... 39 Sex differences in PTC/PROP sensitivity and density of fungiform papillae...... 41 xi Comparative analyses of primate taste sensitivity...... 44 Primate feeding ecology ...... 49 The chemical properties of primate foods ...... 49 The role of taste in primate food selection...... 50 Sex differences in non-human primate feeding ecology...... 52 Dissertation objectives...... 53 References...... 59

Chapter 2: Interspecific variation in the primate gustatory system ...... 99 Abstract...... 99 Introduction...... 100 The role of taste in primate food selection...... 100 Primate taste sensitivity and dietary niche...... 101 Density of fungiform papillae and taste sensitivity ...... 108 DFP, taste sensitivity, and dietary intake in humans ...... 109 Objective...... 114 Predictions...... 114 A model of sweet taste threshold, body mass, and diet ...... 114 Associations among DFP, taste thresholds, and diet ...... 115 DFP, FP area, and taste sensitivity...... 115 Taste sensitivity and diet...... 116 Methods...... 117 Sample...... 117 DFP: Counting of fungiform papillae and determination of surface area ...... 118 Body mass...... 120 Thresholds...... 120 Diet ...... 121 Live subject protocol...... 121 Capture and anesthetization procedures...... 121 The effects and safety of methylene blue biological stain...... 122

xii Analyses...... 123 Correcting for body mass...... 123 Statistical analysis...... 123 Phylogenetic analyses ...... 126 Results...... 126 Tongue area, fungiform papillae, and body mass...... 126 Body mass, fungiform papillae, and taste thresholds ...... 128 Diet and taste threshold...... 130 DFP, papilla area, and diet...... 131 Strepsirrhines ...... 132 Platyrrhines ...... 133 Catarrhines ...... 135 Discussion...... 136 Testing a model of sweet taste sensitivity, body mass, and diet...... 136 Phylogenetic differences in fungiform papillae, sweet taste sensitivity, and diet ...... 141 The catarrhine gustatory system and detection of bitter compounds.147 Further investigation ...... 151 Summary and conclusions ...... 155 References...... 215

Chapter 3: Sex differences in the density of fungiform papillae ...... 246 Abstract...... 246 Introduction...... 247 Sex differences in non-human primate feeding ecology...... 247 Sex differences in the human gustatory system...... 252 Lingual anatomy: Density of fungiform papillae and taste sensitivity ...... 253 Hormonal variation and taste sensitivity...... 256 Objective and hypothesis ...... 257 Methods...... 257

xiii Sample...... 257 Calculating the density of fungiform papillae ...... 258 Capture and anesthetization procedures...... 258 The effects and safety of methylene blue biological stain...... 262 Statistical analysis...... 263 Results...... 265 Sex differences in DFP ...... 265 Sex differences in DFP ratio...... 270 Discussion...... 271 Sex differences in DFP and sexual size dimorphism...... 271 Cebus - Pan convergence...... 272 Life history and reproductive cost ...... 272 Sex differences in feeding behavior...... 275 Summary and conclusion...... 279 References...... 281

Chapter 4: Phenylthiocarbamide (PTC) taste ability in chimpanzees: The T2R38 gene, fungiform papillae, and sex differences ...... 305 Abstract...... 305 Introduction...... 307 Phenylthiocarbamide (PTC) taste ability in humans ...... 307 Psychophysical measures of PTC/PROP taste ability ...... 307 PTC/PROP taste ability and dietary intake...... 313 Anatomy of the mammalian gustatory system...... 315 PTC/PROP sensitivity and density of fungiform papillae ...... 318 Sex differences in PTC/PROP sensitivity and density of fungiform papillae...... 318 Genetics of PTC taste sensitivity in humans...... 319 PTC genotype, phenotype, and density of fungiform papillae ...... 321 PTC taste ability in non-human primates...... 329 Genetics of PTC taste sensitivity in chimpanzees ...... 330

xiv Objective and predictions ...... 331 Methods...... 333 Sample...... 333 Functional assay for chT2R38 genotype...... 333 Behavioral testing for PTC phenotype...... 333 Calculating the density of fungiform papillae ...... 335 Capture and anesthetization procedures...... 337 Statistical analysis...... 337 Results...... 338 PTC genotype and phenotype ...... 338 DFP and PTC genotype and phenotype...... 342 Sex differences...... 345 Discussion...... 349 PTC genotype and phenotype ...... 349 DFP and PTC genotype and phenotype...... 350 Sex differences...... 352 Selection for PTC polymorphism ...... 354 Summary...... 356 References...... 358

Chapter 5: Conclusions ...... 377 Effects of body mass...... 377 Taste sensitivity and diet...... 379 Sex differences...... 380 Further investigation ...... 381 References...... 387

xv Appendix: Data for individual samples ...... 395

Bibliography ...... 404

Vita ...... 475

xvi List of Tables

Table 2.1: List of species ...... 201 Table 2.2: Comparison of live and cadaveric specimens within species...... 203 Table 2.3: Average papilla area, number of FP, entire tongue area, tDFP, and body mass...... 204 Table 2.4: Fungiform papillae, body mass, and diet...... 204 Table 2.5: Thresholds for sucrose and fructose...... 208 Table 2.6: Quinine hydrochloride thresholds and DFP data in non-human primates..... 209 Table 2.7: Results of Spearman’s rank correlation tests with thresholds for sucrose, fructose and quinine hydrochloride in all taxa...... 210 Table 2.8: Results of Spearman’s rank correlation tests for DFP and diet in all taxa. ... 212 Table 2.9: Results of Spearman’s rank correlation tests for DFP and diet for strepsirrhines, platyrrhines, and catarrhines separately...... 213 Table 2.10: Results of Spearman’s rank correlation tests for papilla area and diet for strepsirrhines, platyrrhines, and catarrhines separately...... 214 Table 3.1: Sex differences in the feeding behavior of non-human primates ...... 249 Table 3.2: Sample: Species studied and sample sizes...... 258 Table 3.3: Body mass sexual dimorphism ...... 265 Table 3.4: Results of Wilcoxon rank sum tests for sex differences in DFP ...... 266 Table 4.1: Distribution of males and females by PROP genotype in Duffy et al., (2004)...... 323 Table 4.2: Distribution of males and females by PROP genotype in Hayes et al., (2008)...... 325 Table 4.3: Results of PTC/PROP analyses in humans and chimpanzees ...... 327 Table 4.4: Previously reported DFPs and statistical tests for non-, medium-, and high-sensitivity tasters...... 328 Table 4.5: PTC phenotype, DFP, and sex of individuals in each genotype...... 339 Table 4.6: PTC phenotype, DFP, and sex of individuals in each genotype...... 342

xvii List of Figures

Figure 1.1: Lingual gustatory papillae and taste buds ...... 7 Figure 1.2: SEM of a fungiform papilla on the tongue of Otolemur crassicaudatus ...... 7 Figure 1.3: Rabbit taste bud...... 8 Figure 1.4: Serrated sublingua of Otolemur garnetti...... 10 Figure 1.5: Innervation of the gustatory system ...... 18 Figure 1.6: Illustration of the relationship between PROP and NaCl sensitivity for non-tasters, medium-sensitivity tasters, and high-sensitivity tasters...... 35 Figure 2.1: Lingual gustatory papillae and taste buds ...... 160 Figure 2.2: Stained cadaveric tongue of Macaca mulatta ...... 160 Figure 2.3: Illustration of area included in calculations of tongue surface area using 3D scans...... 161 Figure 2.4: Tongue of wild Cercopithecus aethiops...... 161 Figure 2.5: Effects of tongue size on DFP calculation for the anterior 0.5cm of the tongue...... 162 Figure 2.6: Cladogram based on SINEs...... 166 Figure 2.7: Bivariate plot of the area of the dorsal surface of the tongue and body mass...... 167 Figure 2.8: Bivariate plot of the number of fungiform papillae and the dorsal surface of the tongue ...... 168 Figure 2.9: Bivariate plot of tDFP and body mass...... 169 Figure 2.10: Bivariate plot of DFP on the anterior 0.5cm of the tongue and body mass in all taxa...... 170 Figure 2.11: Bivariate plots of papilla area and body mass...... 172 Figure 2.12: Bivariate plot of papilla area and DFP ...... 173 Figure 2.13: Bivariate plot of papilla area and DFP in strepsirrhines ...... 174 Figure 2.14: Bivariate plot of papilla area and DFP in platyrrhines...... 175 Figure 2.15: Bivariate plot of papilla area and DFP in catarrhines ...... 176 xviii Figure 2.16: Box plots of area ratios and area residuals in catarrhines, platyrrhines and strepsirrhines ...... 177 Figure 2.17: Bivariate plot of sucrose thresholds and body mass...... 178 Figure 2.18: Bivariate plot of fructose thresholds and body mass...... 179 Figure 2.19: Bivariate plots of sucrose thresholds and DFP or DFP ratio...... 180 Figure 2.20: Bivariate plot of fructose thresholds and DFP ...... 181 Figure 2.21: Bivariate plots of sucrose threshold and papilla area...... 183 Figure 2.22: Bivariate plot of quinine hydrochloride threshold and DFP ...... 185 Figure 2.24: Bivariate plot of sucrose and fructose thresholds and the percent of leaves in the diet for all taxa...... 186 Figure 2.25: Bivariate plots of DFP and the percent of leaves in the diet for all taxa.... 187 Figure 2.26: Bivariate plot of papilla area and the percent of fruit and flowers in the diet for all taxa ...... 188 Figure 2.27: Bivariate plot of papilla area and percent leaves in diet for all taxa ...... 189 Figure 2.28: Bivariate plots of DFP and percent fruit and flowers in the diet of strepsirrhines...... 190 Figure 2.29: Bivariate plots of DFP and percent leaves in the diet of strepsirrhines ..... 191 Figure 2.30: Bivariate plot of papilla area residual and percent fruit and flowers in the diet of strepsirrhines...... 192 Figure 2.31: Bivariate plots of DFP and percent leaves in the diet platyrrhines ...... 193 Figure 2.32: Bivariate plot of papilla area and percent fruit and flowers in the diet of platyrrhines ...... 194 Figure 2.33: Bivariate plot of papilla area and percent leaves in the diet of platyrrhines ...... 195 Figure 2.34: Bivariate plot of DFP and percent of fruit and flowers in the diet of catarrhines...... 196 Figure 2.35: Bivariate plot of DFP and percent leaves in the diet of catarrhines...... 197 Figure 2.36: Bivariate plot of papilla area and percent of fruit and flowers in the diet of catarrhines...... 198 xix Figure 2.37: Bivariate plot of papilla area and percent leaves in the diet of catarrhines...... 199 Figure 2.38: Box plots of DFPs among folivore and non-folivore cercopithecoids...... 200 Figure 3.1: Lingual gustatory papillae and taste buds ...... 255 Figure 3.2: Stained cadaveric tongue of Macaca mulatta ...... 261 Figure 3.3: Tongue of Pan troglodytes...... 262 Figure 3.4: Trap used for Cercopithecus aethiops in Pretoria, South Africa ...... 259 Figure 3.5: Histogram of sex differences in the density of fungiform papillae...... 267 Figure 3.6: Distributions of DFPs for females and males in all five non-human primate species...... 268 Figure 3.7: Histogram of sex differences in DFP ratio...... 271 Figure 4.1: Illustration of the bimodal distribution of PTC/PROP thresholds of tasters and non-tasters...... 309 Figure 4.2: Illustration of the relationship between PROP and NaCl sensitivity for non-tasters, medium-sensitivity tasters, and high-sensitivity tasters...... 311 Figure 4.3: Illustration of hypothetical delineations among non-tasters, medium-tasters, and high-sensitivity tasters...... 312 Figure 4.4: Lingual gustatory papillae and taste buds ...... 317 Figure 4.5: Tongue of captive Pan troglodytes stained with methylene blue ...... 336 Figure 4.6: Histogram of the distribution of genotypes within each phenotype rating .. 340 Figure 4.7: Histogram of the percent of PTC phenotypes in each genotype category ... 341 Figure 4.8: Box plot of the distribution of DFPs in each genotype ...... 343 Figure 4.9: Box plot of the distribution of DFPs in each phenotype ...... 344 Figure 4.10: Histogram of sex differences in PTC AGG_non-taster (AGG/AGG) and ATG_taster (ATG/ATG and ATG/AGG) genotype categories...... 346 Figure 4.11: Histogram of sex differences in PTC genotypes...... 347 Figure 4.12: Box plot of sex differences in DFP...... 348

xx Chapter 1: Introduction

THE FIVE PRIMARY TASTE CATEGORIES

The function of the gustatory system is to determine the chemical contents of food items. While it is not possible to identify each individual compound found in food, humans are able to discriminate among categories of similar tasting chemicals. For example, one may not be able to distinguish between the compounds fructose and sucrose, but can identify both as belonging to a sweet taste category. Scientists and philosophers have struggled with defining taste categories since the earliest Western writings on the topic. Aristotle (384 – 322 B.C.) listed seven taste categories, including sweet, salty, bitter, sour, astringent, pungent, and harsh (Beare, 1906). Since Aristotle’s time, suggestions have ranged from two major taste categories (sweet and bitter) (Valentin, 1853), to an unlimited number of tastes (Rudolphi, 1823), and have included categories such as insipid (the absence of taste), spirituous, alkaline, metallic, acrid, putrid, rough, and aromatic (Bartoshuk, 1978). Currrently, advances in molecular biology and genetics support the presence of a limited number of primary taste categories. A primary taste is defined as one that is (1) evidently different from other primary tastes, (2) cannot be reproduced by mixing other primary taste stimuli, (3) is induced by compounds found in many foods, and (4) has intrinsic taste receptors and taste neurons specific to it (Kurihara and Kashiwayanagi, 1998). Given these criteria, five primary tastes have been identified in humans: sweet, umami (i.e., savory or meaty), salty, bitter, and sour. The taste evoked by a chemical may not be universal among all species, although other animals do have behavioral responses similar to those of humans when presented with oral stimuli (Smith and Margolis, 1999). The primary taste categories reflect complementary strategies to obtain essential nutrients and avoid harmful chemicals (Freeland and Janzen, 1974; Hladik and Simmen, 1 1996). Sweet, umami, and salty are associated with specific classes of nutrients. Sweet taste usually indicates the detection of soluble carbohydrates, a high-caloric source of energy, but other substances are also sweet tasting. In addition to sugars (e.g., fructose, glucose, and sucrose), D-amino acids, peptides (e.g., aspartame), certain organic anions (e.g., saccharin), and some proteins (e.g., monellin and thaumatin) are also perceived as sweet tasting by humans (Hladik and Simmen, 1996; Purves et al., 1997). Umami is associated with the detection of L-amino acids, which are the building blocks for proteins and may also function as metabolic fuel (Nelson et al., 2002). Umami taste is induced by glutamic acid, inosinic acid, and guanylic acid, which exist in salt form, usually as monosodium glutamate (MSG), disodium inosinate, or disodium guanylate (Kurihara and Kashiwayanagi, 1998). Umami is often described as “savory” or “meaty”, although many foods in addition to meat contain these compounds. Such foods include vegetables and sea vegetables (Kurihara and Kashiwayanagi, 1998). Salty taste indicates the presence of sodium, lithium, or potassium (Bartoshuk and Beauchamp, 1994). The detection of salts, such as NaCl, is integral to the maintenance of ion and water homeostasis in the body (Lindemann, 2001; Sugita, 2006). Unlike sweet, umami, and salty, tastes categorized as sour and bitter are associated with compounds that are potentially harmful (but see Glendinning, 1994). Sour taste is the detection of acid (i.e., free protons or H+ ions). Although acceptable at low concentrations, sour taste elicits a rejection response at higher concentrations and can be used to detect unripe fruits and spoiled foods (Lindemann, 2001; Roper, 2007). The perception of bitter taste is associated with secondary compounds including alkaloids (e.g., caffeine, strychnine, quinine, and glycosides). Such secondary compounds can be toxic or inhibit digestion (Glander, 1982; Milton, 1979, 1984; Waterman and Kool, 1994). 2 Among primates, preferences for foods with particular nutrients are largely the result of taste discrimination (Laska, 2001; Laska et al., 2000; Provenza, 1996). The ability to discriminate among nutrients is limited by the gustatory anatomy of an individual, and the anatomy, physiology, and sensitivity of the gustatory system can differ even among closely related species (Lindemann, 2001). It is likely that these differences reflect the adaptation of the gustatory system to distinct ecological niches and should thus be associated with species-specific diets (Ganzhorn, 1989; Lindemann, 2001; Nelson et al., 2001). Furthermore, dietary intake is a key factor in reproductive success, particularly for females (Altmann, 1980; Gaulin and Konner, 1977; van Noordwijk and van Schaik, 1999; Whitten, 1983). This introduction provides background information on the gustatory system and primate diets. The following chapter is comprised of four major sections related to the gustatory system: anatomy and physiology, genetics, psychophysical research, and non- human primate feeding ecology. First, I will review the anatomy of the gustatory system and discuss the transduction pathways for each of the five taste categories. Second, I will discuss the genetics of taste receptors and what is known of their evolution among humans and non-human primates. Third, I will detail what is known about taste sensitivity, particularly in the case of the bitter tasting compound phenylthiocarbamide, or PTC. Lastly, I will describe how the chemical and structural properties of primate foods differ and how the sense of taste aids discrimination among potential food items during the process of foraging. In addition to providing background information, the aim of this chapter is to show the critical importance of gustatory research to our understanding of human and non-human primate behavior, ecology, and evolution.

3 ANATOMY AND PHYSIOLOGY OF THE PRIMATE GUSTATORY SYSTEM

Anatomy of the mammalian gustatory system

Taste is the sensation produced when a chemical stimulus, or tastant, is applied to taste cells (Purves et al., 1997). Taste cells are differentiated epithelial cells that are clustered in groups of 50 to 100, called taste buds (DeFazio et al., 2006; Finger, 2005; Lindemann, 1996). The human gustatory system includes approximately 4000 taste buds (Purves et al., 1997). Each taste bud contains four cell types: Type I (dark), Type II (light), Type III (intermediate), and Type IV (basal) cells, named for their respective affinity or aversion to histological dye (Herness and Gilbertson, 1999; Lindemann, 1996; Northcutt, 2004). The precise function of each cell type has not been entirely elucidated. Type I cells are thought to serve a glial, or supportive, function (Finger, 2005). Type II cells contain elements necessary for taste transduction, such as the receptors for bitter, sweet, and umami taste, and are considered the primary receptor cells in the taste bud (Adler et al., 2000; DeFazio et al., 2006; Romanov et al., 2007; Roper, 2006; Zhang et al., 2003). Type III cells are characterized by synapses with afferent sensory nerves and are called presynaptic, or synaptic cells (DeFazio et al., 2006; Roper, 2006). Type IV cells are basal, or progenitor cells. Basal cells are small round cells at the base of the taste bud that are thought to be stem cells from which other cells are derived during cell turnover (Roper, 2006). Interactions among these cell types will be discussed below with information on taste transduction. Taste buds are located in the soft palate, uvula, epiglottis, pharynx, larynx, esophagus, and tongue. On the tongue, taste buds are found in the lingual epithelium of gustatory papillae (Buck, 2000). There are three types of gustatory papillae on the superior surface of the primate tongue: circumvallate, foliate, and fungiform (Figures 1.1 and 1.2). There are also filiform papillae located across the entire superior surface, but 4 these do not contain taste buds (i.e., they are non-gustatory). Among the gustatory papillae, circumvallate papillae are located along the posterior curve of the tongue and foliate papillae are posterolateral. Fungiform papillae (FP) are located on the anterior two-thirds of the tongue and are more densely concentrated toward the tip. Thus, FP are the only structures on the anterior two-thirds of the tongue containing taste buds and are the first papillae to come in contact with chemicals entering the mouth (Buck, 2000; Purves et al., 1997). Because of their position on the anterior part of the tongue, FP are of primary importance in food selection. FP are formed early in gestation and remain intact throughout life (Janjua and Schwartz, 1997; Mistretta, 1991). FP that have been surgically removed regenerate in three to five weeks with functioning taste buds (Spielman and Brand, unpublished data in Rossier et al., 2004). Because these papillae are easily accessed by researchers, they have been the focus of many psychophysical and electrophysiological studies of taste (Arvidson and Friberg, 1980). Each lingual taste bud has a pore that opens to the surface of the papilla. Taste pores serve a pathway for the microvilli that project from the apex of each gustatory taste cell into the oral cavity (Figure 1.3). On circumvallate and foliate papillae, taste pores are located on the lateral surface of the papilla (Figures 1.1a and 1.1b). On fungiform papillae, taste pores are located on the superior surface of each papilla (Figure 1.1c). Papillae also differ in the number of taste buds they contain. Human fungiform papillae contain 0 – 26 taste buds (Miller, 1986, 1987; Miller and Reedy, 1990; Segovia et al., 2002). One study found a mean number of 4.56 taste pores per papilla and approximately 9% of fungiform papillae investigated contained no taste pores (Miller and Reedy, 1990). The number of fungiform papillae without taste pores ranged from 0 – 35% (Miller and Reedy, 1990). Taste bud density is positively correlated with fungiform papillae density and may decrease the more posterior the location of the papilla (Miller and Reedy, 1990). 5 In a study of ten postmortem human males, fungiform papillae on the anterior 1cm of the tongue contained from one to 18 taste buds, whereas in the mid-region of the tongue (posterior to the first 1cm) fungiform papillae contained zero to five taste buds (Miller, 1986). In the cynomologus macaque (Macaca fascicularis) fungiform papillae contain 0 - 29 taste buds (Arvidson and Friberg, 1980). Circumvallate and foliate papillae contain many hundreds (Fain, 2003; Gilbertson et al., 2000). There appears to be variation among gustatory papillae with regard to which compounds are readily detected within their taste cells. For example, all of the taste buds in circumvallate papillae contain bitter taste receptors, but less than 10% of the taste buds in fungiform papillae contain them (rat and mouse; Adler et al., 2000). The distribution of receptors for sweet and umami are less clear. Some evidence from mice and rats suggests that umami receptors are predominantly located in fungiform taste buds, while sweet taste receptors are predominantly located in circumvallate and foliate taste buds (Hoon et al., 1999; Montmayeur et al., 2001; Nelson et al., 2001). However, electrophysiological data contradict these findings (Danilova and Hellekant, 2003; Inoue et al., 2004; Ninomiya et al., 1993). The distribution of different taste receptors may correspond to the distribution of taste sensitivity on the tongue. Among humans and other primates, areas of the tongue show increased sensitivity to one or more of the primary taste categories. In other words, all five of the taste categories can be detected on all parts of the tongue, but some areas are more sensitive than others to specific tastes. For example, the tip of the tongue, where there is a concentration of fungiform papillae, is more sensitive to sweet tasting stimuli than stimuli from other taste categories. However, a tongue map with discrete areas of the primate tongue designated for a single taste category is based on a misinterpretation of early work on the gustatory system (Hänig, 1901; Purves et al., 1997). 6

Figure 1.1: Lingual gustatory papillae and taste buds. Illustration after Fain, (2003).

Figure 1.2: SEM of a fungiform papilla on the tongue of Otolemur crassicaudatus. Features around the FP are filiform papillae. Image courtesy Tim Smith and Beth Docherty, Slippery Rock University. 7 Taste pore

Figure 1.3: Rabbit taste bud. Image courtesy of BIODIDAC.com.

8 Phylogenetic variation in lingual anatomy among primates

There is limited variation in lingual macro-anatomy among primates. Strepsirrhines and some platyrrhines have sublingua, a smooth, tongue-like structure located inferior to the tongue. The woolly and howling monkeys (Lagothrix lagotricha and Alouatta caraya) are two platyrrhines known to have sublingua (Machida et al., 1967). The sublingua of these two platyrrhines were described as “poorly defined” by Machida et al. (1967), and were shown to have several taste buds at the apex (p.272). Among strepsirrhines, some species have sublingua that are serrated (Figure 1.4). The function of sublingua remains unknown (Machida et al., 1967; Vij, 1976). In addition, many strepsirrhines appear to lack foliate papillae and have fewer circumvallate papillae (Machida et al., 1967; Vij, 1976). Strepsirrhines also have fewer taste buds in their circumvallate papillae compared with haplorhines (Machida et al., 1967; Vij, 1976). In one of the few comparative studies of primate lingual anatomy, Kobayashi et al. (2004) studied the tongues of a tree shrew, tamarin, mandrill, crab-eating monkey, and human using scanning electron microscopy. The authors compared these species with earlier work on other mammals and noted variation in the number of circumvallate papillae: rodents have one, insectivores [sic], rabbits, and guinea pigs have two, the tree shrew, tamarin, and mandrill have three, and the crab-eating monkey and human tongues have between four and 12 circumvallate papillae (Kobayashi, 1992; Kobayashi et al., 2004). With regard to fungiform papillae, the external structure has been described in a few primate species. For instance, Emura et al. (2002) describe the FP of the Macaca fuscata and Cercopithecus aethiops as dome-shaped. However, quantitative data on variation in the number of fungiform papillae have not been reported.

9

Figure 1.4: Serrated sublingua of Otolemur garnetti.

Gustatory receptors and transduction

Our understanding of gustatory transduction is still limited and has lagged behind our understanding of other sensory modalities (Guo and Reed, 2001; Roper, 2006, 2007). Furthermore, the transduction pathways in the gustatory system involve a variety of mechanisms and appear to differ from the transduction mechanisms of the other special senses (Kinnamon and Margolskee, 1996; Roper, 2006, 2007). Here I describe gustatory transduction in two parts. Salty and sour taste will be discussed first, as very little is known about their transduction. Second will be a discussion of sweet, umami, and bitter tastes, which are transduced via G-protein-coupled receptors.

Salty and sour taste transduction

Transduction of compounds within all five of the taste categories occurs via second messenger systems (Drayna, 2005). In most cases, second messenger systems

10 cause the release of calcium (Ca2+) from intracellular stores, leading to cell depolarization (Akabas et al., 1988; Bernhardt et al., 1996; Bufe et al., 2005; Chen et al., 2006). Salty and sour taste transduction occur in the microvilli of taste cells and along the basolateral membranes (Ye et al., 1994). Nerve responses to NaCl are categorized into amiloride- sensitive and amiloride-insensitive components. The former is Na+ specific, while the

+ + + latter is non-specific, sensitive to Na , K and NH4 (Lindemann, 2001). Amiloride, an epithelial sodium channel (ENaC) blocker, suppresses the transepithelial current usually initiated by NaCl. Thus, ENaC must provide a sodium-specific pathway into taste cells

(Heck et al., 1984; Heck et al., 1989). The subunits ENaCα, ENaCβ, and ENaCγ are expressed in taste buds, but it is uncertain whether amiloride-sensitive and amiloride- insensitive pathways map onto these subunits, and if so, how they do (Lin et al., 1999). In humans, transduction of salt is predominantly amiloride-insensitive (Feldman et al., 2003). The molecular and cellular mechanisms responsible for amiloride-insensitive salt taste transduction are largely uncharacterized (Sugita, 2006). In 2004, Lyall and colleagues showed that the amiloride-insensitive salt taste receptor is a non-selective cation channel derived from the vanilloid receptor-1 (VR1) gene. The channel is non- functional in VR1 knockout mice. This unnamed receptor accounts for all of the amiloride-insensitive chorda tympani nerve response to Na+ salts and part of the response

+ + 2+ to K , NH4 , and Ca salts (Lyall et al., 2004). It is speculated that stimulation with salts may elicit membrane depolarization by the influx of Na+ and K+ ions through apically located VR1 variants. However, basolaterally located VR1 variants, permeable to Na+, K+, and Ca2+, may lead to further depolarization (Sugita, 2006). Sour taste is thought to be mediated by either an acid sensitive ion channel, or a receptor. However, no such channel or receptor has been identified, and almost all of the 11 proposed proton sensors, (including cyclic nucleotide gated ion channels and ENaC channels) have proved not to be responsible for acid transduction (Richter et al., 2003; Roper, 2007). One newly proposed candidate is a proton sensing G-protein-coupled receptor (GPCR), GPR4 (Ludwig et al., 2003). This receptor is expressed in human fungiform papillae, but data have not been published showing its role in sour transduction within the gustatory system (Huque et al., in press cited in Roper, 2007). While efforts to identify sour taste channels and receptors continue, the proximate stimulus in sour taste may not be the extracellular tastant, but intracellular proton concentration (pH) (Lyall et al., 2001; Richter et al., 2003). Organic acids that are uncharged (i.e., electrically neutral) can permeate the cell membranes of taste cells, enter the cytosol, and release protons inside the cell. Proton release lowers intracellular pH (Richter et al., 2003; Roper, 2007). Citric acid and HCl applied to taste buds causes a decrease in pH in more than 90% of taste cells. However, intracellular Ca2+ increases only in a subset of these cells, thought to be Type III (presynaptic) cells (Richter et al., 2003; Roper, 2007).

Sweet, umami, and bitter taste transduction

Compared with salt and sour transduction, more progress has been made with regard to our understanding of sweet, umami, and bitter taste transduction. Sweet, umami, and bitter are transduced using GPCRs located in the apical microvilli of Type II cells (Adler et al., 2000; Caicedo et al., 2002; Li et al., 2002; Nelson et al., 2002; Nelson et al., 2001; Zhang et al., 2003; Zhao et al., 2003). During sweet, umami, and bitter transduction, tastants act as agonists, binding to GPCRs and resulting in the initiation of signal transduction cascades. GPCRs couple to specific intracellular G-proteins. The G- protein subunit α-gustducin (Gα gustducin) participates in bitter and sweet taste

12 transduction (Adler et al., 2000; McLaughlin et al., 1992; Ming et al., 1999; Ming et al., 1998; Nelson et al., 2001; Ruiz-Avila et al., 1995; Ruiz-Avila et al., 2001; Wong et al.,

1996). The subunit Gγ13 is also involved in bitter taste transduction (Huang et al., 1999). While other G-proteins are involved in sweet, umami, and bitter taste transduction, the specifics of which G-proteins are at work, and how specific they are to different receptors is currently unclear (Drayna, 2005). Sweet, bitter, and umami taste reception operate through distinct signaling pathways independent of salty and sour reception (Zhang et al., 2003). Two major cascades triggered by stimulation of GPCRs have been identified. In one cascade, changes in the intracellular second messenger cyclic adenosine monophosphate (cAMP) lead to transmitter release from taste cells, but how this happens is not known (Avenet et al., 1988; Tonosaki and Funakoshi, 1988; Trubey et al., 2006). The other intracellular messenger stream involves phospholipase Cβ2 (PLCβ2) and 1,4,5-triphosphate (IP3) (Bernhardt et al., 1996; Clapp et al., 2001; Hofmann et al., 2003; Pérez et al., 2002; Zhang et al., 2003). In addition, the transient receptor potential (TRP) ion channel, TRPM5 has been identified as a taste-specific ion channel common to sweet, bitter, and umami responding cells (Hofmann et al., 2003; Liu and Liman, 2003; Pérez et al., 2002; Prawitt et al., 2003). While much is still speculative, it is thought that GPCR stimulation activates PLCβ2, which produces IP3. IP3R3 receptors are then stimulated and release Ca2+ from intracellular stores. Increased intracellular Ca2+ activates TRPM5 and Na+ influx leading to cell depolarization and secretion of neurotransmitter (Roper, 2007).

Notably, however, TRPM5 and PLCβ2 knockout mice still respond to bitter, sweet, and umami stimulation (Damak et al., 2006; Dotson et al., 2005). Thus, it is clear that other, unidentified pathways are also at work in sweet, umami, and bitter taste transduction.

13 Events after depolarization are clearly atypical compared with the other special senses. Type II cells (containting GPCRs) do not synapse with afferent sensory nerves (Clapp et al., 2004). Conversely, Type III (presynaptic) cells do have morphologically identifiable synapses with afferent sensory nerves, but do not contain elements of the taste transduction cascade for sweet, umami, and bitter (DeFazio et al., 2006; Yang et al., 2000). Given the complementary attributes of these two cell types, Roper (2006) has suggested that groups of Type II and Type III cells form a “gustatory processing unit” (p. 1495). It is known that Type II cells secrete the paracrine transmitter adenosine triphosohate (ATP) and that Type III cells secrete serotonin, but how the transmitters function is not known (Finger et al., 2005; Huang et al., 2005). In one model, taste stimuli act on Type II cells, which then secrete ATP. ATP in turn stimulates Type III cells to release serotonin and elicit afferent nerve output (Roper, 2006, 2007). It is also possible that ATP from Type II cells is secreted onto afferent fibers without the typical structural features associated with synapses (Roper, 2006, 2007). In summary, the molecular details of gustatory transduction are emerging, but relatively little is currently known, especially for salty and sour taste transduction. Most work on gustatory transduction mechanisms is conducted on rodents, and research using human subjects has made clear that gustatory transduction mechanisms are far from identical in rodents and humans (Feldman et al., 2003; Shi and Zhang, 2006). As this area of study is in its infancy relative to other sensory systems, interspecific variation and the evolution of salty and sour transduction in primates will be the subject of future work. Genetic work has revealed more about interspecific variation and the evolution of GPCRs involved in sweet, umami, and bitter taste transduction. These genetic findings will be discussed below.

14 Innervation and cortical processing

Different cranial nerves mediate sensory input from the anterior two-thirds and posterior third of the tongue. Among vertebrates, the taste cells in fungiform papillae (anterior two-thirds) are innervated by the chorda tympani, a branch of the facial nerve (cranial nerve VII). The taste cells in foliate and circumvallate papillae (posterior third) are innervated by the greater petrosal nerve, which travels in the lingual branch of the glossopharyngeal nerve (cranial nerve IX) (Buck, 2000; Møller, 2003; Scott and Plata- Salaman, 1999). Each sensory fiber innervates several papillae, several taste buds within those papillae, and several Type III taste cells within those taste buds (Buck, 2000). The first synapse within the gustatory system is at the terminals of the sensory afferent fibers and individual synaptic cells (Buck, 2000). In primates, input from the chorda tympani nerve synapses at the geniculate ganglion and input from the glossopharyngeal nerve synapse at the petrosal ganglion (Figure 1.5). Subsequently, fibers from both the chorda tympani and glossopharyngeal nerve enter the solitary tract of the medulla and synapse in rostral and lateral divisions of the nucleus of the solitary tract, (also called the gustatory nucleus). From the gustatory nucleus, neurons project to the parvocellular region of the ventral posterior medial nucleus of the thalamus and then to neurons along the border between the anterior insula and frontal operculum (AI/FO) in the ipsilateral cerebral cortex. The AI/FO, or gustatory cortex, is responsible for conscious discrimination of gustatory stimuli (Buck, 2000; Møller, 2003; Scott and Plata- Salaman, 1999). Destruction of the insula causes ageusia, the total inability to perceive any tastant (Penfield and Faulk, 1955). Specifically, perception of taste intensity and taste quality is impaired when lesions include the dorsal aspect of the rostral insula (Pritchard et al., 1999). Damage to the right insula produces deficits in ipsilateral recognition of tastants 15 and perception of their intensity (Pritchard et al., 1999). Damage to the left insula causes deficits in ipsilateral taste intensity and also causes a bilateral deficit in tastant recognition (Pritchard et al., 1999). Unlike other sensory systems, signals from the tongue are thought to project to the cortex along ipsilateral pathways (Pritchard et al., 1989). However, the resulting bilateral deficit from damage to the left insula suggests that taste information from both sides of the tongue passes through this area (Pritchard et al., 1999). Projections from the gustatory cortex reach the basal forebrain and hypothalamus via the central nucleus of the amygdala and also run anteriorly to the dysgranular caudolateral region of the orbitofrontal cortex where they join with those from the visual and olfactory areas. It is here that the convergence of visual, olfactory, and gustatory sensory input allow for an awareness of flavor, which is the combination of taste, olfaction, and somatosensory perception (such as texture and pain) (Mombaerts, 2004; Rolls, 2005; Scott and Plata-Salaman, 1999). Taste, olfactory, and visual information often times even converge on the same neurons (Critchley and Rolls, 1996a; Rolls and Baylis, 1994). The convergence of input from multiple sensory modalities is key to the modulation of feeding behavior (Critchley and Rolls, 1996a). Importantly, the ability to detect a compound and preference for a compound, (i.e. the perception of pleasantness), are mediated separately in the brain (Rolls, 2005). Once satiated with a particular food, humans report that taste intensity of that food remains consistent, but the pleasantness of the food decreases significantly (Rolls et al., 1983). Accordingly, the reward value of food originates in the orbitofronal cortex, where information from multiple sensory modalities converge, along with internal information about hunger (Rolls, 2005; Scott and Plata-Salaman, 1999). Whereas the nucleus of the solitary tract and AI/FO are 16 unaffected by satiety (Rolls et al., 1988; Yaxley et al., 1988; Yaxley et al., 1985), satiety with a particular food eliminates responses of neurons in the secondary taste cortex. Both odor-responsive and visually responsive neurons within the orbitofrontal cortex show decreased response to the odor or sight of a food with which an individual has been satiated (Critchley and Rolls, 1996a). In contrast, olfactory or visual responses to foods not recently consumed are relatively unaffected, compared with the responses to the satiating food (Critchley and Rolls, 1996a). Changing the flavor, color, shape and texture of a food delays satiation with that food and increases its consumption (Rolls et al., 1981). Thus, the sensory properties of food influence satiety and the termination of feeding behavior more than, or before, internal signals from the nutritional quality of the food (Critchley and Rolls, 1996a). The gustatory system of rodents and primates differ substantially (Verhagen et al., 2004). In primates there is a direct projection from the nucleus of the solitary tract to the ventral posterior medial nucleus of the thalamus (Norgren, 1984; Pritchard et al., 1989). In rodents, projections from the nucleus of the solitary tract first enter the pontine parabrachial taste nuclei and then project to the thalamus, hypothalamus, and amygdala (Norgren, 1984). Thus, the pontine taste nuclei of rodents provide direct access to subcortical structures (i.e. hypothalamus and amygdala). These subcortical structures are important in motivational and learning behaviors essential to feeding, before there is conscious discrimination of taste stimuli (Rolls, 1999).

17

Figure 1.5: Innervation of the gustatory system. Figure based on Rolls (2005).

Encoding stimuli

Two gustatory encoding mechanisms have been suggested: across-fiber pattern coding and labeled-line. In the model of across-fiber pattern coding, taste cells and afferent fibers respond to multiple stimuli, though they may be more sensitive to one particular type. Central neurons then compare input from a population of afferent fibers. In a labeled-line system, taste cells are specific to a single primary taste and information is transmitted separately from the taste cell to the cortex via a single fiber.

18 Evidence from the periphery of the gustatory system supports a mixture of these two models. The origin of cross-fiber pattern theory of taste came from work done by Carl Pfaffmann (Bartoshuk, 1978). Pfaffmann tested individual nerve fibers of the cat chorda tympani and found that the basic tastes were not mediated by specific fibers (Pfaffmann, 1941). Although some nerve fibers respond to several taste categories, they are classified according to the taste to which they respond best, such as sweet-best or salt- best (Gilbertson et al., 2000). This is comparable to the coding of the auditory and visual systems in which fibers are more sensitive to a particular frequency, but are also broadly tuned across the visual or auditory spectrum (Buck, 2000; Purves et al., 1997). Other data from rats suggest that the taste system uses labeled-line coding. Some nerve fibers, for instance, are taste specific (Lundy and Contreras, 1999). Separate encoding of sweet, umami, and bitter taste is also in alignment with evidence from research on taste receptors, which shows no overlap between taste cells containing T1Rs (sweet and umami) and T2Rs (bitter) (Hoon et al., 1999). Nor is there overlap between taste cells expressing T1R1 (umami when paired with T1R3) and T1R2 (sweet when paired with T1R3) (Nelson et al., 2001). In addition, the few taste cells in fungiform papillae that do contain T2Rs appear to be clustered and could thus be innervated by single fibers of the chorda tympani (Adler et al., 2000). Bitter, sweet and umami, sour, and salty are all transduced separately, as well (Zhang et al., 2003). Still, a recent study showed that among taste cells in the FP of mice, about 70% responded to only one type of tastant, while about 30% responded to two or more taste category stimuli (Yoshida et al., 2006). Thus, evidence supporting the hypothesis that there is functional segregation of taste categories (labeled-line coding) at the level of taste cells is accumulating but non- conclusive.

19 Whether taste coding is across-fiber pattern or labeled-line remains uncertain, but an alternative accounting for much of the contrasting evidence has been suggested in Roper’s (2006) model. Taste signals for sweet, umami, and bitter are generated in narrowly tuned Type II cells and then transmitted to Type III synaptic cells. Accordingly, Roper suggests that Type III cells could be more broadly tuned, receiving information from several Type II cells. This model would reconcile the fact that some cells are narrowly tuned while others respond to multiple chemical stimuli (Caicedo et al., 2002).

GENETICS OF TASTE RECEPTORS

Genetics of sweet and umami taste receptors

The T1R family of GPCRs is responsible for detection of both sweet and umami substances (Hoon et al., 1999; Nelson et al., 2001). Within mammals the T1R family consists of three genes, T1R1, T1R2, and T1R3, with their encoded receptors. In the rat, T1R receptors are predominately found in fungiform papillae (Hoon et al., 1999). However, it should be noted that when human, rat, and mouse T1R receptors were sequenced, the human and rodent sequences were only 70% identical (Nelson et al., 2001). The T1R receptors work as heterodimers; T1R2 and T1R3 combine to function as a sweet taste receptor and T1R1 and T1R3 combine to form an umami taste receptor. T1R1 (umami) and T1R2 (sweet) are expressed in non-overlapping taste cells, but both are always expressed with T1R3 (Nelson et al., 2001). Thus, sweet and umami transduction are functionally distinct. Interestingly, only this limited number of sweet taste receptors has been identified and it is unknown how these few receptors distinguish among different sweet tasting compounds (Nelson et al., 2001).

20 Genetics of bitter taste receptors

Bitter taste transduction has been associated with the T2R family of taste receptors (Adler et al., 2000; Chandrashekar et al., 2000; Matsunami et al., 2000). In the rat, T2R receptors are predominantly found in circumvallate papillae, whereas only about 10% of fungiform papillae contain bitter taste receptors (Adler et al., 2000), although there is a great deal of variation between rodent and human T2Rs. Identities between the three potentially orthologous pairs of human and mouse T2Rs are between 46% and 67% (Adler et al., 2000). Twenty-five human T2R genes and eight pseudogenes have been identified, located on chromosomes 12, 7, and 5 (Go et al., 2005; Reed et al., 1999; Shi et al., 2003). Bitter tasting molecules are numerous and diverse (Conte et al., 2003). It is still unknown how this limited number of receptors is able to facilitate detection of thousands of bitter tasting compounds (Adler et al., 2000; Sugita, 2006), or to which specific compounds T2R receptors are tuned. One possibility is that T2R receptors do not account for all bitter taste reception (Maruyama et al., 2006; Palmer, 2007). Multiple T2R genes are expressed in each bitter taste receptor cell, which may account for the uniform taste of many structurally diverse bitter molecules (Chandrashekar et al., 2000). Among the 25 functional T2R genes that have been identified, a limited number of compounds (or ligands) detected by T2R receptors are known. The human T2R10 gene codes for a receptor that detects strychnine (Bufe et al., 2002), and as discussed below, human T2R38 codes for a receptor that detects PTC (Kim et al., 2003). Interestingly, analysis of the PTC gene indicates the possibility that different alleles of each gene encode receptors that are associated with different ligands (Wooding et al., 2004). If this is the case, identifying T2R ligands may prove to be a difficult, since all the alleles in T2R genes will need to be assessed (Drayna, 2005; Kim et al., 2005).

21 Evolution of sweet-umami and bitter taste receptor genes among vertebrates

Shi and Zhang (2006) compared T1R and T2R genes in 11 vertebrates. Their dataset, comprised of the T1R and T2R taste receptor genes of six mammals, (human, mouse, rat, dog, cow, and opossum), and five non-mammals, (chicken, frog, and three species of fish), showed very different modes of evolution in the two gene families. According to Shi and Zhang, the size of the T1R family of genes is fairly consistent across vertebrates, ranging from three to six functional or putatively functional T1R genes (mammals all have three T1R genes). Furthermore, among the 20 vertebrate T1R genes sequenced, no pseudogenes were detected. Thus, at the protein sequence level, T1R genes appear to evolve slowly. In addition, two species were missing T1R genes. The chicken lacks T1R2, which codes for sweet taste receptors, and the western clawed frog lacks T1R genes altogether (Shi and Zhang, 2006). Conversely, the bitter taste gene family showed much more variation between mammalian and non-mammalian vertebrates. The number of T2R genes ranges from 21 to 42 among the mammals that were tested, while non-mammalian vertebrates had only three to six T2R genes. The exception to this was the western clawed frog, which had 64 T2R genes. (It is interesting to note that the frog, which had the greatest number of functional or putatively functional T2R genes among vertebrates, was also lacking all T1R genes.) The percentage of T2R pseudogenes was also distinctly different between mammalian and non-mammalian vertebrates. Again, with the exception of the frog (19% of their 64 T2R genes are pseudogenes), the non-mammalian vertebrates (the chicken and three fish) showed no pseudogenes, while the mammalian species had between 12 and 44% T2R pseudogenes. The cow had the greatest number of T2R pseudogenes (44%) and human the second greatest (31%). Taken together, these data indicate that T2R genes have diverged rapidly among vertebrates. This rapid divergence among T2R genes is in 22 contrast to the relatively slow evolution of T1R genes, although both gene families are thought to have evolved under positive selection (Shi and Zhang, 2006; Shi et al., 2003). Given the large number of T2R genes in the clawed frog, Shi and colleagues suggest an initial T2R gene expansion in tetrapods followed by additional expansion independently in frogs and mammals. The diversity of T2R genes suggests large variation in number and type of bitter tastants detected by different species (Shi and Zhang, 2006).

Evolution of bitter taste receptor genes among human and non-human primates

The adaptive importance of bitter taste perception among non-human primates is evident in the accumulating data on T2R genes across the primate order. For example, Go et al. (2005) investigated bitter taste receptor genes across a broad range of primate species. The authors sequenced the T2R family of genes in 12 non-human primate species including Pan troglodytes, Pongo pygmaeus, Hylobates agilis, Macaca mulatta, Trachypithecus cristatus, Callithrix jacchus, Cebus apella, Otolemur crassicaudatus, Galago senegalensis, Nycticebus, cougang, and Lemur catta, in addition to Tupaia glis (tree shrew). They also compared these gene sequences with human and mouse T2R gene sequences from the literature (Conte et al., 2002, 2003; Shi et al., 2003). This work showed that primates have accumulated more pseudogenes than mice, indicating that functional constraints against T2R genes are more relaxed in primates (the term constraints can be understood as genetic consistency or a lack of genetic change). Success in amplifying genes in non-human primates decreases with relatedness to humans due to a lack of primer specificity, and fewer than 20 genes were obtained for the strepsirrhines in Go et al.’s study. Accordingly, strepsirrhines were not discussed. Among haplorhine primates, differences in the proportion of pseudogenes were not significant.

23 Fisher et al. (2005) found the same result in their analysis of bitter taste receptors in humans and five non-human primates (Pan troglodytes, P. paniscus, Gorilla gorilla, Pongo pygmaeus, Macaca mulatta, and Papio hamadryas). Fisher and colleagues agreed that bitter taste receptor genes are under little or no constraints in primates, and may even be subject to positive selection. In addition, they argue that T2R genes did not evolve under species-specific selection pressure (although data are less clear for Macaca and Papio) (Fischer et al., 2005). In contrast, Go et al. found that each species investigated had species-specific pseudogenes. Of the 23 lineage-specific pseudogenes, three were found in humans. In comparison, all but one of the non-human primates had only one or two lineage-specific pseudogenes. Furthermore, the rate of pseudogenization was significantly higher in humans than in non-human primates. In other words, humans have accumulated significantly more pseudogenes per unit time than other haplorhines, suggesting a rapid deterioration of bitter taste ability in humans (Go et al., 2005). The only non-human primate with three lineage-specific pseudogenes was the silvered leaf monkey (T. cristatus), the one primate leaf-specialist to date for which there are genetic data on T2R genes. Interestingly, the cow, a ruminant, had the greatest percentage of T2R pseudogenes of any vertebrate tested (Shi and Zhang, 2006). Shi and Zhang (2006) hypothesize that this high number of T2R pseudogenes in the cow could be due to the detoxification process during forestomach fermentation. Because ruminants are generally more tolerant of plant toxins compared with non-ruminants, they should not need a large repertoire of T2R receptors (Freeland and Janzen, 1974). Conversely, omnivorous mammals such as the mouse, rat, and opossum have the largest T2R gene repertoire and the lowest proportion of pseudogenes (Shi and Zhang, 2006). Similarly, leaf-specialist primates, such as T. cristatus, digest food via forestomach fermentation and are, thus, more tolerant of secondary compounds than other, more omnivorous, 24 primates (Lambert, 1998; Parra, 1978). Like cows, therefore, primate leaf-specialists may also have had a more rapid deterioration of bitter taste ability compared with other non- human primates. Data consistently show that the T2R gene family within non-human primates, and particularly in humans, is under relaxed constraints (Fischer et al., 2005; Go et al., 2005; Parry et al., 2004; Wang et al., 2004). It is less clear whether bitter taste perception in humans has deteriorated (Go et al., 2005; Wang et al., 2004), or adapted to changing environments (Go et al., 2005; Kim et al., 2005; Parry et al., 2004; Wang et al., 2004; Wooding et al., 2004). Relaxed functional constraints may indicate that humans rely less on their sense of taste in order to avoid bitter toxins (Go et al., 2005; Wang et al., 2004). Significant dietary changes during human evolution may have decreased the importance of T2R genes (Wang et al., 2004). Particularly, the increasing amount of meat and decreasing amount of plant material in the hominid diet around two million years ago may have decreased the importance of bitter taste perception, because animal tissue contains fewer bitter, toxic compounds than plant foods (Glendinning, 1994; Milton, 2003; Wang et al., 2004). Furthermore, control of fire around 790,000 years ago may also be related with low selective constraint in T2R genes, because cooking may help to detoxify poisonous foods (Goren-Inbar et al., 2004; Harris, 1992; Wang et al., 2004). Alternatively, functional relaxation of bitter taste receptor genes may allow the appearance of new T2R alleles that code for receptors to previously unrecognized ligands (Wang et al., 2004). An investigation by Kim et al. (2005) of all 25 T2Rs in 55 humans from worldwide populations, suggests that bitter taste receptor genes have adapted to recognize toxins found in local environments. A comparison with more than 1500 other genes showed that there is an excess of amino acid substitutions in T2R genes compared with other most other genes examined. Thus, human T2R genes show significantly 25 greater levels of diversity than expected. Among African, European, and Asian human populations, variation in T2R genes differs more than does the variation of most other genes. This level of diversity in T2R genes is likely the result of natural selection within local populations and leads to the possibility that human populations might differ significantly in the frequency of bitter taste phenotypes (Kim et al., 2005). Kim and colleagues argue that an absence of natural selection on T2R genes could explain the excess of amino acid substitutions and the presence of pseudogenes (as noted above), but fails to explain significantly high levels of differentiation among populations. Thus, given comparative data on human and non-human primates, as well as recent data on intraspecific human variation, it appears that T2R gene diversity can be accounted for by natural selection (Parry et al., 2004). Because gustation has an important role in the evaluation of food contents, rapid adaptation may be important as environments change (Parry et al., 2004). Rapid modification of the T2R gene repertoire may have been important as the last common ancestor of humans and chimpanzees encountered a greater range of environments around 5.5 million years ago (Go et al., 2005; Kumar and Hedges, 1998; Parry et al., 2004). Later, several T2R genes appear to have undergone selective pressure when humans moved into new environments during the dispersal from sub- Saharan Africa about 100,000 years ago (Kim et al., 2005; Soranzo et al., 2005; Wooding et al., 2004). Evidence for the adaptive importance of bitter taste perception also comes from a comparison with the olfactory system. Humans have accumulated olfactory receptor coding region disruptions three- to fourfold faster than other catarrhines (Pan troglodytes, Gorilla gorilla, Pongo pygmaeus, and Macaca mulatta) (Gilad et al., 2003). More than 60% of human olfactory receptor genes are pseudogenes, which is almost twice as high as the ratio of pseudogenes among non-human primates (Gilad et al., 2005; Gilad et al., 26 2003). In contrast, 31% of human T2Rs are pseudogenes, which is not significantly different from the 15 to 28% of T2R pseudogenes among non-human catarrhines (Fischer et al., 2005; Go et al., 2005). The olfactory system of humans appears to have lost a great deal more functionality than the human gustatory system, in comparison with non-human primates (Go et al., 2005; Kim et al., 2005; Wooding et al., 2004). Accordingly, Parry et al. (2004) argue that as primate olfactory function deteriorated, bitter taste receptors may have become more important.

Genetics of phenylthiocarbamide (PTC) taste sensitivity

Phenylthiocarbamide (PTC) is a bitter tasting, synthetic compound related to bitter tasting compounds found naturally in vegetables such as cabbage, broccoli, Brussels sprouts, turnips, and kale (Barnicot et al., 1951; Harris and Kalmus, 1949; Jerzsa-Latta et al., 1990; Tepper, 1998). The ability of humans to taste PTC is a phenotypic polymorphism. While PTC sensitivity is a continuous variable, individuals are often categorized as PTC tasters or non-tasters for research purposes (Bartoshuk, 1979 ; Fischer et al., 1961; Fischer and Griffin, 1961; Fox, 1932; Hall et al., 1975; Kalmus, 1971; Snyder, 1931). Although there is variability in each category, tasters report PTC as intensely bitter, while non-tasters report PTC as having sweet or sour qualities, or as being like water (Kalmus, 1971). Since its discovery in 1931, tens of thousands of humans, worldwide, have been tested for PTC phenotype (Fox, 1932; Guo and Reed, 2001; Wooding, 2006). The percentage of PTC non-tasters ranges from zero to 66.7%, depending on the population tested (Guo and Reed, 2001). In North America, approximately 30% of Caucasians are non-tasters and 70% are tasters (Blakeslee, 1932; Snyder, 1931).

27 The genetics of PTC “taste blindness” were first studied in large groups of related individuals, or pedigrees, in addition to parent-child groups, and siblings, including twin studies (Blakeslee, 1932; Levit and Soboleva, 1935; Martin, 1975; Snyder, 1931). From these studies, it was originally thought that PTC taste ability was the result of classic Mendelian inheritance, in which high-sensitivity tasters were homozygous dominant (TT), medium-sensitivity tasters were heterozygotes (Tt), and non-tasters were homozygous recessive (tt) (Blakeslee, 1932; Kalmus, 1958; Kalmus, 1971; Reed et al., 1995; Snyder, 1931). Yet, other studies reported non-taster parents with taster children (Das, 1958; Merton, 1958), suggesting that PTC tasting may be a more complex trait. Furthermore, non-taster frequencies vary widely among different populations (0 – 66.7%) and, thus, do not adhere to a pattern of Mendelian inheritance (Guo and Reed, 2001). We now know that the genetics of PTC taste ability has features that are intermediate between a simple Mendelian trait and a complex trait (Drayna, 2005). Most phenotypic variation for PTC taste ability is produced by a single major locus on chromosome 7. The human PTC gene is designated hT2R38 (or hTAS2R38) (Bufe et al., 2005; Drayna et al., 2003; Kim et al., 2003), which has also been cited as T2R61 (Conte et al., 2002; Parry et al., 2004). Variation in hT2R38 is responsible for all of the bimodality and about 75% of observed phenotypic variance in PTC taste perception (Kim et al., 2003; Prodi et al., 2004). Although specific genes have not been identified, some of the remaining variance also appears to be genetically determined (Drayna, 2005). The PTC gene encodes for a seven-transmembrane domain GPCR. Taster and non-taster alleles exhibit three important codon differences (Kim et al., 2003). The most common taster allele in humans codes for proline, alanine, and valine at these three amino acid sites and produces the PAV form of the receptor. The most common non-taster allele in humans codes for alanine, valine, and isoleucine at those sites and produces the AVI form 28 of the receptor (Kim et al., 2003). Five other rare alleles have also been identified in humans (mostly in sub-Saharan African populations), and they are presumed to be recombinants of the common taster and non-taster haplotypes (Wooding et al., 2004). While a great deal of research has investigated PTC, another synthetic, bitter compound related to PTC, 6-n-propylthiouracil (PROP), is now more commonly used (Fischer and Griffin, 1959; Fischer and Kaelbling, 1966). The ability to taste PROP is highly correlated with PTC taste ability (Barnicot et al., 1951; Chang et al., 2006; Scott et al., 1998; Tepper, 1998). Much psychophysical taste research now uses PROP because it lacks the sulphurous odor of PTC, and because safety limits have been set for its use as a medication for hypothyroidism (Lawless, 1980). In vivo and in vitro studies have shown that the receptor for PTC also responds to PROP, although these responses are not identical (Bufe et al., 2005). The hT2R38 receptor is two to three times more sensitive to PTC than to PROP, suggesting that PROP may be a suboptimal ligand to associate with this receptor (Bufe et al., 2005; Drayna, 2005; Miguet et al., 2006).

Population genetics and selection for the PTC polymorphism in humans

Early in PTC research, Fisher et al. (1939) hypothesized that balancing natural selection has maintained high levels of phenotypic variation in PTC perception. Wooding and colleagues (2004) tested this hypothesis by analyzing the frequency of PTC haplotypes in populations worldwide (including African, Asian, European, and North American samples). They found that differentiation among continents for the PTC gene was low in comparison with other genes, and argue that the two major PAV and AVI haplotypes are too divergent and too common to be due to genetic drift. In addition, they adjusted statistical tests (Tajima’s D and Fu and Li’s D) to account for human population

29 growth over the last 100,000 years and found significant deviation from neutrality. Thus, Wooding et al. provide significant evidence that balancing natural selection has acted to maintain PTC taster and non-taster alleles in humans. Yet, the exact selection pressure that has maintained diverse PTC alleles in humans remains unknown. Drewnowski and Rock (1995) theorized that the PTC polymorphism persisted because it provided a selective advantage, allowing for the avoidance of harmful compounds in the environment, which are often bitter tasting. While their explanation is plausible, it does not explain the existence of non-tasters in approximately 45% of the global population (Guo and Reed, 2001). Wooding et al. (2004) suggest, therefore, that the AVI allele might encode for a receptor associated with another bitter substance. Sensitivity to this unidentified, bitter ligand could act as the selective force maintaining the non-taster allele in worldwide populations. Wooding and colleagues further suggests that a functional AVI allele may be indicative of a heterozygote advantage wherein the PAV allele confers sensitivity to PTC and the AVI allele confers sensitivity to another compound or compounds. Heterozygotes, then, would have the ability to regulate intake of a wider range of bitter compounds, which might lead to a fitness advantage over homozygotes (Fisher et al., 1939; Wooding, 2006; Wooding et al., 2004).

PTC sensitivity and genetics in non-human primates

Fisher et al., (1939) first tested PTC sensitivity in Pan troglodytes, and found a polymorphism similar to that of humans. Thirty-five percent of the 27 captive chimpanzees they tested were non-tasters. Later studies with larger sample sizes showed a percentage of non-tasters between seven and 35% (Chiarelli, 1963, n = 70; Eaton and

30 Gavin, 1965, n = 56; Polcari, 1971, n = 44). PTC phenotype, in this case the ability or inability to detect PTC at a single concentration, has been tested in numerous other non- human primate species. In almost every non-human primate species for which at least ten individuals were tested, both PTC tasters and non-tasters have been identified (the exception to this being Macaca fuscata, for which only tasters were found) (Chiarelli, 1963; Eaton and Gavin, 1965; Fisher et al., 1939; Polcari, 1971). In comparison to chimpanzees, the percentage of PTC non-tasters is similar for another great ape, Gorilla gorilla (24%, n = 25), but differs greatly in Pongo pygmaeus (Chiarelli, 1963; Polcari, 1971). Eighty-six percent of the 50 orangutans tested were non- tasters (Chiarelli, 1963; Polcari, 1971). Percentages of PTC phenotypes vary widely among other phylogenetic groups of primates as well. Among cercopithecoids, 14% of Macaca mulatta were non-tasters (n = 57), and 20% of Papio cynocephalus were non- tasters (n = 10). Colobus polykomos had 13% non-tasters (n = 8). Several cebids had fewer tasters than non-tasters, including Cebus apella (86% non-tasters, n= 15), C. capuchinus (86% non-tasters, n= 15), Ateles paniscus (78% non-tasters, n = 9), A. geoffroyi (88% non-tasters, n = 8), and Lagothrix lagotricha (88% non-tasters, n = 17), although Saimiri sciureus had 7% non-tasters (n = 15). Eight species of callitrichidae were tested. Although sample sizes ranged from only one to six animals, all were tasters. Sample sizes were also low for strepsirrhines (between two and six individuals), but 16 Lemur catta were tested and half of them were non-tasters (Chiarelli, 1963; Polcari, 1971). In an attempt to determine the PTC genotypes of non-human primates, Kim et al. (2003) sequenced the T2R38 gene in five primate species (Pan, Gorilla, Pongo, Macaca, and Ateles). Their results showed that all individuals in all five species were homozygous for the PAV form. This finding indicated that the AVI form arose after the divergence of 31 humans from the nearest common primate ancestor, but did not explain the genetic basis for the PTC non-taster phenotype among numerous non-human primate species (Kim et al., 2003). Recently, however, Wooding and colleagues (2006) discovered that PTC taste sensitivity in chimpanzees is also predominantly controlled by two T2R38 alleles, neither of which are shared with humans (Wooding et al., 2006). Sequencing the T2R38 orthologue in 37 wild born chimpanzees representing three subspecies (P. troglodytes troglodytes, P. t. verus, and P. t. schweinfurthii), they found that a site in the second position of the initiation codon is responsible for the chimpanzee PTC polymorphism. The substitution at this site changes the codon from ATG to AGG, resulting in a different downstream start codon and production of a truncated receptor that does not respond to PTC. The authors then tested whether chT2R38(AGG) was, in fact, the non-taster allele in chimpanzees by testing for an association between chT2R38 genotype and PTC phenotype in 39 unrelated captive chimpanzees. They found that 18 out of 30 ATG/ATG and ATG/AGG individuals displayed a taster PTC phenotype, while all nine AGG/AGG individuals showed a non-taster PTC phenotype. Thus, a number of genotypic PTC tasters did not display the taster phenotype of rejecting the bitter tasting PTC. The authors hypothesize that some individuals with taster genotypes have PTC thresholds above those used in the test. Alternatively, they suggest that some chimpanzees did perceive the PTC sample, but did not have an aversion to it in terms of preference. Similar overlap also occurs in the association between the human PAV and AVI genotypes and PTC phenotypes (Kim et al., 2003). In all, Wooding and colleagues conclude that chT2R38 genotype is highly predictive of PTC taste ability in chimpanzees. The alleles that control for PTC non-taster status among other non-human primate species are still unknown.

32

PSYCHOPHYSICAL TASTE RESEARCH

PTC taste sensitivity in humans

Bartoshuk et al. (1994) tested the ability of humans to taste a range of compounds, including PTC. After determining thresholds for PTC, Bartoshuk and colleagues categorized the subjects into three taste status groups: non-tasters, medium- sensitivity tasters, and high-sensitivity tasters (termed “supertasters”) (Bartoshuk, 1993; Kalmus, 1971). High-sensitivity tasters can detect PTC at the lowest perceivable concentrations known for humans and, once detected, find PTC to be the most intensely bitter (Figure 1.6) (Bartoshuk et al., 1994; Yakinous and Guinard, 2002). In the United States, proportions of non-tasters, medium-, and high-sensitivity tasters are estimated to be 25, 50, and 25 percent, respectively (Bartoshuk, 1993; Bartoshuk et al., 1994). Although PTC taste ability is categorized into three types, there is considerable overlap between the PTC taste sensitivities of medium- and high-sensitivity tasters (Bartoshuk, 2000; Bartoshuk et al., 1994; Drewnowski et al., 1998b; Pasquet et al., 2002; Reed et al., 1995; Tepper et al., 2001). Thus, studies vary in whether they treat medium- and high- sensitivity tasters separately, or as a single taster group. PROP is now more commonly used in tests of taste sensitivity and food preference (Fischer and Griffin, 1959), but we now know from research on the PTC gene, T2R38, that PROP is probably not a ligand that is best associated with the PTC receptor (Bufe et al., 2005; Drayna, 2005; Miguet et al., 2006). Heretofore, PROP and PTC have been considered equal measures of genetic taste ability, because sensitivity to the two compounds is highly correlated (Barnicot et al., 1951; Chang et al., 2006; Scott et al., 1998). It remains to be seen how this recent genetic discovery will influence

33 psychophysical taste studies. For the purposes of understanding the associations between genetic taste ability and dietary intake, research on PTC and PROP taster status will both be discussed below. Determination of PTC/PROP taster status is accomplished using various methods. Filter paper impregnated with PTC/PROP can be used to determine taster or non-taster status. Tests using serial dilutions are more informative, however, because they give more precise information about detection thresholds (Kalmus, 1971). A detection threshold is the lowest concentration of a test substance that can be distinguished from water (Kalmus, 1971; Miller and Bartoshuk, 1991). If a threshold is relatively high (i.e., relatively more of the substance is needed for the individual to detect its presence), sensitivity is considered low. Conversely, if a threshold is relatively low this indicates that sensitivity is high. Once a compound is detected, the perceived intensity of a suprathreshold stimulus is also indicative of an individual’s gustatory ability. Ratings of suprathreshold intensity are used to distinguish medium- from high-sensitivity tasters, for example (Bartoshuk et al., 1994). In one method of comparing perceptions of intensity across tasters and non- tasters, subjects are presented with a standard dilution of the stimulus and told to assign the number 10 to that intensity. Subjects rate subsequent stimuli such that a rating of 20 is assigned to the dilution that seems twice as strong as the standard dilution (Bartoshuk, 2000). Taste intensities can also be determined by cross-modality matching. In this case, PTC or PROP is scaled to subjects’ ratings of another tastant, such as NaCl (Bartoshuk, 2000). The ratio of PTC/PROP to NaCl intensity can be used to distinguish medium- and high-sensitivity tasters (Figure 1.6). A dilution of 0.003M of PROP is much more bitter than 1M of NaCl to a high-sensitivity taster than it is to a medium-sensitivity taster, who

34 will rate the two compounds as having similar intensities (Bartoshuk, 2000; Bartoshuk et al., 1994).

Figure 1.6: Illustration of the relationship between PROP or PTC and NaCl sensitivity for non-tasters, medium-sensitivity tasters, and high-sensitivity tasters. PROP/PTC is represented by the solid line and NaCl is represented by dashed line. Based on Bartoshuk et al. 1994 and Tepper and Nurse 1997.

PTC/PROP taste sensitivity and dietary intake

PTC taste ability is positively correlated with taste sensitivity to other compounds. PTC taster status has been associated with threshold and preference ratings for fructose, sucrose, saccharine, quinine, and caffeine (Bartoshuk, 1979; Bartoshuk, 2000; Bartoshuk et al., 1998; Drewnowski et al., 1998a; Drewnowski et al., 1997b; Duffy and Bartoshuk, 2000; Duffy et al., 2003; Falconer, 1947; Gent and Bartoshuk, 1983; Hall et al., 1975; Kalmus, 1971; Leach and Noble, 1986; Looy and Weingarten, 1992; Lucchina et al., 1998; Miller and Reedy, 1990; Pasquet et al., 2002). Taster status is also related to the intensity of oral sensations, such as astringency, fat, and heat (e.g., capsaicin) (Duffy et

35 al., 2004; Pickering et al., 2004; Tepper, 1999; Tepper and Nurse, 1997, 1998). Because PTC/PROP taster status is associated with such a diverse range of compounds and oral sensations, it would follow that taster status might affect dietary intake. Accordingly, numerous investigations have assessed the relationship between sensitivity to PTC and PROP, as a genetic marker for taste ability, and the foods that humans select to ingest. When considering associations between gustatory ability and dietary intake, identification of individuals’ preferences serve as an intermediary step (Dinehart et al., 2006). Studies assess the relationship between PTC/PROP taster status and likes or dislikes for isolated compounds or food items. Ostensibly, those likes and dislikes affect dietary intake. Early studies showed that humans with high PTC/PROP sensitivity have more food dislikes (Fischer et al., 1961; Glanville and Kaplan, 1965). Conversely, humans with low PTC/PROP sensitivity prefer stronger tasting foods and a wider range of foods than individuals with high PTC/PROP sensitivity (Duffy et al., 2003; Glanville and Kaplan, 1965). Ratings of PTC/PROP and other isolated compounds, such as bitter tasting caffeine or sweet tasting sucrose, have continued to be linked with self-reported food preferences and with self-reported frequencies of food intake (Ly and Drewnowski, 2001). However, data illustrating the relationships among an individual’s taste ability, their preferences, and their dietary intake have yielded contradictory results. Bitter taste is one reason for low acceptance of cruciferous vegetables among humans (Drewnowski and Rock, 1995), and PROP taster status may be related to individual variation in this trend. PROP tasters have been found to rate cruciferous and green leafy vegetables such as asparagus, broccoli, Brussels sprouts, cabbage, kale, and spinach, as more bitter than non-tasters do (Drewnowski et al., 1999; Kaminski et al., 2000). Accordingly, tasters have a lower preference for these foods and, therefore, consume vegetables less frequently than PROP non-tasters (Dinehart et al., 2006; 36 Drewnowski et al., 2000; Kaminski et al., 2000). The relationship among PROP taster status, bitter taste perception, and food intake also extends to other food types. In a study of 118 women, positive PROP taster status was associated with lower acceptance of bitter or tart fruits such as grapefruit and lemons, in addition to lower acceptance of cruciferous vegetables (Brussels sprouts, cauliflower, cabbage, and radish) (Drewnowski et al., 1998b). PROP sensitivity is also negatively correlated with preference for bitter tasting beverages such as coffee (Drewnowski et al., 1999; Ly and Drewnowski, 2001). However, other results contradict findings associating PROP taster status and intake of bitter tasting foods. For instance, Yakinous and Guinard (2002) found that PROP taster status was not significantly associated with the consumption of bitter fruit and vegetables. Their study showed that female high-sensitivity PROP tasters ate significantly less green salad, but there was no difference found for the consumption of sprouts, broccoli, cauliflower, spinach, or mustard greens (Yakinous and Guinard, 2002). Instead, women’s PROP taster status was associated with the percentage of energy they acquired from fat, protein, and fruit. Female PROP tasters consumed a higher percentage of energy from fat than non-tasters, and a lower percentage of energy from protein and fruit. The relationship between PROP taster status and energy intake was not found among males in this study (Yakinous and Guinard, 2002). PROP taster status may be more effective in determining food dislikes, than food likes (Drewnowski et al., 1998b). Drewnowski and colleagues (2000) argue that high PROP taste sensitivity is associated with aversions to vegetables, but not with a preference for them. They found that 34 out of 35 high-sensitivity PROP tasters disliked cruciferous vegetables, whereas liking of vegetables was not associated with any particular PROP taster status group (Drewnowski et al., 2000).

37 Evidence for the relationship between PTC/PROP taster status and intake of sweet and fatty foods is also mixed. Some findings show that PROP non-tasters find sucrose more palatable than PROP tasters (Hayes et al., in press; Looy and Weingarten, 1992). Similarly, PROP non-tasters have been shown to have a greater preference for higher fat content in dressing, while medium- and high-sensitivity tasters did not show this preference (Tepper and Nurse, 1998). As mentioned above, female PROP tasters were shown to eat less fruit and consume a higher percentage of their daily energy from fat (Yakinous and Guinard, 2002). In contrast, other research suggests that there is no correlation between PROP taster status and intensity ratings of sucrose (Drewnowski et al., 1997a; Drewnowski et al., 1997b; Ly and Drewnowski, 2001). Drewnowski et al. (1997, 1998) found no relationship between PROP taster status and sucrose or fat preference (Drewnowski et al., 1997b). Likewise, Yakinous and Guinard (2002) found that PROP taster status was not significantly associated with the consumption of creamer or sweetener in tea or coffee. In all, studies of PTC/PROP taster status and dietary intake have failed to show a consistent and strong correlation to dietary habits. Many adults eat very few vegetables (Jerzsa-Latta et al., 1990). Consequently, finding a correlation between PROP taster status and reported vegetable intake may be difficult. Study design may also account for some of variation found among results. For instance, some studies do not account for food preparation, and cooking vegetables alters their structural and chemical properties such that they are often more acceptable (Dinehart et al., 2006; Yakinous and Guinard, 2002). Many researchers attribute inconclusive results to social and experiential factors (Jerzsa-Latta et al., 1990; Reed et al., 1997; Tepper, 1998; Yakinous and Guinard, 2002). As a result, studies are now starting to focus on the food preferences of children, who are 38 thought to be less influenced by sociocultural factors, such as inhibition (Tepper, 1998). Anliker and colleagues (1991) were the first to test the relationship between PROP taster status and food preferences in children. They determined the PROP taster status of 30 children age five to seven, and asked them to rank 11 foods and beverages in order of preference. Although not statistically significant, the tasters always ranked vegetables lower than the non-tasters (Anliker et al., 1991). Likewise, PROP taster children were also reported to rate raw broccoli, cheese, and whole milk as less preferable than non- tasters (Keller et al., 2002; Tepper and Steinmann, unpublished data in Tepper, 1998; Tepper, 1999). Taster status has also been associated with daily energy intake among nine year olds. High-sensitivity PROP tasters consumed almost 300 fewer calories each day compared with PROP non-taster children (no significant differences were found in the percentage of energy consumed from fat, protein, or carbohydrates) (Goldstein et al., 2007). Yet, just as in studies of adults, tests of children’s food preferences in relation to their PROP taster status have been inconsistent. Turnbull and Matisoo-Smith (2002), for example, found that among three to six year old children, PROP tasters had a significant dislike of raw spinach. However, PROP taster status did not affect preferences for other foods in this study, including raw broccoli (Turnbull and Matisoo-Smith, 2002).

PTC/PROP sensitivity and density of fungiform papillae

Studies of human subjects show that an underlying source of variation in PTC/PROP sensitivity is variation in gustatory papillae. Specifically, the density of fungiform papillae (DFP) on the anterior portion of the tongue is positively correlated with taster status and sensitivity to PTC and PROP (Bartoshuk et al., 1994; Delwiche et

39 al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002). For example, one study found average DFPs of 54, 73, and 98 for non-tasters, medium-sensitivity tasters, and high-sensitivity tasters, respectively (Bartoshuk et al., 1994). DFP has also been associated with sensitivity to other compounds such as NaCl, citric acid, quinine hydrochloride, sucrose, saccharine, and sucrose octaacetate (Doty et al., 2001; Miller and Reedy, 1990; Miller and Whitney, 1989; Smith, 1971). Individuals with a high DFP have higher taste sensitivity and are therefore able to detect chemical compounds with relatively little of the compound present (Bartoshuk et al., 1994). Although the genetic control for DFP is unknown, humans with a high DFP do have a propensity to experience the most intense taste sensations (Duffy and Bartoshuk, 2000; Duffy et al., 2004). DFP can vary among individuals by as much as three to six fold (Essick et al., 2003; Miller and Reedy, 1990), and an individual’s DFP is positively correlated with the density of taste buds in their papillae (Bartoshuk et al., 1994; Miller and Reedy, 1990; Prutkin et al., 2000; Reedy et al., 1993; Segovia et al., 2002). In other words, if an individual has a high DFP, on average he or she also has a high density of taste buds on each papilla. Taste sensitivity is likely determined by the number of taste receptors in taste cells, so there should also be a positive association between DFP and taste sensitivity. In all, it is recognized that those individuals with a high DFP, and concomitant and high PTC/PROP sensitivity, “have a different oral sensory world” from those who have a lower DFP and taste sensitivity (Duffy and Bartoshuk, 2000, p. 649). The correlation between DFP and taste function is not perfect, but as FP are anatomically stable structures, they are the most accurate measure of genetically endowed taste ability 40 outside genotyping (Bartoshuk, 2000; Janjua and Schwartz, 1997; Mistretta, 1991). Accordingly, DFP is considered a non-invasive proxy for gustatory innervation and sensitivity (Hayes et al., in press). Furthermore, because FP taste buds contain a spectrum of receptors, DFP is an important assay for sensitivity to a wide range of gustatory stimuli (Adler et al., 2000; Nelson et al., 2001).

Sex differences in PTC/PROP sensitivity and density of fungiform papillae

Sex differences have been reported in both human gustatory sensitivity and lingual anatomy. Generally, females have higher taste sensitivity and a higher DFP than do males, although there is considerable overlap between the sexes. Within Mvae and Yassa populations in Cameroon, for example, glucose sensitivity was found to be higher among females than males (Hladik and Simmen, 1996). Women also rate suprathreshold concentrations of caffeine and citric acid as being stronger, compared with ratings by men (Hyde and Feller, 1981). Sex differences in PTC/PROP sensitivity have been researched more extensively. Since some of the earliest PTC studies, researchers have found that there are significantly more tasters (or high-sensitivity tasters) among females than among males (Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Fernberger, 1932; Lucchina et al., 1998; Patel, 1971; Simmons et al., 1956). In addition, analyses of detection thresholds show that the distribution of PTC sensitivities is skewed higher for females than it is for males (Bartoshuk et al., 1994; Falconer, 1947; Fernberger, 1932; Whissell-Beuchy, 1990). Sex differences in PTC genotype have not yet been investigated. On average, females also have higher DFPs and greater variation in FP density than do males (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Tepper and Nurse,

41 1997). For instance, Tepper and Nurse (1997), found that women had an average of 66.6±2.2 FP/cm2 while men had 55.6±2.1 FP/cm2 (F[1, 74] = 25.5, p < 0.0001). In another study, the correlation between DFP and suprathrehsold intensity of PROP was significant for women, but not for men (Prutkin et al., 2000). Psychophysical and anatomical sex differences related to the gustatory system may affect food preferences and dietary intake. Duffy and Bartoshuk (2000) found that there was a significant negative association between PROP sensitivity and the preference for sweet tasting and fatty foods among women. The opposite was true for men, among whom there was a non-significant trend for PROP sensitivity to be positively associated with a preference for sweets and fatty foods (sweet p = 0.06, fatty p = 0.11; Duffy and Bartoshuk, 2000). Similarly, Yackinous and Guinard (2002) found that PROP taster females consumed less fruit than non-taster women. In contrast, PROP taster status did not affect the food intake of males (Yakinous and Guinard, 2002). Similar effects of taster status on food preferences have also been reported among preschool children, who should be less affected by sociocultural influences (Tepper, 1998). PROP taster girls showed a lower preference for fat, whereas taster status was not associated with fat preference in boys (Keller et al., 2002). However, in contrast to Duffy and Bartoshuk’s (2000) findings, PROP taster females in Yackinous and Guinard’s study consumed more calories from fat than non-taster females (Yakinous and Guinard, 2002). Thus, like data presented earlier for PTC/PROP taste sensitivity and dietary intake, there are significant, but conflicting reports on the interatctions among sex, PTC/PROP sensitivity, and dietary intake. One factor that may contribute to sex differences in gustatory sensitivity is the influence of hormones on taste perception. Few studies have investigated the connection between hormone levels and gustatory sensitivity. However, females do show greater 42 variance in PROP taste sensitivity than men, even when DFP (i.e., genetic variation) is held constant (Bartoshuk et al., 2007; Lucchina et al., 1998; Prutkin et al., 2000). Furthermore, variation in taste sensitivity over the menstrual cycle, called taste cycling, has been observed (Etter, 1999). Thus, changes in females’ taste sensitivity occur while DFP remains consistent within one individual (Duffy and Bartoshuk, 2000). Prutkin et al. (2000) suggest that the number of taste buds, or access to them, may vary across the menstrual cycle. Further evidence for the role of hormones in determining taste sensitivity comes form a study of 46 women who rated intensity and preference for NaCl, sucrose, citric acid, and quinine hydrochloride (QHCl) over the course of pregnancy (Duffy et al., 1998). Of particular interest, intensity ratings for QHCl rose from pre-pregnancy to the first trimester and then declined during the second and third trimester, whereas intensity ratings for sucrose did not change over the course of the pregnancies (Duffy et al., 1998). The authors suggest that increased bitter taste sensitivity in the first trimester may serve to support healthy pregnancies by helping women to avoid toxins during a critical phase of fetal development (Duffy et al., 1998). Even outside pregnancy, it is likely that enhanced taste sensitivity may be more critical for females compared with males. Small quantities of secondary compounds can delay sexual maturity, inhibit reproduction, and shorten lifespan, all of which are important factors in determining females’ reproductive success (Freeland and Janzen, 1974). The importance of females’ ability to detect secondary compounds is reflected in women’s greater sensitivity to PTC and PROP, which are related to toxic compounds found in nature (Barnicot et al., 1951; Bartoshuk et al., 1994; Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Falconer, 1947; Fernberger, 1932; Harris and

43 Kalmus, 1949; Jerzsa-Latta et al., 1990; Lucchina et al., 1998; Patel, 1971; Simmons et al., 1956; Tepper, 1998; Whissell-Beuchy, 1990).

Comparative analyses of primate taste sensitivity

Previous comparative research on the evolution of primate taste perception has largely been limited to analyses of taste thresholds, which are often determined by employing a two-bottle test (Hladik et al., 2002; Hladik and Simmen, 1996; Laska et al., 1999a; Laska et al., 1999b; Schilling et al., 2004; Simmen et al., 1999; Simmen and Hladik, 1998). Two-bottle tests are conducted by presenting an animal with two drinking bottles, one of which contains water (the control) and the other containing a dilution of the test substance. The amount of the two liquids consumed is measured, and the test is repeated with increasing amounts of the test stimulus until there is a significant difference between the amounts consumed from each bottle. Once a test substance is detected by the individual, significantly more of the test stimulus will be consumed if it is a preferred stimuli such as sugar, and more of the control will be consumed if the test stimulus is aversion-causing, such as quinine hydrochloride. The first point at which there is a significant difference in consumption between the two bottles is considered the detection threshold. Although the results of two-bottle tests are comparable to those recorded directly from peripheral taste nerves (Glaser and Hellekant, 1977), they should be interpreted with some caution, as they show preference or aversion for a compound, as well as the ability to detect it (Simmen et al., 1999). Additionally, threshold data may vary among individuals or species due to inaccuracy or differences in the methods used to determine them (Simmen et al., 1999).

44 Across mammals, phylogenetic differences are thought to play a major role in gustatory system variation (Hellekant and Danilova, 1996). For instance, not all stimuli that are perceived as sweet to humans elicit a gustatory response in other mammals (Hellekant and Danilova, 1996). However, in a study of fructose, glucose, and sucrose thresholds in 39 mammalian species, Ramirez (1990) found that most mammalian species are able to detect sugars at low levels (≤3.6% in water). Indeed, most plants contain enough of these sugars to be detectable by most of the 39 mammals he analyzed, with the exception of felids (e.g., cat, jaguar, leopard, lion) and insectivores (e.g., hedgehog, armadillo, tree shrew). The fact that carnivorous and insectivorous animals have weak responses to sugars is predictable given how little sugars occur in their diets (Li et al., 2005; Ramirez, 1990). In contrast, an analysis of quinine hydrochloride thresholds in 30 mammalian species, showed that carnivores were the most sensitive to this bitter tasting compound. The next most sensitive trophic group was omnivores (including primates), with herbivores being the least sensitive (Glendinning, 1994). Primates tend to have much lower sensitivity to sugars than most other mammals. Humans, for instance, show weak responses to sugars that are preferred in other mammals (Ramirez, 1990). Furthermore, within the primate order, sweet taste sensitivity is quite low compared with the sensitivity for bitter tasting stimuli (Glaser, 1980). For instance, in Pan troglodytes the detection threshold for fructose is 40-50mM whereas the threshold for tannic acid is 2.9 – 5.9mM (Simmen and Charlot, 2003). Relatively more fructose must be present for an individual to perceive a sweet taste reward (e.g., low sensitivity), whereas little tannic acid is required to elicit a rejection response (e.g., high sensitivity). This is also the case in humans, for which the detection threshold for sucrose is 6 – 7mM and it is recognized as sweet at about 25mM, while the detection threshold for quinine is 1.6µM (Arbisi et al.; James et al., 1997; Stevens et al., 2001). 45 Studies of primates from diverse taxa have attempted to associate taste thresholds with dietary niche, with particular emphasis on thresholds for sugars. Some studies have done this by investigating thresholds for only one species (Hubener and Laska, 1998; Laska, 1996, 1999, 2000; Laska et al., 1996, 1998; Laska et al., 1999b; Riba-Hernández et al., 2003). For instance, because Ateles geoffroyi is especially sensitive to sucrose, it was hypothesized that sucrose might be more important in the process of fruit selection compared with fructose or glucose (Laska et al., 1996, 1998; Riba-Hernández et al., 2003). Riba-Hernández et al., (2003) compared the preference thresholds for sucrose, fructose, and glucose, with the relative concentration of these sugars in fruits eaten and not eaten by a group of spider monkeys. They found that laboratory preference tests did not correspond with sugar levels found in fruits eaten in the wild. Sucrose was found in significantly lower concentrations than fructose or glucose in fruits eaten by A. geoffroyi. Furthermore, fruits not eaten by the spider monkeys had significantly lower concentration of fructose and glucose than fruits that were eaten, but levels of sucrose did not differ between fruits eaten and not eaten. The authors suggest that a high sensitivity to sucrose might be adaptive during periods of food scarcity, when a low sucrose threshold might render a broader range of food items palatable. Other studies have taken a comparative approach assessing the thresholds of two or more species in order to better understand the relationship between taste sensitivity and diet. Bonnaire and Simmen (1994) determined fructose thresholds in six lemur species, including four frugivorous Eulemur species and two species of bamboo lemur (Hapalemur griseus griseus and Hapalemur simus). All of the species had similar threshold responses, with the exception of E. mongoz which was much more sensitive to fructose than the other five species. Given the great dietary divergence between the Eulemur and Hapalemur species, they authors suggest that fructose thresholds may not 46 be associated with diet. While bamboo lemurs are folivores, two bamboo plants (Bambusa and Cephalostachium) known to be eaten by both Hapalemur species, have soluble sugar contents that are well above their fructose thresholds (Bonnaire and Simmen, 1994; Ganzhorn, 1988). Thus, fructose sensitivity may, in fact, provide a gustatory reward and be important for the selection process in the diets of bamboo lemurs. Among platyrrhines, Simmen (1994) compared thresholds for fructose in eight callitrichid species (Callimico goeldii; marmosets: Cebuella pygmaea, Callithrix jacchus, C. geoffroyi, C. argenta; tamarins: Saguinus oedipus, Leontopithecus chrysomelas and L. rosalia). Fructose thresholds were similar in all eight species, but there were differences in the consumption rate at near-threshold levels, indicating differences in the attractiveness of the sugar. Goeldi’s monkeys, which feed on ripe fruits and nectars, had a high intake of near-threshold levels of fructose. In contrast, marmosets, which are the most gummivorous and incorporate relatively little fleshy fruits in their diet, had a lower intake of near-threshold levels of fructose (Simmen, 1994). Similarly, taste thresholds for fructose and a fructose-tannic acid mixture were compared among three ape species: Pan troglodytes, Pongo pygmaeus, and Gorilla gorilla (Simmen and Charlot, 2003). All three species exhibited a high tolerance to tannic acid compared with other primates. Moreover, gorillas had an extremely high tolerance for tannic acid: 14.7mM – the highest amount tested – compared with 2.9-5.9mM in the chimpanzee, and 2.9-3.5mM in the orangutan. In contrast, gorillas also had the lowest sensitivity for fructose: 70-80mM, compared with 40-50mM in the chimpanzee and 10- 20mM in the orangutan. Low sensitivity to tannins and high sensitivity to fructose may facilitate the consumption of a wider range of foods, because more foods should be perceived as palatable. Foods with relatively low levels of sugar will then provide a taste 47 reward, while relatively high levels of tannins will fail to elicit a rejection response. Thus, the combination of thresholds found in the great apes is thought to facilitate the eclectic, omnivorous diets that are required to meet the nutritional needs of primates with such large body sizes (Simmen and Charlot, 2003). This facilitation may be particularly effective among gorillas due to their low sensitivity to tannic acid (Remis and Kerr, 2002; Simmen and Charlot, 2003). In one of the few broad, comparative analyses of the primate taste thresholds, Simmen and Hladik (1998) found that body mass was positively associated with sensitivity to sweet tasting fructose and sucrose. The authors hypothesize that larger animals have a larger surface area of the tongue and therefore room for more taste receptors (Simmen and Hladik, 1998). Yet, the relationship between sweet taste sensitivity and body mass may be confounded by phylogeny. Catarrhines appear to be more sensitive to sweet tasting compounds than platyrrhines and strepsirrhines (Glaser, 2002; Glaser et al., 1996). In contrast to the relationship found between sweet taste sensitivity and body mass, Simmen and Hladik (1998) found no relationship between body size and bitter taste sensitivity. The association found between sweet tasting substances and body mass and the lack of associations for bitter tasting substances prompted Simmen and Hladik (1998) to suggest that frugivorous species with high energy expenditure (e.g., Saimiri) may use an immediate sweet taste reward in food selection, and that gustation may not be as important for leaf-eating primates in determining food selection.

48 PRIMATE FEEDING ECOLOGY

The chemical properties of primate foods

To survive and reproduce, individuals must ingest adequate amounts of proteins, carbohydrates, fats, vitamins, minerals, water, and trace elements. Primates acquire these nutrients from myriad food sources, including fruit pulp, seeds, flowers, leaves, plant exudates, insects, vertebrates and other items (Garber, 1987). Foods also contain anti- predator defenses, such as structural carbohydrates, or fiber, which cannot be easily digested by most primates (Janson and Chapman, 1999; Richard, 1985). Many plants also produce secondary compounds, such as toxins and digestion inhibitors (tannins) to deter predators (Glander, 1982; Milton, 1979, 1984; Waterman and Kool, 1994). Chemical content varies considerably among different food sources. For example, the pulp of ripe fruit is typically easily digested and high in sugars and minerals (Janzen, 1983). Conversely, insects and vertebrates are a rich source of protein and fat, and leaves are high in protein and minerals (Glander, 1982; Janson and Chapman, 1999). Seeds are also high in fats, protein, and minerals (Janson and Chapman, 1999). However, there is a tradeoff imposed by selectively feeing on any one type of food. Fruits typically lack proteins and fat, necessitating frugivores to include insects and/or leaves in their diet (Hladik, 1981). Insects may contain secondary compounds from the plants they eat and have a chitinous exoskeleton that cannot be readily digested without specialized dentition and gastrointestinal system (Kay and Scheine, 1979). Similarly, seeds may be protected by a hard shell of structural carbohydrates and often contain toxins (Janson and Chapman, 1999). Finally, a primate ingesting leaves must contend with their secondary compounds and high fiber content (Glander, 1982; Janson and Chapman, 1999; Lambert, 1998; Milton, 1980).

49 The chemical content of a single food item can also vary as it matures over time, or even by time of day (Ganzhorn and Wright, 1994). Immature fruits, for instance, are harder in texture, contain more structural carbohydrates, and are more chemically defended than mature fruit (Cipollini and Levey, 1997). As they mature, fruits generally become more acidic as starches are converted into sugars (Dominy, 2004b; Janson and Chapman, 1999). Likewise, the nutrient content of leaves varies with maturity. Young leaves tend to be higher in protein and lower in structural carbohydrates and secondary compounds than mature leaves (Dominy and Lucas, 2001, 2004; Garber, 1987; Janson and Chapman, 1999; Milton, 1979). The nutritional content of fruit can also vary seasonally. O’Driscoll Worman and Chapman (2005) tested the fruit of Celtis durandii, which is an important component of the diet of Cercopithecus ascanius, C. mitis, and Lophocebus albigena in Kibale National Park, Uganda. The lipid content of Celtis durandii fruits increased significantly during the wet season and was positively correlated with consumption by all three primate species (O’Driscoll Worman and Chapman, 2005).

The role of taste in primate food selection

In light of the importance of maintaining a high quality diet to an individual’s fitness, it is advantageous to be highly selective before foods are ingested (Gaulin and Konner, 1977; Glander, 1982; Hladik, 1981; Janson and Chapman, 1999). A number of sensory modalities are used in the process of selecting food items with beneficial properties (vision Dominy, 2004a; Dulai et al., 1999; Regan et al., 2001; olfaction Dudley, 2002; Dudley, 2004; touch Hoffmann et al., 2004). For instance, trichromatic color vision may have evolved for detecting ripe fruit, or new, red leaves (Dominy and

50 Lucas, 2001, 2004; Regan et al., 2001) and touch is an informative cue in the selection of fruits. By palpating a fruit, primates can assess hardness, which is negatively correlated with total sugar content (Dominy, 2004b). The sense of taste is an obvious source of information about food contents, and food selection is widely considered to be a function of palatability (Gaulin and Konner, 1977). Nonetheless, the gustatory system has received little attention in studies of primate ecology. The nature of gustatory feedback has probably been shaped by two major sets of selection pressures: the need to acquire beneficial nutrients and energy and the need to avoid secondary compounds or spoiled foods (Hladik et al., 2002; Lindemann, 1996). Gustatory rewards are thought to positively motivate behavior and are obtained when beneficial nutrients enter the mouth and are perceived as pleasant (Glaser, 2002; Rolls, 1999). For example, a preference for sweet tasting compounds is innate in both human neonates and non-human primates, regardless of their natural diet (Steiner et al., 2001; Ueno et al., 2004). Sugars and certain amino-acids are both valuable nutrients that are perceived as sweet tasting (Haefeli et al., 1998; Rui-Liin et al., 1982; Schiffman, 1980). Fat is also an important source of energy and essential fatty acids. However, the presence of fat is identified by its texture in the mouth, rather than by taste receptors (Rolls, 2005). Finally, with the exception of salty tasting sodium and potassium (Dominy et al., 2001), vitamins and minerals are generally not readily detectable or actively sought, but are obtained as a result of ingesting a variety of foods (Johns, 1999; Simmen et al., 1999). An exception to this may be geophagy, in which primates may be seeking out soils specifically for their mineral properties (Bolton et al., 1998). Gustatory warnings, or rejection responses, are elicited when noxious substances enter the mouth. For instance, the unpleasant perception of some alkaloids and acids as bitter and sour tasting, respectively, serve as a taste warning (Dominy et al., 2001; Galef, 51 1996). Like the inherent preference for sweet tasting substances, human and non-human primate neonates show obvious displeasure at being given bitter or sour tasting compounds (Steiner et al., 2001; Ueno et al., 2004). Accordingly, the aversion to bitter and sour tasting compounds is also innate. Likewise, the gustatory system alerts primates to the presence of tannins. Tannins are perceived as astringent, creating a feeling of dryness in the mouth. This feeling is largely considered a tactile sensation, but it has been argued that the tannin-sense may be a sixth primary taste category (Critchley and Rolls, 1996b). Finally, structural carbohydrates are odorless and tasteless (Dominy, 2004b; Teaford et al., 2006), so fiber content must be assessed by means other than the gustatory system, such as measures of toughness (Dominy et al., 2001).

Sex differences in non-human primate feeding ecology

Primate females undergo about a 25% increase in metabolic rate when gestating and about a 50% increase when lactating (Gittleman and Thompson, 1988; Portman, 1970). In many species females spend more time feeding than males do despite males often having greater body mass (Boinski, 1988; Chivers, 1977; Dunbar, 1977; Isbell, 1998; McCabe and Fedigan, 2005; O'Brien and Kinnaird, 1997; Overdorff, 1993; Pollock, 1977; Smith, 1977). In fact, not until male body size exceeds female body size by 60% or more do male energetic costs exceed that of females (Key and Ross, 1999). The increase in energetic costs due to reproduction may lead females to consume more high-quality resources (Boinski, 1988; Dasilva, 1992; Gaulin and Sailer, 1985). Along with increasing gross energy intake, obtaining particular nutrients from food items and avoiding toxins is crucial to healthy pregnancies and females’ reproductive success (Gaulin and Konner, 1977). In many primate species, females feed

52 on foods that are sugar- and protein-rich, compared with males (Boinski, 1988; Byrne et al., 1993; Clutton-Brock, 1977; Cords, 1986; Gautier-Hion, 1980; Isbell, 1998; McCabe and Fedigan, 2005; Morland, 1991; O'Brien and Kinnaird, 1997; Overdorff, 1993; Pollock, 1977; Rodman, 1977; Whitten, 1983). Both protein and energy consumption are critical, and the ideal ratio between the two is determined by needs for growth, gestation, and lactation (Portman, 1970; Provenza et al., 2003). Accordingly, sex differences in feeding behavior are sometimes more pronounced when females are pregnant or lactating, attesting to the importance of diet in reproduction. For example, in her study of three species of Cercopithecus, Gautier-Hion (1980) found that females consume significantly more leaves and animal matter than males, especially when females were pregnant or lactating.

DISSERTATION OBJECTIVES

New genetic and molecular data have resulted in novel discoveries in gustatory research. For example, data are now emerging on the evolutionary patterns of some taste receptor classes (i.e. T1Rs and T2Rs) (Fisher et al., 2005; Go et al., 2005; Kim et al., 2005; Parry et al., 2004; Shi and Zhang, 2006; Shi et al., 2003; Wang et al., 2004; Wooding et al., 2004). Still, in light of the importance of the gustatory system and feeding ecology to primate biology, relatively little is known about the evolution of the sense of taste in non-human primates. It is assumed, for instance, that the evolution of the gustatory system and, consequently, taste sensitivity are related to dietary niche. Primate species do differ in taste sensitivity to a number of compounds (Bonnaire and Simmen, 1994; Dennys, 1991; Glaser, 1986; Laska, 1996; Laska et al., 1996; Pritchard et al., 1994; Simmen, 1991; Simmen, 1992; Simmen, 1994; Simmen and Charlot, 2003; Simmen and

53 Hladik, 1988; Simmen and Hladik, 1998). However, behavioral evidence on taste thresholds has failed to consistently support the claim that taste sensitivity is related to dietary niche (Bonnaire and Simmen, 1994; Glaser, 2002; Glaser et al., 1996; Hubener and Laska, 1998; Laska, 1996, 1999, 2000; Laska et al., 1996, 1998; Laska et al., 1999b; Remis and Kerr, 2002; Riba-Hernández et al., 2003; Simmen, 1994; Simmen and Charlot, 2003; Simmen and Hladik, 1998). Genetic data are also currently unable to elucidate the relationship between taste sensitivity and diet. This dissertation addresses the relationship between the primate gustatory system and dietary niche through a broad comparative analysis of lingual macroanatomy. This approach is a first step, using our current knowledge of the human gustatory system as a starting point for understanding the evolution of the primate gustatory system. The predictions made within are based on the premise that interspecific patterns in gustatory anatomy will mirror intraspecific patterns previously found in humans. For example, predictions about interspecific differences in DFP among non-human primates are based on the assumption that the relationship between DFP and taste sensitivity found within humans also holds across species. There are a number of variables that may influence the outcomes of these investigations, but analyzing the impact these potentially confounding variables is outside the scope of this dissertation. Assessments of DFP, for example, do not account for the role of taste buds within other gustatory papillae, or taste buds located in non-lingual structures such as the uvula, pharynx, larynx, epiglottis, esophagus and, importantly, the soft palate. Currently, we do not have comparative data on the number of taste buds within fungiform papillae, or the number of taste cells present. We also do not know whether papilla size is associated with differences in the density of taste receptor cells within the papilla of different species. Furthermore, taste receptors for compounds in 54 different taste categories are not found in the same proportions in all gustatory papillae (Adler et al., 2000). It remains to be seen whether the taste receptors for compounds in different taste categories are found in similar proportions in the papillae of various species. These limitations aside, as the first broad comparative analysis of DFP in non- human primates, the intent of this dissertation is to serve as a catalyst for new questions and future research into primate gustatory evolution. The goal of this dissertation is to conduct a detailed comparative study of lingual fungiform papillae in non-human primates to better understand the factors that have influenced the evolution of the primate gustatory system. This goal will be accomplished through analyses of DFP in three different ways. To begin, the next chapter will address whether lingual anatomy reflects interspecific variation in dietary intake. Intraspecific research on humans shows that DFP is correlated with sensitivity to several compounds, including PTC and PROP (Bartoshuk et al., 1994; Delwiche et al., 2001; Doty et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990; Miller and Whitney, 1989; Prutkin et al., 2000; Reedy et al., 1993; Smith, 1971; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002). It is not known whether DFP is also associated with interspecific variation in primate taste sensitivity. Human studies on the relationship between taste sensitivity (and associated DFP), and dietary intake have yielded contradictory results (Anliker et al., 1991; Dinehart et al., 2006; Drewnowski et al., 1999; Drewnowski et al., 1997a; Drewnowski et al., 2000; Drewnowski et al., 1997b; Drewnowski et al., 1998b; Drewnowski and Rock, 1995; Goldstein et al., 2007; Hayes et al., in press; Kaminski et al., 2000; Keller et al., 2002; Looy and Weingarten, 1992; Ly and Drewnowski, 2001; Tepper, 1999; Tepper and Nurse, 1998; Turnbull and Matisoo-Smith, 2002; Yakinous and Guinard, 2002). Likewise, non-human primate research on the relationship between 55 taste sensitivity and dietary niche has remained inconclusive (Bonnaire and Simmen, 1994; Ganzhorn, 1988; Glaser, 2002; Glaser et al., 1996; Hubener and Laska, 1998; Laska, 1996, 1999, 2000; Laska et al., 1996, 1998; Riba-Hernández et al., 2003; Simmen, 1994; Simmen and Charlot, 2003; Simmen and Hladik, 1998). In this study, I aim to provide clarification on these relationships by analyzing data from 37 primate species representing diverse phylogenetic relationships and dietary niches. Data on sucrose taste sensitivity, quinine taste sensitivity, and feeding ecology have been acquired from the literature, and will be used in comparative analyses to determine whether these variables are associated with differences in DFP across taxa. Following these interspecific comparisons are two separate intraspecific comparisons. First, DFP data will be tested for male-female differences in five non- human primate species, including Alouatta palliata (n = 14), Cebus apella (n = 12), Cercopithecus aethiops (n = 12), Pan troglodytes (n = 46), and Varecia variegata (n = 18). Among humans, sex differences have been found in both DFP and taste sensitivity (Bartoshuk et al., 1994; Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Duffy and Bartoshuk, 2000; Falconer, 1947; Fernberger, 1932; Hladik and Simmen, 1996; Lucchina et al., 1998; Patel, 1971; Prutkin et al., 2000; Simmons et al., 1956; Tepper and Nurse, 1997; Whissell-Beuchy, 1990). In addition, studies have shown that sex differences in human gustatory anatomy affect dietary intake (Duffy and Bartoshuk, 2000; Keller et al., 2002; Yakinous and Guinard, 2002). These results from human studies raise the possibility that intraspecific variation in gustatory anatomy underlie the sex differences in the feeding behavior of non-human primates as well. This study will provide the first analysis of sex differences in primate lingual anatomy by assessing the density of lingual fungiform papillae in five species with disparate dietary niches and phylogenetic relationships. 56 In the second intraspecific comparison, a study modeled after human research on PTC has been conducted with 38 captive chimpanzees (Pan troglodytes). In this research, PTC (chT2R38) genotype, PTC taster status, and DFP will be analyzed for correlations among these three variables, as well as for sex differences. We know that chimpanzees show phenotypic variation in PTC taste ability, just as in humans (Chiarelli, 1963; Polcari, 1971; Wooding et al., 2006). Yet, different genes control PTC taster status in humans and chimpanzees (Wooding et al., 2006). We do not know, however, whether DFP is associated with PTC taster status in chimpanzees, as it is in humans (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002). Nor do we know whether there are sex differences in PTC status or DFP among chimpanzees. The intraspecific comparison of chimpanzees presented here will distinguish characteristics of the human gustatory system that are unique to our species and those that are homologous with our closest living relative. Human research has made clear that not all variation in PTC taste ability is heritable (Guo and Reed, 2001). Rather, PTC threshold is determined by a complex set of genetic and environmental factors (Kalmus, 1971). However, to the degree that PTC taste sensitivity is genetically determined and associated with dietary preferences and intake, research into the genetics of PTC taste sensitivity in non-human primates will be informative. Especially considering the confounding sociocultural factors that affect the dietary intake of humans (Reed et al., 1997; Tepper, 1998), approaching the study of the evolution of the primate gustatory system from a comparative perspective will prove extremely valuable.

57 In conjunction, the three studies that comprise chapters two, three, and four will provide an extensive investigation of fungiform papillae density among non-human primates, beginning with a broad interspecific comparison of 37 species and narrowing to a detailed comparison of humans and chimpanzees. All three studies aim to provide new data on primate FP densities and a clearer understanding of the relationships among DFP, taste sensitivity, sex differences, and diet. A vast body of literature is available on investigations of these variables in humans. The significance of this dissertation lies in the fact that it provides a foundation for investigations of lingual anatomy, taste sensitivity, sex differences, and diet among non-human primates. Furthermore, this work provides an evolutionary context for future investigations of the human gustatory system.

58 REFERENCES Adler, E., Hoon, M. A., Mueller, K. L., Chandrashekar, J., Ryba, N. J. P. and Zuker, C. S.

(2000) A novel family of mammalian taste receptors. Cell 100, 693-702.

Akabas, M. H., Dodd, J. and Al-Awqati, Q. (1988) A bitter substance induces a rise in

intracellular calcium in a subpopulation of rat taste cells. Science 242, 1047-1050.

Altmann, J. (1980) Baboon Mothers and Infants. Harvard University Press, Cambridge.

Anliker, J. A., Bartoshuk, L., Ferris, A. M. and Hooks, L. D. (1991) Children's food

preferences and genetic sensitivity to the bitter taste of 6-n-propylthiouracil

(PROP). American Journal of Clinical Nutrition 54, 316-320.

Arbisi, P. A., Billington, C. J. and Levine, A. S. The effect of naltrexone on taste

detection and recognition threshold. Appetite 32, 241-249.

Arvidson, K. and Friberg, U. (1980) Human taste: Response and taste bud number in

fungiform papillae. Science 209, 807-808.

Avenet, P., Hofmann, F. and Lindemann, B. (1988) Transduction in taste receptor cells

requires cAMP protein kinase. Nature 331, 351-354.

Barnicot, N. A., Harris, H. and Kalmus, H. (1951) Taste thresholds of further eighteen

compounds and their correlation with PTC thresholds. Annals of Eugenics,

London 16, 119-128.

Bartoshuk, L. (1979) Bitter taste of saccharin related to the genetic ability to taste the

bitter substance 6-n-propylthiouracil. Science 205, 934-935.

Bartoshuk, L., Marino, S. E. and Snyder, D. J. (2007) Age and hormonal effects of sweet

taste and preference. Appetite 49, 277.

59 Bartoshuk, L. M. (1978) History of taste research. In Handbook of Perception, Vol. VIA,

Tasting and Smelling, Carterette, E. C. and Friedman, M. P. eds, pp. 3-18.

Academic Press, New York.

Bartoshuk, L. M. (1993) The biological basis of food perception and acceptance. Food

Quality and Preference 4, 21-32.

Bartoshuk, L. M. (2000) Comparing sensory experiences accross individuals: Recent

psychophysical advances illuminate genetic variation in taste perception.

Chemical Senses 25, 447-460.

Bartoshuk, L. M. and Beauchamp, G. K. (1994) Chemical senses. Annual Review of

Psychology 45, 419-449.

Bartoshuk, L. M., Duffy, V. B., Lucchina, L. A., Prutkin, J. and Fast, K. (1998) PROP (6-

n-propylthiouracil) supertasters and saltiness of NaCl. Annals of the New York

Academy of Sciences 855, 793-796.

Bartoshuk, L. M., Duffy, V. B. and Miller, I. J. (1994) PTC/PROP tasting: Anatomy,

psychophysics, and sex effects. Physiology & Behavior 56, 1165-1171.

Beare, J. I. (1906) Greek theories of elementary cognition from Alcmaeon to Aristotle.

Clarendon Press, Oxford.

Bernhardt, S. J., Naim, M., Zehavi, U. and Lindemann, B. (1996) Changes in IP3 and

cytosolic Ca2+ in response to sugars and non-sugar sweeteners in transduction of

sweet taste in the rat Journal of Physiology 490, 325-336

60 Blakeslee, A. F. (1932) Genetics of sensitivity thresholds: Taste for phenyl thio

carbamide. Proceedings of the National Academy of Sciences of the United States

of America 18, 120-130.

Blakeslee, A. F. and Salmon, M. R. (1931) Odor and taste blindness. Eugenical News 16,

105-109.

Boinski, S. (1988) Sex differences in the foraging behavior of squirrel monkeys in a

seasonal habitat. Behavioral Ecology and Sociobiology 23, 177-186.

Bolton, K. A., Campbell, V. M. and Burton, F. D. (1998) Chemical analysis of soils of

Kowloon (Hong Kong) eaten by hybrid macaques. Journal of Chemical Ecology

24, 195-205.

Bonnaire, L. and Simmen, B. (1994) Taste perception if fructose solutions and diet in

lemuridae. Folia Primatalogica 63, 171-176.

Boyd, W. C. and Boyd, L. G. (1936) New racial blood group studies in Europe and

Egypt. Science 84, 328-329.

Boyd, W. C. and Boyd, L. G. (1937) Sexual and racial variations in ability to taste

phenylthiocarbamide, with some data in the inheritance. Annals of Eugenics,

London 8, 46-51.

Buck, L. M. (2000) Smell and taste: The chemical senses. In Principals of Neural

Sciance, Kandel, E. R., Schwartz, J. H. and Jessell, T. M. eds, pp. 625-647.

McGraw-Hill, New York.

Bufe, B., Breslin, P. A. S., Kuhn, C., Reed, D. R., Tharp, C. D., Slack, J. P., Kim, U.-K.,

Drayna, D. and Meyerhof, W. (2005) The molecular basis of individual 61 differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Current Biology 15, 322-327.

Bufe, B., Hofmann, T., Krauttwurst, D., Raguse, J. D. and Meyerhof, W. (2002) The

human TAS2R16 receptor mediates bitter taste in response to β-glucopyranosides

Nature Genetics 32, 397-401.

Byrne, R. W., Whiten, S. P., Henzi, S. P. and McCulloch, F. M. (1993) Nutritional

constraints on mountain baboons (Papio ursinus): implications for baboon

socioecology. Behavioral Ecology and Sociobiology 33, 233-246.

Caicedo, A., Kim, K.-N. and Roper, S. D. (2002) Individual mouse taste cells respond to

multiple chemical stimuli. The Journal of Physiology Online 544, 501-509.

Chandrashekar, J., Mueller, K. L., Hoon, M. A., Adler, E., Feng, L., Guo, W., Zuker, C.

S. and Ryba, N. J. P. (2000) T2Rs function as bitter taste receptors. Cell 100, 703-

711.

Chang, W.-I., Chung, J.-W., Kim, Y.-K., Chung, S.-C. and Kho, H.-S. (2006) The

relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil

(PROP) taster status and taste thresholds for sucrose and quinine. Archives of

Oral Biology 51, 427-432.

Chen, M. C., Wu, S. V., Reeve, J. R. and Rozengurt, E. (2006) Bitter stimuli induce Ca2+

signaling and CCK release in enteroendocrine STC-1 cells: Role of L-type

voltage-sensitive Ca2+ channels. American Journal of Cell Physiology 291, C726-

C739.

62 Chiarelli, B. (1963) Sensitivity to P.T.C. (phenyl-thio-carbamide) in primates. Folia

Primatologica 1, 88-94.

Chivers, D. J. (1977) The feeding behaviour of Saimang (Symphalangus syndactylus). In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 355-382. Academic Press, New York.

Cipollini, M. L. and Levey, D. J. (1997) Secondary metabolites of fleshy vertebrate-

dispersed fruits: Adaptive hypotheses and implications for seed dispersal.

American Naturalist 150, 346-372.

Clapp, T. R., Stone, L. M., Margolskee, R. F. and Kinnamon, S. C. (2001)

Immunocytochemical evidence for co-expression of Type III IP3 receptor with

signaling components of bitter taste transduction. BMC Neuroscience 2, 6-14.

Clapp, T. R., Yang, R., Stoick, C. L., Kinnamon, S. C. and Kinnamon, J. C. (2004)

Morphologic characterization of rat taste receptor cells that express components

of the phospholipase C signaling pathway. Journal of Comparative Neurology

468, 311–321

Clutton-Brock, T. H. (1977) Some aspects of intraspecific variation in feeding and

ranging behaviour in primates. In Primate Ecology: Studies of Feeding and

Ranging Behaviour in Lemurs, Monkeys and Apes, Clutton-Brock, T. H. ed, pp.

539-556. Academic Press, New York.

Conte, C., Ebeling, M., Marcuz, A., Nef, P. and Andres-Barquin, P. J. (2002)

Identification and characterization of human taste receptor genes belonging to the

TAS2R family. Cytogenetic and Genomic Research 98, 45-53. 63 Conte, C., Ebeling, M., Marcuz, A., Nef, P. and Andres-Barquin, P. J. (2003)

Evolutionary relationships of the TAS2R receptor gene families in mouse and

human. Physiological Genomics 14, 73-82.

Cords, M. (1986) Interspecific and intraspecific variation in diet of two forest guenons,

Cercopithecus ascanius and C. mitis. Journal of Animal Ecology 55, 811-827.

Critchley, H. D. and Rolls, E. T. (1996a) Hunger and satiety modify the responses of

olfactory and visual neurons in the primate orbitofrontal cortex. Journal of

Neurophysiology 75, 1673-1686.

Critchley, H. D. and Rolls, E. T. (1996b) Resposnes of primate taste cortex neurons to the

astringent tastant tannic acid. Chemical Senses 21, 135-145.

Damak, S., Rong, M., Yasumatsu, K., Kokrashvili, Z., Pérez, C. A., Shigemura, N.,

Yoshida, R., Jr., B. M., Glendinning, J. I., Ninomiya, Y. and Margolskee, R. F.

(2006) TRPM5 null mice respond to bitter, sweet, and umami compounds

Chemical Senses 31, 253–264.

Danilova, V. and Hellekant, G. (2003) Comparison of the responses of the chorda

tympani and glossopharyngeal nerves to taste stimuli in C57BL/6J mice. BMC

Neuroscience 4, 5-20.

Das, S. (1958) Inheritance of the PTC taste characeter in man: An analysis of 126 Rarhi

Brahmin families of West Bengal. Annals of Human Genetics 22, 200-212.

Dasilva, G. (1992) The western black-and-white colobus as a low-energy strategist:

Activity budgets, energy expenditure and energy intake. The Journal of Animal

Ecology 61, 79-91. 64 DeFazio, R. A., Dvoryanchikov, G., Maruyama, Y., Kim, J. W., Pereira, E., Roper, S. D.

and Chaudhari, N. (2006) Separate populations of receptor cells and presynaptic

cells in mouse taste buds. Journal of Neuroscience 26, 3971-3980.

Delwiche, J. F., Buletic, Z. and Breslin, P. A. S. (2001) Relationship of papillae number

to bitter intensity of quinine and PROP within and between individuals.

Physiology & Behavior 74, 329-337.

Dennys, V. (1991) Approche du rôle de la perception gustative dans la différenciation et

la régulation du comportement alimentaire des lémuriens. Vol. Ph.D. Université

Paris - XIII, Villetaneuse.

Dinehart, M. E., Hayes, J. E., Bartoshuk, L. M., Lanier, S. L. and Duffy, V. B. (2006)

Bitter taste markers explain variability in vegetable sweetness, bitterness, and

intake. Physiology & Behavior 87, 304-313.

Dominy, N. (2004a) Color as an indicator of food quality to anthropoid primates:

Ecological evidence and an evolutionary scenario. In Anthropoid Origins: New

Visions, Ross, C. F. and Kay, R. F. eds, pp. 615-644. Kluwer Academic, New

York.

Dominy, N. (2004b) Fruits, fingers, and fermentation: The sensory cues available to

foraging primates. Integrated and Comparative Biology 44, 295-303.

Dominy, N. and Lucas, P. W. (2001) Ecological importance of trichromatic vision to

primates. Nature 410, 363-366.

Dominy, N. and Lucas, P. W. (2004) Significance of color, calories, and climate to the

visual ecology of catarrhines. American Journal of Primatology 62, 189-207. 65 Dominy, N., Lucas, P. W., Osorio, D. and Yamashita, N. (2001) The sensory ecology of

primate food perception. Evolutionary Anthropology 10, 171-186.

Dotson, C. D., Roper, S. D. and Spector, A. C. (2005) PLCβ2-independent behavioral

avoidance of prototypical bitter-tasting ligands. Chemical Senses 30, 593–600.

Doty, R. L., Bagla, R., Morgenson, M. and Mirza, N. (2001) NaCl thresholds:

Relationship to anterior tongue locus, area of stimulation, and number of

fungiform papillae. Physiology & Behavior 72, 373-378.

Drayna, D. (2005) Human taste genetics. Annual Review of Genomics and Human

Genetics 6, 217-235.

Drayna, D., Coon, H., Kim, U.-K., Elsner, T., Cromer, K., Otterud, B., Baird, L., Peiffer,

A. P. and Leppert, M. (2003) Genetic analysis of a complex trait in the Utah

Genetic Reference Project: A major locus for PTC taste ability on chromosome 7q

and a secondary locus on chromosome 16p. Human Genetics 112, 567-572.

Drewnowski, A., Ahlstrom Henderson, S. and Barratt-Fornell, A. (1998a) Genetic

sensitivity to 6-n-Propylthiouracil and sensory responses to sugar and fat

mixtures. Physiology & Behavior 63, 771-777.

Drewnowski, A., Ahlstrom Henderson, S., Levine, A. and Hann, C. (1999) Taste and

food preferences as predictors of dietary practices in young women. Public Health

Nutrition 2, 513–519.

Drewnowski, A., Ahlstrom Henderson, S. and Shore, A. B. (1997a) Genetic sensitivity to

6-n-propylthiouracil (PROP) and hedonic responses to bitter and sweet tastes.

Chemical Senses 22, 27-37. 66 Drewnowski, A., Henderson, S. A., Hann, C. S., Berg, W. A. and Ruffin, M. T. (2000)

Genetic taste markers and preferences for vegetables and fruit of female breast

care patients. Journal of the American Dietetic Association 100, 191-197.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1997b)

Nontasters, tasters, and supertasters of 6-n-Propylthiouracil (PROP) and hedonic

response to sweet. Physiology & Behavior 62, 649-655.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1998b) Sensory

responses to 6-n-propylthiouracil (PROP) or sucrose solutions and food

preferences in young women. Annals of the New York Academy of Sciences 855,

797-801.

Drewnowski, A. and Rock, C. L. (1995) The influence of genetic taste markers on food

acceptance. American Journal of Clinical Nutrition 62, 506-511.

Dudley, R. (2002) Fermenting fruit and the historical ecology of ethanol ingestion: Is

alcoholism in modern humans an evolutionary hangover? Addiction 97, 381-388.

Dudley, R. (2004) Ethanol, fruit ripening, and the historical origins of human alcoholism

in primate frugivory. Integrated and Comparative Biology 44, 315-323.

Duffy, V. B. and Bartoshuk, L. M. (2000) Food acceptance and genetic variation in taste.

Journal of the American Dietetic Association 100, 647-655.

Duffy, V. B., Bartoshuk, L. M., Striegel-Moore, R. and Rodin, J. (1998) Taste changes

across pregnancy. Annals of the New York Academy of Sciences 855, 805-809.

Duffy, V. B., Davidson, A. C., Kidd, J. R., Kidd, K. K., Speed, W. C., Pakstis, A. J.,

Reed, D. R., Snyder, D. J. and Bartoshuk, L. M. (2004) Bitter receptor gene 67 (TAS2R38), 6-n-Propylthiouracil (PROP) bitterness and alcohol intake.

Alcoholism: Clinical and Experimental Research 28, 1629-1637.

Duffy, V. B., Peterson, J. M., Dinehart, M. E. and Bartoshuk, L. (2003) Genetic and

environmental variation in taste: Associations with sweet intensity, preference,

and intake. Topics in Clinical Nutrition 18, 209-220.

Dulai, K. S., von Dornum, M., Mollon, J. D. and Hunt, D. M. (1999) The evolution of

trichromatic color vision by opsin gene duplication in new world and old world

primates. Genome Research 9, 629-638.

Dunbar, R. I. M. (1977) Feeding ecology of gelada baboons: A preliminary report. In

Primate Ecology, Clutton-Brock, T. H. ed, pp. 251-273. Academic Press, London.

Eaton, J. W. and Gavin, J. A. (1965) Sensitivity to P-T-C among primates. American

Journal of Physical Anthropology 23, 381-388.

Emura, S., Hayakawa, D., Chen, H. and Shoumura, S. (2002) Morphology of the dorsal

lingual papillae in the Japanese macaque and savanna monkey. Anatomia,

Histologia, Embryologia: Journal of Veterinary Medicine Series C 31, 313-316.

Essick, G. K., Chopra, A., Guest, S. and McGlone, F. (2003) Lingual tactile acuity, taste

perception, and the density and diameter of fungiform papillae in female subjects.

Physiology & Behavior 80, 289-302.

Etter, L. (1999) Variation in taste perception across the menstrual cycle. M.D. Yale

University.

Fain, G. (2003) Sensory transduction. Sinauer Associates, Inc. Publishers, Sunderland,

Mass. 68 Falconer, D. S. (1947) Sensory thresholds for solutions of phenylthiocarbamide: Results

of tests on a large sample, made by R. A. Fisher. Annals of Eugenics, London 13,

211-222.

Feldman, G. M., Mogyorosi, A., Heck, G. L., DeSimone, J. A., Santos, C. R., Clary, R.

A. and Lyall, V. (2003) Salt-evoked lingual surface potential in humans. Journal

of Neurophysiology 90, 2060–2064.

Fernberger, S. W. (1932) A preliminary study of taste deficiency. Journal of Psychology

44, 322-326.

Finger, T. E. (2005) Cell types and lineages in taste buds. Chemical Senses 30, i54 - i55.

Finger, T. E., Danilova, V., Barrows, J., Bartel, D. L., Vigers, A. J., Stone, L., Hellekant,

G. and Kinnamon, S. C. (2005) ATP signaling is crucial for communication from

taste buds to gustatory nerves 310, 1495-1499.

Fischer, A., Gilad, Y., Man, O. and Paabo, S. (2005) Evolution of bitter taste receptors in

humans and apes. Molecular and Biology and Evolution 22, 432-436.

Fischer, R., Griffen, F., England, S. and Garn, S. M. (1961) Taste thresholds and food

dislikes. Nature 191, 1328.

Fischer, R. and Griffin, F. (1959) On factors involved in the mechanism of taste

blindness. Experientia 15, 447-448.

Fischer, R. and Griffin, F. (1961) Taste blindness and variations in taste-threshold in

relation to thyroid metabolism. Journal of Neuropsychiatry 3, 98-104.

69 Fischer, R. and Kaelbling, R. (1966) Increase in taste acuity with sympatric stimulation:

The relation of just-noticeable taste difference to a systemic psychotropic drug

use. Recent Advances in Biological Psychiatry 9, 183-195.

Fisher, R. A., Ford, E. B. and Huxley, J. (1939) Taste-testing the anthropoid apes. Nature

114, 750.

Fox, A. L. (1932) The relationship between chemical constitution and taste. Proceedings

of the National Academy of Sciences of the United States of America 18, 115-120.

Freeland, W. J. and Janzen, D. H. (1974) Strategies in herbivory by mammals: The role

of plant secondary compounds. The American Naturalist 108, 269-289.

Galef, B. G. (1996) Food selection: Problems in understanding how we choose foods to

eat. Neuroscience and Biobehavioral Reviews 20, 67-73.

Ganzhorn, J. (1989) Primate species separation in relation to secondary plant chemicals.

Human Evolution 4, 125-132.

Ganzhorn, J. U. (1988) Food partitioning among Malagasy primates. Oecologica (Berlin)

75, 436-450.

Ganzhorn, J. U. and Wright, P. C. (1994) Temporal patterns in primate leaf eating: The

possible role of leaf chemistry. Folia Primatologica 63, 203-208.

Garber, P. A. (1987) Foraging strategies among living primates. Annual Review of

Anthropology 16, 339-364.

Gaulin, S. J. C. and Konner, M. (1977) On the natural diet of primates, including humans.

In Nutrition and the Brain, Vol. 1, Wurtman, R. J. and Wurtman, J. J. eds, pp. 1-

86. Raven Press, New York. 70 Gaulin, S. J. C. and Sailer, L. D. (1985) Are females the ecological sex? American

Anthropologist 87, 111-119.

Gautier-Hion, A. (1980) Seasonal variations of diet related to species and sex in a

community of cercopithecus monkeys. Journal of Animal Ecology 49, 237-269.

Gent, J. F. and Bartoshuk, L. M. (1983) Sweetness of sucrose neohesperidin

dihydrochalcone, and saccharin is related to genetic ability to taste 6-n-

propylthiouracil. Chemical Senses 7, 265-272.

Gilad, Y., Man, O. and Glusman, G. (2005) A comparison of the human and chimpanzee

olfactory receptor gene repertoires. Genome Research 15, 224-230.

Gilad, Y., Man, O., Paabo, S. and Lancet, D. (2003) Human specific loss of olfactory

receptor genes. Proceedings of the National Academy of Sciences of the United

States of America 100, 3324-3327.

Gilbertson, T. A., Damak, S. and Margolskee, R. F. (2000) The molecular physiology of

taste transduction. Current opinion in Neurobiology 10, 519-527.

Gittleman, J. L. and Thompson, S. D. (1988) Energy allocation in mammalian

reproduction. American Zoologist 28, 863-875

Glander, K. E. (1982) The impact of plant secondary compounds on primate feeding

behavior. Yearbook of Physical Anthropology 25, 1-18.

Glanville, E. V. and Kaplan, A. R. (1965) Food preferences and sensitivity of taste for

bitter compounds. Nature 205, 851-853.

Glaser, D. (1980) Die leistugen des geschmacksorgans beim menschen im vergleich zu

nichtmenschlichen primaten. Lebensm.-Wiss u. -Technol. 13, 276-282. 71 Glaser, D. (1986) Geschmacksforschung bei Primaten. Vjsehr Naturf Ges Zürich 131, 92-

110.

Glaser, D. (2002) Experimental studies of primate sensory capacity. Evolutionary

Anthropology Supp 1, 136-139.

Glaser, D. and Hellekant, G. (1977) Verhaltens- und electrophysiologische experimente

über den geschmackssinn bei Saguinus midas tamarin (Callitrichidae). Folia

Primatologica 28, 43-51.

Glaser, D., Tinti, J.-M. and Nofre, C. (1996) Gustatory repsonses of non-human primates

to dipeptide deratives or analogues, sweet in man. Food Chemistry 56, 313-321.

Glendinning, J. I. (1994) Is the bitter rejection response always adaptive? Physiology &

Behavior 56, 1217-1227.

Go, Y., Satta, Y., Takenaka, O. and Takahashi, N. (2005) Lineage-specific loss of

function of bitter taste receptor genes in humans and nonhuman primates.

Genetics 170, 313-326.

Goldstein, G. L., Daun, H. and Tepper, B. J. (2007) Influence of PROP taster status and

maternal variables on energy intake and body weight of pre-adolescents.

Physiology & Behavior 90, 809-817.

Goren-Inbar, N., Alperson, N., Kislev, M. E., Simchoni, O., Melamed, Y., Ben-Nun, A.

and Werker, E. (2004) Evidence of hominin control of fire at Gesher Benot

Ya`aqov, Israel. Science 304, 725 - 727.

Guo, S.-W. and Reed, D. R. (2001) The genetics of phenylthiocarbamide perception.

Annals of Human Biology 28, 111-142. 72 Haefeli, R. J., Solms, J. and Glaser, D. (1998) Taste responses to amino acids in common

marmosets (Callithrix jacchus jacchus, Callitrichidae) a non-human primate in

comparison to humans. Lebensm.-Wiss u. -Technol. 31, 371-376.

Hall, M. J., Bartoshuk, L. M., Cain, W. S. and Stevens, J. C. (1975) PTC taste blindnes

and the taste of caffeine. Nature 253, 442-443.

Hänig, D. P. (1901) Zur psychophysik des geschmackssinnes. Philosophische Studien 17,

576-623.

Harris, D. R. (1992) Human diet and subsistence. In The Cambridge encyclopedia of

human evolution, Jones, S., Martin, R. and Pilbeam, D. eds, pp. 69-74. Cambridge

University Press.

Harris, H. and Kalmus, H. (1949) The measurement of taste sensitivity to phenylthiourea

(PTC). Annals of Eugenics, London 15, 32-45.

Hayes, J. E., Dinehart, M. E. and Duffy, V. B. (in press) Optimal liking of fat-sweet

mixtures varies with markers of bitter taste and anatomy. Appetite, 23.

Heck, G. L., Mierson, S. and DeSimone, J. D. (1984) Salt taste transduction occurs

through an amiloride-sensitive sodium transport pathway. Science 223, 403-405.

Heck, G. L., Persuand, K. C. and DeSimone, J. A. (1989) Direct measurement of

translingual epithelial NaCl and KCl currents during the chorda tympani taste

response. Biophysical Journal 55, 843-857.

Hellekant, G. and Danilova, V. (1996) Species differences toward sweeteners. Food

Chemistry 56, 323-328.

73 Herness, M. S. and Gilbertson, T. A. (1999) Cellular mechanisms of taste transduction.

Annual Review of Physiology 61, 873-900.

Hladik, C. M. (1981) Diet and the evolution of feeding strategies among forest primates.

In Omnivorous Primates: Gathering and Hunting in Human Evolution, Harding,

R. S. O. and Teleki, G. eds. Columbia University Press, New York.

Hladik, C. M., Pasquet, P. and Simmen, B. (2002) New perspectives on taste and primate

evolution: The dichotomy in gustatory coding for perception of beneficent versus

noxious substances as supported by correlations among human thresholds.

American Journal of Physical Anthropology 117, 342-348.

Hladik, C. M. and Simmen, B. (1996) Taste perception and feeding behavior in

nonhuman primates and human populations. Evolutionary Anthropology 5, 58-71.

Hoffmann, J. N., Montag, A. G. and Dominy, N. (2004) Meissner corpuscles and

somatosensory acuity: The prehensile appendages of primates and elephants. The

Anatomical Record Part A 281A, 1138-1147.

Hofmann, T., Chubanov, V., Gudermann, T. and Montell, C. (2003) TRPM5 Is a voltage-

modulated and Ca2+-activated monovalent selective cation channel. Current

Biology 13, 1153–1158.

Hoon, M. A., Adler, E., Lindemeier, J., Battey, J. F., Ryba, N. J. P. and Zuker, C. S.

(1999) Putative mammalian taste receptors: A class of taste-specific GPCRs with

distinct topographic selectivity. Cell 96, 541–551.

Hosako-Naito, Y., Lucchina, L. A., Snyder, D. J., Boggiano, M. K., Duffy, V. B. and

Bartoshuk, L. M. (1996) Number of fungiform papillae in nontasters, medium 74 tasters, and supertasters of PROP (6-n-propylthiouracil). Chemical Senses 21,

616.

Huang, L., Shanker, Y. G., Dubauskaite, J., Zheng, J. Z., Yan, W., Rosenzweig, S.,

Spielman, A. I., Max, M. and Margolskee, R. F. (1999) Gγ13 colocalizes with

gustducin in taste receptor cells and mediates IP3 responses to bitter denatonium.

Nature Neuroscience 12, 1055-1062.

Huang, Y.-J., Maruyama, Y., Lu, K.-S., Pereira, E., Plonsky, I., Baur, J. E., Wu, D. and

Roper, S. D. (2005) Mouse taste buds use serotonin as a neurotransmitter. The

Journal of Neuroscience 25, 843– 847.

Hubener, F. and Laska, M. (1998) Assessing olfactory performance in an Old World

primate, Macaca nemistrina. Physiology & Behavior 64, 521-527.

Huque, T., Lischka, F. W., Bresliin, P. A., Feldman, R. S., Spielman, A. I. and Brand, J.

G. (in press) Expression of GPR4, a aproton sensing GPCR, in human fungiform

papillae. Chemical Senses.

Hyde, R. J. and Feller, R. P. (1981) Age and sex effects on taste of sucrose, NaCl, citric

acid and caffeine. Neurobiology of Aging 2, 315-318.

Inoue, M., Beauchamp, G. K. and Bachmanov, A. A. (2004) Gustatory neural responses

to umami taste stimuli in C57BL/6ByJ and 129P3/J Mice. Chemical Senses 29,

789-795.

Isbell, L. A. (1998) Diet for a small primate: Insectivory and gummivory in the (large)

patas monkey (Erythrocebus patas pyrrhonotus). American Journal of

Primatology 45, 381-398. 75 James, C. E., Laing, D. G. and Oram, N. (1997) A comparison of the ability of 8–9-year-

old children and adults to detect taste stimuli. Physiology & Behavior 62, 193-

197.

Janjua, T. and Schwartz, S. (1997) unpublished data. In Duffy, V. B. and L. M.

Bartoshuk (2000) Food acceptance and genetic variation in taste. Journal of the

American Dietetic Association 100, 647-655.

Janson, C. H. and Chapman, C. A. (1999) Resources and primate community structure. In

Primate Communities, Fleagle, J. G., Janson, C. H. and Reed, K. E. eds, pp. 237-

267. Cambridge University Press, New York.

Janzen, D. H. (1983) Dispersal of seeds by vertebrate guts. In Coevolution, Futuyma, D.

J. and Slatkin, M. eds, pp. 232-262. Sinauer, Sunderland, Mass.

Jerzsa-Latta, M., Krondl, M. and Coleman, P. (1990) Use and perceived attributes of

cruciferous vegetables in terms of genetically-mediated taste sensitivity. Appetite

15, 127-134.

Johns, T. (1999) The Chemical Ecology of Human Ingestive Behaviors. Annual Review

of Anthropology 28, 27-50.

Kalmus, H. (1958) Improvements in the classification of the taster genotypes. Annals of

Human Genetics 22, 222-230.

Kalmus, H. (1971) Genetics of taste. In Taste, Vol. 4, Chemical Senses, Part 2, Beidler,

L. M. ed, pp. 165-179. Springer-Verlag Berlin, Heidelberg.

76 Kaminski, L. C., Henderson, S. A. and Drewnowski, A. (2000) Young women's food

preferences and taste repsonsiveness to 6-n-porpylthiouracil (PROP). Physiology

& Behavior 68, 691-697.

Kay, R. F. and Scheine, W. S. (1979) On the relationship between chitin particle size and

digestibility in the primate Galago senagalensis. American Journal of Physical

Anthropology 50, 301-308.

Keller, K. L., Steinmann, L., Nurse, R. J. and Tepper, B. J. (2002) Genetic taste

sensitivity to 6-n-propylthiouracil influences food preference and reported intake

in preschool children. Appetite 38, 3-12.

Key, C. and Ross, C. (1999) Sex differences in energy expenditure in non-human

primates. Proceedings of the Royal Society B: Biological Sciences 266, 2479-

2485.

Kim, U., Wooding, S., Ricci, D., Jorde, L. B. and Drayna, D. (2005) Worldwide

haplotype diversity and coding sequence variation at human bitter taste receptor

loci. Human Mutation 26, 199-204.

Kim, U.-K., Jorgenson, E., Coon, H., Leppert, M., Risch, N. and Drayna, D. (2003)

Positional cloning of the human quantitative trait locus underlying taste sensitivity

to phenlythiocarbamide. Science 299, 1221-1225.

Kinnamon, S. C. and Margolskee, R. F. (1996) Mechanisms of taste transduction.

Current Opinion in Neurobiology 6, 506-513.

77 Kobayashi, K. (1992) Stereo architecture of the interface of the epithelial cell layer and

connective tissue core of the foliate papilla in the rabbit tongue. Acta Anatomica

143, 109-117.

Kobayashi, K., Kumakura, M., Yoshimura, K., Takahashi, M., Zeng, J. H., Kageyama, I.,

Kobayashi, K. and Hama, N. (2004) Comparative morphological studies on the

stereo structure of the lingual papillae of selected primates using scanning

electron microscopy. Annals of Anatomy - Anatomischer Anzeiger 186, 525-530.

Kumar, S. and Hedges, S. B. (1998) A molecular timescale for vertebrate evolution.

Nature 392, 917-920.

Kurihara, K. and Kashiwayanagi, M. (1998) Introductory remarks on umami taste.

Annals of the New York Academy of Sciences 855.

Lambert, J. E. (1998) Primate digestion: Interactions among anatomy, physiology, and

feeding ecology. Evolutionary Anthropology 7, 8-20.

Laska, M. (1996) Taste preference thresholds for food-associated sugars in the squirrel

monkey (Saimiri sciureus). Primates 37, 91-95.

Laska, M. (1999) Taste responsiveness to food-associated acids in the squirrel monkey

(Saimiri sciureus). Journal of Chemical Ecology 25, 1623-1631.

Laska, M. (2000) Gustatory responsiveness to food-associated sugars and acids in pigtail

macaques, Macaca menestrina. Physiology & Behavior 70, 495-504.

Laska, M. (2001) A comparison of food preferences and nutrient composition in captive

squirrel monkeys, Saimiri sciureus, and pigtail macaques, Macaca nemestrina.

Physiology & Behavior 73, 111-120. 78 Laska, M., Carrera Sanchez, E. and Rodriguez Luna, E. (1996) Gustatory thresholds for

food associated sugars in the spider monkey (Ateles geoffroyi). American Journal

of Primatology.

Laska, M., Carrera Sanchez, E. and Rodriguez Luna, E. (1998) Taste preferences for

food-associated sugars in the spider monkey (Ateles geoffroyi). Primates 39, 91-

96.

Laska, M., Hernandez Salazar, L. T. and Rodriguez Luna, E. (2000) Food preferences

and nutrient composition in captive spider monkeys, Ateles geoffroyi.

International Journal of Primatology 21, 671-683.

Laska, M., Scheuber, H.-P., Carrera Sanchez, E. and Rodriguez Luna, E. (1999a) Taste

difference thresholds for sucrose in two species of nonhuman primates. American

Journal of Primatology 48, 153-160.

Laska, M., Schull, E. and Scheuber, H.-P. (1999b) Taste preference thresholds for food

associated sugars in baboons (Papio hamadryas anubis). International Journal of

Primatology 20, 25-34.

Lawless, H. (1980) A comparison of different methods used to assess sensitivity to the

taste of phenylthiocarbamide (PTC). Chemical Senses 5, 247-256.

Leach, E. J. and Noble, A. C. (1986) Comparison of bitterness of caffiene and quinine by

a time-intensity procedure. Chemical Senses 11, 339-345.

Levit, S. G. and Soboleva, G. V. (1935) Comparative intrapair correlations of fraternal

twins and siblings. Journal of Genetics 30, 389-396.

79 Li, X., Li, W., Wang, H., Cao, J., Maehashi, K., Huang, L., Bachmanov, A. A., Reed, D.

R., Legrand-Defretin, V., Beauchamp, G. K. and Brand, J. G. (2005)

Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward

sugar. PLoS Biology 1, 27-35.

Li, X., Staszewski, L., Xu, H., Durick, K., Zoller, M. and Adler, E. (2002) Human

receptors for sweet and umami taste. Proceedings of the National Academy of

Sciences of the United States of America 99, 4692-4696.

Lin, W., Finger, T. E., Rossier, B. C. and Kinnamon, S. C. (1999) Epithelial Na+channel

subunits in rat taste cells: Localization and regulation by aldosterone. Journal of

Comparative Neurology 405, 406–420.

Lindemann, B. (1996) Taste reception. Physiological Reviews 76, 719-766.

Lindemann, B. (2001) Receptors and transduction in taste. Nature 413, 219-225.

2+ Liu, D. and Liman, E. R. (2003) Intracellular Ca and the phospholipid PIP2 regulate the

taste transduction ion channel TRPM5. Proceedings of the National Academy of

Sciences of the United States of America 100, 15160-15165.

Looy, H. and Weingarten, H. P. (1992) Facial expressions and genetic sensitivity to 6-n-

Propylthiouracil predict hedonic response to sweet Physiology & Behavior 52, 75-

82.

Lucchina, L. A., Curtis, O. F., Putnam, P., Drewnowski, A., Prutkin, J. M. and Bartoshuk,

L. M. (1998) Psychophysical measurement of 6-n-propylthiouracil (PROP) taste

perception. Annals of the New York Academy of Sciences 855, 816-819.

80 Ludwig, M.-G., Vanek, M., Guerini, D., Gasser, J. A., Jones, C. E., Junker, U.,

Hofstetter, H., Wolf, R. M. and Seuwen, K. (2003) Proton-sensing G-protein-

coupled receptors. Nature 425, 93-98.

Lundy, R. F., Jr. and Contreras, R. J. (1999) Gustatory neuron types in rat geniculate

ganglion. J Neurophysiol 82, 2970-2988.

Ly, A. and Drewnowski, A. (2001) PROP (6-n-propylthiouracil) tasting and sensory

responses to caffeine, sucrose, neohesperidin dihydrochalcone and chocolate.

Chemical Senses 26, 41-47.

Lyall, V., Alam, R. I., Phan, D. Q., Ereso, G. L., Phan, T.-H. T., Malik, S. A., Montrose,

M. H., Chu, S., Heck, G. L., Feldman, G. M. and Desimone, A. J. A. (2001)

Decrease in rat taste receptor cell intracellular pH is the proximate stimulus in

sour taste transduction. American Journal of Physiology: Cell Physiology 281,

C1005 – C1013.

Lyall, V., Heck, G. L., Vinnikove, A. K., Ghosh, S., Phan, T. T., Alam, R. I., Russell, O.

F., Malik, S. A., Bigbee, J. W. and DeSimone, J. A. (2004) The mammalian

amiloride-insensitive non-specific taste receptor a vanilloid receptor-1 variant.

Journal of Physiology 558, 147-159.

Machida, H., Perkins, E. and Giacommetti, L. (1967) The anatomical and histochemical

properties of the tongue of primates. Folia Primatologica 5, 264-279.

Martin, N. G. (1975) Phenylthiocarbamide tasting in a sample of twins. Annals of Human

Genetics 38, 321-326.

81 Maruyama, Y., Pereira, E., Margolskee, R. F., Chaudhari, N. and Roper, S. D. (2006)

Umami responses in mouse taste cells indicate more than one receptor. Journal of

Neuroscience 26, 2227.

Matsunami, H., Montmayeur, J.-P. and Buck, L. B. (2000) A family of candidate taste

receptors in human and mouse. Nature 404, 601-604.

McCabe, G. and Fedigan, L. M. (2005) Eating for two: The effect of reproductive state

on the diet and nutrition of free-ranging female white-faced capuchins (Cebus

capuchinus) in Costa Rica. American Journal of Primatology 66, 112-113.

McLaughlin, S. K., McKinnon, P. J. and Margolskee, R. F. (1992) Gustducin is a taste-

cell-specific G protein closely related to transducins. Nature 357, 563-569.

Merton, B. (1958) Taste sensitivity to PTC in 60 Norwegian families with 176 children.

Acta Genetica et Statistica Medica 8, 114-128.

Miguet, L., Zhang, Z. and Grigorov, M. G. (2006) Computational studies of ligand-

receptor interactions in bitter taste receptors. Journal of Receptors and Signal

Transduction 26, 611-630.

Miller, I. J. (1986) Variation in human taste bud densities among regions and subjects.

The Anatomical Record 216, 474-482.

Miller, I. J. (1987) Human fungiform taste bud density and distribution. Annals of the

New York Academy of Sciences 510, 501.

Miller, I. J. and Bartoshuk, L. M. (1991) Taste perception, taste bud distribution, and

spatial relationships. In Smell and Taste in Health and Disease, Getchell, T. V.,

82 Doty, R. L., Bartoshuk, L. M. and Snow, J. B. J. eds, pp. 205-233. Raven Press,

New York.

Miller, I. J. and Reedy, F. E. (1990) Variations in human taste bud density and taste

intensity perception. Physiology & Behavior 47, 1213-1219.

Miller, I. J. and Whitney, G. (1989) Sucrose octaacetate-taster mice have more vallate

taste buds than non-tasters. Neuroscience Letters 100, 271-275.

Milton, K. (1979) Factors influencing leaf choice by howler monkeys: A test of some

hypotheses of food selection by generalost herbivores. American Naturalist 114,

362-378.

Milton, K. (1980) The foraging strategy of howler monkeys. Columbia University Press,

New York.

Milton, K. (1984) The role of food-processing factors in primate food choice. In

Adaptations for Foraging in Nonhuman Primates: Contributions to an

Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 249-279. Columbia University Press, New York.

Milton, K. (2003) The critical role played by animal source foods in human (Homo)

evolution. Journal of Nutrition 133, 3886S-3892S.

Ming, D., Ninomiya, Y. and Margolskee, R. F. (1999) Blocking taste receptor activation

of gustducin inhibits gustatory responses to bitter compounds. Proceedings of the

National Academy of Sciences of the United States of America 96, 9903–9908.

Ming, D., Ruiz-Avila, L. and Margolskee, R. F. (1998) Characterization and

solubilization of bitter-responsive receptors that couple to gustducin. Proceedings 83 of the National Academy of Sciences of the United States of America 95, 8933–

8938.

Mistretta, C. M. (1991) Developmental neurobiology of the taste system. In Smell and

Taste in Health and Disease, Getchell, T. V., Doty, R. L., Bartoshuk, L. M. and

Snow, J. J. eds, pp. 35-64. Raven Press, New York.

Møller, A. R. (2003) Sensory Systems: Anatomy and Physiology. Academic Press,

London.

Mombaerts, P. (2004) Genes and ligands for ororant, vomeronasal and taste receptors.

Nature Reviews: Neuroscience 5, 263-278.

Montmayeur, J.-P., Liberles, S. D., Matsunami, H. and Buck, L. B. (2001) A candidate

taste receptor gene near a sweet taste locus. Nature Neuroscience 5, 492 - 498.

Morland, H. S. (1991) Social organization and ecology of the black and white ruffed

lemurs (Varecia variegata) in lowland rain forest, Nosy Mangabe, Madagascar.

Yale University, New Haven, Connecticut.

Nelson, G., Chandrashekar, J., Hoon, M. A., Feng, L., Zhao, G., Ryba, N. J. P. and

Zuker, C. S. (2002) An amino acid taste receptor. Nature 416, 199-202.

Nelson, G., Hoon, M. A., Chandrashekar, J., Zhang, Y., Ryba, N. J. P. and Zuker, C. S.

(2001) Mammalian sweet taste receptors. Cell 106, 381-390.

Ninomiya, Y., Kajiura, H. and Mochizuki, K. (1993) Differential taste responses of

mouse chorda tympani and glossopharyngeal nerves to sugars and amino acids.

Neuroscience Letters 163, 197-200.

84 Norgren, R. (1984) Central neural mechanisms of taste. In Handbook of Physiology: The

Nervous System, Sensory Processes. , Vol. III, pp. 1087–1128. American

Physiological Society, Washington, D.C.

Northcutt, G. R. (2004) Taste buds: Development and evolution. Brain, Behavior and

Evolution 64, 198-206.

O'Brien, T. G. and Kinnaird, M. F. (1997) Behavior, diet, and movements of the Sulawesi

crested black macaque (Macaca nigra). International Journal of Primatology 18,

321-351.

O’Driscoll Worman, C. and Chapman, C. (2005) Seasonal variation in the quality of a

tropical ripe fruit and the response of three frugivores. Journal of Tropical

Ecology 21, 689–697.

Overdorff, D. J. (1993) Ecological and reproductive correlates to range use in red-bellied

lemurs (Eulemur rubriventer) and roufous lemurs (Eulemur fulvus rufus). In

Lemur Social Systems and Their Ecological Basis, Kappeler, P. M. and Ganzhorn,

J. U. eds. Plenum Press, New York.

Palmer, R. K. (2007) The pharmacaology and signaling of bitter, sweet, and umami taste

sensing. Molecular Interventions 7, 87-98.

Parra, R. (1978) Comparison of foregut and hindgut fermentation in herbivores. In The

Ecology of Arboreal Folivores, Montgomery, G. G. ed, pp. 205-229. Smithsonian

Institution Press, Washington DC.

85 Parry, C. M., Erkner, A. and le Coutre, J. (2004) Divergence of T2R chemosensory

receptor families in humans, bonobos, and chimpanzees. Proceedings of the

National Academy of Sciences of the United States of America 101, 14830-14834.

Pasquet, P., Oberti, B., El Ati, J. and Hladik, C. M. (2002) Relationships between

threshold-based PROP sensitivity and food preferences of Tunisians. Appetite 39,

167-173.

Patel, S. (1971) ABO blood groups, PTC tasting and derrnatoglyphics of Tibetans at

Chandragiri, Orissa. American Journal of Physical Anthropology 35, 149-150.

Penfield, W. and Faulk, M. E. (1955) The insula: Further observations on its function.

Brain 78, 445-470.

Pérez, C. A., Huang, L., Rong, M., Kozak, J. A., Preuss, A. K., Zhan, H., Max, M. and

Margolskee, R. F. (2002) A transient receptor potential channel in taste receptor

cells. Nature Neuroscience 5, 1169-1176.

Pfaffmann, C. (1941) Gustatory afferent impulses. Journal of Cellular and Comparative

Physiology 17, 243-258.

Pickering, G. J., Simunkova, K. and DiBattista, D. (2004) Intensity of taste and

astringency sensations elicited by red wines is associated with sensitivity to PROP

(6-n-propylthiouracil). Food Quality and Preference 15, 147-154.

Polcari, R. (1971) De nouvelles données sur la sensibilité à la phenil-thio-carbamide chez

les primates. Paper presented at the Proceeding of the Third International

Congress of Primatology, Zurich, 1971.

86 Pollock, J. I. (1977) The ecology and sociology of feeding in Indri indri. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 38-69. Academic Press, New York.

Portman, O. (1970) Nutritional requirements of non-human primates. In Feeding and

Nutrition of Non-human Primates, Harris, R. ed, pp. 87-116. Academic Press,

New York.

Prawitt, D., Monteilh-Zoller, M. K., Brixel, L., Spangenberg, C., Zabel, B., Fleig, A. and

Penner, R. (2003) TRPM5 is a transient Ca2+-activated cation channel responding

2+ to rapid changes in [Ca ]i Proceedings of the National Academy of Sciences of

the United States of America 100, 15166 –15171.

Pritchard, T. C., Hamilton, R. B. and Norgren, R. (1989) Neural coding of gustatory

information in the thalamus of Macaca mulatta. Journal of Neurophysiology 61,

1-14.

Pritchard, T. C., Macaluso, D. A. and Eslinger, P. J. (1999) Taste perception in patients

with insular cortex lesions. Behavioral Neuroscience 113, 663-671.

Pritchard, T. C., Reilly, S., Hamilton, R. B. and Norgren, R. (1994) Taste preference of

Old World monkeys: I. A single-bottle preference test. Physiology & Behavior 55,

447-481.

Prodi, D. A., Drayna, D., Forabosco, P., Palmas, M. A., Maestrale, G. B., Piras, D. and

Angius, A. (2004) Bitter taste study in a Sardinian genetic isolate supports the

association of phenylthiocarbamide sensitivity to the TAS2R38 bitter receptor

gene. Chemical Senses 29, 697-702. 87 Provenza, F. D. (1996) Acquired aversions as the basis for varied diets of ruminants

foraging on rangelands. Journal of Animal Science 74, 2010-220.

Provenza, F. D., Villalba, J. J., Dziba, L. E., Atwood, S. B. and Banner, R. E. (2003)

Linking herbivore experience, varied diets, and plant biochemical diversity. Small

Ruminant Research 49, 257-274.

Prutkin, J., Duffy, V. B., Etter, L., Fast, K., Gardner, E., Lucchina, L. A., Snyder, D. J.,

Tie, K., Weiffenbach, J. and Bartoshuk, L. M. (2000) Genetic variation and

inferences about perceived taste intensity in mice and men. Physiology &

Behavior 69, 161-173.

Purves, D., Fitzpatric, D., Katz, L. C., LaMantia, A.-S. and McNamara, J. O. (1997)

Neuroscience. Sinaur Associates, Inc., Sunderland, MA.

Ramirez, I. (1990) Why do sugars taste good? Neuroscience & Biobehavioral Reviews

14, 125-134.

Reed, D. R., Bachmanov, A. A., Beauchamp, G. K., Tordoff, M. and Price, R. A. (1997)

Heritable variation in food preference and their contribution to obesity. Behavior

Genetics 27, 373-387.

Reed, D. R., Bartoshuk, L. M., Duffy, V. B., Marino, S. and Price, A. (1995)

Propylthiouracil tasting: Determination of underlying threshold distributions

using maximum liklihood. Chemical Senses 20, 529-533.

Reed, D. R., Nanthakumar, E., North, M., Bell, C., Bartoshuk, L. M. and Price, R. A.

(1999) Localization of a gene for bitter taster perception to human chromosome

5p15. American Journal of Human Genetics 64, 1478-1480. 88 Reedy, F. E., Bartoshuk, L. M., Miller, I. J., Duffy, V. B., Lucchina, L. A. and

Yanagisawa, K. (1993) Relationships among papillae, taste pores, and 6-n-

propythiouracil (PROP) suprathreshold taste sensitivity. Chemical Senses 18, 618-

619.

Regan, B. C., Julliot, C., Simmen, B., Vienot, F., Charles-Dominique, P. and J.D., M.

(2001) Fruits, foliage and the evolution of primate colour vision. Philosophical

Transactions of the Royal Society of London. Series B: Biological Sciences 356,

229-283.

Remis, M. J. and Kerr, M. E. (2002) Taste responses to fructose and tannic acid among

gorillas (Gorilla gorilla gorilla). International Journal of Primatology 23, 251-

261.

Riba-Hernández, P., Stoner, K. E. and Lucas, P. W. (2003) The sugar composition of

fruits in the diet of spider monkeys (Ateles geoffroyi) in tropical humid forest in

Costa Rica. Journal of Tropical Ecology 19, 709-716.

Richard, A. (1985) Primates in Nature. W.H. Freeman and Company, New York.

Richter, T. A., Caicedo, A. and Roper, S. D. (2003) Sour taste stimuli evoke Ca2+ and pH

responses in mouse taste cells. The Journal of Physiology Online 547, 475-483.

Rodman, P. S. (1977) Feeding behavior of orangutans in the Kutai Reserve, East

Kalimantan. In Primate Ecology: Studies of Feeding and Ranging Behaviour in

Lemurs, Monkeys and Apes, pp. 383–413. Academic Press, London.

89 Rolls, B. J., Rowe, E. A., Rolls, E. T., Kingston, B., Megson, A. and Gunary, R. (1981)

Variety in a meal enhances food intake in man. Physiology & Behavior 26, 215-

221.

Rolls, E. T. (1999) The Brain and Emotion. Oxford University Press, Oxford.

Rolls, E. T. (2005) Taste, olfactory, and food texture processing in the brain, and the

control of food intake. Physiology & Behavior 85, 45-56.

Rolls, E. T. and Baylis, L. L. (1994) Gustatory, olfactory, and visual convergence within

the primate orbitofrontal cortex. Journal of Neuroscience 14, 5437-5452.

Rolls, E. T., Rolls, B. J. and Rowe, E. A. (1983) Sensory-specific and motivation-specific

satiety for the sight and taste of food and water in man. Physiology & Behavior

30, 185-192.

Rolls, E. T., Scott, T. R., Sienkiewicz, Z. J. and Yaxley, S. (1988) The responsiveness of

neurones in the frontal opercular gustatory cortex of the macaque monkey is

independent of hunger. Journal of Physiology 397, 1-12.

Romanov, R. A., Rogachevskaja, O. A., Bystrova, M. F., Jiang, P., Margolskee, R. F. and

Kolesnikov, S. S. (2007) Afferent neurotransmission mediated by hemichannels

in mammalian taste cells. The EMBO Journal 26, 657-667.

Roper, S. D. (2006) Cell communication in taste buds. Cellular and Molecular Life

Sciences 63, 1494-1500.

Roper, S. D. (2007) Signal transduction and information processing. Pflugers Archiv.

European Journal of Physiology 454, 759-776.

90 Rossier, O., Cao, J., Huque, T., Spielman, A. I., Feldman, R. S., Medrano, J. F., Brand, J.

G. and le Coutre, J. (2004) Analysis of human fungiform papillae cDNA library

and identification of taste-related genes. Chemical Senses 29, 13-23.

Rudolphi, K. A. (1823) Grundriss der Physiologie. Ferdinand Dümmler, Berlin.

Rui-Liin, N., Tanaka, T., Zhou, J. and Tanaka, O. (1982) Phlorizin and trilobatin, sweet

dihydrochalcone-glucosides from leaves of Lithocarpus litseifolius (Hance) Rehd.

(Fagaceae). Agricultural and Biological Chemistry, 46, 1933–1934.

Ruiz-Avila, L., McLaughlin, S. K., Wildman, D., McKinnon, P. J., Robichon, A.,

Spickofsky, N. and Margolskee, R. F. (1995) Coupling of bitter receptor to

phosphodiesterase through transducin in taste receptor cells. Nature 376, 80-85.

Ruiz-Avila, L., Wong, G. T., Damak, S. and Margolskee, R. F. (2001) Dominant loss of

responsiveness to sweet and bitter compounds caused by a single mutation in α-

gustducin. Proceedings of the National Academy of Sciences of the United States

of America 98, 8868 – 8873.

Schiffman, S. (1980) Magnitude estimation of amino acids for young and elderly

subjects. In Olfaction and Taste, Vol. 7, Van der Starre, H. ed, pp. 379–383. IRL

Press, London.

Schilling, A., Danilova, V. and Hellekant, G. (2004) Behavioral study in the gray mouse

lemur (Microcebus murinus) using compounds considered sweet by humans.

American Journal of Primatology 62, 43-48.

91 Scott, T. R., Giza, B. K. and Yan, J. (1998) Electrophysiological responses to bitter

stimuli in primate cortex. Annals of the New York Academy of Sciences 855, 498-

501.

Scott, T. R. and Plata-Salaman, C. R. (1999) Taste in the monkey cortex. Physiology &

Behavior 76, 489-511.

Segovia, C., Hutchinson, I., Laing, D. G. and Jinks, A. L. (2002) A quantitative study of

fungiform papillae and taste pore density in adults and children. Developmental

Brain Research 138, 135-146.

Shi, P. and Zhang, J. (2006) Contrasting modes of evolution between vertebrate

sweet/umami receptor genes and bitter receptor genes. Molecular Biology and

Evolution 23, 292-300.

Shi, P., Zhang, J., Yang, H. and Zhang, Y.-P. (2003) Adaptive diversification of bitter

taste receptor genes in mammalian evolution. Molecular Biology and Evolution

20, 805-814.

Simmen, B. (1991) Stratégies Alimentaires des Primates Néotropiceaux en Fonction de la

Perception des Produits de l'environment. Vol. Ph.D. Université Paris - XIII,

Villetaneuse.

Simmen, B. (1992) Seuil de discrimination et réponses supraliminaires à des solution de

fructose en function du régime alimentaire des Primates Callithricidae. Comptes

Rendus de l'Académie des Sciences 315, 151-157.

Simmen, B. (1994) Taste discrimination and diet differentiation among New World

primates. In The Digestive System of Mammals: Food, Form, and Function, 92 Chivers, D. J. and Langer, P. eds, pp. 150-165. Cambridge University Press,

Cambridge.

Simmen, B. and Charlot, S. (2003) A comparison of taste thresholds for sweet and

astringent-tasting compounds in great apes. Comptes Rendus Biologies 326, 449-

445.

Simmen, B. and Hladik, C. M. (1988) Seasonal variation of taste threshold for sucrose in

a prosimian primate species, Microcebus murinus. Folia Primatologica 51, 152-

157.

Simmen, B. and Hladik, C. M. (1998) Sweet and bitter taste discrimination in primates:

Scaling effects across species. Folia Primatologica 69, 129-138.

Simmen, B., Hladik, A., Ramasiarisoa, P., Iaconelli, S. and Hladik, C. M. (1999) Taste

discrimination in lemurs and other primates, and the relationships to distribution

of plant allelochemicals in different habitats of Madagascar. In New Directions in

Lemur Studies, Rakotosamimanana, B., Rasamimanana, H., Ganzhorn, J. U. and

Goodman, S. M. eds, pp. 201-219. Plenum Publishers, New York.

Simmons, R. T., Graydon, J. J., Semple, N. M. and Swindlwer, D. R. (1956) A blood

group genetical survey in West Nakanai, New Britian. 14, 275-286.

Smith, C. C. (1977) Feeding behaviour and social organization in howling monkeys. In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 97-126. Academic Press, London.

93 Smith, D. V. (1971) Taste intenstiy as a function of areas and concentration:

Differentiation between compounds. Journal of Experimental Psychology 87,

163-171.

Smith, D. V. and Margolis, F. L. (1999) Taste processing: Whetting our appetites.

Current Biology 9, R453-R455.

Snyder, L. H. (1931) Inherited taste deficiency. Science 74, 151-152.

Soranzo, N., Bufe, B., Sabeti, P. C., Wilson, J. F., Weale, M. E., Marguerie, R.,

Meyerhof, W. and Goldstein, D. B. (2005) Positive selection on a high-sensitivity

allele of the human bitter-taste receptor TAS2R16. Current Biology 15, 1257-

1265.

Steiner, J. E., Glaser, D., Hawilo, M. E. and Berridge, K. C. (2001) Comparative

expression of hedonic impact: affective reactions to taste by human infants and

other primates. Neuroscience and Biobehavioral Reviews 25, 53-74.

Stevens, D. R., Seifert, R., Bufe, B., Müller, F., Kremmer, E., Gauss, R., Meyerhof, W.,

Kaupp, U. B. and Lindemann, B. (2001) Hyperpolarization-activated channels

HCN1 and HCN4 mediate responses to sour stimuli. Nature 413, 631-635.

Sugita, M. (2006) Taste perception and conding in the periphery. Cellular and Molecular

Life Sciences 63, 2000-2015.

Teaford, M. F., Lucas, P. W., Ungar, P. S. and Glander, K. E. (2006) Mechanical

defenses in leaves eaten by Costa Rican howling monkeys (Alouatta palliata).

American Journal of Physical Anthropology 129, 99-104.

94 Tepper, B. (1998) 6-n-propylthiouracil: A genetic marker for taste with implications for

food preference and dietary habits. American Journal of Human Genetics 63,

1271-1276.

Tepper, B. J. (1999) Does genetic taste sensitivity to PROP influence food preferences

and body weight? Appetite 32, 422.

Tepper, B. J., Christensen, C. M. and Cao, J. (2001) Development of brief methods to

classify individuals by PROP taster status. Physiology & Behavior 73, 571-577.

Tepper, B. J. and Nurse, R. J. (1997) Fat perception is related to PROP taster status.

Physiology & Behavior 61, 494-954.

Tepper, B. J. and Nurse, R. J. (1998) PROP taster status is related to fat perception and

preference. Annals of the New York Academy of Sciences 855, 802-804.

Tonosaki, K. and Funakoshi, M. (1988) Cyclic mucleotides mediate taste transduction.

Nature 331, 354-356.

Trubey, K. R., Culpepper, S., Maruyama, Y., Kinnamon, S. C. and Chaudhari, N. (2006)

Tastants evoke cAMP signal in taste buds that is independent of calcium

signaling. American Journal of Cell Physiology 291, C237-244.

Turnbull, B. and Matisoo-Smith, E. (2002) Taste sensitivity to 6-n-propylthiouracil

predicts acceptance of bitter-tasting spinach in 3-6-y-old children. American

Journal of Clinical Nutrition 76, 1101-1105.

Ueno, A., Ueno, Y. and Tomonaga, M. (2004) Facial response to four basic tastes in

newborn rhesus macaques (Macaca mulatta) and chimpanzees (Pan troglodytes).

Behavioural Brain Research 154, 261-271. 95 Valentin, G. A. (1853) A textbook of physiology. Henry Renshaw, London. van Noordwijk, M. A. and van Schaik, C. P. (1999) The affects of dominance rank and

group size on female lifetime reproductive success in wild Long-tailed macaques,

Macaca fascicularis. Primates 40(1), 105-130.

Verhagen, J. V., Kadohisa, M. and Rolls, E. T. (2004) Primate insular/opercular taste

cortex: neuronal representations of the viscosity, fat texture, grittiness,

temperature, and taste of foods. Journal of Neurophysiology 92, 1685–1699.

Vij, S. (1976) Observations on the comparative anatomy of the tongues of some South

East Asian primates. Journal of the Singapore National Academy of Sciences 5,

31-35.

Wang, X., Thomas, S. D. and Zhang, J. (2004) Relaxation of selective constraint and loss

of function in the evolution of human bitter taste receptor genes. Human

Molecular Genetics 13, 2671-2678.

Wasser, P. (1977) Feeding, ranging and group size in the Mangabe, Cercocebus albigena.

In Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs,

Monkeys and Apes, Clutton-Brock, T. H. ed, pp. 183-222. Academic Press, New

York.

Waterman, P. G. and Kool, K. (1994) Colobine food selection and plant chemistry. In

Colobine Monkeys: Their Ecology, Behavior, and Evolution, Davies, A. G. and

Oates, J. F. eds, pp. 251-284. Cambridge University Press, Cambridge.

Whissell-Beuchy (1990) Effects of age and sex on taste sensitivity to phenyltiocarbamide

(PTC) in the Berkley Guidance sample. Chemical Senses 15, 39-57. 96 Whitten, P. L. (1983) Diet and dominance among female vervet monkeys (Cercopithecus

aethiops). American Journal of Primatology 5, 139-159.

Wong, G., Gannon, K. S. and Margolskee, R. F. (1996) Transduction of bitter and sweet

taste by gustducin. Nature 381, 796-800.

Wooding, S. (2006) Phenylthiocarbamide: A 75-year adventure in genetics and natural

selection Genetics 172, 2015-2023.

Wooding, S., Bufe, B., Grassi, C., Howard, M. T., Stone, A. C., Vazquez, M., Dunn, D.

M., Meyerhof, W., Weiss, R. B. and Bamshad, M. J. (2006) Independent

evolution of bitter-taste sensitivity in humans and chimpanzees. Nature 440, 930-

934.

Wooding, S., Kim, U.-k., Bamshad, M. J., Larsen, J., Jorde, L. B. and Drayna, D. (2004)

Natural selection and molecular evolution in PTC, a bitter-taste receptor gene.

American Journal of Human Genetics 74, 637-646.

Yakinous, C. A. and Guinard, J.-X. (2001) Relation between PROP taster status and fat

perception, touch, and olfaction. Physiology & Behavior 72, 427-437.

Yakinous, C. A. and Guinard, J.-X. (2002) Relation between PROP (6-n-propythiouracil)

tater status, taste anatomy, and dietary intake measure for young men and women.

Appetite 38, 201-209.

Yang, R., Crowley, H. H., Rock, M. E. and Kinnamon, J. C. (2000) Taste cells with

synapses in rat circumvallate papillae display SNAP-25-like immunoreactivity.

The Journal of Comparative Neurology 424, 205–215.

97 Yaxley, S., Rolls, E. T. and Sienkiewicz, Z. J. (1988) The responsiveness of neurons in

the insular gustatory cortex of the macaque monkey is independent of hunger.

Physiology & Behavior 42, 223-229.

Yaxley, S., Rolls, E. T., Sienkiewicz, Z. J. and Scott, T. R. (1985) Satiety does not affect

gustatory activity in the nucleus of the solitary tract of the alert monkey. Brain

Research 347, 85-93.

Ye, Q., Heck, G. L. and DeSimone, J. A. (1994) Effects of voltage perturbation of the

lingual receptive field on chorda tympani responses to Na + and K + salts in the

rat: Implications for gustatory transduction. Journal of General Physiology 104,

885-907.

Yoshida, R., Shigemura, N., Sanematsu, K., Yasumatsu, K., Ishizuka, S. and Ninomiya,

Y. (2006) Taste responsiveness of fungiform taste cells with action potentials.

Journal of Neurophysiology 96, 3088-3095.

Zhang, Y., Hoon, M. A., Chandrashekar, J., Mueller, K. L., Cook, B., Wu, D., Zuker, C.

S. and Ryba, N. J. P. (2003) Coding of sweet, bitter, and umami tastes: Different

receptor cells sharing similar signaling pathways. Cell 112, 293-301.

Zhao, G., Zhang, Y., Hoon, M. A., Chandrashekar, J., Erienbach, I., Ryba, N. J. P. and

Zuker, C. S. (2003) The receptors for mammalian sweet and umami taste. Cell

115, 255-266.

98 Chapter 2: Interspecific variation in the primate gustatory system

ABSTRACT

Selection of nutritive foods and avoidance of toxins are essential to primate survival and reproductive success. In the context of food selection, the sense of taste is an important means of discerning the chemical contents of food items. To date, few studies have investigated the evolution of the primate gustatory system and little is known of its comparative anatomy. The objective of this chapter was to conduct a detailed analysis of interspecific differences in the density of fungiform papillae of primates in order to better understand how diet has influenced the evolution of the primate gustatory system. This objective was accomplished through an analysis of data on taste sensitivity, density and size of fungiform papillae, and diet in 37 primate species representing a wide diversity of taxa. In addition to analyses of all primate taxa together, strepsirrhines, platyrrhines, and catarrhines were also analyzed separately using non-parametric statistics. In humans, the density of fungiform papillae (DFP) is positively correlated with an individual’s taste sensitivity. The results of the interspecific analyses in this chapter show that sucrose sensitivity was negatively correlated with DFP, but positively correlated with the size of papillae among primates. Among strepsirrhines, DFP was negatively correlated, and papilla area was positively correlated, with the percent of fruit and flowers in the diet. Conversely, DFP was negatively correlated, and papilla area was positively correlated, with the percent of leaves in the diet among platyrrhines. Among catarrhines, DFP was positively correlated with fruit and flower feeding and negatively correlated with leaf feeding, but papilla area was not correlated with diet. Unlike strepsirrhines and platyrrhines, DFP and papilla area were not correlated with each other among catarrhines. Together these results suggest that papilla area may be a better measure of interspecific

99 variation in gustatory sensitivity among strepsirrhines and platyrrhines, while DFP may be a more appropriate measure of intraspecific variation in gustatory sensitivity. Very few data on taste sensitivity are available for catarrhines. Thus, taste sensitivity may not correlate with anatomical measures in catarrhines in the same way that it does in strepsirrhines and platyrrhines. This research makes clear that the gustatory systems of strepsirrhine, platyrrhine, and catarrhine primates do not share the same relationship between diet and density or area of fungiform papillae. Accordingly, the gustatory systems of strepsirrhine, platyrrhine, and catarrhine primates probably evolved under disparate selection pressures. Further investigation is warranted, specifically into quantities of taste buds, taste cells, receptors, and genetics, in conjunction with additional psychophysical and dietary data.

INTRODUCTION

The role of taste in primate food selection

Primates use a multitude of food resources to acquire the protein, carbohydrates, fats, vitamins, and minerals necessary for survival and reproduction. In addition to nutrients, foods also contain anti-predator defenses. For example, leaves are high in protein and minerals, but typically contain secondary compounds such as toxins and structural carbohydrates that cannot be easily digested without specialized dentition and gastrointestinal systems (Glander, 1982; Janson and Chapman, 1999; Lambert, 1998; Milton, 1980). Thus, in order to obtain necessary nutrients while avoiding toxicosis, it is important for primates to be highly selective in their food choices (Gaulin and Konner, 1977; Glander, 1982; Hladik, 1981; Janson and Chapman, 1999). Primates have been shown to use the special senses including vision, olfaction, and touch when selecting 100 food items to ingest (Dominy, 2004a, b; Dominy and Lucas, 2001; Dudley, 2002, 2004; Dulai et al., 1999; Hoffmann et al., 2004; Laska et al., 2007; Regan et al., 2001). Just as important, the sense of taste provides valuable information about food contents. While food selection is widely considered to be a function of palatability, studies of the evolution and sensory ecology of the primate gustatory system are lacking (Gaulin and Konner, 1977). The primate gustatory system aids in the acquisition of beneficial nutrients and the avoidance secondary compounds or spoiled foods. Acquisition and avoidance is facilitated through a system of rewards and warnings (Hladik et al., 2002; Lindemann, 1996). Gustatory rewards positively motivate behavior and are obtained when beneficial nutrients, such as sweet tasting sugars, enter the mouth (Glaser, 2002a; Rolls, 1999). A preference for sweet tasting compounds is innate in both human and non-human primate neonates, regardless of their natural diet (Steiner et al., 2001; Ueno et al., 2004). Gustatory warnings, or rejection responses, are elicited when noxious substances such as bitter tasting secondary compounds enter the mouth (Dominy et al., 2001; Galef, 1996). Like the inherent preference for sweet tasting substances, the aversion to bitter and sour tasting compounds is also innate. Human and non-human primate neonates show an obvious rejection response at being given bitter or sour tasting compounds (Steiner et al., 2001; Ueno et al., 2004).

Primate taste sensitivity and dietary niche

Primates vary in their ability to detect different chemical compounds. Taste sensitivities to individual compounds have often been ascertained using two-bottle tests (Glaser et al., 1996; Hladik et al., 2002; Hladik and Simmen, 1996; Laska et al., 1999a;

101 Laska et al., 1999b; Nofre et al., 1996; Schilling et al., 2004; Simmen et al., 1999; Simmen and Hladik, 1998). In two-bottle tests, individuals are offered one bottle with a control substance (usually water) and another with a dilution of the test substance. This trial is repeated with increasing concentrations of the test substance until the amount consumed from the two bottles is significantly different (usually determined by a t-test). The concentration of the test substance when significance is reached is considered the preference threshold for that individual. A low threshold indicates high sensitivity to a compound. Discriminative ability (i.e. threshold) is thought to determine the range of foods a primate will perceive as palatable and, therefore, be conditioned to ingest based on post-ingestive reward or toxic effects (Bonnaire and Simmen, 1994). Investigations of primate taste thresholds and how they relate to dietary niche have used a multitude of approaches, but a coherent understanding of the threshold-diet relationship is still lacking. Many primates select fruits with high levels of soluble sugars (Dominy and Lucas, 2006; Laska, 2001; Visalberghi et al., 2003). Because they provide a sweet taste reward, sugars may function as motivation to seek out fruits (Hladik, 1981; Hladik and Simmen, 1996; Simmen, 1994; Simmen and Hladik, 1998), which are patchily distributed in space and time and require traveling a greater distance to obtain, compared with other food sources (Clutton-Brock, 1977; Clutton-Brock and Harvey, 1980; Isbell, 1991). Accordingly, it has been hypothesized that species relying more on fruit will have greater sweet taste sensitivity, as the increasing intensity of a sweet taste reward will serve to positively motivate fruit seeking behavior (Hladik and Simmen, 1996). High sugar sensitivity has also been hypothesized to facilitate the incorporation of more leaves into the diet. In the broadest comparative analysis of primate taste thresholds and dietary niche to date, Simmen and Hladik (1998) found a positive correlation 102 between sweet taste sensitivity (measured by sucrose and fructose thresholds) and body mass (also see Hladik and Simmen, 1996). They noted that among primates, as body mass increases, more leaves and fewer high-quality foods are incorporated into the diet (Clutton-Brock and Harvey, 1977). Thus, larger-bodied primates contend with a wider variety of foods than small primates. Simmen and Hladik (1998) suggest that as body mass increases, so does the surface area of the lingual mucosa. According to their scenario, because more taste buds and associated taste receptors are available with larger surface area, sweet taste sensitivity increases with body mass. Higher sugar sensitivity then facilitates the ingestion of more diverse foods, and especially leaves, because even foods with low levels of sugars would be found palatable. Thus, Simmen and Hladik hypothesize that species with high sweet taste sensitivity ingest more leaves than species with low sweet taste sensitivity (Hladik and Simmen, 1996; Simmen and Hladik, 1998). Evidence for the relationship between sweet taste sensitivity and dietary niche is tenuous and inconsistent. For instance, Bonnaire and Simmen (1994) tested the hypothesis that differences in lemur sweet taste sensitivity correspond to diet. Their study of six lemur species with diverse diets failed to support this hypothesis. The species investigated included Eulemur macaco macaco, E. fulvus albifrons, E. coronatus, E. mongoz, Hapalemur griseus griseus, and H. simus. Hapalemur species feed mainly on the leaves, pith and stalks of bamboo (Grassi, 2001), whereas Eulemur species feed more on fruit, nectar, and some leaves (Birkinshaw, 1995; Curtis, 1997; Ganzhorn, 1988). Yet, taste thresholds for fructose were at the same order of magnitude (7 – 31 mM) in all but one species. The exception to this was E. mongoz (100 – 119 mM). This analysis thus found no clear relationship between fructose sensitivity and differences in gross dietary categories. Bonnaire and Simmen speculate that lemurs may be adapted to foods with

103 varying levels of sugar. For instance, in eastern Madagascar levels of soluble sugars in the fruits selected by E. fulvus albifrons range from 4 to 25% (Ganzhorn, 1988). In a different approach, when Simmen and Hladik (1998) found that sucrose and fructose thresholds were positively correlated with body mass, they noted that the sweet taste thresholds of some species deviated a great deal from the regression line. Nycticebus coucang, for instance, had the lowest sensitivity to sucrose. Simmen and Hladik argued that if sucrose threshold is indicative of a generalized low taste sensitivity, low taste sensitivity may enable N. coucang to ingest pungent insects and other prey that would not be palatable to most primates (Hladik, 1979). In contrast, the sucrose threshold of Saimiri sciureus was the furthest from the regression line among primates with high sucrose sensitivity. The authors suggest that the highly frugivorous diet of S. sciureus would be facilitated by an especially high sucrose sensitivity (Hladik and Simmen, 1996; Simmen and Hladik, 1998). Other tests of the relationship between taste threshold and dietary niche often include only one or two species. For instance, Laska et al. (1999) hypothesized that the omnivorous Papio hamadryas anubis would have a sucrose sensitivity much lower than that of a frugivorous species (Ateles geoffroyi) (Laska et al., 1999b). They found, however, that the baboons are among the most sugar-sensitive primates (Laska et al., 1999a). In a more direct comparison of sweet taste sensitivity, food preference, and food nutrient content, Laska and colleagues (2000, 2001) investigated captive Saimiri sciureus and Ateles geoffroyi, which both have high sweet taste sensitivity and high levels of fruit in their diet. In both species, preference ranking of foods was not significantly correlated with total carbohydrate content. Squirrel and spider monkeys preferred items with the greatest energy content irrespective of whether the source of energy was from carbohydrates or lipids (Laska, 2001; Laska et al., 2000). 104 Given the inconsistency in the data relating sweet taste sensitivity and fruit eating, the ability to detect sweet-tasting compounds may not be related to diet, but is rather ubiquitous (Ramirez, 1990). Sugar content does not reflect gross energy content of food items, nor is it correlated with the presence of any other nutrients important in primate nutrition (Ramirez, 1990). Furthermore, other important nutrients found in fruits, such as starch and fat, have little or no taste (Simmen et al., 1999). Although tasteless, the fat content of fruit may be more important in the food selection process than soluble sugar content. Varying adaptations in sweet taste sensitivity may be found in higher-level mammalian clades, such as among different orders. Most mammals are able to detect compounds that taste sweet to humans and respond favorably to them (Ramirez, 1990). One exception to the favorable sweet taste response is found among felid carnivorans (Li et al., 2005). The gene coding for the felid sweet taste receptor (T1R2) is a pseudogene, rendering the sweet taste receptor nonfunctional (Li et al., 2005). The absence of a functioning sweet taste system among felids has been associated with its hyper- carnivorous feeding behavior (Li et al., 2005). Cats do have about 250 fungiform papillae with many open taste pores (Robinson and Winkles, 1990), which might be important for the detection of amino acids. Although canines are also mainly carnivorous, they are more omnivorous than felids and appear to have functional sweet taste ability (Bradshaw, 2006; Ferrell, 1984; but see Glaser, 2002b). It is likely that the perceived pleasantness of gustatory sensation, more than detection threshold, determines preference to a compound (Bonnaire and Simmen, 1994). Detection ability is not equivalent to the perception of the pleasantness of a taste stimulus (Rolls, 2005), and responses to above threshold levels of sugars may be more important in shaping feeding behavior than threshold levels per se (Simmen, 1994). Among 105 humans, taste preferences (liking or disliking) appear to be more important than thresholds for determining dietary intake (Drewnowski et al., 1985). In psychophysical studies of non-humans primates, suprathreshold intake levels may indicate preference. If significantly more of a sugar mixture is ingested compared with water, preference for the sugar mixture is assumed. For example, in his study of eight callitrichid species, Simmen (1994) found that fructose thresholds were similar for all eight species, but species differed in how much of the test substance was consumed at near-threshold levels. Callimico goeldii had a high intake of fructose at near-threshold levels, which may be a good indication of the attractiveness of fructose to this species. In contrast, marmosets (Cebuella pygmaea, Callithrix jacchus, C. geoffroyi, C. argenta), had a lower intake of near-threshold fructose levels. These differences in near-threshold consumption, which may correspond to preference, are consistent with the diet of the two genera. Whereas Callimico feeds mostly on ripe fruits and nectars, marmosets are gummivorous and incorporate relatively few fleshy fruits in their diets (Simmen, 1994). Simmen suggests that Callimico might be highly motivated to seek fruits because it finds sweet compounds especially palatable. In contrast, he posits that gum feeding in marmosets may not depend on a sweet taste reward. Ingestion of gums might be maintained by long-tem conditioning rather than immediate sensory rewards (Hladik, 1979, 1981). In addition to sweet taste discrimination, discrimination of secondary compounds may be associated with species-specific diets (Bonnaire and Simmen, 1994). Bitter taste is associated with plant toxins (Hladik, 1978, but see Glendinning, 1994). High sensitivity to bitter taste would trigger a rejection response to relatively low concentrations of toxins. Indeed, human data show that individuals with highest bitter taste sensitivity tend to find green leafy foods less palatable and therefore eat less of them (Dinehart et al., 2006; Drewnowski et al., 2000; Kaminski et al., 2000). Conversely, 106 lower sensitivity to bitter taste would allow greater amounts of toxins to be ingested without triggering the rejection response. Low bitter taste sensitivity may be beneficial for leaf-specialists, which digest food via forestomach fermentation and can tolerate secondary compounds much better than more omnivorous primates (Lambert, 1998; Parra, 1978). Similar to earlier suggestions about gummivory, Hladik and Simmen (1996) suggested that for leaf-specialists post-ingestive effects, rather than taste, may be the major factor determining food selection (Hladik, 1979, 1981; Hladik and Simmen, 1996; Simmen, 1994). Non-folivore primates are exposed to a wide range of different chemicals and therefore do not maintain detoxification systems (Glander, 1982). Rather than detoxify, non-leaf-specialists can adjust plant intake, diversifying plant species ingested and minimizing the amount of any one toxic compound (Freeland and Janzen, 1974; Glander, 1982; Provenza et al., 2003). In all, primate preferences for foods with particular nutrients are thought to be largely the result of taste discrimination (Laska, 2001; Laska et al., 2000; Provenza, 1996). The ability to discriminate among nutrients is limited by the gustatory anatomy of an individual, and the anatomy, physiology, and sensitivity of the gustatory system can differ even among closely related species (Lindemann, 2001). It is likely that these differences reflect the adaptation of the gustatory system to distinct ecological niches (Ganzhorn, 1989; Lindemann, 2001; Nelson et al., 2001) and should thus be associated with species-specific diets. To date, however, no one hypothesis regarding taste thresholds and dietary niche has been consistently supported by the data.

107 Density of fungiform papillae and taste sensitivity

Fungiform papillae (FP) are the only structures on the anterior two-thirds of the tongue that contain taste buds (Figure 2.1) (Buck, 2000; Lindemann, 1996; Purves et al., 1997). FP taste buds contain taste cells with receptors for bitter, sweet, and umami (i.e. savory or meaty) tasting stimuli (Adler et al., 2000; Nelson et al., 2001). The density of fungiform papillae (DFP) of an individual is positively correlated with the density of taste buds in his or her papillae (Miller and Reedy, 1990b). Human studies have shown that DFP is positively associated with taste sensitivity to compounds such as NaCl, citric acid, quinine hydrochloride, sucrose, saccharine, and sucrose octaacetate (Bartoshuk et al., 1994; Doty et al., 2001; Miller and Reedy, 1990b; Miller and Whitney, 1989; Smith, 1971). Individuals with a high DFP and associated high taste sensitivity are able to detect chemical compounds even when relatively small amounts of the compound are present (Bartoshuk et al., 1994). Along with greater taste sensitivity, humans with a higher DFP also experience the more intense taste sensations (Duffy and Bartoshuk, 2000). While the correlation between DFP and taste sensitivity is not perfect, FP are anatomically stable structures and are currently thought to be the most accurate measure of genetically endowed taste ability outside genotyping (Bartoshuk, 2000; Janjua and Schwartz, 1997; Mistretta, 1991). Papillae size differs from DFP in its relationship to taste sensitivity. Among humans, the size of fungiform papillae is negatively correlated with DFP (Essick et al., 2003). Whereas DFP is positively correlated with taste sensitivity among humans, individuals with higher bitter taste sensitivity have fungiform papillae with smaller surface areas (Essick et al., 2003; Reedy et al., 1993).

108 DFP, taste sensitivity, and dietary intake in humans

Human studies have shown that DFP and, consequently, taste sensitivity affect food preferences. The compounds most commonly studied in tests of human DFP and taste sensitivity are phenylthiocarbamide (PTC) and its close relative 6-n-propylthiouracil (PROP). The ability to detect bitter-tasting PTC/PROP is genetically determined (Bufe et al., 2005; Drayna et al., 2003; Kim et al., 2003). PTC/PROP threshold is negatively correlated with subjective ratings of suprathreshold intensity (i.e. bitterness) (Drewnowski et al., 2000; Hayes et al., 2008). Generally, individuals that can detect

PTC/PROP at very low concentrations will experience the compound as being more intensely bitter compared with individuals with high PTC/PROP thresholds. PTC/PROP sensitivity in humans is positively correlated with DFP (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002). Like DFP, PTC/PROP sensitivity is positively correlated with taste sensitivity to compounds such as citric acid, sodium chloride, fructose, sucrose, saccharine, quinine, and caffeine (Bartoshuk, 1979; Bartoshuk, 2000; Bartoshuk et al., 1998; Drewnowski et al., 1998a; Drewnowski et al., 1997b; Duffy and Bartoshuk, 2000; Duffy et al., 2003; Falconer, 1947; Gent and Bartoshuk, 1983; Hall et al., 1975; Hayes et al., 2008; Kalmus, 1971; Leach and Noble, 1986; Looy and Weingarten, 1992; Lucchina et al., 1998; Miller and Reedy, 1990b; Pasquet et al., 2002). However, these correlations are not always consistent. For example, some findings show that individuals who rate PROP as more intensely bitter, also rate sucrose as sweeter (Bartoshuk, 1979; Bartoshuk et al., 1992; Duffy et al., 2003; PTC Fischer and Griffen, 1964; Gent and Bartoshuk, 1983; Hayes et al., 2008). In contrast, other research has failed to find a correlation between PROP sensitivity and intensity 109 ratings of sucrose (Drewnowski et al., 1998a; Drewnowski et al., 1997a; Drewnowski et al., 1997b; Holt et al., 2000; Ly and Drewnowski, 2001). Because of correlations found between PTC and PROP bitterness and the perceived intensity of sweet, sour, salty, and bitter stimuli, PTC and PROP bitterness is considered an accurate indicator of global oral sensation (Hayes et al., 2008). In other words, PTC/PROP phenotype is thought to be a significant predictor of perceived taste intensity for sweet, sour, salty, and bitter stimuli (Hayes et al., 2008). Numerous studies have assessed sensitivity to PROP and its relationship to human food preferences and diet. PROP is used more often than PTC in these studies, because safety limits have been set for the use of PROP as a medication for hypothyroidism (Lawless, 1980). When considering associations between taste sensitivity and dietary intake, preference ratings serve as an intermediary step (Dinehart et al., 2006). PROP sensitivity is thought to be more effective in determining food “dislikes” than food “likes” (Drewnowski et al., 2000; Drewnowski et al., 1998b). For example, among humans one reason for low acceptance of cruciferous vegetables is their bitter taste (Drewnowski and Rock, 1995). Accordingly, individuals with higher PROP sensitivity rate cruciferous and green leafy vegetables, (e.g. asparagus, broccoli, Brussels sprouts, cabbage, kale, and spinach), as more bitter than individuals with lower PROP sensitivity (Drewnowski et al., 1999). Because of their bitter taste sensitivity, individuals with higher PROP sensitivity have a lower preference for these foods and consume them less frequently than individuals who are not PROP sensitive (Dinehart et al., 2006; Drewnowski et al., 2000). PROP sensitivity is also correlated with lower acceptance of bitter tasting fruits (e.g. grapefruit and lemons) and beverages (e.g. coffee) (Drewnowski et al., 1999; Drewnowski et al., 1998b; Ly and Drewnowski, 2001).

110 Similar patters have been found among children, who are thought to be less influenced by sociocultural influences (Tepper, 1998). Anliker and colleagues (1991) tested the relationship between PROP sensitivity and food preferences in 30 children age five to seven. They found that children with high PROP sensitivity always ranked vegetables lower than the non-sensitive children, although the result was not statistically significant (Anliker et al., 1991). Other results contradict findings showing correlations between PROP sensitivity and bitter food aversion. For instance, Yakinous and Guinard (2002) found that PROP taste sensitivity was not significantly associated with the consumption of bitter fruit and vegetables. Their study showed that females with high sensitivity to PROP ate significantly less green salad than females with low PROP sensitivity, but PROP sensitivity did not determine the consumption of sprouts, broccoli, cauliflower, spinach, or mustard greens in males or females (Yakinous and Guinard, 2002). Among studies of children, Turnbull and Matisoo-Smith (2002) found that three to six year old children with high PROP sensitivity had a significant dislike of raw spinach. However, PROP sensitivity did not affect preferences for other foods, including raw broccoli (Turnbull and Matisoo-Smith, 2002). The relationships among sweet taste sensitivity, preference, and intake are even less clear than for bitter taste sensitivity. Whereas stimuli that are perceived as more bitter are more strongly disliked, preference ratings for sweet taste are highly diverse (Drewnowski, 1997). Preference ratings for sweet stimuli, such as sucrose, can be (a) positively correlated with increasing perception of sweetness, (b) negatively correlated with increasing sweetness, (c) show an inverse U-shaped response, or (d) show a flat response (Drewnowski, 1986; Duffy et al., 2006; Thompson et al., 1976; Witherly et al., 1980). Individuals are often categorized as sweet “likers” or “dislikers” according to their 111 preference ratings for sweetness. Sweet likers report increasing preference for sucrose as concentration of sucrose increases, whereas dislikers report decreasing preference for sucrose at with increasing concentration (Looy and Weingarten, 1992). In relation to PROP sensitivity, some studies show that individuals who experience greater taste intensity in response to PROP and sucrose are most often sweet dislikers (Looy and Weingarten, 1992; Peterson et al., 1999). Conversely, those who are the least sensitive to PROP are almost always sweet likers (Looy and Weingarten, 1992). The relationship between PROP and sweet taste intensity is not consistent, however. Duffy and Bartoshuk (2000) found that perceived bitterness of PROP was negatively correlated with liking of sweet tasting foods (fruits and desserts) among women, whereas there was a trend for the perceived bitterness of PROP to be positively associated with liking of sweet tasting foods among men (Duffy and Bartoshuk, 2000). In contrast, Drewnowski et al. (1997) found that sucrose intensity and preference ratings were unrelated to PROP intensity ratings, as did Holt et al. (2000. Whether sweet taste preferences directly affect dietary intake is also unclear. Neonates and children consistently show a preference for high sucrose solutions (Grinker et al., 1976; Steiner et al., 2001) and children’s food choices are usually determined by sweetness and familiarity (along with the avoidance of bitter) (Birch, 1992, 1999). Dietary preferences are also greatly influenced by experience and associative learning, in addition to genetic factors (Birch, 1999; Birch et al., 1990; Drewnowski, 1997; Rozin and Vollmecke, 1986). Thus, reports of the effects of sweet taste sensitivity on dietary intake are conflicting. For instance, Drewnowski et al. (1999) found that higher sucrose preferences were associated with increased preferences for sweet desserts and sugar in tea. Those increased preferences for sweet tasting foods were associated with measures of current diet (Drewnowski et al., 1999). PROP sensitivity was also shown to be an 112 indicator of sweet food intake as well. Individuals that are highly sensitive to PROP may find some sweet foods less pleasant because the sweetness is too intense (Peterson et al., 1999). For instance, Duffy et al. (2003) found that those who rated PROP as more bitter reported eating sweet foods less frequently. Moreover, sweet foods were preferred significantly more by those who rated them as more sweet and rated PROP as less bitter (Duffy et al., 2003). Others have found that PROP bitterness ratings were not significantly associated with either sweetness intensity or preference ratings, or with intake of total sugars, refined sugars, sweet foods, or sweet drinks (Holt et al., 2000). These studies of human gustatory sensitivity and dietary intake illustrate the variation present in human taste experience. Aversion to bitter tasting substances is a significant factor in the rejection of green leafy foods (Drewnowski and Rock, 1995). Several studies show the effects of bitter taste aversion on dietary preferences (Anliker et al., 1991; Dinehart et al., 2006; Drewnowski et al., 1999; Drewnowski et al., 2000; Drewnowski et al., 1998b; Ly and Drewnowski, 2001), but results from other studies are incongruent (Turnbull and Matisoo-Smith, 2002; Yakinous and Guinard, 2002). In contrast, sweet taste sensitivity is not consistently associated with sweet taste preference or dietary intake (Drewnowski, 1986, 1997; Drewnowski et al., 1999; Duffy et al., 2006; Duffy et al., 2003; Holt et al., 2000; Peterson et al., 1999; Thompson et al., 1976; Witherly et al., 1980). In all, the inter-relationships among the gustatory system, taste perception, food preferences, and decisions about diet are complex, and the precise effects of taste sensitivity on human diet are sill unclear. It is expected that the inter- relationships among the gustatory system, taste perception, food preferences, and dietary niche are equally complex among non-human primates as well.

113 OBJECTIVE

The goal of this chapter is to conduct a comparative analysis of lingual fungiform papillae in primates to better understand the factors that have influenced the evolution of the primate gustatory system. This goal will be accomplished through an analysis of data on fungiform papillae, taste sensitivity, and diet in 37 primate species. The following variables will be considered: (1) lingual macro-anatomy including the size of the tongue, the number of fungiform papillae, the size of fungiform papillae, and the density of fungiform papillae; (2) sweet taste sensitivity as measured by sucrose and fructose thresholds; (3) bitter taste sensitivity as measures by quinine thresholds, and (4) variation in species’ diets as measured by the annual percent of foliage and of fruit and flowers in the diet.

PREDICTIONS

A model of sweet taste threshold, body mass, and diet

Interspecific variation in gustatory anatomy may be influenced by phylogeny, body mass, and diet. Simmen and Hladik (1998) found a significant positive relationship between taste sensitivities for two sugars (sucrose and fructose) and body mass. There was no association found between quinine threshold and body mass. The authors hypothesized that as body mass increases, so does tongue surface area. As tongue surface area increases, the number of taste buds was also predicted to increase, leading to increased sweet taste sensitivity (lower threshold). Simmen and Hladik suggest that species with greater sweet taste sensitivity find a wider range of foods palatable, leading to the incorporation of more leaves in the diet (Simmen and Hladik, 1998). In order to assess this model, the following predictions will be tested:

114 • Sweet taste sensitivity is positively correlated with body mass. • Tongue surface area is positively correlated with body mass. • Tongue surface area is positively correlated with the number of FP. • The number of FP is positively correlated with sweet taste sensitivity. • Papilla area is positively correlated with body mass. • Papilla area is positively correlated with sweet taste sensitivity. • Sweet taste sensitivity is positively correlated with the percent of leaves in the diet.

Associations among DFP, taste thresholds, and diet

DFP, FP area, and taste sensitivity

• DFP is positively correlated with sensitivity to sweet tasting sucrose in humans (Miller and Reedy, 1990b). Therefore, it is predicted that DFP is also positively correlated with sweet taste sensitivity (as measured by sucrose and fructose thresholds) among non- human primate species in an interspecific comparison.

• Humans with high DFPs have higher bitter taste sensitivity (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001; 2002). Accordingly, it is predicted that bitter taste sensitivity (as measured by quinine hydrochloride thresholds) is positively correlated with DFP in an interspecific comparison among primates.

115 • Individuals with higher bitter taste sensitivity have fungiform papillae with significantly smaller surface areas (Essick et al., 2003; Reedy et al., 1993). Thus, it is predicted that FP surface area is negatively correlated with bitter taste sensitivity in an interspecific comparison among primates. Likewise, it is predicted that the area of FP is negatively correlated with sweet taste sensitivity.

Taste sensitivity and diet

• Evidence linking sweet taste sensitivity and primate dietary niche is inconsistent (Bonnaire and Simmen, 1994; Hladik and Simmen, 1996; Laska, 2001; Laska et al., 2000; Laska et al., 1999a; Laska et al., 1999b; Simmen and Hladik, 1998). Furthermore, many beneficial nutrients are not sweet tasting (Ramirez, 1990, Simmen, 1999). Therefore, it is predicted that sweet taste sensitivity is not correlated with the percent of fruit and flowers or the percent of leaves in the diets of non-human primates.

• Bitter taste indicates the presence of toxins (Hladik, 1978), and high bitter taste sensitivity in humans is associated with aversion to green leafy foods (Dinehart et al., 2006; Drewnowski et al., 2000; Drewnowski and Rock, 1995). Therefore, it is predicted that bitter taste sensitivity is negatively correlated with the percent of leaves in the diet.

• While primate leaf-specialists are able to detoxify the toxins found in leaves, non-leaf- specialists are less able to detoxify secondary compounds when they are ingested (Glander, 1982). Thus, more frugivorous species should have higher bitter taste sensitivity in order to detect and avoid toxins. Therefore, it is predicted that bitter taste sensitivity is positively correlated with the percent of fruit and flowers in the diet. 116 DFP and diet • If, in the course of this analysis, it is found that sweet taste sensitivity is not associated with primate diets, then it is predicted that DFP is not correlated with the percent of fruit and flowers or the percent of leaves in the diet across taxa.

• Among humans, individuals with high bitter taste sensitivity tend to ingest fewer green leafy vegetables (Dinehart et al., 2006; Drewnowski et al., 2000; Kaminski et al., 2000). Based on the relationships among DFP, sensitivity to PTC/PROP, and diet in humans, DFPs across primate taxa should be negatively correlated with the percent of leaves in the diet. Using DFP as an assay for bitter taste sensitivity, it is predicted that primate folivores have significantly lower DFPs than non-folivorous primates.

METHODS

Sample

The species for which data were collected are listed in Table 2.1. Data were collected on a total of 38 species. This sample included 14 strepsirrhines, 10 platyrrhines, 13 catarrhines (including three hominoids), and one non-primate euarchontan (Tupaia belangeri). Data were collected on both cadaveric and live animals. Cadaveric samples were preserved as soon after death as possible in 10% buffered formalin. Tongues were removed from cadavers posterior to all circumvallate papillae. In five species, data were obtained from both live and cadaveric specimens (Table 2.2). Data on all other species were either exclusively from live animals, or exclusively from cadaveric specimens.

117 DFP: Counting of fungiform papillae and determination of surface area

The methods for identifying and counting fungiform papillae followed the procedural protocol established for cadavers by Miller and Reedy (1990). In live, sedated animals, plastic tubing was placed between the maxillary and mandibular canines to prop open the mouth. The tongue was then wiped clean with gauze and 0.5% methylene blue biological stain (Fischer Scientific) was applied to the superior surface of the tongue using a pipette. Extra methylene blue was wiped off with Kim Wipes® (Fischer Scientific). Methylene blue adheres to all papillae except fungiform, permitting visual identification of this papilla type (Figure 2.2). Histological verification in rabbits has found this method to provide identification of FP (Miller and Reedy, 1990a). In live strepsirrhines, identification of fungiform papillae was sometimes more difficult than in haplorhines. In such cases, the dye was applied and then wiped off using isopropyl alcohol under the direction of veterinarians. This step served to remove more dye from the fungiform papillae. After dyeing, a high-resolution digital photograph was taken of the tongue at high magnification, using the macro function of a Canon A80. A scale was included in each image for size reference. DFP was determined in two ways. In cadaveric samples of 16 species (Table 2.3), DFP was calculated for the entire surface area of the tongue (referred to as tDFP, for total density of fungiform papillae). In these cases, surface areas were obtained by scanning each tongue with a Minolta® 3D laser digitizer. RapidForm® software was used to calculate the area of the superior surface of the tongue. The posterior edge of the tongue was delineated by the anterior-most circumvallate papillae (Figure 2.3), and all of the FP on the tongue were counted. In 38 species (Table 2.4), DFP was calculated on the anterior 0.5cm of the tongue for both cadaveric and live samples (Figure 2.4). Since DFP can only be determined for 118 the anterior of the tongue in live specimens, using the anterior 0.5cm of the tongue for both live and cadaveric samples facilitated analyses combining live and cadaveric data in the same dataset. Papillae were counted using Adobe Photoshop® software. A 0.5cm line was drawn on the scale in each image. This 0.5cm line was then moved to the medial line of the tongue so that the line began at the anterior-most point at the tip of the tongue and measured 0.5cm back. Next, a square was drawn starting at the posterior edge (top) of the 0.5cm line. The left vertical edge of the square was aligned along the vertical 0.5cm line, providing a right angle from the vertical line. The horizontal (top) edge of the square, placed 0.5cm from the tip of the tongue, provided a guide to draw a horizontal line across the right side of the tongue exactly 0.5cm posterior to the tip. This procedure, using the square as a right angle to the 0.5cm vertical line, was repeated on the left side of the tongue. Once a continuous horizontal line was drawn across the tongue 0.5cm posterior to the tip, the vertical 0.5cm line was removed so that it did not obscure visual access to the FP underneath. Subsequently, all FP anterior to the horizontal line were counted. Each counted papilla was marked with a colored dot in order to avoid counting any papilla more than once. NIH ImageJ® software was used to determine the area of the anterior 0.5cm of the tongue. On three specimens within each species, NIH ImageJ® software was also used to determine the area of ten individual fungiform papillae. The ten papillae were chosen randomly within the anterior 0.5cm of the tongue. The areas of the ten papillae were then averaged. Using the anterior 0.5cm of the tongue raises the possibility that body mass and the size of the tongue will affect FP densities. This possibility results from the fact that a half centimeter is a greater percentage of a small tongue, like that of Microcebus, than it is for larger tongue, like that of Pan. FP are concentrated toward the tip of the tongue, and their density decreases more posteriorly on the tongue (Figure 2.5). However, DFP 119 on the anterior 0.5cm of the tongue is negatively correlated with body mass (data shown below). If using a greater proportion of the tongue to calculate density on smaller animals affected DFP, then DFP would be positively correlated with body mass. Smaller animals would have a lower DFP because more of the posterior of the tongue, where FP are less dense, is included in the calculation. Furthermore, this issue will be addressed in analyses by using values that are corrected for body mass.

Body mass

Body mass data were collected for each live animal at the time of capture, in the wild and in captivity. In cadaveric specimens, when the body mass of an individual was not available, data from Smith and Jungers (1997) were used (Smith and Jungers, 1997). If the sex of the specimen was not available, male and female body masses from Smith and Jungers (1997) were averaged for that individual. Only samples from adult animals were used in this study, as determined by age and body mass. If age and body mass data were not available, dentition was used to determine maturity. While the number of papillae do not change with age, data were only collected on adult primates because the size of the tongue increases with body mass (Janjua and Schwartz, 1997; Mistretta, 1991). If data were collected on sub-adult animals DFP would be high for those individuals, because the number of FP would be the same as adult animals, but the area of the tongue would be smaller.

Thresholds

Sucrose and fructose thresholds were obtained from the literature for 16 and 12 species, respectively (Table 2.5). Thresholds for bitter tasting quinine hydrochloride were 120 obtained from the literature for 9 species for which DFP data were available (Table 2.6). When data from more than one source were available, thresholds were averaged for each species.

Diet

Data on the feeding ecology of each species were collected using published data from long-term field studies on the percent of leaves, fruit, flowers, and nectar in the diet (Table 2.4). When several studies were available for the same species, the percentages in each category were averaged. For analysis, the percents of fruit, flowers, and nectar were combined. Folivores were defined as species with ≥50% of their diet comprised of leaves. Among cercopithecoids, leaf-specialists (with forestomach fermentation) included species within the genera Colobus, Presbytis, Procolobus, and Trachypithecus.

Live subject protocol

Capture and anesthetization procedures

Data collection on live animals was conducted in captive facilities and in the wild (Table 2.1). Captive animals were studied at the Southwest Foundation for Biomedical Research in San Antonio, Texas, the San Antonio Zoo, the Duke Lemur Center at Duke University in Durham, North Carolina, and the Seneca Park Zoo in Rochester, New York. IACUC protocols were obtained from the University of Texas at Austin, Duke University, Seneca Park Zoo in conjunction with the University of Rochester, and the Southwest Foundation for Biomedical Research. In captive facilities, capture and anesthetization were conducted by the staff and veterinarians at each facility and followed a pre-established procedural protocol determined by that facility. 121 Animals were captured from wild populations at La Pacifica in Costa Rica, Pretoria in South Africa, and Ranomafana National Park in Madagascar. In all locations the reflexes, temperature, pulse, and respiratory rate of the animals were monitored. Animal capture in Costa Rica and Madagascar followed the procedure described in Glander et al. 1991 using a Pneu-Dart™ system (Pneu-Dart™ Inc, HC 31, Williamsport, PA 17701). This system employs disposable non-barbed darts with a 3/8-inch needle delivered by a carbon dioxide powered gun. The animals were caught in large nets under the capture location. Darts were loaded with Telazol® at a dosage of 25mg per kg. Weights of each species had been previously established. In Madagascar, all sedation and vital signs were monitored by Felicia Knightly, D.V.M., Andrew Winterborn D.V.M., or Jeff Wyatt D.V.M. No veterinarians were present in Costa Rica. In South Africa, animal capture followed the protocol described in Brett et al. (1982) (Brett et al., 1982). Animals were first trapped and then sedated with a combination of Zoletil® and Dormitor® by weight. Traps were constructed using a wood frame measuring one meter squared by 15cm high, with 2.5cm wire mesh attached to one side. Animals were baited with corncobs attached to a trip wire. All sedation and vital signs were overseen by Magali Jacquier, D.V.M.

The effects and safety of methylene blue biological stain

0.5% methylene blue in ethanol is non-toxic and has been used repeatedly on live human subjects without side effects (Bartoshuk et al., 1994; Miller and Reedy, 1990a; Miller and Reedy, 1990b). In small mammals, methylene blue is frequently used as a therapeutic agent at a dosage of 1.5mg per kg intravenously as an antidote for methemoglobinemia. It is considered safe at this dose, even for domestic cats, which are

122 known to be highly sensitive to its toxic effects. The concentration of 0.5% used in this protocol contains 5mg per mL of the active reagent. In the procedure used, the drops applied were wiped off the tongue immediately after application, so the amount that was available for absorption was miniscule and well below accepted normal therapeutic levels in other veterinary species (Vanderford, 2007).

Analyses

Correcting for body mass

Body mass may affect calculations of DFP (see above and Figure 2.5). Body mass is also strongly associated with diet (Chivers and Hladik, 1980; Kay, 1984; Milton and May, 1976). Thus, correcting for body mass may obscure real differences in the gustatory system that are associated with feeding behavior. Accordingly, tests were conducted using three different values for FP: the density of FP per square centimeter (DFP), the ratio of DFP to the cube root of body mass (DFP ratio), and the residuals of a least squares regression of DFP and body mass (DFP residual). Likewise, three values were used for papilla area including the average papilla area itself, the ratio of papilla area to the cube root of body mass (area ratio), and the residuals of a least squares regression of papilla area and body mass (area residual).

Statistical analysis

Data were averaged for each species before analysis. All figures show averaged data for each species. Statistical analyses were conducted using JMP® version 5.0.1.2 (SAS Institute). The majority of datasets used in this chapter were found to be non-

123 normally distributed using a Shapiro-Wilk W test. Accordingly, non-parametric tests were used. The predictions from Simmen and Hladik’s (1998) model of sweet taste sensitivity was tested as follows. To test the prediction that sweet taste sensitivity is positively correlated with body mass, a Spearman rank correlation was used to assess the relationships between body mass and sucrose threshold, and body mass and fructose threshold. A Spearman rank correlation was also used to examine the predictions that tongue surface area is positively correlated with body mass, and that tongue surface area is positively correlated with the number of FP on the entire tongue (Table 2.3). To test the prediction that the number of FP is positively correlated with sweet taste sensitivity, a Spearman rank correlation was used to examine the relationship between number of FP on the anterior 0.5cm of the tongue and sucrose threshold, and the number of FP and fructose threshold. Similarly, to test the prediction that papilla area is positively correlated with sweet taste sensitivity, a Spearman rank correlation was used to examine the relationship between papilla area and sucrose threshold, and papilla area and fructose threshold. To test the prediction that sweet taste sensitivity is positively correlated with the percent of leaves in the diet, a Spearman rank correlation was used to examine the relationship between the percent of leaves in the diet and sucrose threshold, and the percent of leaves in the diet and fructose threshold. Predictions regarding DFP, taste thresholds, and diet were tested as follows. Tests included all three measures of FP density for the anterior 0.5cm of the tongue, including DFP, DFP ratio, and DFP residual and all three measures of the average area of FP, including papilla area, area ratio, and area residual. The predictions that DFP and papilla area are positively correlated with sweet taste sensitivity were tested using a Spearman rank correlation. To assess the prediction that sweet taste sensitivity is not correlated with 124 the percent of fruit and flowers or the percent of leaves in the diets of non-human primates, the percent of fruit and flowers in the diet and the percent of leaves in the diet were tested for correlations with sucrose threshold and fructose threshold using Spearman rank correlations. To test the prediction that bitter taste sensitivity is negatively correlated with the percent of leaves in the diet, a Spearman rank correlation was used to examine the relationship between quinine hydrochloride threshold and the percent of leaves in the diet. To test the prediction that more frugivorous species have higher bitter taste sensitivity, a Spearman rank correlation was used to examine the relationship between quinine hydrochloride threshold and the percent of fruit and flowers in the diet. To test the prediction that that bitter taste sensitivity is positively correlated with DFP, a Spearman rank correlation was used to examine the relationship between quinine hydrochloride threshold and all three measures of DFP. A Spearman rank correlation was also used to assess the relationships between the percent of fruit and flowers in the diet and the percent of leaves in the diet and all three measures of DFP. Within catarrhines, the prediction that folivores (≥50% of diet comprised of leaves) have significantly lower DFPs than non-folivores was tested. When data were categorized in this way, a chi-square test was used to determine whether there were significant differences in DFP. A chi-square test was also used to evaluate differences in DFP among cercopithecoid leaf-specialists (with forestomach fermentation) and non-leaf- specialsts. Adequate numbers of genera that specialize on leaves were not available to test for differences between folivores and non-folivores among strepsirrhines and platyrrhines.

125 Phylogenetic analyses

To test whether findings for analyses of fungiform papillae, taste thresholds, and diet are the result of phylogenetic inertia, a comparative analysis of independent contrasts was performed. Mesquite 2.0® (Maddison and Maddison, 2006) with the PDAP 1.07 module (Midford et al., 2005) was used to generate independent contrasts and JMP® was used to perform Spearman rank correlations on the independent contrasts. A cladogram was constructed using published trees that were based on short interspersed repetitive elements (SINEs) (Figure 2.6) (Amrine-Madsen et al., 2003; Ray et al., 2005; Roos et al.,

2004; Salem et al., 2003; Singer et al., 2003; Xing et al., 2005). SINEs are tRNA-derived retroposons found throughout eukaryotic genomes that are not likely to be convergent (Shedlock and Okada, 2000). In other words, individuals only share SINES if they have a common ancestor. Branch lengths were set using the method of Grafen setting in Mesquite. In addition, a Wilcoxon rank sum test was used to analyze differences in size corrected DFP and papilla area among strepsirrhines, platyrrhines, and catarrhines. Strepsirrhines, platyrrhines, and catarrhines were also analyzed separately for associations between fungiform papillae and diet.

RESULTS

Tongue area, fungiform papillae, and body mass

The surface area of the entire dorsal tongue was positively correlated with body mass (Figure 2.7, rs = 0.75, p < 0.001), but tongue surface area was not significantly correlated with the number of fungiform papillae (rs = 0.38, ns) (Figure 2.8). Body mass was positively correlated with the absolute number of FP on the entire tongue (n = 16, rs = 0.53, p < 0.03, Table 2.3), but not correlated with the number of papillae on the anterior

126 0.5cm of the tongue (n = 38, rs = 0.0003, ns, Table 2.4). Body mass was negatively correlated with tDFP (n = 16, rs = -0.75, p < 0.001) (Figure 2.9, Table 2.3). DFP for the anterior 0.5cm of the tongue was also negatively correlated with body mass (rs = -0.62, p < 0.0001, Figure 2.10) in the entire sample of 38 species (Table 2.4), which combined live and cadaveric specimens. DFP on the anterior 0.5cm of the tongue was also negatively correlated with body mass when strepsirrhines, platyrrhines, and catarrhines were tested separately (strepsirrhines rs = -0.62, p < 0.05, platyrrhines rs = -0.68, p < 0.01, catarrhines rs = -0.62, p < 0.05). All future references to DFP in this Results section refer to the anterior 0.5cm of the tongue. Papilla area was positively correlated with body mass

(rs = 0.79, p < 0.0001, Figure 2.11) and was negatively correlated with DFP (rs = -0.63, p < 0.0001, Figure 2.12). When strepsirrhines, platyrrhines, and catarrhines were analyzed separately, papilla area was negatively correlated with DFP in strepsirrhines and platyrrhines (strepsirrhines rs = -0.88, p < 0.0001, Figure 2.13a, strepsirrhines without

Microcebus rs = -0.85, p < 0.0001, Figure 2.13b, platyrrhines rs = 0.79, p < 0.01, Figure

2.14), but not in catarrhines (rs = -0.35, ns, Figure 2.15). The DFP ratios of catarrhines differed significantly from platyrrhines and strepsirrhines (catarrhines x platyrrhines z = 2.33, p < 0.05, catarrhines x strepsirrhines z = -2.74, p < 0.01, platyrrhines x strepsirrhines z = 0.09, ns). The DFP residuals of catarrhines, platyrrhines, and strepsirrhines did not differ significantly (catarrhines x platyrrhines z = -1.64, ns, catarrhines x strepsirrhines z = -0.95, ns, platyrrhines x strepsirrhines z = -0.53, ns). The DFP ratios of cebids and callitrichids differed significantly (z = 2.30, p < 0.05), and the difference between the DFP residuals of cebids and callitrichids neared significance (z = 1.83, p < 0.07). The papilla area ratios and area residuals of strepsirrhines and haplorhines were significantly different (catarrhines x platyrrhines, area ratio z = -0.65, ns, area residual z = -0.84, ns, catarrhines x 127 strepsirrhines area ratio z = 3.37, p < 0.001, area residual z = 3.03, p < 0.01, platyrrhines x strepsirrhines area ratio z = 3.89, p < 0.0001, area residual z = 2.84, p < 0.01, Figure 2.16). The area residuals of cebids and callitrichids also differed significantly (z = -2.05, p < 0.05), but area ratios did not (z = -1.37, ns).

Body mass, fungiform papillae, and taste thresholds

Body mass was significantly negatively correlated with sucrose threshold (rs = -0.68, p < 0.01, Figure 2.17), but the correlation between body mass and fructose threshold was not significant (Figure 2.18, Table 2.7) (rs = -0.50, ns). The number of FP on the anterior 0.5cm of the tongue was not correlated with either sucrose or fructose threshold (sucrose rs = 0.08, ns, fructose rs = 0.37, ns, Table 2.7). DFP and DFP ratio were positively correlated with sucrose threshold (DFP rs = 0.59, p < 0.05, DFP ratio rs = 0.67, p < 0.01, Figure 2.19). The positive correlation between DFP and fructose threshold approached significance, but DFP ratio was not significantly correlated with fructose threshold (DFP rs = 0.55, p = 0.06, DFP ratio rs = 0.49, ns, Figure 2.20, Table 2.7). DFP residual was not correlated with sucrose or fructose threshold (sucrose rs = 0.02, ns, fructose rs = 0.45, ns). Papilla area and area residual were significantly negatively correlated with sucrose threshold (papilla area rs = -0.76, p = 0.001, area residual rs = -0.71, p < 0.05, Figure 2.21, Table 2.7). The negative correlation between area ratio and sucrose threshold neared significance (rs = -0.50, p = 0.06). None of the three measures of papilla area were correlated with fructose threshold (papilla area rs = -0.35, ns, area ratio rs = 0.15, ns, area residual rs = -0.30, ns, Table 2.7). When analyzing independent contrasts to correct for phylogeny (among all taxa combined), body mass was not significantly correlated with sucrose thresholds (rs =

128 -0.18, ns) or fructose thresholds (rs = -0.02, ns). Number of FP, DFP, DFP ratio, and DFP residual were not significantly correlated with sucrose thresholds (number of FP rs =

0.14, ns, DFP rs = -0.09, ns, DFP ratio rs = -0.14, ns, DFP residual rs = 0.24, ns) or fructose thresholds (number of FP rs = 0.50, ns, DFP rs = -0.28, ns, DFP ratio rs = -0.19, ns, DFP residual rs = -0.26, ns). Papilla area, area ratio, and area residual were not significantly correlated with sucrose thresholds (papilla area rs = -0.08, ns, area ratio rs =

0.11, ns, area residual rs = 0.03, ns) or fructose thresholds (papilla area rs = 0.33, ns, area ratio rs = -0.46, ns, area residual rs = -0.43, ns). In species for which DFP data were collected, thresholds for quinine hydrochloride were available for a total of 9 species: one strepsirrhine (Microcebus murinus), five platyrrhines, and three catarrhines (including one hominoid, Pan troglodytes) (Table 2.6). There was no correlation between quinine hydrochloride threshold and body mass, number of FP, DFP, DFP ratio, or DFP residual (body mass rs

= -0.37, ns, number of FP rs = -0.16, ns, DFP rs = 0.04, ns, DFP ratio rs = 0.30, ns, DFP residual rs = -0.39, ns, Figure 2.22). Papilla area, area ratio, and area residual were not correlated with threshold for quinine hydrochloride (papilla area rs = -0.51, ns, area ratio rs = -0.20, ns, area residual rs = -0.29, ns). In analyses of independent contrasts the correlation between quinine hydrochloride threshold and body mass approached significance (rs = 0.71, p = 0.07). There was no correlation between quinine hydrochloride and number of FP, DFP, or DFP ratio, or DFP residual (number of FP rs = 0.43, ns, DFP rs = 0.43, ns, DFP ratio rs = -0.36, ns, DFP residual rs = -0.21, ns). Independent contrasts of papilla area, area ratio, and area residual were not correlated with independent contrasts for quinine hydrochloride threshold (papilla area rs = -0.29, ns, area ratio rs = -0.39, ns, area residual rs = -0.61, ns).

129 Diet and taste threshold

The percent of fruit and flowers in the diet and the percent of leaves in the diet of each species are shown in Table 2.4. Sucrose and fructose thresholds are shown in Table 2.5 and quinine hydrochloride thresholds are shown in Table 2.6. For species on which DFP data were collected, data on sucrose threshold were available for 16 species and data on fructose threshold were available for 12 species. Thresholds for quinine hydrochloride were available for 9 species on which DFP data were collected. When all taxa were included in the analysis, sucrose and fructose thresholds were not correlated with the percent of fruit and flowers in the diet (sucrose rs = -0.07, ns, fructose rs = -0.21, ns, Figure 2.23) or the percent leaves in the diet (sucrose rs = -0.25, ns, fructose rs = -0.36, ns, Figure 2.24, Table 2.7). In analyses of independent contrasts for all taxa, sucrose and fructose thresholds were not correlated with the percent of fruit and flowers in the diet (sucrose rs = -0.06, ns, fructose rs = -0.26, ns) or the percent of leaves in the diet (sucrose rs = 0.21, ns, fructose rs = 0.41, ns). When strepsirrhines and platyrrhines were analyzed together, the percent of fruit and flowers and the percent of leaves in the diet were not correlated with either sucrose or fructose thresholds (sucrose rs = -0.08, ns, fructose rs = -0.21, ns). When strepsirrhines and platyrrhines were analyzed separately, fructose threshold was negatively correlated with the percent leaves in the diet among platyrrhines (rs = -0.95, p < 0.05). No other significant correlations were found for strepsirrhines (sucrose x fruit and flowers rs =

0.14, ns, fructose x fruit and flowers rs = -0.10, ns, sucrose x leaves rs = -0.09, ns, fructose x leaves rs = 0.20, ns) or platyrrhines (sucrose x fruit and flowers rs = -0.66, ns, fructose x fruit and flowers rs = -0.70, ns, sucrose x leaves rs = -0.48, ns). Quinine hydrochloride threshold was not correlated with the percent of fruit and flowers or the percent of leaves in the diet (fruit and flowers rs = -0.06, ns, leaves rs = 130 -0.18, ns). Analyses of independent contrasts also showed that quinine hydrochloride threshold was not correlated with the percent of fruit and flowers or the percent of leaves in the diet (fruit and flowers rs = 0.71, ns, leaves rs = -0.29, ns).

DFP, papilla area, and diet

DFP, papilla area, body mass, the percent of fruit and flowers in the diet, and the percent of leaves in the diet of each species are shown in Table 2.4. Data were collected on 14 strepsirrhines, 10 platyrrhines, 13 catarrhines (including three hominoids), and one non-primate euarchontan (Tupaia belangeri). When all taxa were analyzed together, the percent of fruit and flowers in the diet was not significantly correlated with any of the three measures of DFP (DFP rs = -0.18, ns, DFP ratio rs = -0.06, ns, DFP residual rs = -0.23, ns, Table 2.8). DFP and DFP ratio were negatively correlated with the percent leaves in the diet (DFP rs = -0.33, p < 0.05, DFP ratio rs = -0.52, p < 0.01, Figure 2.25), but DFP residual was not significantly correlated with the percent of leaves in the diet (rs = 0.06, ns, Table 2.8). The percent of fruit and flowers in the diet was also not significantly correlated with any of the three measures of papilla area (papilla area rs =

0.05, ns, area ratio rs = 0.07, ns, area residual rs = 0.10, ns, Figure 2.26, Table 2.8). The percent of leaves in the diet was not correlated with area ratio or area residual (area ratio rs = 0.03, ns, area residual rs = 0.17, ns), but was significantly positively correlated with papilla area (rs = 0.39, p < 0.05, Figure 2.27, Table 2.8). Results for tests of independent contrasts area also shown in Table 2.8. In analyses of independent contrasts, the percent of fruit and flowers in the diet was negatively correlated with DFP, nearing statistical significance (rs = -0.32, p = 0.06), as was DFP ratio (rs = -0.30, p = 0.07). Independent contrasts for DFP residual were not

131 correlated with the percent of fruit and flowers in the diet (rs = -0.04, ns). Analyses of independent contrasts showed that the percent leaves in the diet was not correlated with

DFP (rs = -0.06, ns), DFP ratio (rs = -0.10, ns), or DFP residual (rs = -0.05, ns). Analyses of independent contrasts for all three measures of papilla area were not correlated with independent contrasts for either the percent of fruit and flowers in the diet (papilla area rs

= 0.04, ns, area ratio rs = 0.10, ns, area residual rs = -0.03, ns) or percent leaves in the diet

(papilla area rs = 0.04, ns, area ratio rs = 0.26, ns, area residual rs = 0.06, ns). The relationship between DFP and percent of fruit-flowers or leaves in the diet, and the relationship between papilla area and percent of fruit-flowers or leaves in the diet were also tested separately in strepsirrhines, platyrrhines, and catarrhines. The results of Spearman’s rank correlation analyses used to test these relationships can be found in Table 2.9 and are detailed below.

Strepsirrhines

The single Microcebus murinus specimen had a DFP of 473.68. The next highest DFP was found in Otolemur garnetti and was 162.63±70.63. Since the DFP of Microcebus was substantially higher than the DFPs in the rest of the sample, analyses were performed both with and without the Microcebus data. There was a significant negative correlation between DFP and the percent of fruit and flowers in species’ diets regardless of whether Microcebus was included or removed

(rs = -0.58, p < 0.05, without Microcebus rs = 0.60, p < 0.05, Figure 2.28). Correcting for the effects of body mass, there was also a significant negative correlation between DFP residual and the percent of fruit and flowers in species’ diets both with and without

Microcebus (rs = -0.72, p < 0.01, without Microcebus rs = 0.76, p < 0.01). Using DFP

132 ratio, the relationship with fruit and flowers approached significance (rs = -0.52, p = 0.06, without Microcebus rs = 0.53, p = 0.06). There was no significant relationship between any of the three measures of DFP and the percent of leaves in the diet (DFP rs = 0.08, ns, without Microcebus rs = 0.04, ns, DFP ratio rs = -0.03, ns, without Microcebus rs = -0.07, ns, DFP residual rs = 0.24, ns, without Microcebus rs = 0.20, ns, Figure 2.29). Among strepsirrhines, there was a significant positive correlation between area ratio and area residual and the percent of fruit and flowers in the diet both with and without Microcebus (area ratio rs = 0.60, p < 0.05, area ratio without Microcebus rs =

0.62, p < 0.05, area residual rs = 0.67, p < 0.05, area residual without Microcebus rs = 0.70, p < 0.05, Table 2.10, Figure 2.30). There was no significant correlation between papilla area and the percent of fruit and flowers in the diet, with and without Microcebus

(rs = 0.46, ns, without Microcebus rs = 0.45, ns). All three measures of papilla area were not correlated with the percent of leaves in the diet, with and without Microcebus (papilla area rs = -0.06, ns, papilla area without Microcebus rs = -0.02, ns, area ratio rs = -0.31, ns, area ratio without Microcebus rs = -0.28, ns, area residual rs = -0.27, ns, area residual without Microcebus rs = -0.25, ns, Table 2.10).

Platyrrhines

There was no significant relationship between any measure of DFP and the percent fruit and flowers in platyrrhine diets (DFP rs = -0.47, ns, DFP ratio rs = -0.52, ns,

DFP residual rs = -0.37, ns), but there was a significant negative correlation between DFP and the percent of leaves in the diet (rs = -0.67, p < 0.05, Figure 2.31). DFP ratio also showed a significant negative correlation with percent leaves (rs = -0.77, p < 0.01), but

DFP residual did not (rs = -0.22, ns). When callitrichids were removed from the analysis,

133 the correlation between DFP ratio and percent leaves was significant and the correlation between DFP and percent leaves neared significance (DFP rs = -0.71, p = 0.07, DFP ratio rs = -0.82, p < 0.05, DFP residual rs = -0.06, ns). The relationship between all measures of

DFP and percent fruit and flowers was not significant (DFP rs = -0.47, ns, DFP ratio rs =

-0.52, ns, DFP residual rs = 0.37, ns). Among platyrrhines, papilla area and area residual were positively correlated with both the percent of fruit and flowers in the diet (papilla area rs = 0.75, p < 0.05, area residual rs = 0.67, p < 0.05, Figure 2.32) and the percent of leaves in the diet (papilla area rs = 0.91, p = 0.001, area residual rs = 0.89, p < 0.01, Figure 2.33a). Area ratio was not correlated with the percent of fruit and flowers in the diet or the percent of leaves in the diet (fruit and flowers rs = 0.52, ns, leaves rs = 0.52, ns). When Alouatta was removed from the analysis, the correlations between papilla area and area residual, and the percent of leaves in the diet were still significant (papilla area rs = 0.82, p < 0.01, area residual rs = 0.80, p = 0.01, Figure 2.34b). Area ratio and the percent of leaves in the diet were not correlated when Alouatta was removed from the analysis (rs = 0.46, ns). When Alouatta remains in the dataset, but callitrichids are removed, none of the three measures of papilla area were correlated with the percent of fruit and flowers in the diet (papilla area rs =

-0.03, ns, area ratio rs = 0.21, ns, area residual rs = -0.21, ns). With callitrichids removed, papilla area and area residual were significantly positively correlated with the percent of leaves in the diet (papilla area rs = 0.89, p < 0.01, area residual rs = 0.84, p < 0.05), but area ratio was not (area ratio rs = 0.13, ns).

134 Catarrhines

When all catarrhine species were included in the analysis, there were no significant relationships between DFP or DFP ratio and the percent of fruit and flowers

(DFP rs = 0.38, ns, DFP ratio rs = 0.23, ns) or the percent leaves in the diet (DFP rs =

-0.52, ns, DFP ratio rs = -0.44, ns). There was a positive correlation between DFP residual and the percent of fruit and flowers in the diet that neared significance (rs = 0.54, p = 0.06) and a negative correlation between DFP residual and the percent of leaves in the diet was significant (rs = -0.63, p < 0.05). There was no correlation between any measure of papilla area and the percent of fruit and flowers in the diet (papilla area rs =

0.14, ns, area ratio rs = -0.01, ns, area residual rs = -0.22, ns) or the percent of leaves in the diet (papilla area rs = -0.24, ns, area ratio rs = -0.24, ns, area residual rs = -0.03, ns). When apes were removed from the analysis, there was a significant positive correlation between all three measures of DFP and the percent of fruit and flowers in the diet (Figure 2.34) (DFP rs = 0.92, p < 0.001, DFP ratio rs = 0.85, p < 0.01, DFP residual rs = 0.84, p < 0.01) and a significant negative correlation between all three measures of

DFP and the percent of leaves in the diet (Figure 2.35) (DFP rs = -0.85, p < 0.01, DFP ratio rs = 0.84, p < 0.01, DFP residual rs = 0.84, p < 0.01, Table 2.9). There was no correlation between any measure of papilla area and the percent of fruit and flowers in the diet (papilla area rs = -0.34, ns, area ratio rs = -0.17, ns, area residual rs = -0.33, ns,

Figure 2.36) or the percent of leaves in the diet (papilla area rs = -0.17, ns, area ratio rs =

-0.32, ns, area residual rs = -0.18, ns, Figure 2.37). When cercopithecoids were grouped as leaf-specialists (using forestomach fermentation) and non-leaf-specialists, the DFPs, DFP ratios, and DFP residuals of folivores were not significantly different between the two groups (DFP χ2 = 5.73, df = 1, ns, DFP ratio χ2 = 0.27, df = 1, ns, DFP residual χ2 = 2.45, df = 1, ns, Figure 2.38a). 135 There was no significant difference between the papilla areas of leaf-specialists and non- leaf-specialists (papilla area χ2 = 1.32, df = 1, ns, area ratio χ2 = 0.88, df = 1, ns, area residual χ2 = 2.45, df = 1, ns). When grouped as folivores (≥ 50% leaves in diet) and non-folivores, the DFPs, DFP ratios, and DFP residuals of folivorous cercopithecoids were significantly lower than the DFPs of the non-folivores (DFP χ2 = 5.73, df = 1, p < 0.05, DFP ratio χ2 = 3.75, df = 1, p = 0.05, DFP residual χ2 = 5.73, df = 1, p < 0.05, Figure 2.38b). There was no significant difference between the papilla areas of folivores and non-folivores (papilla area χ2 = 0.05, df = 1, ns, area ratio χ2 = 0.00, df = 1, ns, area residual χ2 = 0.41, df = 1, ns).

DISCUSSION

Testing a model of sweet taste sensitivity, body mass, and diet

Simmen and Hladik (1998) argued that sweet taste sensitivity increases with body mass because larger species have larger tongue surface areas. With larger tongue surface area, more taste receptors should be available, leading to greater sweet taste sensitivity.

Simmen and Hladik noted that among primates, increasing body mass is associated with a greater proportion of the diet being comprised of leaves (Clutton-Brock and Harvey,

1977). The authors suggested that increased sweet taste sensitivity enables some species to detect the low levels of sugars found in leaves, making leaves more palatable to larger bodied species with higher sweet taste sensitivity.

Like Simmen and Hladik’s finding, the data in this study show that sucrose sensitivity was positively correlated with body mass (Figure 2.17). However, unlike 136 Simmen and Hladik’s results, fructose sensitivity was not significantly correlated with body mass in this dataset (p = 0.10, Figure 2.18). A larger sample size may be needed for statistical significance when testing the data on fructose thresholds. The sample size for fructose thresholds used here was smaller than the sample of fructose thresholds used by

Simmen and Hladik and also smaller than the sample size used for sucrose thresholds in this study (sucrose threshold n = 16, fructose threshold n = 12).

New data on lingual anatomy show that the surface area of the tongue does increase with body mass, as expected (Figure 2.7). The number of FP on the entire tongue

(n = 16) was positively correlated with body mass, although the number of FP on the anterior 0.5 cm of the tongue (n = 38) was not correlated with body mass. The number of

FP did not increase with the area of the dorsal tongue (Figure 2.8). Furthermore, tDFP and DFP were negatively correlated with body mass (Figures 2.9 and 2.10). On the other hand, papilla area was positively correlated with body mass and negatively correlated with DFP (Figures 2.11 and 2.12). Thus, as body mass and the size of the tongue increase, the size of fungiform papillae also increases, but the density of fungiform papillae decreases. In other words, larger primates have fewer papillae per square centimeter, but each papilla is larger compared with the papilla of smaller bodied primates. Smaller bodied primates have a higher density of papillae, but each papilla is relatively smaller in size.

Sweet taste sensitivity was not correlated with absolute number of FP. However, sucrose sensitivity was negatively correlated with DFP and DFP ratio (Figure 2.19). The same correlation between fructose sensitivity and DFP neared significance (Figure 2.20). 137 Conversely, sucrose sensitivity was positively correlated with papilla area, even when correcting for body mass (area ratio and area residual, Figure 2.21). There was not a similar correlation for fructose sensitivity (Table 2.7). In other words, as sweet taste sensitivity increases, DFP decreases and papilla area increases.

Among humans, DFP is positively associated with taste bud density and sensitivity to sucrose (Bartoshuk et al., 1994; Delwiche et al., 2001; Doty et al., 2001;

Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and

Reedy, 1990b; Miller and Whitney, 1989; Prutkin et al., 2000; Reedy et al., 1993; Smith,

1971; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002).

Furthermore, human fungiform papillae with smaller surface areas have greater taste responses (e.g. higher sensitivity) (Reedy et al., 1993). Accordingly, it was predicted that species with a greater density of papillae would have greater taste sensitivity. On the contrary, sweet taste sensitivity was negatively correlated with DFP across taxa, while the average area of papillae was positively correlated with sucrose sensitivity. Thus, compared with papilla area, DFP may be a preferential measure of sucrose sensitivity for intraspecific analyses, but when analyzing data across multiple primate taxa, papilla area appears to be a better predictor of sucrose sensitivity. It may be that larger papillae have more space to contain a greater number of taste buds, and therefore, and greater number of taste cells. A histological investigation of circumvallate papillae showed that larger primate species do tend to have more taste buds (Machida et al., 1967). The relationship between body size and taste bud density remains to be tested histologically in fungiform papillae. 138 With regard to diet, sucrose and fructose sensitivity were not correlated with the percent of leaves in the diet (n = 16 and 12 species, respectively) (Figure 2.24). Sweet taste sensitivity was also not correlated with the percent of fruit and flowers in the diet

(Figure 2.23). The lack of correlation between thresholds and diet may be due to the low number of taste thresholds available among different species of primates. In contrast, anatomical data can be collected in much greater numbers, and both DFP and papilla area were correlated with sucrose threshold. In other words, using DFP and papilla area as an assay of sucrose sensitivity is useful because anatomical data can be collected on many more samples compared with taste thresholds. Therefore, analyses of DFP, papilla area, and diet may be informative with regard to how taste sensitivity is related to diet. When all taxa were analyzed together (n = 37), DFP and DFP ratio were negatively correlated with the percent of leaves in the diet, and papilla area was positively correlated with the percent of leaves in the diet (Figures 2.25 and 2.27). When correcting for body mass, papilla area was not correlated with the percent of leaves in the diet. If DFP and papilla area are accurate indicators of sucrose sensitivity across all taxa, these results indicate that as sucrose sensitivity increases, the percent of leaves in the diet also increases.

Together, these results support the model proposed by Simmen and Hladik

(1998). Larger species, with higher sweet taste sensitivity, do have larger tongue surface areas and larger papillae. Although the density of papillae decreases in larger species, there may be a greater number of taste buds within larger papillae, thereby providing a greater number of taste receptors. Simmen and Hladik also noted that in primates, greater body mass is associated with the incorporation of more leaves in the diet (Clutton-Brock 139 and Harvey, 1977), which might be facilitated by the ability of larger primates to detect low levels of sugars in leaves. Although sucrose sensitivity was not correlated with the percent of leaves in the diet, there were significant correlations between DFP and papilla area, and folivory. If papilla area is used as an assay for sucrose sensitivity, the positive correlation between papilla area and the percent of leaves in the diet may corroborate the idea that higher sweet taste sensitivity facilitates the ingestion of leaves.

The relationship between papilla area and leaf eating may be due to the relationship that both of these variables have with body mass. Analyses showing that papilla area ratio and area residual were not correlated with the percent of leaves in the diet support this view. However, leaves do in fact contain low levels of sugars and other sweet tasting compounds, especially when compared with sugar levels in fruits

(Wrangham et al., 1991). For instance, the dry matter of fruits eaten by some cercopithecoids contains 14.9% sugars, while leaves contain 8.1% sugars (Danish et al.,

2006). Furthermore, in the diets of chimpanzees, young leaves contain more sugar than mature leaves (Reynolds et al., 1998). Many primates prefer young leaves because they tend to have higher protein content and fewer structural carbohydrates and secondary compounds compared with mature leaves (Dominy and Lucas, 2001, 2004; Garber, 1987;

Janson and Chapman, 1999; Milton, 1979). If the incorporation of leaves into the diets of larger primates is related to an ability to detect sugars at lower concentrations, then the higher sugar content of young leaves compared with mature leaves may also contribute to their preferential ingestion by primates. In addition to sugars, leaves contain sweet tasting amino acids such as alanine, glycine, serine, and threonine (Schiffman, 1980). 140

Phylogenetic differences in fungiform papillae, sweet taste sensitivity, and diet

As seen in Figure 2.11b, there is a grade shift between strepsirrhines and platyrrhines in the size of their fungiform papillae. For their body mass, platyrrhines have larger papillae than strepsirrhines. When Simmen and Hladik (1998) tested variation in sucrose sensitivity (adjusted for body mass) among strepsirrhines, platyrrhines, and catarrhines, the two former groups did not differ from catarrhines, but strepsirrhines and platyrrhines differed significantly from each other (n = 25, p = 0.045). In this study, papilla area adjusted for body mass (i.e. area ratio and area residual) differed significantly between platyrrhines and strepsirrhines (Figure 2.16). Area ratio and area residual also differed significantly between catarrhines and strespsirrhines. Very few data are available on the sucrose thresholds for catarrhines. Simmen and Hladik’s (1998) analysis included three catarrhines, compared with 9 platyrrhines and 13 strepsirrhines. Using papilla area as an assay for sucrose sensitivity, it appears that there may be a difference in sucrose sensitivity among haplorhines and strespsirrhines. In all, analyses of papilla size and sucrose sensitivity indicate that sucrose sensitivity is greatly affected by phylogeny.

Correlations between fungiform papillae and sucrose sensitivity, and between fungiform papillae and percent leaves in the diet were not significant in analyses of independent contrasts (Tables, 2.7 and 2.8) probably due to the significant effects of phylogeny on the gustatory system.

Given the phylogenetic differences in sweet taste detection, tests of DFP, papilla area, and dietary composition were conducted separately in strepsirrhines, platyrrhines, 141 cebids, catarrhines, and cercopithecoids. The results of these analyses can be found in

Tables 2.9 and 2.10. Among strepsirrhines, all three measures of DFP were negatively correlated with the percent of fruit and flowers in the diet (Figure 2.28). Papilla area was positively correlated with the percent of fruit and flowers in the diet when corrected for body mass (Figure 2.30). There were no correlations with the percent of leaves in the diet and DFP or papilla area (Figure 2.29). Using DFP and papilla area as assays for sucrose sensitivity, these results suggest that within strepsirrhines as sucrose sensitivity increases, so does the percent of fruit and flowers in the diet.

The correlations for platyrrhines differed greatly from those of strepsirrhines.

Among platyrrhines, DFP and DFP ratio were not correlated with fruit and flower eating but were negatively correlated with the percent of leaves in the diet (Figure 2.31). Papilla area and area residual were positively correlated with the percent of leaves in the diet, even with Alouatta removed from the dataset (Figure 2.33). Papilla area and area residual were also positively correlated with the percent of fruit and flowers in the diet, but when callitrichids were taken out of the analysis there was no longer a significant relationship between any measure of papilla area and the percent of fruit and flowers in the diet

(Figure 2.32). The gustatory systems of callitrichids differ from those of cebids in their ability to detect sweet tasting compounds (Glaser et al., 1996). Furthermore, callitrichids had significantly lower papilla area residuals than cebids. Consequently, testing callitrichids and cebids separately is preferable. Sample sizes were too small to test callitrichids alone (n = 3), but among cebids it appears that as sucrose sensitivity increases, the amount of leaves ingested also increases. 142 When dietary data for catarrhines were tested, results were markedly different from those of strepsirrhines and platyrrhines. Among all catarrhines, DFP residual was negatively correlated with the percent of leaves the diet, but no other correlations were found. When cercopithecoids were tested alone a clear pattern emerged. Among cercopithecoids, all three measures of DFP were positively correlated with the percent of fruit and flowers in the diet and negatively correlated with the percent of leaves in the diet (Figure 2.34). Among the three great apes, a positive relationship with DFP and fruit- flower feeding, and negative relationship with DFP and leaf feeding, is also apparent

(Figures 2.34 and 2.35). However, there were too few data, (n = 3), to test for the significance of these patterns among the apes alone.

In contrast to DFP, tests of papilla area among all catarrhines and among cercopithecoids alone showed no correlation with diet (Figures 2.36 and 2.37). These results for papillae area differ greatly from those of strepsirrhines and platyrrhines. In strepsirrhines and platyrrhines, when there was a negative correlation between DFP and diet, there was a positive correlation between papilla area and diet. For example, among strepsirrhines, all three measures of DFP were negatively correlated with the percent of fruit and flowers in the diet, while papillae area ratio and area residual were positively correlated with the percent of fruit and flowers in the diet (Figures 2.28 and 2.30).

Among platyrrhines, DFP and DFP ratio were negatively correlated with the percent of leaves in the diet, while papilla are and area residual were positively correlated with the percent of leaves in the diet (Figures 2.31 and 2.33). The complementary results of the

DFP and papilla area data in strepsirrhines and platyrrhines appear to be the effect of the 143 strong negative correlation between DFP and papilla area in these two groups (Figures

2.13 and 2.14). Among catarrhines, however, DFP and papilla area were not correlated

(Figure 2.15).

It should also be noted that among the species for which data were collected on fungiform papillae, sucrose threshold data were only available for two catarrhine species

(Macaca fascicularis and Macaca mulatta). Thus, it is not clear that a correlation between DFP and sucrose sensitivity, or between papillae area and sucrose sensitivity exists within catarrhines as it does in strepsirrhines and platyrrhines. Furthermore, unlike the strepsirrhine and platyrrhine species analyzed, many species in the catarrhine dataset were folivores (with >50% of its diet comprised of leaves), which had significantly lower

DFPs than non-folivores (Figure 2.38). Papilla area did not differ significantly among catarrhine folivores and non-folivores. Among strepsirrhines two species are folivores, and among platyrrhines only Alouatta is a folivore, compared with seven catarrhine folivores. Unfortunately, only one catarrhine species categorized as a folivore (M. mulatta), has been tested for sweet taste thresholds. No primates with forestomach fermentation have been tested for sweet taste sensitivity.

Phylogenetic differences in fungiform papillae, taste sensitivity, and their relationship to diet may offer an explanation for the lack of a consistent model for primate sweet taste sensitivity and diet. For instance, Hladik and Simmen (1996) hypothesized that greater sweet taste sensitivity might motivate fruit seeking behavior because it provides an intense sweet taste reward. Later, Simmen and Hladik (1998) hypothesized that high sucrose sensitivity facilitates leaf-eating. The results shown here 144 suggest that both of these hypotheses may be correct, among different phylogenetic groups. The positive relationship for papilla area (i.e. sucrose sensitivity) and fruit eating in strepsirrhines may indicate that a greater sweet taste reward motivates the ingestion of a greater amount of fruit. In platyrrhines, the positive relationship between papilla area and leaf eating lends support to the hypothesis that high sweet taste sensitivity promotes folivory.

Tests of sensitivity for numerous sweet tasting compounds lend additional evidence to phylogenetic differences in the gustatory system among strepsirrhines, platyrrhines, and catarrhines (Glaser, 2002b; Glaser et al., 1996; Glaser et al., 1997;

Nofre et al., 1996). Studies have identified compounds, some of which are artificial such as aspartame, that are sweet tasting to humans, but are not uniformly detected by other primates. Based on the ability, or lack thereof, to detect 15 sweet tasting compounds, sweeteners have been grouped into three classes: those that are sweet to all primates, those that are sweet to strepsirrhines and catarrhines, and those that are sweet only to catarrhines (e.g. aspartame) (Glaser et al., 1996; Nofre et al., 1996). The differences in responses to the three classes of sweeteners reinforce the fact that the gustatory systems of strepsirrhines, platyrrhines, and catarrhines evolved independently and may be optimized to detect different compounds.

Furthermore, callitrichids and Tupaia belangeri had the same gustatory responses to all tested sweeteners. Using Tupaia as an outgroup, Glaser and colleagues (1996, and

Nofre et al., 1996) argued that callitrichids have retained the most primitive primate gustatory systems. Additional data on responses to sweet tasting amino acids in the 145 common marmoset (Callithrix jacchus) support the claim that callitrichids possess the most primitive sweet taste response in the primate order (Haefeli et al., 1998). Data showing that callitrichids had significantly smaller area residuals than cebids may be related to this, but further investigation into differences in sweet taste receptors among different phylogenetic groups is warranted.

There is some emerging evidence for the genetic basis of phylogenetic differences in sweet taste receptors among primates. Li and colleagues (2003) considered the phylogenetic differences in primates for sensitivity to aspartame and performed preliminary tests of the sweet taste receptor genes T1R2 and T1R3 (which work as a heterodimer). Li et al. obtained T1R2/T1R3 coding sequences for 12 primates able to detect aspartame, and six species unable to detect aspartame. The authors found that at the amino acid level, there were 19 sequence variant sites in T1R2 and eight variant sites in T1R3 when they compared aspartame sensitive and aspartame insensitive primates. It is possible that the identified sequence variants may affect the binding of aspartame to the

T1R2/T1R3 receptor, although this remains to be tested (Li et al., 2003). Together, data on the differences among primate clades to detect sweet tasting compounds, and differences in the coding sequences for sweet taste receptors, suggest that the genetic basis for taste ability differs among primate clades. Thus, it can be reasonably expected that there are differences in the gustatory anatomy of disparate primate clades as well.

There is precedent for crucial distinctions in a sensory system among strepsirrhines, platyrrhines, and catarrhines in the distribution of routine trichromatic color vision in primates. We know much more about the visual system of primates than 146 we do about the gustatory system, and there are clear differences in visual anatomy among strepsirrhines, platyrrhines, and catarrhines. Most strepsirrhines are routinely dichromatic (Jacobs and Deegan II, 1993; Tan and Li, 1999). In most platyrrhine species and in some strepsirrhines, 50-60% of females have trichromatic color vision and all males are dichromatic (Jacobs, 1996; Jacobs and Deegan II, 1993; Tan and Li, 1999).

Catarrhines are the only infraorder with routine trichromatic color vision (Jacobs, 1996).

The catarrhine gustatory system and detection of bitter compounds

Sensitivity for bitter tasting quinine hydrochloride was not correlated with body mass, DFP, papilla area, or diet (Figure 2.22). Considering the importance of bitter taste detection in the avoidance of toxicosis (Glander, 1982; Janson and Chapman, 1999), there is question as to whether these results are due to a small sample size (n = 9).

Data on fungiform papillae showed that papilla area was correlated with DFP and diet among strepsirrhines and platyrrhines. Among catarrhines, however, papilla area was not correlated with DFP, or with the percent of fruit and flowers or the percent of leaves in the diet. Although speculative, it may be that bitter taste sensitivity is correlated with

DFP among catarrhines. Without data available to test bitter taste sensitivity and fungiform papillae in catarrhines, the possibility remains open that DFP is positively correlated with bitter taste sensitivity in this infraorder. If this is the case, the negative association between DFP and leaf eating in catarrhines suggests that as more leaves are incorporated into the diet, a gustatory system with lower bitter taste sensitivity may be beneficial. Conversely, the positive correlation between fruit and flower eating and DFP 147 suggests that when non-folivores eat leaves, high bitter taste sensitivity may be beneficial.

Intraspecific comparisons among humans may offer a model of the relationship between DFP anatomy and bitter taste sensitivity among catarrhine species. In humans, high DFP is associated with high bitter taste sensitivity (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991;

Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002). Furthermore, high bitter taste sensitivity in humans is associated with low acceptance of bitter tasting vegetables

(Dinehart et al., 2006; Drewnowski et al., 1999; Drewnowski et al., 2000; Drewnowski and Rock, 1995; Kaminski et al., 2000).

Genetic data on bitter taste receptors also support the view that the secondary compounds in leaves were an important selection pressure on the cercopithecoid gustatory system. In a study of 12 non-human primate species, each had species-specific pseudogenes. All but one non-human primate had either one or two lineage specific- pseudogenes. Only Trachypithecus cristatus, the silvered leaf monkey, had three lineage specific-pseudogenes. In contrast, the closest relative of leaf monkeys with sequenced bitter taste receptors, Macaca mulatta, is well-known to be omnivorous and has only two unique pseudogenes (Go et al., 2005). While more data on colobines will help to distinguish whether this pattern is consistent among leaf-specialists, these data may indicate that selection for bitter taste ability is more relaxed in primates with forestomach fermentation. Furthermore, Shi and Zhang (2006) found that cows have a high number of 148 bitter taste pseudogenes, compared with other mammals (44% compared with x

19.40±7.89 for humans, mouse, rat, dog, and opossum). The authors note that ruminants are generally more tolerant of plant toxins compared with non-ruminants (Freeland and

Janzen, 1974). Accordingly, they argue that animals using forestomach fermentation should not need a large repertoire of bitter taste receptors.

It should be noted, though, that T. gelada and M. mulatta had DFPs within the range of the colobines. In addition, A. palliata is the only platyrrhine species that primarily feeds on leaves, and this species has a much lower DFP (22.81 ±9.00) than all other platyrrhine species (x 127.65±87.62), even when only cebids are considered (x

73.42±14.51, Table 2.4). While all three of these species incorporate a great deal of leaves into their diet, neither T. gelada and M. mulatta, nor A. palliata use forestomach stomach fermentation for digestion (Dunbar, 1977; Dunbar and Dunbar, 1974; Glander,

1975, 1978; Iwamoto, 1979; Milton, 1980; Smith, 1977). Thus, it follows that the ability to eat bitter tasting foods without triggering a rejection response may be beneficial to primates ingesting a high proportion of leaves, regardless of the ability to detoxify bitter secondary compounds using foregut fermentation in particular.

Whereas folivores may benefit from low bitter taste sensitivity, non-folivores should benefit from having higher bitter taste sensitivity because they are less able to detoxify secondary compounds if they are ingested. Non-folivores must diversify their intake of secondary compounds so that no one toxin accumulates within the digestive system (Freeland and Janzen, 1974; Glander, 1982; Provenza et al., 2003). Non-folivores, then, should have higher DFPs compared with leaf eating primates, a pattern shown in the 149 data presented here (Figure 2.38). Although anatomical data were not collected,

Glendinning (1994) found this pattern between bitter taste sensitivity and diet in a comparative investigation of mammals. Glendinning investigated thresholds for quinine hydrochloride in 30 mammalian species, including several of the primates investigated here. He hypothesized that the bitter rejection response would depend on the relative occurrence of bitter compounds in the diet of a species. He predicted that species with high levels of bitter compounds in their diet would have evolved high bitter taste thresholds and tolerance to toxic compounds, because rejecting too many bitter foods would greatly restrict their dietary intake. Species with relatively low levels of bitter compounds in their diet would have high sensitivity (low thresholds) and low tolerance to toxins. In his sample, browsing herbivores were categorized as species with the most bitter compounds in their diet, compared with carnivores with the least bitter compounds in their diet. Thresholds and tolerance to toxins in omnivores would fall in between those of browsing herbivores and carnivores. Glendinning’s predictions were supported by the data. Herbivores had the highest thresholds for quinine hydrochloride, omnivores the second highest, and carnivores the lowest. In other words, herbivores were considered to be the least sensitive to bitter tasting, and potentially toxic compounds, while omnivores were more sensitive. With regard to tolerance for toxins, Glendinning showed that the lethal dosage of several toxins is much lower for carnivores than for omnivores or herbivores. Furthermore, as mentioned above, ruminants tend to be more tolerant of plant poisons (Freeland and Janzen, 1974). Although thresholds for quinine hydrochloride are only known for a small number of primate species (only two cercopithecoids were in the 150 dataset analyzed here), data on catarrhine DFPs follow the same pattern that would be predicted by Glendinning’s data if DFP were correlated with bitter taste sensitivity.

Further investigation

The results presented here emphasize how little is known about the comparative anatomy and function of the primate gustatory system. Although the macroanatomy of fungiform papillae may be an informative assay of taste ability, it is the least precise assay. This study makes clear that interspecific analyses of lingual papillae must be approached with phylogenetic differences in mind. At the very least, it is clear that the fungiform papillae of strepsirrhines, platyrrhines, and catarrhines are not equivalent with regard to how they relate to taste sensitivity and diet. Even more, the fungiform papillae of cebids and callitrichids, and cercopithecoids and colobines, may also differ significantly. Investigation of taste buds, taste cells, taste receptors, and genetics will yield more precise measures of taste ability among various primate clades. Histological data on the numbers or taste buds and number of taste cells in the FP of primates will help us to understand the relationship between the densities of these structures and sensitivity to various compounds. Data are also needed on the receptors responsible for the detection of various compounds, and on which receptors are expressed in the FP of various primate species. The comparative primate studies on the genetics of taste perception have shown major differences among primate species (Fischer et al., 2005; Go et al., 2005). For example, the genes responsible for sensitivity to PTC are different in

151 Pan troglodytes and Homo sapiens, two very closely related species (Bufe et al., 2005;

Drayna et al., 2003; Kim et al., 2003; Wooding et al., 2006).

Studies of taste thresholds have been valuable to our understanding of the influence of taste on dietary selection, however much more data will be required in order to gain an accurate picture of gustatory system-diet interaction. Although using anatomy as a proxy for psychophysical response is informative, it is difficult to separate measures of papilla anatomy from other variables such as body mass and sensitivity to multiple compounds. Direct psychophysical measures are, of course, preferable. Currently, there are major limitations to the data available for testing the relationships among the primate gustatory system and dietary niche. Due to the difficulty of obtaining them, few taste thresholds are currently known. Not only will it be helpful to obtain thresholds for additional species, especially leaf-specialists, but thresholds for numerous compounds found in primate foods would be informative as well. In addition to individual compounds, it is necessary to test mixtures of compounds. Chemical compounds are not isolated within a food source, and the intensity and quality of taste stimuli are modified when combined with other tastants (Keast and Breslin, 2002). For example, sensitivity to sweet tasting sugars can offset the aversive effects of bitter tasting secondary compounds, making them more palatable (Laska, 1999; Remis and Kerr, 2002; Simmen, 1994). Thus, the particular combination of compounds in a food item, and their combined taste effects in a primate species, are essential in determining food preference and should be tested accordingly.

152 With regard to diet, the data provided here on the percent of leaves, fruit, and flowers in the diet are more detailed than analyses of categorical data in which species are labeled as folivores or frugivores, for example (Oftedal, 1991), but percentage data still obscure the complexity of primate diets. Other dietary variables that may have influenced the evolution of the primate gustatory system include variation in the chemical composition of individual food item, (i.e. food item maturity), and the role of fallback foods in the diet of a species. Although two species may have similar percents of fruit and flowers, or leaves in their diet, diverse species of plants with varying levels of maturity comprise these categories. The chemical properties of young and mature leaves differ significantly, as do the chemical properties of immature and mature fruits

(Cipollini and Levey, 1997; Dominy and Lucas, 2001, 2004; Garber, 1987; Janson and

Chapman, 1999; Milton, 1979). Furthermore, the nutritional content of fruit can also vary seasonally, even by time of day, and at different heights within a tree crown (Ganzhorn and Wright, 1994; Houle et al., 2007; O’Driscoll Worman and Chapman, 2005).

Predominant use of immature or mature resources could reflect significant differences in the gustatory systems of different primates. In this dataset, Pan troglodytes is a known ripe fruit specialist (Conklin-Brittain et al., 1998; Furuichi et al., 2001; Reynolds et al.,

1998), while Pongo pygmaeus is known to emphasize unripe unripe fruits in its diet

(Knott, 1998; Mackinnon, 1974; Rodman, 1977). Data on fungiform papillae also differ in these species, with P. troglodytes having a greater average density of papillae and a larger average papilla size (Pan troglodytes DFP 50.22, DFP ratio 12.48, DFP residual

0.22, papilla area 5.145, area ratio 1.28, area residual -0.33; Pongo pygmaeus DFP 153 32.97, DFP ratio 10.00, DFP residual -0.05, papilla area 3.075, area ratio 0.93 area residual -0.39). Accordingly, analyses of diet and lingual anatomy that do not take fruit and leaf maturity into account, may mask real differences in the gustatory system.

In addition to precise data on the composition of primate diets throughout the year, data on seasonal variation in diet may be informative. The hypotheses tested here associate gustatory anatomy, taste sensitivity, and average percent of sweet (fruit and flowers) and bitter (foliage) foods in a species’ diet over the course of the year. An alternative possibility is that the gustatory system is adapted for optimal foraging of fallback foods, which are not accurately represented in percentage diet data. Fallback foods are resources that are of relatively poor nutritional quality. Yet, because fallback foods tend to be more abundant than preferred foods, they are ingested particularly when preferred foods are scarce (Marshall and Wrangham, 2007). Marshall and Wrangham

(2007) argue that, because they are more difficult to process, fallback foods exert selection pressure on primates’ adaptations for food processing, such as gut and tooth morphology. Conversely, they state that because they are less abundant and more difficult to locate, preferred foods exert selection pressure on foraging adaptations, such as spatial navigation, vision, and olfaction. Following this logic, adaptations in the gustatory system would also be associated with foraging for preferred foods. However, the sense of taste might be especially important in the assessment of fallback foods. Compared with preferred foods, poorer quality foods have lower levels of nutrients and higher levels of secondary compounds that must be contended with. Thus, using the sense of taste to select items with fewer secondary compounds may be more important when a greater 154 percentage of the diet is comprised of low-quality fallback foods. Data on the fallback foods used by primate species as well as additional data on the gustatory system may be informative in this regard.

The data shown here are the first quantitative data available on the lingual anatomy of numerous non-human primate species. These results emphasize the need for much future investigation into the evolution of the primate gustatory system. Ideally, knowledge of the numbers of taste buds and taste cells, genetics of taste receptors and the presence of those receptors in papillae, psychophysical responses to numerous individual compounds and mixtures of compounds, more precise data on primate diets, and the chemical composition of foods eaten by primates would all be available for numerous species.

SUMMARY AND CONCLUSIONS

The purpose of this chapter was to conduct a detailed analysis of lingual fungiform papillae in primates to better understand the factors that have influenced the evolution of the primate gustatory system. Previous analyses of primate taste thresholds found a positive association between sweet taste sensitivity and body mass (Hladik and

Simmen, 1996; Simmen and Hladik, 1998). Based on those findings, it was suggested by

Simmen and Hladik (1998) that the relationship between sweet taste sensitivity and body mass reflects a positive relationship with the amount of leaves included in primate diets

(Hladik and Simmen, 1996; Simmen and Hladik, 1998). The chapter presented here is the

155 first test of their hypothesis using a comparative analysis of lingual anatomy, taste sensitivity, and diet.

The major findings of this chapter fall into four categories. First, anatomical measures were analyzed, including body mass, the surface area of the dorsal tongue,

DFP, number of FP, and papilla area. Second, taste thresholds were analyzed with anatomical measures of fungiform papillae, such as DFP and papilla area, and with primate diets. Third, the relationships among measures of fungiform papillae and diet were analyzed separately in different taxonomic groups. Finally, phylogenetic differences in the macroanatomy of fungiform papillae were also compared in different taxonomic groups. These findings are summarized below.

1) Anatomy: Surface area of the dorsal tongue and the number of FP on the entire dorsal surface of the tongue were positively correlated with body mass, but absolute number of

FP was not correlated with the area of the dorsal tongue. DFP was negatively correlated with body mass and papilla area was positively correlated with body mass.

2) Taste thresholds, FP anatomy and diet: Sucrose sensitivity was not correlated with absolute number of FP and was negatively correlated with DFP. Sucrose sensitivity was positively correlated with body mass and papilla area. Sucrose sensitivity was not correlated with the percent of leaves in the diet or the percent of fruit and flowers in the diet among all taxa. Sensitivity for bitter tasting quinine hydrochloride was not correlated with body mass, DFP, papilla area, or diet. 156

3) FP anatomy and diet in different clades: When analyses were conducted across all taxa, DFP was negatively correlated with the percent of leaves in the diet and papilla area was positively correlated with the percent of leaves in the diet. Among strepsirrhines,

DFP was negatively correlated with the percent of fruit and flowers in the diet and papilla area was positively correlated with the percent of fruit and flowers in the diet. Among cebids, DFP and papilla area were not correlated with fruit and flower eating but were negatively correlated with the percent of leaves in the diet, even with Alouatta removed from the dataset. Among cercopithecoids, all three measures of DFP were positively correlated with the percent of fruit and flowers in the diet and negatively correlated with the percent of leaves in the diet. Papilla area among cercopithecoids showed no correlation with diet. Folivores had significantly lower DFPs than non-folivores.

4) FP anatomy in different clades: Callitrichids had significantly lower papilla area residuals than cebids. Area ratio and area residual were significantly different between platyrrhines and strepsirrhines and between catarrhines and strespsirrhines.

These results support the model proposed by Simmen and Hladik (1998). Larger species, with higher sweet taste sensitivity, do have larger tongue surface areas and larger papillae. Sweet taste sensitivity may be correlated with leaf-eating among all taxa, as indicated by the positive correlation between papilla area and the percent of leaves in the

157 diet. In addition to support of the Simmen and Hladik model, the following conclusions were proposed:

1) In comparative analyses across multiple primate taxa, papilla area appears to be a better predictor of sucrose sensitivity than DFP. Larger papillae may have more space to contain a greater number of taste buds, and therefore, a greater number of taste cells. This hypothesis needs to be tested histologically. DFP may be a preferential measure of sucrose sensitivity for intrasepcific analyses.

2) Phylogenetic differences in fungiform papillae, taste sensitivity, and their relationship to diet may offer an explanation for the lack of a consistent model for primate sweet taste sensitivity and diet. Interspecific analyses of lingual papillae, and the primate gustatory system in general, must be approached with phylogenetic differences in mind.

3) Sensitivity for bitter tasting quinine hydrochloride was not correlated with body mass,

DFP, papilla area, or diet. I may be that bitter taste sensitivity is correlated with DFP only among catarrhines. As more leaves are incorporated into the diet, a gustatory system with lower bitter taste sensitivity may be beneficial. Threshold data are available for very few catarrhine species, none of which are forestomach fermenters. Data on the thresholds for sweet and bitter tasting compounds in catarrhines, including leaf-specialists, are needed to fill this gap in the current data.

158 4) Data on the numbers of taste buds and taste cells, genetics of taste receptors and the presence of those receptors in papillae, psychophysical responses to numerous individual compounds and mixtures of compounds, more precise data on primate diets, and the chemical composition of foods eaten by primates for numerous species are suggested for future research.

159

Figure 2.1: Lingual gustatory papillae and taste buds. Illustration after Fain (2003).

Figure 2.2: Stained cadaveric tongue of Macaca mulatta. The dark area is comprised of filiform papillae and has been dyed with methelyne blue biological stain. Light spots are fungiform papillae and do not absorb the stain.

160

Figure 2.3: Illustration of area included in calculations of tongue surface area using 3D scans. A line was drawn at the anterior circumvallate papillae to delineate the posterior limit of the analyzed region of the tongue. Surface area is shown in grey.

Figure 2.4: Tongue of wild Cercopithecus aethiops. Papillae were counted on the anterior 0.5cm of the tongue. Numbers in white boxes denote the number of FP on each side the 0.5cm area. The black line shows the area that was calculated using NIH ImageJ® software.

161

Figure 2.5: Effects of tongue size on DFP calculation for the anterior 0.5cm of the tongue

162

Strepsirrhines

Platyrrhines

Catarrhines

(a)

163

(b) Strepsirrhines

164

(c) Platyrrhines

165

(d) Catarrhines

Figure 2.6: Cladogram based on SINEs (see text)

166

40

) 35 2

30

25 ongue (cm T 20 osal 15

10 ea of Dr

Ar 5

0 0 5 10 15 20 Body Mass (kg)

Figure 2.7: Bivariate plot of the area of the dorsal surface of the tongue and body mass. This plot includes primates from all taxa. Tongue area and body mass were significantly positively correlated (rs = 0.75, p < 0.001).

167

Figure 2.8: Bivariate plot of the number of fungiform papillae and the dorsal surface of the tongue. Number of fungiform papillae and the dorsal surface of the tongue were not correlated (rs = 0.38, ns).

168

Figure 2.9: Bivariate plot of tDFP and body mass. tDFP and body mass were significantly negatively correlated (rs = -0.75, p < 0.001). Species in the rectangle include Callithrix jacchus and Cebuella pygmaea.

169

Figure 2.10: Bivariate plot of DFP on the anterior 0.5cm of the tongue and body mass in all taxa. Data were averaged for each species. There is a significant negative correlation between DFP and body mass (rs = -0.62, p < 0.0001). DFP residuals were calculated from the regression line (log10 DFP = 2.06 - 0.36[log10 body mass], R2 = 0.52, p < 0.0001).

170

(a)

Platyrrhines Catarrhines

Strepsirrhines

(b)

171

(c)

Figure 2.11: Bivariate plots of papilla area and body mass. (a) Papilla area was positively

correlated with body mass (rs = 0.79, p < 0.0001). (b) Polygons show the distributions of strepsirrhines, platyrrhines, and catarrhines. (c) Data are categorized by diet. Only species in which ≥ fruit, leaves, or gums were included, in addition to Tupaia for comparison (n = 35). Propithecus edwardsi, Papio cynocephalus anubis, and Otolemur crassicaudatus are the three species not included in the figure.

172

Figure 2.12: Bivariate plot of papilla area and DFP. Papilla area was negatively

correlated with DFP (rs = -0.63, p < 0.0001).

173

(a)

(b)

Figure 2.13: Bivariate plot of papilla area and DFP in strepsirrhines. (a) Microcebus is indicated in the square. There was a significant negative correlation between papilla and DFP (rs = -0.87, p < 0.0001). (b) Plot of papilla area and DFP in strepsirrhines without Microcebus. The negative correlation between papilla area and DFP was also significant when Microcebus was excluded from the dataset (rs = -0.85, p < 0.001).

174

Figure 2.14: Bivariate plot of papilla area and DFP in platyrrhines. There was a

significant negative correlation between papilla area and DFP (rs = -0.79, p < 0.01). Data point in square is Alouatta.

175

Figure 2.15: Bivariate plot of papilla area and DFP in catarrhines. There was not a

significant correlation between papilla and DFP (rs = -0.35, ns).

176

( (a)

(b)

Figure 2.16: Box plots of papilla area ratios and area residuals in catarrhines, platyrrhines and strepsirrhines. (a) The area ratios of halplorhines and strepsirrhines differ significantly, * p < 0.001, **p < 0.0001. (b) The area residuals of halplorhines and strepsirrhines differ significantly, * p < 0.01.

177 1.5

1.0 eshold

Thr 0.5 ose 0.0

-0.5 Log 10 Sucr

-1.0

-1.5 0.0 0.5 1.0 1.5 2.0 2.5 Log 10 Body Mass (kg)

Figure 2.17: Bivariate plot of sucrose thresholds and body mass. There was a significant negative correlation between sucrose threshold and body mass (rs = -0.68, p < 0.01).

178

2.1

1.9 eshold 1.7 Thr

1.5

1.3

1.1 Log 10 Fructose

0.9

0.7 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 Log 10 Body Mass

Figure 2.18: Bivariate plot of fructose thresholds and body mass. The negative correlation between fructose threshold and body mass was not significant using these

data (rs = -0.50, p < 0.10, n = 12).

179

(a)

(b)

Figure 2.19: Bivariate plots of sucrose thresholds and DFP or DFP ratio. There is a significant positive correlation between sucrose threshold and DFP or DFP ratio (DFP rs = 0.59, p < 0.05, DFP ratio rs = 0.67, p < 0.01). As DFP increases, sucrose sensitivity decreases. Macaca fascicularis and M. mulatta (shown in squares) are the only catarrhines in this dataset. When they are removed from analyses, results are still significant (DFP rs = 0.78, p < 0.001, DFP ratio rs = 0.62, p < 0.05). 180

2.1

1.9 eshold 1.7 Thr

1.5

1.3

1.1 Log 10 Fructose

0.9

0.7 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 Log 10 DFP (#FP/cm2)

Figure 2.20: Bivariate plot of fructose thresholds and DFP. The positive correlation between fructose threshold and DFP neared significance (rs = 0.55, p = 0.06). Pan troglodytes and Pongo pygmaeus (shown in squares) are the only catarrhines in this dataset. When they are removed from analysis, the correlation does not near significance (rs = 0.53, p = 0.12).

181

(a)

(b)

182

(c)

Figure 2.21: Bivariate plots of sucrose threshold and papilla area. Papilla area (a), area ratio (b), and area residual (c) are negatively correlated with sucrose threshold (papilla area rs = -0.76, p = 0.001, area ratio rs = -0.50, p = 0.06, area residual rs = -0.71, p < 0.05).

183

Figure 2.22: Bivariate plot of quinine hydrochloride threshold and DFP. There was not a

significant correlation between QHCl threshold and DFP (DFP rs = 0.42, ns).

184

(a)

(b)

Figure 2.23: Bivariate plots of sucrose and fructose thresholds and the percent of fruit and flowers in the diet for all taxa. Sucrose (a) and fructose (b) thresholds were not correlated with the percent of fruit and flowers in the diet (sucrose rs = -0.07, ns, fructose rs = -0.21, ns).

185

(a)

(b)

Figure 2.24: Bivariate plot of sucrose and fructose thresholds and the percent of leaves in the diet for all taxa. Neither sucrose (a) nor fructose (b) were correlated with percent of leaves in the diet (sucrose rs = -0.25, ns, fructose rs = -0.36, ns).

186

(a)

(b)

Figure 2.25: Bivariate plots of DFP and the percent of leaves in the diet for all taxa. DFP (a) and DFP ratio (b) were negatively correlated with the percent of leaves in the diet (DFP rs = -0.33, p < 0.05, DFP ratio rs = -0.52, p < 0.01).

187

Figure 2.26: Bivariate plot of papilla area and the percent of fruit and flowers in the diet for all taxa. There was no correlation between any of the three measures of papilla area and the percent of fruit and flowers in the diet when all taxa were analyzed together (papilla area rs = 0.05, ns, area ratio rs = 0.07, ns, area residual rs = 0.10, ns).

188

Figure 2.27: Bivariate plot of papilla area and percent leaves in diet for all taxa. The percent of leaves in the diet was significantly positively correlated with

papilla area (rs = 0.39, p < 0.05), but not with area ratio or area residual

(area ratio rs = 0.03, ns, area residual rs = 0.17, ns).

189

500

450

400 ) 2 350

300 (#FP/cm 250

200

150 verage DFP

A 100

50

0 0 20 40 60 80 100 120 Percent Fruit and Flowers in Diet

(a)

180

160

) 140 2

120

(#FP/cm 100

80

60 verage DFP

A 40

20

0 0 20 40 60 80 100 120 Percent Fruit and Flowers in Diet

(b)

Figure 2.28: Bivariate plots of DFP and percent fruit and flowers in the diet of strepsirrhines. (a) Data point in square is Microcebus. (b) DFP and percent fruit and flowers in the diet of strepsirrhines without Microcebus This negative correlation was significant whether Microcebus was included (rs = -0.58, p < 0.05) or removed (rs = 0.60, p < 0.05).

190

(a)

(b)

Figure 2.29: Bivariate plots of DFP and percent leaves in the diet of strepsirrhines. (a) Data point in square is Microcebus. (b) DFP and percent leaves in the diet of strepsirrhines without Microcebus There was not a significant correlation between DFP and percent leaves whether Microcebus was included or removed from the analysis (rs = 0.08, ns, without Microcebus rs = 0.04, ns).

191

Figure 2.30: Bivariate plot of papilla area residual and percent fruit and flowers in the diet of strepsirrhines. The positive correlations between area residual and percent fruit and flowers in the diet and between area ratio and percent fruit and flowers in the diet were significant (area ratio rs = 0.60, p < 0.05, area residual rs = 0.67, p < 0.05).

192

350

300 ) 2 250

200 (#FP/cm

150

100 verage DFP A 50

0 -10 0 10 20 30 40 50 60 Percent Leaves in Diet

(a)

(b)

Figure 2.31: Bivariate plots of DFP and percent leaves in the diet of platyrrhines. Open circles are callitrichids. (a) Data point in square is Alouatta. (b) Bivariate plot without Alouatta. The negative correlation between DFP and percent leaves is significant (rs = -0.67, p < 0.05).

193

Figure 2.32: Bivariate plot of papilla area and percent fruit and flowers in the diet of platyrrhines (rs = 0.91, p = 0.001). Callitrichids are indicated by open circles and Alouatta is indicated by the square.

194

(a)

(b)

Figure 2.33: Bivariate plot of papilla area and percent leaves in the diet of platyrrhines. Open circles indicate callitrichids. (a) Includes Alouatta, which is indicated in the square (rs = 0.75, p < 0.05). (b) Without Alouatta (rs = 0.82, p < 0.01).

195

140

120 ) 2 100

80 (#FP/cm

60

40 verage DFP A

20

0 0 10 20 30 40 50 60 70 80 90 Percent Fruit and Flowers in Diet

Figure 2.34: Bivariate plot of DFP and percent of fruit and flowers in the diet of catarrhines. Data points in the square (open circles) are hominoids (Hylobates, Pan, and Pongo). When the hominoids were removed from the sample, all three measures of DFP showed a significant positive correlation with percent fruit and flowers (DFP rs = 0.92, p < 0.001, DFP ratio rs = 0.85, p < 0.01, DFP residual rs = 0.84, p < 0.01).

196 140

120 ) 2 100

80 (#FP/cm

60

40 verage DFP A

20

0 0 20 40 60 80 100 Percent Leaves in Diet

Figure 2.35: Bivariate plot of DFP and percent leaves in the diet of catarrhines. Data points (open circles) in the square are pongids (Hylobates, Pan, and Pongo). When hominoids were removed from the sample, all three measures of DFP showed a significant negative correlation with percent leaves (DFP rs = -0.85, p < 0.01, DFP ratio rs = -0.84, p < 0.01, DFP residual rs = -0.84, p < 0.01).

197

Figure 2.36: Bivariate plot of papilla area and percent of fruit and flowers in the diet of catarrhines. Open circles are hominoids (Hylobates, Pan, and Pongo). There was no correlation between papilla area and the percent of fruit and flowers

in the diet with hominoids included or excluded (rs = 0.14, ns, without hominoids rs = -0.34, ns).

198

Figure 2.37: Bivariate plot of papilla area and percent leaves in the diet of catarrhines. Open circles are hominoids (Hylobates, Pan, and Pongo). Papilla area was not correlated with the percent of leaves in the diet when hominoids were included from the analysis (rs = -0.24, ns) or excluded (rs = -0.17, ns).

199

(a)

(b) Figure 2.38: Box plots of DFPs among folivore and non-folivore cercopithecoids. (a) There is not a significant difference between the DFPs of primates that use forestomach fermentation, and those that do not (χ2 = 1.84, df = 1, ns). (b) There is a significant difference between the DFPs of folivores and non- folivores (χ2 = 5.73, df = 1, p < 0.05). Folivores include species with ≥50% of their diet comprised of leaves.

200 Table 2.1: List of species

Species N Location† Strepsirrhines Cheirogaleus major 1 Eulemur fulvus colaris 5 Duke Lemur Center, Durham, NC Eulemur macaco macaco 4 Duke Lemur Center, Durham, NC Eulemur mongoz 1 Hapalemur griseus griseus 3 Lemur catta 3 Microcebus murinus 1 Otolemur crassicaudatus 3 Otolemur garnetti 3 Propithecus coquereli 4 Duke Lemur Center, Durham, NC Propithecus edwardsi 6 Ranomafana National Park, Madagascar Propithecus tattersali 2 Varecia rubra 1 Duke Lemur Center, Durham, NC Varecia variegata 18 Ranomafana National Park, Madagascar Platyrrhines Alouatta palliata 13 La Pacifica, Costa Rica Aotus trivirgatus 3 Aotus vociferans 5 Ateles geoffroyi 5 Seneca Park Zoo, Rochester, NY Ateles paniscus 2 Callithrix jacchus 10 Cebuella pygmea 1 Cebus apella 12 Saguinus oedipus 2 Saimiri sciureus 7 Catarrhines Cercopithecus aethiops 16 Pretoria, South Africa Colobus guereza 2 San Antonio Zoo, Texas Colobus polykomos 3 Hylobates lar 2 Seneca Park Zoo, Rochester, NY Macaca fascicularis 3 Macaca mulatta 5 Pan troglodytes 46 Papio cynocephalus anubis 4 Procolobus badius 1 Pongo pygmaeus pygmaeus 1 Seneca Park Zoo, Rochester, NY Presbytis fransoisi 1 Theropithecus gelada 1 Trachypithecus cristatus 1

201 (Table 2.1 continued) Outgroup Tupaia belangeri 6 †Data on species for which a location is not listed were collected from cadaver samples. Cadaveric samples were courtesy of the following individuals: Annie M. Burrows, Duquesne University; Nate Dominy, University of California at Santa Cruz; Duke Lemur Center, Duke University; Rich Kay, Duke University; Christopher Kirk, University of Texas at Austin; Liza Shapiro, University of Texas at Austin; Timothy D. Smith, Slippery Rock University; Suzette Tardif, University of Texas Health Science Center at San Antonio; Carl J. Terranova, CUNY Medical School; Russel Tuttle, University of Chicago; Chris Vinyard, Northeastern Ohio Universities College of Medicine; Joseph Wagner, Manheimer Foundation; Steve Ward, Northeastern Ohio Universities College of Medicine; and Jeff Wyatt, University of Rochester & Seneca Park Zoo

202 Table 2.2: Comparison of live and cadaveric specimens within species.

Sample Average of Average DFP St. Species N type Number of FP DFP Dev. Ateles geoffroyi Cadaveric 29 54 2.37 3 Live 25 40 - 2 Cercopithecus aethiops Cadaveric 60 96 31.75 5 Live 65 130 36.93 18 Eulemur macaco macaco Cadaveric 33 74 - 1 Live 21 50 11.90 3 Propithecus coquereli Cadaveric 38 73 - 1 Live 56 100 9.45 3 Varecia variegata Cadaveric 38 77 - 1 Live 24 58 13.81 17

203 Table 2.3: Average papilla area, number of FP, entire tongue area, tDFP, and body mass.

Total Body number of Area of dorsal mass Species FP tongue (cm2) tDFP (kg)a N Ateles geoffroyi 94±37 5.82±0.87 15.85±3.96 7.54 2 Ateles paniscus 100±37 6.56±0.83 15.27±5.33 7.54 3 Callithrix jachcus 116±13 1.67±0.16 69.63±0.90 0.32 2 Cebuella pygmaea 108±24 0.92±0.21 122.99±53.88 0.12 2 Cercopithecus aethiops 105 7.12 14.5 2.98 1 Cercopithecus ascanius 106±14 6.24±0.83 16.98±0.02 3.31 2 Cercopithecus diana 51 7.90 6.46 5.20 1 Cercopithecus neglectus 179 6.46 27.70 4.13 1 Cercopithecus petaurista 47±2 10.00±0.77 4.66±0.14 3.65 2 Colobus polykomos 158±25 10.20±3.44 16.34±4.12 8.83 3 Hylobates lar 112 6.35 17.65 5.34 1 Macaca mulatta 187±92 14.97±3.60 12.70±6.55 9.53 3 Otolemur crassicaudatus 91 7.32 12.44 1.19 1 Papio cynocephalus 507±56 36.06±6.34 14.37±2.89 17.05 4 Saimiri scireus 30 1.95 15.42 0.78 1 Theropithecus gelada 346 27.14 12.75 19.00 1 aBody mass data are from Smith and Jungers (1997). The surface area of the dorsal tongue was measured to include the surface anterior to the circumvallate papillae and was positively associated with body mass (rs = 0.75, p < 0.001). Surface area was not significantly associated with the number of fungiform papillae (rs = 0.38, ns).

204 Table 2.4: Fungiform papillae, body mass, and diet.

Species DFP #FP Area BM FF L Diet reference

Strepsirrhines Cheirogaleus major 102.65 31.00 0.540 0.44 92 0 (Lahann, 2007)

Eulemur fulvus collaris 64.48 31.80 0.800 2.19 89 6 (Donati et al., 2007) ±9.76 ±3.49 ±0.063

Eulemur macaco macaco 55.86 23.75 0.966 2.29 85 13 (Birkinshaw, 1995) ±16.36 ±10.31 ±0.227

Eulemur mongoz 99.74 38.00 0.395 1.21 79 17 (Curtis, 1997)

Hapalemur griseus griseus 136.77 40.00 0.460 0.77 14 83 (Grassi, 2001) ±6.10 ±4.36 ±0.073

Lemur catta 71.16 31.00 0.607 2.37 56 43 (Simmen et al., 2003; ±31.14 ±6.24 ±0.317 Sussman, 1977)

Microcebus murinus 473.68 72.00 0.122 0.06 50 14 (Hladik et al., 1980)

Otolemur crassicaudatus 101.87 30.00 0.503 1.11 33 0 (Charles-Dominique, 1977 ) ±20.63 ±7.81 ±0.346

Otolemur garnetti 162.36 50.67 0.387 0.77 50 0 (Charles-Dominique, 1977 ) ±70.63 ±14.47 ±0.058

Propithecus coquereli 93.31 51.25 0.834 3.98 44 50 (Richard, 1978; Simmen et ±11.31 ±9.36 ±0.120 al., 2003)

Propithecus edwardsi 67.37 34.50 0.877 5.56 27 43 (Hemingway, 1998; ±4.81 ±6.66 ±0.353 Pochron and Wright, in review (Sept 2007)) Propithecus tattersali 130.58 44.50 0.691 3.64 55 39 (Meyers and Wright, 1993) ±30.41 ±0.075 Varecia rubra 53.76 30.00 0.942 3.30 97 4 (Vasey, 2000) ±0.074 Varecia variegata 59.38 24.78 1.091 3.83 95 3 (Balko, 1998; Britt, 2000; ±14.28 ±8.63 ±0.425 Morland, 1992) (continued)

205 (Table 2.4 continued)

Species DFP #FP Area BM FF L Diet reference

Platyrrhines Alouatta palliata 22.81 15.00 1.865 4.93 42 55 (Glander, 1975, 1978; ±9.00 ±6.45 ±0.740 Milton, 1980; Smith, 1977)

Aotus trivirgatus 83.08 41.33 1.391 0.80 69 8 (Wright, 1985) ±5.09 ±3.51 ±0.086

Aotus vociferans 85.77 39.80 1.090 0.70 100 0 (Puertas et al., 1992) ±16.53 ±6.91 ±0.369

Ateles geoffroyi 48.76 27.60 2.503 7.74 83 17 (Campbell, 2000) ±11.72 ±4.51 ±0.846

Ateles paniscus 79.65 40.50 1.800 7.54 89 8 (van Roosmalen and Klein, ±0.71 1988) Callithrix jacchus 225.54 52.90 0.510 0.33 38 4 (Garber, 1984) ±38.75 ±8.14 ±0.052

Cebuella pygmea 327.19 71.00 0.321 0.12 0 0 (Ramirez et al., 1977) ±0.041 Cebus apella 85.13 51.42 1.755 3.40 65 6 (Galetti and Pedroni, 1994) ±22.73 ±12.43 ±0.732

Saguinus oedipus 155.61 41.00 0.881 0.41 39 4 (Garber, 1984) ±7.07 ±0.097 Saimiri sciureus 58.12 18.86 0.857 0.75 55 0 (Lima and Ferrari, 2003) ±25.18 ±10.51 ±0.161

(continued)

206 (Table 2.4 continued)

Species DFP #FP Area BM FF L Diet reference

Catarrhines Cercopithecus aethiops 122.57 63.56 2.612 3.76 55 16 (Whitten, 1982) ±37.31 ±12.68 ±1.421

Colobus guereza 23.14 32.50 3.597 10.50 13 84 (Harris and Chapman, ±6.36 ±0.279 2007; Oates, 1977; Oates and Davies, 1994) Colobus polykomos 46.97 29.67 4.282 8.83 6 57 (Davies et al., 1999) ±20.56 ±4.04

Hylobates lar 36.91 31.50 2.546 7.65 69 18 (MacKinnon and ±7.78 ±0.359 MacKinnon, 1978; Palombit, 1997; Raemaekers, 1979; Ungar, 1995) Macaca fascicularis 128.99 78.33 2.070 4.47 78 8 (Ungar, 1995; Wheatley, ±2.41 ±11.06 ±0.613 1980; Yeager, 1996)

Macaca mulatta 85.62 45.80 1.828 9.24 29 71 (Goldstein and Richard, ±18.71 ±15.93 ±0.463 1989; Lindburg, 1977)

Pan troglodytes 50.22 65.26 5.145 65.13 81 17 (Ghiglieri, 1984; ±12.46 ±14.12 ±1.784 Wrangham et al., 1998)

Papio cynocephalus anubis 116.08 89.50 1.729 17.05 44 35 (Barton, 1989; Depew, ±39.41 ±20.00 ±0.252 1983 Dunbar, 1974 #1227; Harding, 1976; Popp, 1978) Pongo pygmaeus pygmaeus 32.97 48.00 3.075 35.80 66 19 (Knott, 1998; Rodman, 1977) Presbytis fransoisi 83.89 76 3.092 7.53 25 53 (Zhou et al., 2006)

Procolobus badius 93.28 50 1.242 8.21 22 52 (Davies et al., 1999)

Theropithecus gelada 26.68 23 0.916 19.00 13 87 (Dunbar, 1977; Dunbar and Dunbar, 1974; Iwamoto, 1979) Trachypithecus cristatus 93.46 60 1.757 5.76 33 61 (Kool, 1993)

Outgroup (Scandentia) Tupaia belangeri 117.32 29.83 0.746 1.25 37 - (Emmons, 2000) ±29.68 ±6.24 Sample sizes can be found in Table 2.1. #FP = Average number of FP on anterior 0.5cm of tongue, Area = Papilla area (cm2 x 1000), BM = Body Mass (kg), FF = Percent fruit and flowers in diet, L = Percent leaves in diet

207 Table 2.5: Thresholds for sucrose and fructose.

Species S F Reference

Aotus trivirgatus 17 (Glaser, 1986) Ateles geoffroyi 3 15 (Laska et al., 1996) Ateles paniscus 16 (Simmen, 1991)

Callithrix jacchus 25 30 (Glaser, 1986; Simmen, 1992; Simmen, 1994) Cebuella pygmea 33 44 (Glaser, 1986; Simmen, 1992) Cebus apella 8 (Simmen, 1991) Cheirogaleus major 150 (Dennys, 1991) Eulemur fulvus 9 23 (Bonnaire and Simmen, 1994; Dennys, 1991) Eulemur macaco 8 11 (Bonnaire and Simmen, 1994; Dennys, 1991) Eulemur mongoz 125 100 (Bonnaire and Simmen, 1994; Glaser, 1986) Hapalemur griseus 12 (Bonnaire and Simmen, 1994) Macaca fascicularis 3 (Pritchard et al., 1994) Macaca mulatta 6 (Glaser, 1986) (Glaser, 1986; Simmen and Hladik, 1988; Microcebus murinus 106 48 Simmen and Hladik, 1998) Pan troglodytes 10 (Simmen and Charlot, 2003) Pongo pygmaeus 40 (Simmen and Charlot, 2003) Propothecus verreauxi 53 (Dennys, 1991) Saguinus oedipus 125 16 (Glaser, 1986; Simmen, 1992; Simmen, 1994) Saimiri sciureus 8 40 (Glaser, 1986; Laska, 1996) When data for a species were reported in more than one publication, thresholds were averaged. S = Sucrose threshold (mM), F = Fructose threshold (mM)

208

Table 2.6: Quinine hydrochloride thresholds and DFP data in non-human primates.

QHCl preference threshold Species DFP (x0.1 mM) Threshold reference Aotus trivirgatus 83.08±5.09 15.6 (Glaser, 1986)

Callithrix jaccus 225.54±38.75 5.25 (Simmen, 1994) (Glaser, 1986; Simmen, Cebuella pygmea 327.19 7.63 1994) Macaca fascicularis 128.99±2.41 1 (Pritchard et al., 1994)

Macaca mulatta 85.62±18.71 4.9 (Glaser, 1986)

Microcebus murinus 473.68 8 (Glaser, 1986)

Pan troglodytes 50.22±12.46 1.56 (Glaser, 1986)

Saguinus oedipus 155.61 0.65 (Simmen, 1994)

Saimiri sciureus 58.12±25.18 8 (Glaser, 1986)

209 Table 2.7: Results of Spearman’s rank correlation tests with thresholds for sucrose, fructose and quinine hydrochloride in all taxa.

Sucrose threshold Fructose threshold QHCl threshold (n = 16) (n = 12) (n = 9)

rs p rs p rs p Body mass (kg) -0.68 0.003 -0.50 0.097 -0.37 0.329 Number of FP 0.08 0.764 0.37 0.239 -0.16 0.682 DFP 0.59 0.015 0.55 0.060 0.04 0.915 DFP ratio 0.67 0.004 0.49 0.108 0.30 0.431 DFP residual 0.02 0.930 0.45 0.143 -0.39 0.295 Papilla area -0.76 0.001 -0.35 0.318 -0.51 0.160 Area ratio -0.50 0.059 0.15 0.688 -0.20 0.604 Area residual -0.71 0.003 -0.30 0.393 -0.29 0.458 % Fruit and flowers in diet -0.07 0.777 -0.21 0.504 -0.06 0.881 % Leaves in diet -0.25 0.360 -0.36 0.251 -0.18 0.639 Note that a high threshold indicates low sensitivity. P-values in bold are statistically significant or near significance. (continued)

210 (Table 2.7 continued) Analyses of Sucrose threshold Fructose threshold QHCl threshold independent contrasts (n = 15) (n = 11) (n = 8)

rs p rs p rs p Body mass (kg) -0.18 0.532 -0.02 0.958 0.71 0.071 Number of FP 0.14 0.611 -0.50 0.117 0.43 0.337 DFP -0.09 0.742 -0.28 0.401 0.43 0.337 DFP ratio -0.14 0.629 -0.19 0.574 -0.36 0.432 DFP residual 0.24 0.398 -0.26 0.450 -0.21 0.645 Papilla area -0.08 0.782 0.33 0.347 -0.29 0.535 Area ratio 0.11 0.714 -0.46 0.187 -0.39 0.383 Area residual 0.03 0.911 -0.43 0.215 -0.61 0.148 % Fruit and flowers in diet -0.06 0.840 -0.26 0.433 0.71 0.071 % Leaves in diet 0.21 0.443 0.41 0.201 -0.29 0.535 Note that a high threshold indicates low sensitivity. P-values in bold are near significance.

211

Table 2.8: Results of Spearman’s rank correlation tests for DFP and diet in all taxa.

% Fruit and flowers % Leaves

rs p rs p All species (n = 37) DFP -0.18 0.289 -0.33 0.043 DFP ratio -0.06 0.704 -0.52 0.001 DFP residual -0.23 0.156 0.06 0.744 Papilla area 0.05 0.773 0.39 0.024 Area ratio 0.07 0.708 0.03 0.863 Area residual 0.10 0.566 0.17 0.332 Independent contrasts (n =37) DFP -0.32 0.056 -0.06 0.747 DFP ratio -0.30 0.073 -0.10 0.564 DFP residual 0.04 0.837 0.05 0.755 Papilla area 0.04 0.812 0.04 0.808 Area ratio 0.10 0.552 0.26 0.133 Area residual -0.03 0.886 0.06 0.715 P-values in bold are statistically significant or near significance.

212 Table 2.9: Results of Spearman’s rank correlation tests for DFP and diet for strepsirrhines, platyrrhines, and catarrhines separately.

% Fruit and flowers % Leaves

rs p rs p Strepshirrhines (n = 14) DFP -0.58 0.029 0.08 0.792 DFP ratio -0.52 0.057 -0.03 0.922 DFP residual -0.72 0.004 0.24 0.410 Strepsirrhines without Microcebus (n = 13) DFP -0.60 0.029 0.04 0.900 DFP ratio -0.53 0.060 -0.07 0.816 DFP residual -0.76 0.003 0.20 0.503 Platyrrhines (n = 10) DFP -0.47 0.173 -0.67 0.033 DFP ratio -0.52 0.127 -0.77 0.009 DFP residual -0.37 0.293 -0.22 0.537 Platyrrhines without callitrichids (n = 7) DFP 0.57 0.180 -0.71 0.074 DFP ratio 0.43 0.337 -0.82 0.024 DFP residual 0.59 0.159 -0.06 0.907 Catarrhines (n = 13) DFP 0.38 0.204 -0.52 0.067 DFP ratio 0.23 0.459 -0.44 0.133 DFP residual 0.54 0.059 -0.63 0.020 Cercopithecoids (n = 10) DFP 0.92 0.000 -0.85 0.002 DFP ratio 0.85 0.002 -0.84 0.002 DFP residual 0.84 0.002 -0.84 0.002 P-values in bold are statistically significant or near significance.

213 Table 2.10: Results of Spearman’s rank correlation tests for papilla area and diet for strepsirrhines, platyrrhines, and catarrhines separately.

% Fruit and flowers % Leaves

rs p rs p Strepshirrhines (n = 14) Papilla area 0.46 0.134 -0.06 0.845 Area ratio 0.60 0.040 -0.31 0.329 Area residual 0.67 0.017 -0.27 0.390 Strepsirrhines without Microcebus (n = 13) Papilla area 0.45 0.16 -0.02 0.958 Area ratio 0.62 0.043 -0.28 0.399 Area residual 0.70 0.017 -0.25 0.465 Platyrrhines (n = 10) Papilla area 0.75 0.020 0.91 0.001 Area ratio 0.52 0.154 0.52 0.148 Area residual 0.67 0.050 0.89 0.002 Platyrrhines without callitrichids (n = 7) Papilla area -0.03 0.939 0.89 0.007 Area ratio 0.21 0.645 0.12 0.786 Area residual -0.21 0.645 0.84 0.019 Catarrhines (n = 13) Papilla area 0.14 0.654 -0.24 0.437 Area ratio -0.01 0.986 -0.24 0.437 Area residual -0.22 0.476 -0.03 0.929 Cercopithecoids (n = 10) Papilla area -0.34 0.366 -0.17 0.669 Area ratio -0.17 0.667 -0.32 0.407 Area residual -0.33 0.391 -0.18 0.637 P-values in bold are statistically significant.

214 REFERENCES Adler, E., Hoon, M. A., Mueller, K. L., Chandrashekar, J., Ryba, N. J. P. and Zuker, C. S.

(2000) A novel family of mammalian taste receptors. Cell 100, 693-702.

Anliker, J. A., Bartoshuk, L., Ferris, A. M. and Hooks, L. D. (1991) Children's food

preferences and genetic sensitivity to the bitter taste of 6-n-propylthiouracil

(PROP). American Journal of Clinical Nutrition 54, 316-320.

Amrine-Madsen, H., Koepfli, K.-P., Wayne, R. K. and Springera, M. S. (2003) A new

phylogenetic marker, apolipoprotein B, provides compelling evidence for eutherian

relationships. Molecular Phylogenetics and Evolution 28, 225–240.

Balko, E. A. (1998) A behaviorally plastic response to forest composition and logging

disturbance by Varecia variegata variegata in Ranomafana National Park,

Madagascar. Ph.D. Thesis, pp. 3145. State University of New York, Syracuse.

Barton, R. A. (1989) Foraging strategies, diet and competition in olive baboons. Ph.D.

Thesis, University of St. Andrews.

Bartoshuk, L. (1979) Bitter taste of saccharin related to the genetic ability to taste the

bitter substance 6-n-propylthiouracil. Science 205, 934-935.

Bartoshuk, L. M. (2000) Comparing sensory experiences accross individuals: Recent

psychophysical advances illuminate genetic variation in taste perception.

Chemical Senses 25, 447-460.

Bartoshuk, L. M., Duffy, V. B., Lucchina, L. A., Prutkin, J. and Fast, K. (1998) PROP (6-

n-propylthiouracil) supertasters and saltiness of NaCl. Annals of the New York

Academy of Sciences 855, 793-796. 215 Bartoshuk, L. M., Duffy, V. B. and Miller, I. J. (1994) PTC/PROP tasting: anatomy,

psychophysics, and sex effects. Physiology & Behavior 56, 1165-1171.

Bartoshuk, L. M., Fast, K., Karrer, T. A., Marino, S., Price, R. A. and Reed, D. A. (1992)

PROP supertatsters and the perception of sweetness and bitterness. Chemical

Senses 17, 594.

Birch, L. L. (1992) Children's preferences for high-fat foods. Nutrition Reviews 50, 249-

255.

Birch, L. L. (1999) Development of food preferences. Annual Review of Nutrition 19, 41-

62.

Birch, L. L., McPhee, L., Steinberg, L. and Sullivan, S. (1990) Conditioned flavor

preferences in young children. Physiology & Behavior 47, 501-505.

Birkinshaw, C. R. (1995) The importance of the black lemur 'Eulemur macaco'

(Lemuridae, primates), for seed dispersal Lokobe Forest, Madagascar. Vol. PhD.

University College London, London.

Bonnaire, L. and Simmen, B. (1994) Taste perception if fructose solutions and diet in

lemuridae. Folia Primatalogica 63, 171-176.

Bradshaw, J. W. S. (2006) The evolutionary basis for the feeding behavior of domestic

dogs (Canis familiaris) and cats (Felis catus). Journal of Nutrition 136, 1927S-

1931.

Brett, F. L., Turner, T. R., Jolly, C. J. and Cauble, R. (1982) Trapping baboons and vervet

monkeys from wild, free-ranging populations. Journal of Wildlife Management

46, 164-174. 216 Britt, A. (2000) Diet and Feeding Behaviour of the Black-and-White Ruffed Lemur

(Varecia variegata variegata) in the Betampona Reserve, Eastern Madagascar.

Folia Primatologica 71, 133-141.

Buck, L. M. (2000) Smell and taste: The chemical senses. In Principals of Neural

Sciance, Kandel, E. R., Schwartz, J. H. and Jessell, T. M. eds, pp. 625-647.

McGraw-Hill, New York.

Bufe, B., Breslin, P. A. S., Kuhn, C., Reed, D. R., Tharp, C. D., Slack, J. P., Kim, U.-K.,

Drayna, D. and Meyerhof, W. (2005) The molecular basis of individual

differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Current Biology 15, 322-327.

Campbell, C. J. (2000) The reproductive biology of black-handed spider monkeys (Ateles

geoffroyi): Integrating Behavior and Endocrinology. Ph.D. Thesis, pp. 183.

University of California, Berkeley.

Charles-Dominique, P. ( 1977 ) Ecology and Behavior of Nocturnal Primates. Duckworth

Press London.

Chivers, D. J. and Hladik, C. M. (1980) Morphology of the gastrointestinal tract in

primates: Comparisons with other mammals in relation to diet. Journal of

Morphology 166, 337-386.

Cipollini, M. L. and Levey, D. J. (1997) Secondary metabolites of fleshy vertebrate-

dispersed fruits: Adaptive hypotheses and implications for seed dispersal.

American Naturalist 150, 346-372.

217 Clutton-Brock, T. H. (1977) Some aspects of intraspecific variation in feeding and

ranging behaviour in primates. In Primate Ecology: Studies of Feeding and

Ranging Behaviour in Lemurs, Monkeys and Apes, Clutton-Brock, T. H. ed, pp.

539-556. Academic Press, New York.

Clutton-Brock, T. H. and Harvey, P. H. (1977) Species differences in feeding and ranging

behavior in primates. In Primate Ecology: Studies of Feeding and Ranging

Behavior in Lemurs,Monkeys, and Apes, Clutton-Brock, T. H. and Harvey, P. H.

eds, pp. 557-584. Academic Press, London.

Clutton-Brock, T. H. and Harvey, P. H. (1980) Primates, brains and ecology. Journal of

Zoology, London 190, 309-323.

Conklin-Brittain, N. L., Wrangham, R. W. and Hunt, K. D. (1998) Dietary response of

chimpanzees and cercopithecines to seasonal variation in fruit abundance. II.

Macronutrients. International Journal of Primatology 19, 971-332.

Curtis, D. J. (1997) The Mongoose Lemur (Eulemur mongoz): A Study of Behaviour and

Ecology. Ph.D. Thesis, pp. 178. Universität of Zürich.

Danish, L., Chapman, C. A., Hall, M. B., Rode, K. D. and Worman, C. O. D. (2006) The

role of sugar in diet selectin in redtail and red colobus monkeys. In Feeding

Ecology in Apes and Other Primates, Hohman, G., Robbins, M. M. and Boesch,

C. eds, pp. 473-487. Cambridge University Press, Cambridge.

Davies, A. G., Oates, J. F. and Dasilva, G. (1999) Patterns of frugivory in three west

African colobine monkeys. International Journal of Primatology 20, 327-357.

218 Delwiche, J. F., Buletic, Z. and Breslin, P. A. S. (2001) Relationship of papillae number

to bitter intensity of quinine and PROP within and between individuals.

Physiology & Behavior 74, 329-337.

Dennys, V. (1991) Approche du rôle de la perception gustative dans la différenciation et

la régulation du comportement alimentaire des lémuriens. Ph.D. Thesis Université

Paris - XIII, Villetaneuse.

Depew, L. A. (1983) Ecology and behaviour of baboons (Papio anubis) in the Shai Hills

Game Production Reserve, Ghana. . Vol. M.Sc. Cape Coast University.

Dinehart, M. E., Hayes, J. E., Bartoshuk, L. M., Lanier, S. L. and Duffy, V. B. (2006)

Bitter taste markers explain variability in vegetable sweetness, bitterness, and

intake. Physiology & Behavior 87, 304-313.

Dominy, N. (2004a) Color as an indicator of food quality to anthropoid primates:

Ecological evidence and an evolutionary scenario. In Anthropoid Origins: New

Visions, Ross, C. F. and Kay, R. F. eds, pp. 615-644. Kluwer Academic, New

York.

Dominy, N. (2004b) Fruits, fingers, and fermentation: The sensory cues available to

foraging primates Integrated and Comparative Biology 44, 295-303.

Dominy, N. and Lucas, P. W. (2001) Ecological importance of trichromatic vision to

primates. Nature 410, 363-366.

Dominy, N. and Lucas, P. W. (2004) Significance of color, calories, and climate to the

visual ecology of catarrhines. American Journal of Primatology 62, 189-207.

219 Dominy, N. and Lucas, P. W. (2006) Primate sensory systems and foraging behavior. In

Feeding Ecology in Apes and Other Primates, Hohmann, G., Robbins, M. M. and

Boesch, C. eds, pp. 489-509. Cambridge University Press, Cambridge.

Dominy, N., Lucas, P. W., Osorio, D. and Yamashita, N. (2001) The sensory ecology of

primate food perception. Evolutionary Anthropology 10, 171-186.

Donati, G., Bollen, A., Borgognini-Tarli, S. M. and Ganzhorn, J. U. (2007) Feeding over

the 24-h cycle: dietary flexibility of cathemeral collared lemurs (Eulemur collaris)

Behavioral Ecology and Sociobiology in press.

Doty, R. L., Bagla, R., Morgenson, M. and Mirza, N. (2001) NaCl thresholds:

relationship to anterior tongue locus, area of stimulation, and number of

fungiform papillae. Physiology & Behavior 72, 373-378.

Drayna, D., Coon, H., Kim, U.-K., Elsner, T., Cromer, K., Otterud, B., Baird, L., Peiffer,

A. P. and Leppert, M. (2003) Genetic analysis of a complex trait in the Utah

Genetic Reference Project: a major locus for PTC taste ability on chromosome 7q

and a secondary locus on chromosome 16p. Human Genetics 112, 567-572.

Drewnowski, A. (1986) Sweetness and obesity. In Sweetness (ILSI Human Nutritions

Reviews), Dobbing, J. ed, pp. 177-192. Springer, Berlin.

Drewnowski, A. (1997) Taste preferences and food intake. Annual Review of Nutrition

17, 237-253.

Drewnowski, A., Ahlstrom Henderson, S. and Barratt-Fornell, A. (1998a) Genetic

sensitivity to 6-n-Propylthiouracil and sensory responses to sugar and fat

mixtures. Physiology & Behavior 63, 771-777. 220 Drewnowski, A., Ahlstrom Henderson, S., Levine, A. and Hann, C. (1999) Taste and

food preferences as predictors of dietary practices in young women. Public Health

Nutrition 2, 513–519.

Drewnowski, A., Ahlstrom Henderson, S. and Shore, A. B. (1997a) Genetic sensitivity to

6-n-propylthiouracil (PROP) and hedonic responses to bitter and sweet tastes.

Chemical Senses 22, 27-37.

Drewnowski, A., Brunzell, J. D., Sande, K., Iverius, P. H. and Greenwood, M. R. C.

(1985) Sweet tooth reconsidered: Taste responsiveness in human obesity.

Physiology & Behavior 35, 617-622.

Drewnowski, A., Henderson, S. A., Hann, C. S., Berg, W. A. and Ruffin, M. T. (2000)

Genetic taste markers and preferences for vegetables and fruit of female breast

care patients. Journal of the American Dietetic Association 100, 191-197.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1997b)

Nontasters, tasters, and supertasters of 6-n-Propylthiouracil (PROP) and hedonic

response to sweet. Physiology & Behavior 62, 649-655.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1998b) Sensory

responses to 6-n-propylthiouracil (PROP) or sucrose solutions and food

preferences in young women. Annals of the New York Academy of Sciences 855,

797-801.

Drewnowski, A. and Rock, C. L. (1995) The influence of genetic taste markers on food

acceptance. American Journal of Clinical Nutrition 62, 506-511.

221 Dudley, R. (2002) Fermenting fruit and the historical ecology of ethanol ingestion: Is

alcoholism in modern humans an evolutionary hangover? Addiction 97, 381-388.

Dudley, R. (2004) Ethanol, fruit ripening, and the historical origins of human alcoholism

in primate frugivory. Integrated and Comparative Biology 44, 315-323.

Duffy, V. B. and Bartoshuk, L. M. (2000) Food acceptance and genetic variation in taste.

Journal of the American Dietetic Association 100, 647-655.

Duffy, V. B., Hayes, J. E. and Dinehart, M. E. (2006) Genetic differences in sweet taste

perception. In Optimising sweet taste in foods, Spillane, W. J. ed, pp. 30-53.

Woodhead Publishing, Cambridge.

Duffy, V. B., Peterson, J. M., Dinehart, M. E. and Bartoshuk, L. (2003) Genetic and

environmental variation in taste: Associations with sweet intensity, preference,

and intake. Topics in Clinical Nutrition 18, 209-220.

Dulai, K. S., von Dornum, M., Mollon, J. D. and Hunt, D. M. (1999) The evolution of

trichromatic color vision by opsin gene duplication in new world and old world

primates Genome Research 9, 629-638.

Dunbar, R. I. M. (1977) Feeding ecology of gelada baboons: A preliminary report. In

Primate Ecology, Clutton-Brock, T. H. ed, pp. 251-273. Academic Press, London.

Dunbar, R. I. M. and Dunbar, P. (1974) Ecological relations and niche separation

between sympatric terrestrial primates in Ethiopia. Folia Primatologica 21, 36–

60.

Emmons, L. H. (2000) Tupai: A field study of Bornean Tree Shrews. University of

California Press, Berkely. 222 Essick, G. K., Chopra, A., Guest, S. and McGlone, F. (2003) Lingual tactile acuity, taste

perception, and the density and diameter of fungiform papillae in female subjects.

Physiology & Behavior 80, 289-302.

Fain, G. (2003) Sensory transduction. Sinauer Associates, Inc. Publishers, Sunderland,

Mass.

Falconer, D. S. (1947) Sensory thresholds for solutions of phenylthiocarbamide. Results

of tests on a large sample, made by R. A. Fisher. Annals of Eugenics, London 13,

211-222.

Ferrell, F. (1984) Preference for sugars and nonnutritive sweeteners in young beagles.

Neuroscience & Biobehavioral Reviews 8, 199-203.

Fischer, A., Gilad, Y., Man, O. and Paabo, S. (2005) Evolution of bitter taste receptors in

humans and apes. Molecular and Biology and Evolution 22, 432-436.

Fischer, R. and Griffen, F. (1964) Pharmacogenetic aspects of gustation.

Arzneimittelforschung 14, 673-686.

Freeland, W. J. and Janzen, D. H. (1974) Strategies in herbivory by mammals: The role

of plant secondary compounds. The American Naturalist 108, 269-289.

Furuichi, T., Hashimoto, C. and Tashiro, Y. (2001) Fruit availability and habitat use by

chimpanzees in the Kalinzu Forest, Uganda: Examination of fallback foods.

International Journal of Primatology 22, 929-945.

Galef, B. G. (1996) Food selection: Problems in understanding how we choose foods to

eat. Neuroscience and Biobehavioral Reviews 20, 67-73.

223 Galetti, M. and Pedroni, F. (1994) Seasonal diet of capuchin monkeys (Cebus apella) in a

semideciduous forest in South-East Brazil. Journal of Tropical Ecology 10, 27-

39.

Ganzhorn, J. (1989) Primate species separation in relation to secondary plant chemicals.

Human Evolution 4, 125.

Ganzhorn, J. U. (1988) Food partitioning among Malagasy primates. Oecologica (Berlin)

75, 436-450.

Ganzhorn, J. U. and Wright, P. C. (1994) Temporal patterns in primate leaf eating: The

possible role of leaf chemistry. Folia Primatologica 63, 203-208.

Garber, P. (1984) Proposed nutritional importance of plant exudates in the diet of the

Panamanian tamarin, Saguinus eodipus geoffroyi. International Journal of

Primatology 5, 1-15.

Garber, P. A. (1987) Foraging strategies among living primates. Annual Review of

Anthropology 16, 339-364.

Gaulin, S. J. C. and Konner, M. (1977) On the natural diet of primates, including humans.

In Nutrition and the Brain, Vol. 1, Wurtman, R. J. and Wurtman, J. J. eds, pp. 1-

86. Raven Press, New York.

Gent, J. F. and Bartoshuk, L. M. (1983) Sweetness of sucrose neohesperidin

dihydrochalcone, and saccharin is related to genetic ability to taste 6-n-

propylthiouracil. Chemical Senses 7, 265-272.

Ghiglieri, M. P. (1984) Feeding ecology and sociality of chimpanzees in Kibale Forest,

Uganda. In Adaptations for Foraging in Nonhuman Primates: Contributions to an 224 Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 161-194. Columbia University Press, New York.

Glander, K. E. (1975) Habitat and Resource Utilization: An Ecological View of Social

Organization in Mantled Howling Monkeys. Ph.D. Thesis University of Chicago.

Glander, K. E. (1978) Howling monkey feeding behavior and plant secondary

compounds: A study of strategies. In The Ecology of Arboreal Folivores,

Montgomery, G. G. ed, pp. 561-574. Smithsonian Institution Press, Washington

DC.

Glander, K. E. (1982) The impact of plant secondary compounds on primate feeding

behavior. Yearbook of Physical Anthropology 25, 1-18.

Glander, K. E., Fedigan, L. M., Fedigan, L. and Chapman, C. (1991) Field methods for

capture and measurement of three monkey species in Costa Rica. Folia

Primatologica 57, 70-82.

Glaser, D. (1986) Geschmacksforschung bei Primaten. Vjsehr Naturf Ges Zürich 131, 92-

110.

Glaser, D. (2002a) Experimental studies of primate sensory capacity. Evolutionary

Anthropology Supp 1, 136-139.

Glaser, D. (2002b) Specialization and phyletic trends of sweetness reception in animals.

Pure and Applied Chemistry 74, 1153-1158.

Glaser, D., Tinti, J.-M. and Nofre, C. (1996) Gustatory repsonses of non-human primates

to dipeptide deratives or analogues, sweet in man. Food Chemistry 56, 313-321.

225 Glaser, D., Tinti, J.-M. and Nofre, C. (1997) Taste preference in nonhuman primates to

compounds sweet in man. Chemical Senses 22, 687.

Go, Y., Satta, Y., Takenaka, O. and Takahashi, N. (2005) Lineage-specific loss of

function of bitter taste receptor genes in humans and nonhuman primates.

Genetics 170, 313-326.

Goldstein, S. J. and Richard, A. F. (1989) Ecology of rhesus macaques (Macaca mulatta)

in northwest Pakistan International Journal of Primatology 10, 531-567.

Grassi, C. (2001) The behavioral ecology of Hapalemur griseus griseus: The influences

of microhabitat and population density on this small-bodied prosimian folivore.

Ph.D. Thesis, pp. 345. The University of Texas at Austin.

Grinker, J. A., Price, J. M. and Greenwood, M. R. C. (1976) Studies of taste in childhood

obesity. In Hunger: Basic mechanisms and clinical applications, Novin, D.,

Wyrwicka, W. and Bray, G. A. eds, pp. 441-457. Raven, New York.

Haefeli, R. J., Solms, J. and Glaser, D. (1998) Taste responses to amino acids in common

marmosets (Callithrix jacchus jacchus, Callitrichidae) a non-human primate in

comparison to humans. Lebensm.-Wiss u. -Technol. 31, 371-376.

Hall, M. J., Bartoshuk, L. M., Cain, W. S. and Stevens, J. C. (1975) PTC taste blindnes

and the taste of caffiene. Nature 253, 442-443.

Harding, R. S. O. (1976) Ranging patterns of a group of baboons (Papio anubis) in

Kenya. Folia Primatologica 25, 143-185.

Harris, T. R. and Chapman, C. A. (2007) Variation in diet and ranging of black and white

colobus monkeys in Kibale National Park, Uganda. Primates 48, 208-221. 226 Hayes, J. E., Bartoshuk, L., Kidd, J. R. and Duffy, V. B. (2008) Supertasting and PROP

bitterness depends on more than the TAS2R38 gene Chemical Senses 33, 255-

265.

Hemingway, C. A. (1998) Selectivity and variability in the diet of Milne-Edwards’

sifakas (Propithecus diadema edwardsi): Implications for folivory and seed-

eating International Journal of Primatology 19, 355-377.

Hladik, C. M. (1978) Adaptive strategies of primates in relation to leaf-eating. In The

Ecology of Arboreal Folivores, Montgomery, G. G. ed, pp. 373-395. Smithsonian

Institution Press, Washington DC.

Hladik, C. M. (1979) Diet and ecology of prosimians. In The Study of Prosimian

Behavior, Doyle, G. A. and Martin, R. D. eds, pp. 307-357. Academic Press, New

York.

Hladik, C. M. (1981) Diet and the evolution of feeding strategies anong forest primates.

In Omnivorous Primates: Gathering and Hunting in Human Evolution, Harding,

R. S. O. and Teleki, G. eds. Columbia University Press, New York.

Hladik, C. M., Charles-Dominique, P. and Petter, J. J. (1980) Feeding strategies of five

nocturnal prosimians in the dry forest of the West coast of Madagascar. In

Nocturnal Malagasy Primates: Ecology, Physiology, and Behavior, Charles-

Dominique, P., Cooper, H. M., Hladik, A., Hladik, C. M., Pages, E., Pariente, G.

F., Petter-Rousseaux, A., Petter, J. J. and Schilling, A. eds, pp. 41-73. Academic

Press, New York.

227 Hladik, C. M., Pasquet, P. and Simmen, B. (2002) New perspectives on taste and primate

evolution: The dichotomy in gustatory coding for perception of beneficent versus

noxious substances as supported by correlations among human thresholds.

American Journal of Physical Anthropology 117, 342-348.

Hladik, C. M. and Simmen, B. (1996) Taste perception and feeding behavior in

nonhuman primates and human populations. Evolutionary Anthropology 5, 58-71.

Hoffmann, J. N., Montag, A. G. and Dominy, N. (2004) Meissner corpuscles and

somatosensory acuity: The prehensile appendages of primates and elephants. The

Anatomical Record Part A 281A, 1138-1147.

Holt, S. H. A., Cobiac, L., Beaumont-Smith, N. E., Easton, K. and Best, D. J. (2000)

Dietary habits and the perception and liking of sweetness among Australian and

Malaysian students: A cross-cultural study. Food Quality and Preference 11, 299-

312.

Hosako-Naito, Y., Lucchina, L. A., Snyder, D. J., Boggiano, M. K., Duffy, V. B. and

Bartoshuk, L. M. (1996) Number of fungiform papillae in nontasters, medium

tasters, and supertasters of PROP (6-n-propylthiouracil). Chemical Senses 21,

616.

Houle, A., Chapman, C. and Vickery, W. (2007) Intratree variation in fruit production

and implications for primate foraging. International Journal of Primatology 28,

1197-1217.

Isbell, L. (1991) Contest and scramble competition: patterns of female aggression and

ranging behavior among primates. Behavioral Ecology 2, 143-155. 228 Iwamoto (1979) Feeding Ecology. In Ecological and Social Studies of the Gelada

Baboon, Kawai, M. ed, pp. 279-330. Kodansha, Tokyo.

Jacobs, G. H. (1996) Primate photopigments and primate color vision. Proceedings of the

National Academy of Sciences of the USA 93, 577-581.

Jacobs, G. H. and Deegan II, J. F. (1993) Photopigments underlying colorvision in

ringtail lemurs (Lemur catta) and brown lemurs (Eulemur fulvus). American

Journal of Primatology 30, 243-256.

Janjua, T. and Schwartz, S. (1997) unpublished data. In Duffy, V. B. and L. M.

Bartoshuk (2000) Food acceptance and genetic variation in taste. Journal of the

American Dietetic Association 100, 647-655.

Janson, C. H. and Chapman, C. A. (1999) Resources and primate community structure. In

Primate Communities, Fleagle, J. G., Janson, C. H. and Reed, K. E. eds, pp. 237-

267. Cambridge University Press, New York.

Kalmus, H. (1971) Genetics of taste. In Taste, Vol. 4, Chemical Senses, Part 2, Beidler,

L. M. ed, pp. 165-179. Springer-Verlag Berlin, Heidelberg.

Kaminski, L. C., Henderson, S. A. and Drewnowski, A. (2000) Young women's food

preferences and taste repsonsiveness to 6-n-porpylthiouracil (PROP). Physiology

& Behavior 68, 691-697.

Kay, R. F. (1984) On the use of anatomical features to infer foraging behavior in extinct

primates. In Adaptations for Foraging in Nonhuman Primates: Contributions to

Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 21-53. Columbia University Press, New York. 229 Keast, R. S. J. and Breslin, P. A. S. (2002) An overview of binary taste–taste interactions

Food Quality and Preference 14, 111–124

Kim, U.-k., Jorgenson, E., Coon, H., Leppert, M., Risch, N. and Drayna, D. (2003)

Positional cloning of the human quantitative trait locus underlying taste sensitivity

to phenlythiocarbamide. Science 299, 1221-1225.

Knott, C. D. (1998) Changes in orangutan caloric intake, energy balance, and ketones in

response to fluctuating fruit availability International Journal of Primatology 19,

1061-1079.

Kool, K. (1993) The diet and feeding behavior of the silver leaf monkey (Trachypithecus

auratus sondaicus) in Indonesia. International Journal of Primatology 14, 667-

701.

Lahann, P. (2007) Feeding ecology and seed dispersal of sympatric cheirogaleid lemurs

(Microcebus murinus, Cheirogaleus medius, Cheirogaleus major) in the littoral

rainforest of south-east Madagascar. Journal of Zoology 271, 88-98.

Lambert, J. E. (1998) Primate digestion: Interactions among anatomy, physiology, and

feeding ecology. Evolutionary Anthropology 7, 8-20.

Laska, M. (1996) Taste preference thresholds for food-associated sugars in the squirrel

monkey (Saimiri sciureus). Primates 37, 91-95.

Laska, M. (1999) Taste responsiveness to food-associated acids in the squirrel monkey

(Saimiri sciureus). Journal of Chemical Ecology 25, 1623-1631.

230 Laska, M. (2001) A comparison of food preferences and nutrient composition in captive

squirrel monkeys, Saimiri sciureus, and pigtail macaques, Macaca nemestrina.

Physiology & Behavior 73, 111-120.

Laska, M., Carrera Sanchez, E. and Rodriguez Luna, E. (1996) Gustatory thresholds for food

associated sugars in the spider monkey (Ateles geoffroyi). American Journal of

Primatology.

Laska, M., Freist, P. and Krause, S. (2007) Which senses play a role in nonhuman

primate food selection? A comparison between squirrel monkeys and spider

monkeys American Journal of Primatology 69, 282–294.

Laska, M., Hernandez Salazar, L. T. and Rodriguez Luna, E. (2000) Food preferences

and nutrient composition in captive spider monkeys, Ateles geoffroyi.

International Journal of Primatology 21, 671-683.

Laska, M., Scheuber, H.-P., Carrera Sanchez, E. and Rodriguez Luna, E. (1999a) Taste

difference thresholds for sucrose in two species of nonhuman primates. American

Journal of Primatology 48, 153-160.

Laska, M., Schull, E. and Scheuber, H.-P. (1999b) Taste preference thresholds for food

associated sugars in baboons (Papio hamadryas anubis). International Journal of

Primatology 20, 25-34.

Lawless, H. (1980) A comparison of different methods used to assess sensitivity to the

taste of phenylthiocarbamide (PTC) Chemical Senses 5, 247-256.

Leach, E. J. and Noble, A. C. (1986) Comparison of bitterness of caffiene and quinine by

a time-intensity procedure. Chemical Senses 11, 339-345. 231 Li, X., Li, W., Mascioli, K. J., Bachmanov, A. A., Tordoff, M. G., Epple, G.,

Beauchamp, G. K. and Reed, D. R. (2003) Comparative analysis of the T1R taste

receptor genes in primates. Chemical Senses 28, 296.

Li, X., Li, W., Wang, H., Cao, J., Maehashi, K., Huang, L., Bachmanov, A. A., Reed, D.

R., Legrand-Defretin, V., Beauchamp, G. K. and Brand, J. G. (2005)

Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward

sugar. PLoS Biology 1, 27-35.

Lima, E. M. and Ferrari, S. F. (2003) Diet of a Free-Ranging Group of Squirrel Monkeys

(Saimiri sciureus) in Eastern Brazilian Amazonia. Folia Primatologica 74, 150-

158.

Lindburg, D. G. (1977) Feeding behavior and diet of Rhesus monkeys (Macaca mulatta)

in Siwalik Forest in North India. In Primate Ecology: Studies of Feeding and

Ranging Behavior in Lemurs, Monkeys and Apes, Clutton-Brock, T. H. and

Harvey, P. H. eds, pp. 223-249. Academic Press, London.

Lindemann, B. (1996) Taste reception. Physiological Reviews 76, 719-766.

Lindemann, B. (2001) Receptors and transduction in taste. Nature 413, 219-225.

Looy, H. and Weingarten, H. P. (1992) Facial expressions and genetic sensitivity to 6-n-

Propylthiouracil predict hedonic response to sweet Physiology & Behavior 52, 75-

82.

Lucchina, L. A., Curtis, O. F., Putnam, P., Drewnowski, A., Prutkin, J. M. and Bartoshuk,

L. M. (1998) Psychophysical measurement of 6-n-propylthiouracil (PROP) taste

perception. Annals of the New York Academy of Sciences 855, 816-819. 232 Ly, A. and Drewnowski, A. (2001) PROP (6-n-propylthiouracil) tasting and sensory

responses to caffeine, sucrose, neohesperidin dihydrochalcone and chocolate.

Chemical Senses 26, 41-47.

Machida, H., Perkins, E. and Giacommetti, L. (1967) The anatomical and histochemical

properties of the tongue of primates. Folia Primatologica 5, 264-279.

MacKinnon, J. (1974) The behaviour and ecology of wild orang-utans (Pongo

pygmaeus). Animal Behaviour 22, 3-74.

MacKinnon, J. R. and MacKinnon, K. C. (1978) Comparative feeding ecology of six

sympatric primates in West Malaysia. In Recent Advances in Primatology, Vol. 1:

Behavior, Chivers, D. J. and Herbert, J. eds, pp. 305-321. Academic Press,

London.

Maddison, W. P. and Maddison, D. R. (2006) Mesquite: a modular system for

evolutionary analysis. Version 1.12 http://mesquiteproject.org.

Marshall, A. and Wrangham, R. (2007) Evolutionary Consequences of Fallback Foods.

International Journal of Primatology 28, 1219-1235.

Meyers, D. M. and Wright, P. C. (1993) Resource tracking: Food availability and

Propithecus seasonal reproduction. In Lemur Social Systems and their Ecological

Basis, Kappeler, P. M. and Ganzhorn, J. U. eds. Plenum Press, New York.

Midford, P. E., Garland Jr., T. and Maddison, W. P. (2005) PDAP Package of Mesquite.

Version 1.07.

Miller, I. J. and Bartoshuk, L. M. (1991) Taste perception, taste bud distribution, and

spatial relationships. In Smell and Taste in Health and Disease, Getchell, T. V., 233 Doty, R. L., Bartoshuk, L. M. and Snow, J. B. J. eds, pp. 205-233. Raven Press,

New York.

Miller, I. J. and Reedy, F. E. (1990a) Quantification of fungiform papillae and taste pores

in living human subjects. Chemical Senses 15, 281-294.

Miller, I. J. and Reedy, F. E. (1990b) Variations in human taste bud density and taste

intensity perception. Physiology & Behavior 47, 1213-1219.

Miller, I. J. and Whitney, G. (1989) Sucrose octaacetate-taster mice have more vallate

taste buds than non-tasters. Neuroscience Letters 100, 271-275.

Milton, K. (1979) Factors influencing leaf choice by howler monkeys: a test of some

hypotheses of food selection by generalost herbivores American Naturalist 114,

362-378.

Milton, K. (1980) The foraging strategy of howler monkeys. Columbia University Press,

New York.

Milton, K. and May, M. L. (1976) Body weight, diet and home range area in primates.

Nature 259, 459-462.

Mistretta, C. M. (1991) Developmental neurobiology of the taste system. In Smell and

Taste in Health and Disease, Getchell, T. V., Doty, R. L., Bartoshuk, L. M. and

Snow, J. J. eds, pp. 35-64. Raven Press, New York.

Morland, H. S. (1992) Social organization and ecology of black and white ruffed lemurs

(Varecia variegata variegata) in lowland rainforest, Nosy Mangabe, Madagascar.

Ph.D. Thesis, pp. 419. Yale University.

234 Nelson, G., Hoon, M. A., Chandrashekar, J., Zhang, Y., Ryba, N. J. P. and Zuker, C. S.

(2001) Mammalian sweet taste receptors. Cell 106, 381-390.

Nofre, C., Tinti, J. M. and Glaser, D. (1996) Evolution of the sweetness receptor in

primates. II. Gustatory responses of non-human primates to nine compounds

known to be sweet in man. Chemical Senses 21, 747-762.

O’Driscoll Worman, C. and Chapman, C. (2005) Seasonal variation in the quality of a

tropical ripe fruit and the response of three frugivores. Journal of Tropical

Ecology 21, 689–697.

Oates, J. F. (1977) The guereza and its food. In Primate Ecology: Studies of Feeding and

Ranging Behavior in Lemurs, Monkeys, and Apes, Clutton-Brock, T. H. ed, pp.

275-321. Academic Press, New York.

Oates, J. F. and Davies, A. G. (1994) What are the colobines? In Colobine Monkeys:

Their Ecology, Behavior, and Evolution, Davies, A. G. and Oates, J. F. eds, pp. 1-

9. Cambridge University Press, Cambridge.

Oftedal, O. T. (1991) The nutritional consequences of foraging in primates: the

relationship of nutrient intakes to nutrient requirements. Philosophical

Transactions of the Royal Society B: Biological Sciences 334, 161–170.

Palombit, R. A. (1997) Inter- and intraspecific variation in the diets of sympatric siamang

(Hylobates syndactylus) and Lar Gibbon (Hylobates lar). Folia Primatologica 68,

321-337.

235 Parra, R. (1978) Comparison of foregut and hindgut fermentation in herbivores. In The

Ecology of Arboreal Folivores, Montgomery, G. G. ed, pp. 205-229. Smithsonian

Institution Press, Washington DC.

Pasquet, P., Oberti, B., El Ati, J. and Hladik, C. M. (2002) Relationships between

threshold-based PROP sensitivity and food preferences of Tunisians. Appetite 39,

167-173.

Peterson, J. M., Bartoshuk, L. M. and Duffy, V. B. (1999) Intensity and preference for

sweetness is influenced by genetic taste variation. Journal of the American

Dietetic Association 99, A28-A28.

Pochron, S. and Wright, P. C. (in review) Diet competition in a female-dominant

prosimian primate, the Milne-Edwards' sifaka (Propithecus edwardsi). Primates.

Popp, J. L. (1978) Male baboons and evolutionary principles. Ph.D. Thesis. Harvard

University.

Pritchard, T. C., Reilly, S., Hamilton, R. B. and Norgren, R. (1994) Taste preference of

Old World monkeys: I. A single-bottle preference test. Physiology & Behavior 55,

447-481.

Provenza, F. D. (1996) Acquired aversions as the basis for varied diets of ruminants

foraging on rangelands. Journal of Animal Science 74, 2010-220.

Provenza, F. D., Villalba, J. J., Dziba, L. E., Atwood, S. B. and Banner, R. E. (2003)

Linking herbivore experience, varied diets, and plant biochemical diversity. Small

Ruminant Research 49, 257-274.

236 Prutkin, J., Duffy, V. B., Etter, L., Fast, K., Gardner, E., Lucchina, L. A., Snyder, D. J.,

Tie, K., Weiffenbach, J. and Bartoshuk, L. M. (2000) Genetic variation and

inferences about perceived taste intensity in mice and men. Physiology &

Behavior 69, 161-173.

Puertas, P. E., Aquino, R. and Encarnación, F. (1992) Uso de alimentos y competición

entre el mono nocturno Aotus vociferans y otros mamíferos, Loreto, Perú. Folia

Amazonia 4, 135–144.

Purves, D., Fitzpatric, D., Katz, L. C., LaMantia, A.-S. and McNamara, J. O. (1997)

Neuroscience. Sinaur Associates, Inc., Sunderland, MA.

Raemaekers, J. J. (1979) Ecology of sympatric gibbons. Folia Primatologica 31, 227-

245.

Ramirez, I. (1990) Why do sugars taste good? Neuroscience & Biobehavioral Reviews

14, 125-134.

Ramirez, M. F., Freese, C. H. and Revilla C., J. (1977) Feeding ecology of the pygmy

marmoset, Cebuella pygmaea, in Northeastern Peru. In Biology and conservation

of the callitrichidae, Kleiman, D. G. ed, pp. 91-104. Smithsonian Institution

Press, Washington D.C.

Ray, D. A., Xinga, J., Hedgesa, D. J., Halla, M. A., Labordea, M. E., Anders, B. A.,

Whitea, B. R., Stoilovaa, N., Fowlkesa, J. D., Landry, K. E., Chemnickb, L. G.,

Ryderb, O. A. and Batzera, M. A. (2005) Alu insertion loci and platyrrhine

primate phylogeny. Molecular Phylogenetics and Evolution 35, 117–126.

237 Reedy, F. E., Bartoshuk, L. M., Miller, I. J., Duffy, V. B., Lucchina, L. A. and

Yanagisawa, K. (1993) Relationships among papillae, taste pores, and 6-n-

propythiouracil (PROP) suprathreshold taste sensitivity. Chemical Senses 18, 618-

619.

Regan, B. C., Julliot, C., Simmen, B., Vienot, F., Charles-Dominique, P. and Mollen, J.

D. (2001) Fruits, foliage and the evolution of primate colour vision. Philosophical

Transactions of the Royal Society of London. Series B: Biological Sciences 356,

229-283.

Remis, M. J. and Kerr, M. E. (2002) Taste responses to fructose and tannic acid among

gorillas (Gorilla gorilla gorilla). International Journal of Primatology 23, 251-

261.

Reynolds, V., Plumptre, A. J., Greenham, J. and Harborne, J. (1998) Condensed tannins

and sugars in the diet of chimpanzees (Pan troglodytes schweinfurthii) in the

Budongo Forest, Uganda. Oecologia 115, 331-336.

Richard, A. F. (1978) Variability in feeding behavior of a Malagasy prosimian,

Propithecus verreauxi: Lemuriformes. In The Ecology of Arboreal Folivores,

Montgomery, G. G. ed, pp. 519-533. Smithsonian Institution Press, Washington

DC.

Robinson, P. P. and Winkles, P. A. (1990) Quantitative study of fungiform papillae and

taste buds on the cat's tongue. The Anatomical Record 226, 108-111.

238 Rodman, P. S. (1977) Feeding behavior of orangutans in the Kutai Reserve, East

Kalimantan. In Primate Ecology: Studies of Feeding and Ranging Behaviour in

Lemurs, Monkeys and Apes, pp. 383–413. Academic Press, London.

Rolls, E. T. (1999) The Brain and Emotion. Oxford University Press, Oxford.

Rolls, E. T. (2005) Taste, olfactory, and food texture processing in the brain, and the

control of food intake. Physiology & Behavior 85, 45-56.

Roos, C., Schmitz, J. and Zischler, H. (2004) Primate jumping genes elucidate

strepsirrhine phylogeny. Proceedings of the National Academy of Sciences of the

United States of America 101, 10650–10654.

Rozin, P. and Vollmecke, T. A. (1986) Food likes and dislikes. Annual Review of

Nutrition 6, 433-456.

Salem, A.-H., Ray, D. A., Xing, J., Callinan, P. A., Myers, J. S., Hedges, D. J., Garber, R.

K., Witherspoon, D. J., Jorde, L. B. and Batzer, M. A. (2003) Alu elements and

hominid phylogenetics. Proceedings of the National Academy of Sciences of the

United States of America 100, 12787–12791

Schiffman, S. (1980) Magnitude estimation of amino acids for young and elderly

subjects. In Olfaction and Taste, Vol. 7, Van der Starre, H. ed, pp. 379–383. IRL

Press, London.

Schilling, A., Danilova, V. and Hellekant, G. (2004) Behavioral study in the gray mouse

lemur (Microcebus murinus) using compounds considered sweet by humans.

American Journal of Primatology 62, 43-48.

239 Shedlock, A. M. and Okada, N. (2000) SINE insertions: Powerful toods for molecular

systematics. Bioessays 22, 148-160.

Shi, P. and Zhang, J. (2006) Contrasting modes of evolution between vertebrate sweet/umami

receptor genes and bitter receptor genes Molecular Biology and Evolution 23, 292-300.

Simmen, B. (1991) Stratégies Alimentaires des Primates Néotropiceaux en Fonction de la

Perception des Produits de l'environment. Ph.D. Thesis. Université Paris - XIII,

Villetaneuse.

Simmen, B. (1992) Seuil de discrimination et réponses supraliminaires à des solution de

fructose en function du régime alimentaire des Primates Callithricidae. Comptes

Rendus de l'Académie des Sciences 315, 151-157.

Simmen, B. (1994) Taste discrimination and diet differentiation among New World

primates. In The Digestive System of Mammals: Food, Form, and Function,

Chivers, D. J. and Langer, P. eds, pp. 150-165. Cambridge University Press,

Cambridge.

Simmen, B. and Charlot, S. (2003) A comparison of taste thresholds for sweet and

astringent-tasting compounds in great apes. Comptes Rendus Biologies 326, 449-

445.

Simmen, B., Hladik, A. and Ramasiarisoa, P. (2003) Food intake and dietary overlap in

native Lemur catta and Propithecus verreauxi and introduced Eulemur fulvus at

Berenty, Southern Madagascar International Journal of Primatology 24, 949-968.

Simmen, B., Hladik, A., Ramasiarisoa, P., Iaconelli, S. and Hladik, C. M. (1999) Taste

discrimination in lemurs and other primates, and the relationships to distribution 240 of plant allelochemicals in different habitats of Madagascar. In New Directions in

Lemur Studies, Rakotosamimanana, B., Rasamimanana, H., Ganzhorn, J. U. and

Goodman, S. M. eds, pp. 201-219. Plenum Publishers, New York.

Simmen, B. and Hladik, C. M. (1988) Seasonal variation of taste threshold for sucrose in

a prosimian primate species, Microcebus murinus. Folia Primatologica 51, 152-

157.

Simmen, B. and Hladik, C. M. (1998) Sweet and bitter taste discrimination in primates:

Scaling effects across species. Folia Primatologica 69, 129-138.

Singer, S. S., Schmitz, J., Schwiegk, C. and Zischler, H. (2003) Molecular cladistic

markers in New World monkey phylogeny (Platyrrhini, Primates). Molecular

Phylogenetics and Evolution 26, 490–501.

Smith, C. C. (1977) Feeding behaviour and social organization in howling monkeys. In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 97-126. Academic Press, London.

Smith, D. V. (1971) Taste intenstiy as a function of areas and concentration:

Differentiation between compounds. Journal of Experimental Psychology 87,

163-171.

Smith, R. J. and Jungers, W. L. (1997) Body mass in comparative primatology. Journal

of Human Evolution 32, 523-559.

Steiner, J. E., Glaser, D., Hawilo, M. E. and Berridge, K. C. (2001) Comparative

expression of hedonic impact: affective reactions to taste by human infants and

other primates. Neuroscience and Biobehavioral Reviews 25, 53-74. 241 Sussman, R. W. (1977) Feeding behaviour of Lemur catta and Lemur fulvus. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 1-36. Academic Press, London.

Tan, Y. and Li, W.-H. (1999) Trichromatic vision in prosimians. Nature 402, 36.

Tepper, B. (1998) 6-n-propylthiouracil: A genetic marker for taste with implications for

food preference and dietary habits. American Journal of Human Genetics 63,

1271-1276.

Tepper, B. J. (1999) Does genetic taste sensitivity to PROP influence food preferences

and body weight? Appetite 32, 422.

Tepper, B. J. and Nurse, R. J. (1997) Fat perception is related to PROP taster status.

Physiology & Behavior 61, 494-954.

Tepper, B. J. and Nurse, R. J. (1998) PROP taster status is related to fat perception and

preference. Annals of the New York Academy of Sciences 855, 802-804.

Thompson, D. A., Moskowitz, H. R. and Campbell, R. (1976) Effects of body weight and

food intake on pleasantness ratings for sweet stimuli. Journal of Applied

Psychology 41, 77-83.

Turnbull, B. and Matisoo-Smith, E. (2002) Taste sensitivity to 6-n-propylthiouracil

predicts acceptance of bitter-tasting spinach in 3-6-y-old children. American

Journal of Clinical Nutrition 76, 1101-1105.

Ueno, A., Ueno, Y. and Tomonaga, M. (2004) Facial response to four basic tastes in

newborn rhesus macaques (Macaca mulatta) and chimpanzees (Pan troglodytes).

Behavioural Brain Research 154, 261-271. 242 Ungar, P. S. (1995) Fruit preferences of four sympatric primate species at Ketambe,

Nothern Sumatra, Indonesia. International Journal of Primatology 16, 221-245. van Roosmalen, M. G. M. and Klein, L. L. (1988) The spider monkeys: Genus Ateles. In

Ecology and Behavior of Neotropical Primates, Vol. 2, Mittermeier, R. A.,

Coimbra-Filho, A. F. and da Fonseca, G. A. B. eds, pp. 455-537. World Wildlife

Fund, Washington D.C.

Vanderford, D. (2007) D.V.M., Duke University. Personal communication.

Vasey, N. (2000) Niche Separation in Varecia variegata rubra and Eulemur fulvus

albifrons: I. Interspecific Patterns. American Journal of Physical Anthropology

112, 411-431.

Visalberghi, E., Sabbatini, G., Stammati, M. and Addessi, E. (2003) Preferences towards

novel foods in Cebus apella: The role of nutrients and social influences.

Physiology & Behavior 80, 341-349.

Wheatley (1980) Feeding and ranging of Eastern Bornean Macaca fascicularis. In The

Macaques: Studies in Ecology, Behavior, and Evolution, Lindburg, D. G. ed, pp.

215-246. Van Nostrand Reinhold Co., New York.

Whitten, P. L. (1982) Female Reproductive Strategies Among Ververt Monkeys.

Department of Anthropology, pp. 292. Harvard University, Cambridge.

Witherly, S. A., Pangborn, R. M. and Stern, J. S. (1980) Gustatory responses and eating

duration of obease and lean adults. Appetite 1, 52-63.

Wooding, S., Bufe, B., Grassi, C., Howard, M. T., Stone, A. C., Vazquez, M., Dunn, D.

M., Meyerhof, W., Weiss, R. B. and Bamshad, M. J. (2006) Independent 243 evolution of bitter-taste sensitivity in humans and chimpanzees. Nature 440, 930-

934.

Wrangham, R., Conklin-Brittain, N. L., Chapman, C. A. and Hunt, K. D. (1991) The

significance of fibrous foods for Kibale Forest chimpanzees. Philosophical

Transactions of the Royal Society B: Biological Sciences 334, 171-178.

Wrangham, R. W., Conklin-Brittain, N. L. and Hunt, D. M. (1998) Dietary responses of

chimpanzees and cercopithecines to seasonal variation in fruit abundance. I.

Antifeedants. International Journal of Primatology 19, 949-969.

Wright, P. C. (1985) The costs and benefits of nocturnality for Aotus trivirgatus (the

night monkey). Ph.D. Thesis, pp. 315. City University of New York, New York.

Xing, J., Wanga, H., Hana, K., Raya, D. A., Huanga, C. H., Chemnick, L. G., Stewartc,

C.-B., Disotelld, T. R., Ryderb, O. A. and Batzer, M. A. (2005) A mobile element

based phylogeny of Old World monkeys Molecular Phylogenetics and Evolution

37, 872–880.

Yakinous, C. A. and Guinard, J.-X. (2001) Relation between PROP taster status and fat

perception, touch, and olfaction. Physiology & Behavior 72, 427-437.

Yakinous, C. A. and Guinard, J.-X. (2002) Relation between PROP (6-n-propythiouracil)

tater status, taste anatomy, and dietary intake measure for young men and women.

Appetite 38, 201-209.

Yeager, C. P. (1996) The feeding ecology of the long-tailed macaque (Macaca

fascicularis) in Kalimantan Tengah, Indonesia. International Journal of

Primatology 17, 51-62. 244 Zhou, Q., Wei1, F., Li1, M., Huang and Luo, B. (2006) Diet and Food Choice of

Trachypithecus francoisi in the Nonggang Nature Reserve, China. International

Journal of Primatology 27, 1441-1460.

245 Chapter 3: Sex differences in the density of fungiform papillae

ABSTRACT

Due to gestation and lactation, female mammals have different nutritional needs from males. Females have an acute need to acquire specific nutrients and avoid toxins specifically during fetal and infant development and, therefore, may need to be more discriminating than males when selecting foods to ingest. Accordingly, a highly sensitive gustatory system among females might aid the food selection process. Research on humans supports this claim. On average, human females have greater gustatory sensitivity than males, and this sensitivity has been shown to affect dietary intake. Human gustatory sensitivity is correlated with lingual anatomy. Specifically, among humans there is a positive relationship between sensitivity to numerous compounds and density of lingual fungiform papillae (DFP). The purpose of this chapter is to determine whether there are sex differences in the gustatory anatomy of non-human primates. DFP was investigated in five non-human primate species to test the hypothesis that females have higher DFPs than males, as seen in humans. To test this hypothesis, DFP was measured in Alouatta palliata (n = 14), Cebus apella (n = 12), Cercopithecus aethiops (n = 12), Pan troglodytes (n = 46), and Varecia variegata (n = 18). In all taxa, females had higher DFPs than males. This sex difference was significant only in C. apella and P. troglodytes (Kruskal-Wallis, p < 0.05 and p < 0.01, respectively). Results for C. apella and P. troglodytes were also significant when correcting for body mass. The three genera with significant sex differences in DFP, Cebus, Pan, and Homo, also share large relative brain sizes and life history parameters, such as delayed sexual maturity, that make each offspring highly costly to females. These results support the hypothesis that sex differences in the gustatory system are pronounced in Cebus, Pan, and Homo, because

246 reproduction is particularly taxing, and fetal or infant loss is particularly costly in females of these genera. Consequently, it has been especially beneficial for reproductive females in these genera to gain nutrients and avoid toxins during gestation and lactation.

INTRODUCTION

Sex differences in non-human primate feeding ecology

Gestation and lactation are energetically expensive for female primates (Gittleman and Thompson, 1988; Portman, 1970). Even in species in which males have greater body mass than females, the reproductive costs incurred by females often outweigh the costs of males’ larger mass (Key and Ross, 1999). In addition, appropriate nutrient acquisition and the avoidance of toxins is particularly critical for gestating and lactating females (Flaxman and Sherman, 2000; Gaulin and Konner, 1977). Females can fill their dietary requirements through greater food intake and by ingesting higher quality foods compared with males. Females in several primate species have been shown to spend more time feeding than do males (Table 3.1) (Boinski, 1988; Chivers, 1977; Dunbar, 1977; Isbell, 1998; McCabe and Fedigan, 2005; O'Brien and Kinnaird, 1997; Overdorff, 1993; Pollock, 1977; Smith, 1977). Female primates have also been shown to feed on more sugar- or protein-rich foods (Table 3.1) (Boinski, 1988; Byrne et al., 1993; Clutton-Brock, 1977; Cords, 1986; Gautier-Hion, 1980; Isbell, 1998; McCabe and Fedigan, 2005; Morland, 1991; O'Brien and Kinnaird, 1997; Overdorff, 1993; Pollock, 1977; Rodman, 1977; Wasser; Whitten, 1983). Moreover, many of the dietary sex differences identified among primates are more pronounced when females are pregnant or lactating (Boinski, 1988; Cords, 1986; Gautier-Hion, 1980; McCabe and Fedigan, 2005; Overdorff, 1993; Whitten, 1983). 247 Primates must be selective while obtaining food resources, especially when ingesting high-protein foods. Amino acids are essential nutrients for reproduction (Brosnan, 1985; National Academy of Sciences, 1990; Sampson and Jansen, 1990), but some sources of protein, such as insects and leaves, are also potential sources of toxins. Insects may contain toxins composing up to 20% of their body weight (Janson and Chapman, 1999; Schmidt, 1979). Leaves also typically contain secondary compounds that can inhibit digestion (Glander, 1982; Janson and Chapman, 1999; Lambert, 1998; Milton, 1980). While many primate studies focus on the digestion inhibiting effects of tannins (Carrai et al., 2003; Iaconelli and Simmen, 2002; Remis, 2006; Remis and Kerr, 2002; Simmen and Charlot, 2003; Takemoto, 2003; Wrangham and Waterman, 1981), other secondary compounds can have a profound effect on reproductive hormones. Estrogens and androgens are steroid hormones that are essential to mammalian reproduction (Nelson, 2000). Some plants produce steroid hormones that do not affect their own asexual reproduction, but can disrupt vertebrate reproduction even at low levels (Labov, 1977; Wynne-Edwards, 2001). In fact, Wynne-Edwards (2001) argues that reproductive impairment is likely to be a particularly effective herbivore-deterring strategy for plants because hormone disruptors are low-cost and would reduce local populations of herbivores. Accordingly, females in particular should benefit from high taste sensitivity in order to avoid secondary compounds that might inhibit their reproduction.

248 Table 3.1: Sex differences in the feeding behavior of non-human primates

Species Reference Notes

Females spend more time feeding

Alouatta palliata (Smith, 1977) Compared with females without infants

(McCabe and More time foraging during lactation (McCabe and Cebus capuchinus Fedigan, 2005; Rose, Fedigan, 2005); Less time foraging during 1994) pregnancy and lactation (Rose, 1994) (Fragaszy, 1986; Cebus olivaceus Fragaszy and Boinski, Females thought to be less efficient than males. 1995) Erythrocebus patas (Isbell, 1998) pyrrhonotus

Eulemur fulvus rufus (Overdorff, 1993) During lactation

Indri indri (Pollock, 1977)

(O'Brien and Macaca nigra Kinnaird, 1997)

Pan troglodytes (Teleki, 1977)

Saimiri oerstedi (Boinski, 1988)

Symphalangus (Chivers, 1977) syndactylus

Females consumed almost twice as much food for Theropithecus gelada (Dunbar, 1977) their weight compared to males.

Females have greater dietary diversity

Cebus olivaceus (Fragaszy, 1986)

Eulemur fulvus rufus (Overdorff, 1993) During lactation

Hapalemur griseus (Grassi, 2002)

249 (Table 3.1 continued) Females eat more fruit and flowers (or flower nectar) than males†(more sugars ingested) (McCabe and Lactating females ingested more fruit than cycling Cebus capuchinus Fedigan, 2005) females during the wet season.

Higher-ranking females ate more preferred flowers Cercopithecus aethiops (Whitten, 1983) during pregnancy and lactation.

Erythrocebus patas Females ate more swollen thorns (very sweet) and (Isbell, 1998) pyrrhonotus fruit.

Eulemur fulvus rufus (Overdorff, 1993) Females ate more flower nectar during lactation.

Eulemur rubriventer (Overdorff, 1993) Females ate more flower nectar during gestation.

Indri indri (Pollock, 1977) Females ate more fruit of some species.

(O’Brien and Macaca nigra Females ate more fruit. Kinnaird, 1997)

Pongo pygmaeus (Rodman, 1977) Females ate more fruit and less bark than male.

Reproductive females foraged for fruit and flowers Saimiri oerstedi (Boinski, 1988) more frequently than non-reproductive females.

Varecia variegata (Morland, 1991) Females spent more time feeding on nectar. variegata

Females eat more insects or arthropods and/or leaves† (more protein ingested)

Females spent less time feeding on fruit and more Cercocebus albigena (Wasser, 1977) time feeding on insects.

Females ate more leaves and insects compared with Cercopithecus ascanius, (Cords, 1986) males. Pregnant and lactating females ate less fruit C. mitis and more insects than non-reproductive females.

Cercopithecus nictitans, Females ate more leaves and arthropods, especially C. pogonias, (Gautier-Hion, 1980) when abundant during pregnancy and early C. cephus lactation.

Colobus badius (Clutton-Brock, 1977) Females ate less fruit and more leaves.

250 (Table 3.1 continued) Erythrocebus patas (Isbell, 1998) Females ate more leaves. pyrrhonotus

Eulemur fulvus rufus (Overdorff, 1993) Females ate more insects during lactation.

Eulemur rubriventer (Overdorff, 1993) Females ate more insects during gestation.

Indri indri (Pollock, 1977) Females ate more young leaves.

Females ate fewer underground storage organs and Papio ursinus (Byrne et al., 1993) more leaves.

Saimiri oerstedi (Boinski, 1988) Females ate more arthropods.

Males spend more time feeding Lactating females fed less than non-lactating Cercopithecus sabaeus (Harrison, 1983) females.

(Fossey and Harcourt, Silverback males spent most time eating and ate Gorilla gorilla beringei 1977) more thistles.

(Knott, 1998; Pongo pygmaeus During masting (Knott 1998) Rodman, 1977)

No sex differences in diet (Pavelka and Knopff, Alouatta pigra 2004) Callicebus torquatus (Kinzey, 1977)

Colobus polykomos (Dasilva, 1992)

Presbytis entellus (Newton, 1992)

Propithecus diadema (Hemingway, 1999) edwardsi Symphalangus (Chivers, 1977) syndactylus

Varecia variegata (Morland, 1991) variegata †Studies in which females ate more fruit and more insects / leaves are listed in both categories.

251 Sex differences in the human gustatory system

The sensory systems of primates have evolved, in part, for the identification of foods appropriate for ingestion (Dominy et al., 2001). The function of the gustatory system in particular is to determine the chemical contents of food items. Thus, the sense of taste is a crucial sense used in the process of food selection. Given that food selection may be more critical for the reproductive success of primate females than for the reproductive success of males (Altmann, 1980; Gaulin and Konner, 1977; van Noordwijk and van Schaik, 1999; Whitten, 1983), there is reason to believe that greater discriminatory ability when foraging (i.e. a more sensitive gustatory system) would be especially beneficial for female primates. Among non-human primates, comparative data are not available to test for sex differences in gustatory sensitivity, in part because sample sizes of psychophysical studies are usually too small. However, data from research on humans supports the idea that females may benefit from higher gustatory sensitivity. Research on humans has shown sex differences in taste sensitivity. For instance, among the Mvae and Yassa of south Cameron, women were found to be significantly more sensitive to glucose than men (Hladik and Simmen, 1996). Research on the bitter- tasting compounds phenylthiocarbomide (PTC) and 6-n-proptlthiourracil (PROP) has shown a sex difference in taste sensitivity as well. PTC and PROP sensitivity are highly correlated (Barnicot et al., 1951; Chang et al., 2006; Scott et al., 1998; Tepper, 1998) and genetically determined (Bufe et al., 2005; Kim et al., 2003). The ability to detect PTC/PROP is polymorphic. Zero to 66.7 percent of populations worldwide are unable to taste PTC/PROP at low concentrations (i.e., “non-tasters”) (Guo and Reed, 2001). On the other hand, some “taster” individuals are highly sensitive to PTC/PROP. Twenty-one percent of Americans tested and 29% of those tested in France are high-sensitivity

252 PTC/PROP tasters (Bartoshuk et al., 1994; Pasquet et al., 2002). Notably, some studies have shown that significantly more women are high-sensitivity tasters than men (Bartoshuk et al., 1994; Lucchina et al., 1998; Whissell-Beuchy, 1990). Studies have linked taste sensitivities for PTC and PROP with taste sensitivities to sucrose, quinine, caffeine, salt, astringency, and fat (Bartoshuk, 2000; Bartoshuk et al., 1998; Drewnowski et al., 1998; Drewnowski et al., 1997; Duffy and Bartoshuk, 2000; Duffy et al., 2004; Gent and Bartoshuk, 1983; Hall et al., 1975; Leach and Noble, 1986; Looy and Weingarten, 1992; Miller and Reedy, 1990b; Pasquet et al., 2002; Pickering et al., 2004; Tepper and Nurse, 1997). In addition, PTC/PROP sensitivity has been associated with food preferences and dietary intake. For example, PROP tasters rate cruciferous and green leafy vegetables (asparagus, broccoli, Brussels sprouts, cabbage, kale, and spinach) as more bitter than do non-tasters (Drewnowski et al., 1999; Kaminski et al., 2000). As a result of their bitter taste sensitivity, tasters have a lower preference for these foods and, therefore, consume them less frequently than PROP non-tasters do (Dinehart et al., 2006; Drewnowski et al., 2000; Kaminski et al., 2000). Together, these studies suggest that there is a trend for women to have greater taste sensitivity compared with men, and that their heightened sensitivity leads to differences in the foods women select to eat. Plausibly, the health and reproductive benefits that have selected for this sex difference (Duffy et al., 1998) might also have selected for sex differences in the gustatory systems of non-human primates.

Lingual anatomy: Density of fungiform papillae and taste sensitivity

Taste receptors are located within taste buds. On the tongue, taste buds are found in the epithelia of papillae (Buck, 2000). There are three types of papillae on the superior

253 surface of the primate tongue that contain taste buds; foliate, circumvallate, and fungiform (Figure 3.1). Foliate and circumvallate papillae are located only on the posterior third, whereas fungiform papillae are located across the entire surface of the tongue. Therefore, fungiform papillae are the only structures on the anterior two-thirds of the tongue that contain taste buds and are the first gustatory structures to come in contact with food items entering the mouth (Buck, 2000; Purves et al., 1997). Because of their anterior location, fungiform papillae are of primary importance in food selection and their density is an important indication of gustatory sensitivity (Bartoshuk et al., 1994; Doty et al., 2001; Essick et al., 2003; Miller and Reedy, 1990b; Reedy et al., 1993; Tepper and Nurse, 1997; Yakinous and Guinard, 2002). The anatomical position of fungiform papillae also makes them easily accessible by researchers and they have been the focus of many psychophysical and electrophysiological studies of human taste (Arvidson and Friberg, 1980). Research on humans has shown that individuals with a higher density of fungiform papillae (DFP) also have a higher density of taste buds with their associated receptor cells (Miller and Reedy, 1990b; Reedy et al., 1993). The taste buds of fungiform papillae contain receptors for a spectrum of compounds found in food, including those that are sweet and bitter tasting (Adler et al., 2000; Nelson et al., 2001). As a result, human DFP is positively correlated with taste sensitivity to numerous compounds including sweet tasting fructose and sucrose and bitter tasting quinine and caffeine (Bartoshuk et al., 1994; Doty et al., 2001; Essick et al., 2003; Miller and Reedy, 1990b; Reedy et al., 1993; Tepper and Nurse, 1997; Yakinous and Guinard, 2002). Like sensitivity to PTC/PROP, on average, females also have higher DFPs and greater variation in DFP than do males (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Tepper and Nurse, 1997). For instance, Tepper and Nurse (1997), found that women had an average of 66.6 FP/cm2 while men had 55.6 FP/cm2 (F[1, 74] = 25.5, p < 0.0001). 254 Papillae are formed early in gestation and remain intact throughout life (Janjua and Schwartz, 1997; Mistretta, 1991). Thus, despite the fact that the correlation between DFP and taste sensitivity is not perfect, DFP is the most accurate measure of genetically determined taste ability aside from genotyping (Bartoshuk, 2000; Janjua and Schwartz, 1997; Mistretta, 1991). Accordingly, DFP is considered a non-invasive proxy for gustatory sensitivity (Hayes et al., in press).

Figure 3.1: Lingual gustatory papillae and taste buds. Illustration after (Fain, 2003).

255 Hormonal variation and taste sensitivity

Hormonal variation may affect gustatory sensitivity and be a contributing factor in sex differences in human taste ability. Very few studies have investigated the relationship between hormones and taste perception, but variation in taste sensitivity over the menstrual cycle, called taste cycling, has been observed (Etter, 1999). Taste sensitivity also changes across pregnancy. Although hormonal data were not collected, in a study by Duffy and colleagues (1998) 46 women rated intensity and preference for

NaCl, sucrose, citric acid, and quinine hydrochloride (QHCl) over the course of their pregnancy. Intensity ratings for bitter tasting QHCl rose between pre-pregnancy and the first trimester and then declined during the second and third trimester. Conversely, intensity ratings for sweet tasting sucrose did not change over the course of the pregnancies (Duffy et al., 1998). The authors hypothesize that increased bitter taste sensitivity in the first trimester may serve to support healthy pregnancies by helping women to avoid toxins during a critical phase of fetal development. On the other hand, high sweet taste intensity may encourage sustained caloric intake to meet the needs of the growing fetus (Duffy et al., 1998). Currently, the mechanism that allows for changes in gustatory sensitivity over menstrual cycles and pregnancy are unknown. Fungiform papillae are stable structures, remaining consistent over time (Janjua and Schwartz, 1997; Mistretta, 1991). Accordingly, changes in female taste sensitivity occur while DFP remains consistent (Duffy and Bartoshuk, 2000). Variation in taste sensitivity within an individual might be the result of changes in the number of taste buds, or access to them, as hormonal levels fluctuate (Prutkin et al., 2000), but this hypothesis remains to be tested.

256 OBJECTIVE AND HYPOTHESIS

Research on humans has shown that individuals with the highest density of fungiform papillae and highest taste sensitivity are most often women (Bartoshuk et al., 1994). Higher gustatory sensitivity may be adaptive for women in order to maintain healthy pregnancies and avoid harmful chemicals (Duffy et al., 1998). The purpose of this chapter is to determine whether non-human primates resemble humans in showing sex differences in lingual anatomy. Following established research on humans, intersexual differences in gustatory anatomy will be assessed by measuring the density of lingual fungiform papillae in five non-human primate species. It is expected that non- human primate females will have higher DFPs than males.

METHODS

Sample

Density of fungiform papillae was determined for five non-human primate species. Data were collected on at least 12 individuals, with a minimum of four individuals of each sex (Table 3.2). Species include Alouatta palliata (n = 14), Cebus apella (n = 12), Cercopithecus aethiops (n = 18), Pan tryglodytes (n = 46), and Varecia variegata (n = 18). Body mass data were collected for each individual. DFP data for humans are from Bartoshuk et al. (1994). Data collection was conducted on live animals in captive facilities and in the wild, and on postmortem samples (Table 3.2). Data on Alouatta palliata, Cercopithecus aethiops, and Varecia variegata were collected in wild populations at La Pacifica in Costa Rica, Pretoria in South Africa, and Ranomafana National Park in Madagascar, respectively. Pan troglodytes were studied at the Southwest Foundation for Biomedical

257 Research in San Antonio, Texas. Cebus apella tongues were cadaveric samples that were preserved in 10% buffered formalin immediately after euthanasia in a captive facility. No animals were euthanized for the purpose of this study. Samples were obtained from animals scheduled to be euthanized for other purposes.

Table 3.2: Sample: Species studied and sample sizes

Taxonomic Species N Location Group M: 5 Alouatta palliata Platyrrhine La Pacifica, Costa Rica F: 9 M: 8 Cebus apella Platyrrhine Captive (cadaveric) F: 4 M: 4 Cercopithecus aethiops Catarrhine Pretoria, South Africa F: 8 M: 24 Pan troglodytes Catarrhine Captive (live) F: 22 M: 10 Ranomafana Nat’l Park, Varecia variegata Strepsirrhine F: 8 Madagascar

Capture and anesthetization procedures

IACUC protocols were obtained from the University of Texas at Austin and the Southwest Foundation for Biomedical Research. At the Southwest Foundation, capture and anesthetization were conducted by the staff and veterinarians and followed a pre- established procedural protocol determined by that facility. In all locations the reflexes, temperature, pulse, and respiratory rate of the animals were monitored during anesthesia.

258 Animal capture in Costa Rica and Madagascar followed the procedure described in Glander, et al. (1991) using a Pneu-Dart™ system (Pneu-Dart™ Inc, HC 31, Williamsport, PA 17701). This system employs disposable non-barbed darts with a 3/8- inch needle delivered by a carbon dioxide powered gun. The animals were caught in large nets under the capture location. The darts were loaded with Telazol® at a dosage of 25 mg per kg (Glander et al., 1991). In Madagascar, all sedation and vital signs were monitored by Felicia Knightly, D.V.M. No veterinarians were present in Costa Rica. In South Africa, animal capture followed the protocol described in Brett et al. (1982). Animals were first trapped and then sedated with a combination of Zoletil® and Dormitor® by weight. Traps were constructed using a wood frame measuring one meter squared by 15cm high, with 2.5cm wire mesh attached to one side (Figure 3.4). Animals were baited with corncobs attached to a trip wire (Brett et al., 1982). All sedation and vital signs were overseen by Magali Jacquier, D.V.M.

Figure 3.4: Trap used for Cercopithecus aethiops in Pretoria, South Africa.

259 Calculating the density of fungiform papillae

The methods for identifying and counting fungiform papillae followed the procedural protocol established for cadavers by Miller and Reedy (1990) (Miller and Reedy, 1990a). In live, sedated animals, plastic tubing was placed between the maxillary and mandibular canines to prop open the mouth. The tongue was pulled forward with either gauze or surgical forceps and wiped clean with gauze. 0.5% methylene blue biological stain (Fischer Scientific) was applied to the superior surface of the tongue using a pipette. Unabsorbed methylene blue was wiped off with Kim Wipes® (Fischer

Scientific). Methylene blue adheres to all papillae except fungiform, permitting visual identification of this papilla type (Figure 3.2). Histological verification in rabbits has found this method to provide accurate identification of fungiform papillae (Miller and Reedy, 1990a). After dyeing, a high-resolution digital photograph was taken of the tongue at high magnification, using the macro function of a Canon A80. A scale was included in each image for size reference. Papillae were counted manually using Adobe Photoshop® software. A 0.5cm line was drawn on the scale in each image. This 0.5cm line was then moved to the medial line of the tongue so that the line began at the anterior- most point at the tip of the tongue and measured 0.5cm back. Next, a square was drawn starting at the posterior edge (top) of the 0.5cm line. The left vertical edge of the square was aligned along the vertical 0.5cm line, providing a right angle from the vertical line. The horizontal (top) edge of the square, placed 0.5cm from the tip of the tongue, provided a guide to draw a horizontal line across the right side of the tongue exactly 0.5cm posterior to the tip. This procedure, using the square as a right angle to the 0.5cm vertical line, was repeated on the left side of the tongue. Once a continuous horizontal line was drawn across the tongue 0.5cm posterior to the tip, the vertical 0.5cm line was removed so that it did not obscure visual access to the FP underneath. Subsequently, all FP anterior 260 to the horizontal line were counted. Each counted papilla was marked with a colored dot in order to avoid counting any papilla more than once. NIH ImageJ® software was used to determine the area of the anterior 0.5cm of the tongue and the density of papillae per square centimeter was calculated.

Figure 3.2: Stained cadaveric tongue of Macaca mulatta. The dark area is comprised of filiform papillae and has been dyed with methelyne blue biological stain. Light spots are fungiform papillae and do not absorb the stain.

261

Figure 3.3: Tongue of captive Pan troglodytes. Papillae were counted on the anterior 0.5cm of the tongue. Numbers in light grey (67) denotes the number of FP on each side the 0.5cm area. The dark grey line shows the area in which FP were counted.

The effects and safety of methylene blue biological stain

0.5% methylene blue in ethanol is non-toxic and has been used repeatedly on live human subjects without side effects (Bartoshuk et al., 1994; Miller and Reedy, 1990a; Miller and Reedy, 1990b). In small mammals, methylene blue is frequently used intravenously as an antidote for methemoglobinemia at a dosage of 1.5 mg per kilogram body weight. It is considered safe at this dose, even for cats, which are known to be highly sensitive to its toxic effects. The concentration of 0.5% used in this protocol contains 5mg per mL of the active reagent. The drops applied were wiped off the tongue

262 immediately after application, so the amount available for absorption was miniscule and well below accepted therapeutic levels in other species (Vanderford, 2007).

Statistical analysis

Data were analyzed using SAS JMP software version 5.0.1.2. Data for several of the species were not normally distributed. Therefore, non-parametric tests were used in all analyses. To test for an association between DFP and body mass, a Spearman’s rank correlation test was used. To test for intraspecific sex differences in DFP, a Wilcoxon rank sum test was used. Statistical tests were considered significant when p ≤ 0.05. In addition, Cohen’s d was calculated for each species to test for effect sizes. Conceptually, a small effect size is a phenomenon not readily noticeable, requiring a large quantity of data consistently showing the effect before the phenomenon could be demonstrated statistically. A large effect size is a phenomenon that would be easily noticed, and few data would be necessary to demonstrate the phenomenon statistically (Cohen, 1988). Cohen’s d is the difference between the group means divided by the average standard deviation between the groups. When the groups being compared are different sample sizes, it is necessary to weight the standard deviations by the group sizes. This weighted value is this is called the pooled standard deviation. Pooled s = √[ ( (N1-1)*var1 + (N2- 1)*var2 ) / (N1 + N2 - 2) ], where N1 is the sample size of the first group, N2 is the sample size of the second group, var1 is the variance (standard deviation squared) of the first group, and var2 is the variance of the second group. Effect sizes range from minus to plus infinity, with zero indicating no effect. General guidelines for interpreting Cohen’s d are to consider an effect of 0.2 as small, 0.5 as medium, and 0.8 as large (Cohen, 1988).

263 When testing for anatomical sex differences, sexual dimorphism may be a confounding variable. If females are significantly smaller within a species and also have smaller tongues, this could influence DFP. For example, if females and males have the same number of fungiform papillae, but females have smaller tongues, FP density would be higher in females as a result of differences in body mass. Table 3.3 shows the sexual dimorphism ratio for each species calculated from the data collected in this study and from data collected in the wild and reported in Smith and Jungers (1997). Sexual dimorphism ratio was calculated by dividing the average male body mass by the average female body mass. In P. troglodytes there was a substantial difference between the sexual dimorphism ratio calculated from the data collected for this analysis and the ratio calculated from data in the literature. There was almost no body mass sexual dimorphism among the chimpanzees in this study (sexual dimorphism ratio = 0.98), whereas data collected in the wild show substantial sexual dimorphism (sexual dimorphism ratio = 1.30). This difference between the two ratios may be the result of obesity among females in the captive population where data were collected. To address the potential influence of body mass (and therefore sexual dimorphism), tests were conducted using two different values for papillae density: DFP, and the ratio of DFP and the cube root of body mass (DFP ratio). In light of the discrepancy between the captive and free-ranging sexual dimorphism ratios in Pan, DFP data for this species were also analyzed using a ratio of DFP divided by the cube root of body mass where the body mass data were from the literature (i.e. all male body masses were the same and all female body masses were the same). Since body mass data were not reported in publications of human DFP data, H. sapiens were not included in analyses of DFP ratio.

264 Table 3.3: Body mass sexual dimorphism. Sexual dimorphism ratio Species (From literature) † Sample type A. palliata 1.22 (1.34) Wild caught C. apella 1.44 (1.45) Captive (cadaveric) C. aethiops 1.39 (1.43) Wild caught P. troglodytes 0.98 (1.30) Captive (live) V. variegata 0.88 (1.03) Wild caught †Sexual dimorphism ratio is male body mass divided by female body mass. Number in parentheses was calculated from data on free-ranging individuals and reported in Smith and Jungers (1997).

RESULTS

Sex differences in DFP

Within all five non-human primate species, females had higher DFPs than males (Table 3.4, Figures 3.5 and 3.6). Wilcoxon rank sum tests showed that sex differences within species were significant in C. apella (z = 1.95, p = 0.05) and P. troglodytes (z = 2.69, p < 0.01). Sex differences in DFP were not significant for A. palliata (z = -1.60, ns), C. aethiops (z = -0.59, ns), or V. variegata (z = 0.22, ns). Several species tested here had small sample sizes (n = 12 – 18). As a result, some of the negative results shown here may be due to Type II error (Jennions and Moller, 2003). Although post hoc power analyses are not recommended, another measure of significance is to assess effect size (Lenth, 2001). Analyses of effect size were accomplished by calculating Cohen’s d. Cohen (1988) suggested guidelines for interpreting d in which 0.20 is a small effect, 0.50 is a medium effect, and 0.80 is a large effect (Cohen, 1988). In operational terms, a small effect is not obvious and would

265 require a large sample in order to detect it, whereas a large effect is clear with just a few samples. The results for Cohen’s d are presented in Table 3.4. The results for Cohen’s d show that Pan and Cebus have d-values above 0.80 (d = 0.88 and 1.47, respectively). The effect size for Alouatta is also large (d = 0.75), whereas the effect size for Cercopithecus is small to medium (d = 0.36), and for Varecia is quite low (d = 0.12). These post hoc analyses suggest that is it possible that there is a sex difference in the DFP of Alouatta, which might be detected given a larger sample size. Varecia, on the other hand, clearly lack a sex difference in DFP.

Table 3.4: Results of Wilcoxon rank sum tests for sex differences in DFP. DFP ratio is DFP divided by the cube root of body mass.

DFP ratio Effect size Species DFP DFP results results (Cohen’s d) A. palliata M: 18.64 ± 7.56 z = -1.60 z = -1.60 0.75 F: 25.13 ± 9.19 p = 0.11 p = 0.11 C. apella M: 75.32 ± 20.71 z = 1.95 z = 2.12 1.47 F: 104.75 ± 18.49 p = 0.05 p = 0.03 C. aethiops M: 114.10 ± 34.83 z = -0.59 z = -1.10 0.36 F: 128.27 ± 41.40 p = 0.55 p = 0.27 P. troglodytes M: 45.61 ± 12.70 z = 2.69 *z = 2.74 0.88 F: 55.25 ± 8.72 p < 0.01 p < 0.01 V. variegata M: 58.60 ± 12.50 z = 0.22 z = 0.04 0.12 F: 60.35 ± 17.51 p = 0.82 p = 0.96 *The sex difference in DFP ratio was also significant for P. troglodytes when body mass data from free-ranging animals were used to calculate the ratio (z = 3.46, p < 0.001). P values in bold are statistically significant.

266 180

160

140

120 * ) 2 100

(FP/cm 80

DFP ** 60

40

20

0 A. palliata C. apella C. aethiops P. troglodytes V. variegata H. sapiens Females Males

Figure 3.5: Histogram of sex differences in the density of fungiform papillae. Data are not corrected for body mass. * p < 0.05, ** p < 0.01 for Wilcoxon rank sum test results. Data for humans are estimated from Figure 6 in Bartoshuk et al., (1994).

267 *

Figure 3.6: Distributions of DFPs for females (open circles) and males (solid squares) in all five non-human primate species. Wilcoxon rank sum * p < 0.05, ** p < 0.01.

268 *

269 Sex differences in DFP Ratio

In order to take body mass into account, DFP ratios were also analyzed (DFP/3√body mass). Spearman’s rank correlation tests showed that body mass was not correlated with DFP in any of the five species (A. palliata rs = -0.28, ns; C. apella rs = -

0.40 ns; C. aethiops rs = -0.23, ns; P. troglodytes rs = -0.10, ns; V. variegata rs = -0.03, ns). Females had had higher DFP ratios compared with males, with the exception of Varecia (Figure 3.7; Varecia DFP ratio, males = 38.17 ± 8.10, females = 37.94 ± 11.84).

Again, a Wilcoxon rank sum test showed that the sex differences in DFP ratio were only statistically significant in C. apella and P. troglodytes (C. apella z = 2.12, p < 0.05, P. troglodytes z = 2.74, p < 0.01) (Table 3.4, Figure 3.7). Sex differences in DFP ratio were not significant in A. palliata, C. aethiops, or, V. variegata (A.palliata z = -1.60, ns; C. aethiops z = -1.10, ns, V. variegata z = 0.04, ns) (Table 3.4, Figure 3.7). In P. troglodytes, there was a notable difference between the sexual dimorphism ratio calculated from body mass data collected on the individuals in this dataset and the sexual dimorphism ratio calculated from body mass data on free-ranging animals (Table 3.3). Accordingly, sex differences in DFP ratio were also tested using the same formula (DFP/3√body mass), where body mass data from free-ranging individuals were used (Smith and Jungers, 1997). The body masses were the same for all males (57.9 kg) and all females (45.8 kg). Using wild-caught body mass data, there was also a significant sex difference in DFP ratio for P. troglodytes (z = 3.46, p < 0.001).

270

120

100

80 **

60 Body Mass ! 3 /

40 DFP

20 **

0 A. palliata C. apella C. aethiops P. troglodytes V. variegata

Females Male

Figure 3.7: Histogram of sex differences in DFP ratio. Wilcoxon rank sum test ** p < 0.01

DISCUSSION

Sex differences in DFP and sexual size dimorphism

In all five non-human primate species tested, a sex difference in lingual anatomy was observed in the expected direction, in which females had higher densities of fungiform papillae than males. This relationship was significant for Cebus and Pan (Figures 3.5 and 3.6, Table 3.4). Given the relationship between DFP and taste sensitivity

271 in humans (Bartoshuk et al., 1994; Doty et al., 2001; Essick et al., 2003; Miller and Reedy, 1990b; Reedy et al., 1993; Tepper and Nurse, 1997; Yakinous and Guinard, 2002), these results indicate that, on average, females have more sensitive gustatory systems than do males in four of the five non-human primate species tested. Moreover, these data suggest that, like human females, capuchins and chimpanzees have significantly more sensitive gustatory systems than males of their species. Body mass was not significantly correlated with DFP in any of the five species. However, to account for the potential influence of sexual size dimorphism, DFP ratio was also analyzed for sex differences. Again, in the four haplorhine species, DFP ratio was higher in females, although this was not the case for Varecia. Wilcoxon signed rank tests were only significant for Cebus and Pan (Figure 3.7, Table 3.4). Notably, Varecia was the only species with virtually no sexual dimorphism in wild populations (Table 3.3). Even if females did have higher papillae densities as the result of having a smaller tongue area compared with males, that density should still be associated with higher taste sensitivity, as is seen in humans (Bartoshuk et al., 1994; Doty et al., 2001; Essick et al., 2003; Miller and Reedy, 1990b; Reedy et al., 1993; Tepper and Nurse, 1997; Yakinous and Guinard, 2002). Accordingly, a functional sex difference in the gustatory system is likely to exist whether that difference results from a greater number of papillae, a smaller tongue area, or both.

Cebus - Pan convergence

Life history and reproductive cost

Although these results should be interpreted with caution due to the limited number of species tested, females in all five non-human primate species had, on average,

272 higher densities of papillae than did males. However, these intersexual differences were only significant in Pan and Cebus. Tests of effect size showed that larger sample sizes may have revealed a significant sex difference in the DFP of Alouatta (Table 3.4). Still, if reproductive demands are associated with the need to select higher quality foods, the results shown here suggest that reproductive demands may be higher for Cebus, Pan, and Homo, than for Cercopithecus, Alouatta, and Varecia. In fact, Cebus, Pan, and Homo share a suite of life history characteristics that are associated with especially large relative brain sizes (Chalmeau et al., 1997; Gibson, 1986; Stephan et al., 1988). Brain tissue is expensive, requiring more than 22 times the amount of metabolic energy compared with an equivalent unit of muscle tissue (Aiello, 1997; Aiello and Wheeler, 1995; Aschoff et al., 1971; Gibson, 1986). Significant intraspecific sex differences in the DFPs of Cebus, Pan, and Homo may be related to both the high costs of large relative brains and concomitant slow reproduction. Large relative brain size is associated with life history parameters such as long periods of infant and juvenile dependency, which lead to a very high cost per offspring (Fragaszy and Bard, 1997; Ross, 2002; Van Schaik and Deaner, 2003; Walker et al., 2006). Capuchin, chimpanzee, and human females invest a great deal in each offspring. Capuchin females can live over 40 years in captivity (age estimates are not available for the wild) (Fragaszy et al., 2004), but may not give birth until 7 years of age and then produce offspring approximately every two years (Di Bitetti and Janson, 2001; Fragaszy et al., 2004). Chimpanzees are a more extreme example of a k-selected species (Ghiglieri, 1984). Females in the wild may live to be over 40 years of age, but do not reach sexual maturity until 10 to 11 years of age. Furthermore, it may take up to three years after maturity for females to give birth (Ghiglieri, 1984; Goodall, 1986). After their first infant, female chimpanzees give birth only every five to seven years (Ghiglieri, 1984; Goodall, 1986) and lifetime reproductive 273 output may be as low as 3.85 offspring on average (Nishida et al., 2003). Moreover, chimpanzee females (along with other great apes) have lower fertility than human females (Kaplan et al., 2000). The average female in a human hunter-gatherer society begins reproduction at 19.7 years of age and stops reproducing at approximately age 39 (Kaplan et al., 2000). With interbirth intervals around 3.44 years (Kaplan et al., 2000), human females have an average of 5.61 offspring compared with 3.85 for chimpanzees (Nishida et al., 2003). On the other hand, Alouatta, Cercopithecus, and Varecia, are all more r-selected than Cebus, Pan, or Homo. The three species that did not show a significant sex difference in DFP all reproduce at an earlier age and have shorter interbirth intervals. Cercopithecus aethiops, for instance, reproduces at 3.5 to five years of age and gives birth annually (Kappeler and Pereira, 2002). Similarly, age at first reproduction for Alouatta palliata is 3.58 to 3.99 years with an interbirth interval of 1.66 years (Kappeler and Pereira, 2002). The most r-selected species in this dataset is Varecia variegata. The age at first reproduction in this species is 1.42 years with an interbirth interval of one year, although mortality rates can be high (Kappeler and Pereira, 2002; Morland, 1992). In addition, Varecia are one of the few primates that give birth to litters, with a modal litter size of two infants (Kappeler and Pereira, 2002; Morland, 1992). Concomitantly, Varecia show virtually no difference between male and female DFPs (Table 3.3). Thus, within this dataset Cebus, Pan, and Homo are unique in having significant sex differences in DFP and being extremely k-selected. With each offspring comprising such a large proportion of the lifetime reproductive output of a female, it may be particularly critical for females in these three genera to procure high-quality resources and to avoid over-ingesting toxins found in leaves and insects. In comparison with other primates it may have benefited Cebus, Pan, and Homo females to have a high DFP which 274 confers high taste sensitivity. As a result, these females may have the ability to detect necessary nutrients or secondary compounds that can be harmful to a growing fetus (Flaxman and Sherman, 2000).

Sex differences in feeding behavior

In addition to life history parameters, there has been a great deal of focus on convergences in the behavioral ecology of Pan and Cebus as well. Both Pan and Cebus show similarities in cognition, tool use, the presence of culture, complex social behaviors such as cooperation, and non-reproductive sexual behavior (cognition Anderson, 1996; tool use Goodall, 1963; McGrew and Marchant, 1997; Ottoni and Mannu, 2003; Visalberghi et al., 1995; culture Caldwell and Whiten, 2007; Whiten and van Schaik, 2007; cooperation Boesch, 2003; Chalmeau et al., 1997; de Waal, 1989; Hattori et al., 2005; Perry, 2003; sexual behavior Manson et al., 1997). Furthermore, Pan and Cebus also show convergence in their feeding behavior. Like many primate species, chimpanzees and capuchins are omnivorous (Fragaszy et al., 2004; Freese and Oppenheimer, 1981; Galetti and Pedroni, 1994; Ghiglieri, 1984; Matsumoto-Odaa and Hayashib, 1999; Nishida and Uehara, 1983; Takemoto, 2003; Teleki, 1981; Wrangham et al., 1998). Unique to these genera are feeding behaviors that include group predation and relatively high rates of extractive foraging (Beosch and Boesch, 1989; Boesch and Boesch, 1990; Fedigan, 1993; Fragaszy, 1986; Fragaszy and Boinski, 1995; Fragaszy et al., 2004; Goodall, 1963, 1968; Goodall, 1986; McGrew, 1979; Nishida and Uehara, 1983; Perry and Rose, 1994; Rose, 1994, 1997; Standford, 1998; Teleki, 1973; Wrangham and van Zinnicq Bergmann Riss, 1990; Wrangham, 2003). Pan and Cebus are the only two non-human primate genera known to systematically prey on relatively large

275 vertebrates (Rose, 1997). Vertebrate predation is well established for chimpanzees, which are reported to prey on at least 25 mammalian species, including bushbucks, bushpigs, and numerous primate species (Beosch and Boesch, 1989; Goodall, 1963; Goodall, 1986; Nishida and Uehara, 1983; Rose, 1997; Standford, 1998; Teleki, 1973; Wrangham and van Zinnicq Bergmann Riss, 1990; Wrangham, 2003). Capuchins, as well, prey on a range of vertebrates including lizards, birds, coatis, and squirrels, and like chimpanzees, they often hunt in groups (Fragaszy et al., 2004; Perry and Rose, 1994; Rose, 1997). In both genera, males hunt much more often and predate upon larger prey, although this sex difference is more pronounced in chimpanzees (Fragaszy and Boinski, 1995; Pandolfi et al., 2003; Rose, 1994, 1997; Standford, 1996; Teleki, 1973). For example, Cebus capucinus males in Santa Rosa National Park caught a vertebrate prey item every 10.7 days, whereas females caught vertebrate prey every 27 days (Rose, 1997). Among chimpanzees, females rarely capture prey themselves, but are sometimes granted meat by males (Boesch, 2003; Goodall, 1986; Teleki, 1973). At Gombe, for instance, males are known to have performed 91% of animal predation since 1982 (Stanford et al., 1994). Conversely, chimpanzee and capuchin females spend more time engaged in extractive foraging. Extractive foraging involves accessing foods that must be removed from other matrices in which they are embedded or encased, such as nut-meat, snails, bone marrow, ants, termites, tubers, and roots (Fragaszy, 1986; Gibson, 1986; Rose, 1994). Foods that require extraction tend to be high-quality foods that provide a concentrated source of energy and protein (Gibson, 1986). Female chimpanzees forage extensively for ants and termites (Boesch and Boesch, 1990; Goodall, 1968; McGrew, 1979), while female capuchins spend more time than males extracting embedded invertebrates (Fedigan, 1993; Fragaszy, 1986; Fragaszy and Boinski, 1995; Rose, 1994). Male bias in predation and female bias in extractive foraging in these two non-human 276 primate species is analogous to sex differences in human foraging behavior. In many well-studied hunter-gatherer societies, males procure almost all of the meat consumed, whereas the procurement of extracted roots is almost exclusively a female activity (Bose, 1964; Hill, 1983; Hill et al., 1984; Hurtado and Hill, 1986; McArthur, 1960; Meehan, 1982; Politis, 1996). Sex differences in the foraging behavior of chimpanzees is viewed by some primatologists as an incipient form, or ancestral condition, for the division of labor that has evolved in the hominid line (Galdikas and Teleki, 1981; Pandolfi et al., 2002). In contrast, sex differences in Cebus feeding behavior probably do not constitute even an ancestral form of sexual division of labor. In her comparison of Cebus and Pan predation behavior, Rose (1997) argues that there is little evidence in capuchins for specialization of feeding behaviors by males and females comparable to that seen in chimpanzees. Although rates vary by sex, both males and females are proficient at hunting and extracting embedded invertebrates (Rose, 1997). Furthermore, unlike chimpanzees, female capuchins benefit little from vertebrate predation by males because male capuchins in her study population rarely share meat (Rose, 1997). (Food sharing in Cebus varies by population and some capuchin populations do share meat more often (Perry and Rose, 1994).) Thus, while there are dietary sex differences among capuchins there is not an incipient form of sexual division of labor equivalent to that seen in chimpanzees. The fact that capuchins show a sex difference in DFP, just as in chimpanzees and humans, suggests that sex differences in lingual anatomy and, perhaps, taste sensitivity are not associated with sexual division of labor. Sex differences in gustatory anatomy and sensitivity are more likely associated with sex differences in the selection of particular food items. There are references to sex differences in feeding behavior, or variation in 277 female feeding behavior with reproductive status (cycling, pregnant, or lactating), in all five non-human primate species tested here, with the exception of C. apella. For example, in one study of P. troglodytes, females spent more time feeding than males (Teleki, 1977). In C. aethiops, higher-ranking females were shown to eat more preferred flowers during pregnancy and lactation than when cycling (Whitten, 1983). In A. palliata, females with infants were observed to spend more time feeding than with females without infants (Smith, 1977). Even Varecia variegata females, who show the least difference from males in DFP, fed on more nectar than males did (Morland, 1991). Although data on sex differences in feeding behavior were not found for C. apella, other Cebus species do show sex differences and variation in feeding behavior with reproductive status. For instance, C. capuchinus females spent more time foraging during lactation, and lactating females were observed to ingest more fruit than cycling females during the wet season (McCabe and Fedigan, 2005). On the other hand, Rose (1994) found that C. capuchinus females spent less time foraging during pregnancy and lactation than when cycling (Rose, 1994). C. olivaceus females were shown to have more dietary diversity and spend more time feeding, but thought to be less efficient than males (Fragaszy, 1986; Fragaszy and Boinski, 1995). These sex differences in feeding behavior may be linked to different nutritional needs as a result of different reproductive costs for males and females. However, effects of sex differences in gustatory sensitivity might be more specific than differences in consumption of fruit or leaves. It may be that the specific species and plant parts ingested are influenced by taste sensitivity. Testing for sex differences in feeding at this level require more specific data analyses. If DFP is associated with bitter taste sensitivity in non-human primates, as it is in humans (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito 278 et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002), Cebus and Pan females may benefit specifically from the ability to reject noxious compounds. Ingesting unfamiliar plant species can be especially risky (Freeland and Janzen, 1974) and detecting secondary compounds might be particularly beneficial for females with high dietary diversity. Chimpanzees, capuchins, and humans all have very diverse diets (Fragaszy et al., 2004; Hayden, 1981; Teleki, 1981), but quantitative analyses of the effects of diversity are difficult because reporting methods differ widely. For instance, some reports include the total number of food species included the diet (Hladik, 1977; Richard, 1978), while others report a dietary diversity index (Fashing, 2001; Grassi, 2001). Still others report which plant species make up more than one percent of the diet (Chapman, 1988; Kool, 1993), or the number of species that account for 90% of the diet (Milton, 1980). To understand the relationship between food-testing in the wild and the function of the gustatory system, data also need to be collected on species that are never eaten, those that are taste-tested and rejected (Glander, 1982), and those that are eaten in the smallest amounts.

SUMMARY AND CONCLUSION

In order to provide nutrients to offspring during gestation and lactation it may be particularly important for females to eat foods that contain adequate proteins, vitamins, and minerals (Portman, 1970). Furthermore, some toxic chemical compounds, while harmless to adults at low levels can be detrimental to a growing fetus (Flaxman and Sherman, 2000). The sense of taste may aid primate females in the process selecting food items that are beneficial to reproduction. In humans, an individual’s density of fungiform

279 papillae is associated with taste sensitivity, (Bartoshuk et al., 1994; Delwiche et al., 2001; Doty et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yakinous and Guinard, 2001, 2002) and human females have, on average, significantly higher DFPs than do males (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Tepper and Nurse, 1997). It was predicted that female non-human primates also have higher DFPs than males. While this hypothesis was only tested in five species, there was a trend for females to have higher papillae densities. Furthermore, there were significant sex differences in the DFPs of C. apella and P. troglodytes, with females having higher DFPs. Since DFP is associated with taste sensitivity in humans, these results suggest that some non-human primates resemble humans in having intersexual differences in guatatory sensitivity. Female primates may have benefited from the ability to detect nutrients and avoid toxins at lower concentrations than their male counterparts. Gestating and lactating females in particular may benefit from more acute taste sensitivity in order to acquire compounds necessary to nourish a fetus or infant and avoid exposing offspring to toxins. Pan, Cebus, and Homo were the only groups in which females were shown to have significantly higher DFPs than males. These three genera share a large relative brain size, slow developmental maturity, and especially high investment in individual offspring (Chalmeau et al., 1997; Fragaszy and Bard, 1997; Gibson, 1986; Kaplan et al., 2000; Ross, 2002; Stephan et al., 1988; Walker et al., 2006). Accordingly, females in these groups may have been under more intense selection pressure than males in order to obtain critical nutrients in the form of high-quality foods, or to have the capacity to detect potential toxins at very low levels.

280 REFERENCES Adler, E., Hoon, M. A., Mueller, K. L., Chandrashekar, J., Ryba, N. J. P. and Zuker, C. S.

(2000) A novel family of mammalian taste receptors. Cell 100, 693-702.

Aiello, L. C. (1997) Brains and guts in human evolution: The expensive tissue

hypothesis. Brazilian Journal of Genetics 20, 141-148.

Aiello, L. C. and Wheeler, P. (1995) The expensive tissue hypothesis: The brain and the

digestive system in human and primate evolution. Current Anthropology 36, 199-

211.

Altmann, J. (1980) Baboon Mothers and Infants. Harvard University Press, Cambridge.

Anderson, J. R. (1996) Chimpanzees and capuchin monkeys: Comparative cognition. In

Reaching Into Thought: The Minds of the Great Apes, Russon, A. E., Bard, K. A.

and Parker, S. T. eds, pp. 23-56. Cambridge University Press, Cambridge.

Arvidson, K. and Friberg, U. (1980) Human taste: Response and taste bud number in

fungiform papillae. Science 209, 807-808.

Aschoff, J., Günther, B. and Kramer, K. (1971) Energiehaushalt und

Temperaturregulation. Urban and Schwarzenberg, Munich.

Barnicot, N. A., Harris, H. and Kalmus, H. (1951) Taste thresholds of further eighteen

compounds and their correlation with PTC thresholds. Annals of Eugenics,

London 16, 119-128.

Bartoshuk, L. M. (2000) Comparing sensory experiences accross individuals: Recent

psychophysical advances illuminate genetic variation in taste perception.

Chemical Senses 25, 447-460. 281 Bartoshuk, L. M., Duffy, V. B., Lucchina, L. A., Prutkin, J. and Fast, K. (1998) PROP (6-

n-propylthiouracil) supertasters and saltiness of NaCl. Annals of the New York

Academy of Sciences 855, 793-796.

Bartoshuk, L. M., Duffy, V. B. and Miller, I. J. (1994) PTC/PROP tasting: anatomy,

psychophysics, and sex effects. Physiology & Behavior 56, 1165-1171.

Beosch, C. and Boesch, H. (1989) Hunting behavior of wild chimpanzees in the Taï

National Park. American Journal of Physical Anthropology 78, 547-573.

Boesch, C. (2003) Complex cooperation among Taï chimpanzees. In Animal Social

Complexity: Intelligence, Culture, and Individualized Societies, de Waal, F. B. M.

and Tyack, P. L. eds, pp. 93-110. Harvard Univeristy Press, Cambridge.

Boesch, C. and Boesch, H. (1990) Tool use and tool making in wild chimpanzees. Folia

Primatologica 54, 86-99.

Boinski, S. (1988) Sex differences in the foraging behavior of squirrel monkeys in a

seasonal habitat. Behavioral Ecology and Sociobiology 23, 177-186.

Bose, S. (1964) Economy of the Onge of Little Andaman. Man in India 44, 298-310.

Brett, F. L., Turner, T. R., Jolly, C. J. and Cauble, R. (1982) Trapping baboons and vervet

monkeys from wild, free-ranging populations. Journal of Wildlife Management

46, 164-174.

Brosnan, F. H. (1985) Mammalian reproduction: An ecological perspective. Biology of

Reproduction 32, 1-26.

282 Buck, L. M. (2000) Smell and taste: The chemical senses. In Principals of Neural

Sciance, Kandel, E. R., Schwartz, J. H. and Jessell, T. M. eds, pp. 625-647.

McGraw-Hill, New York.

Bufe, B., Breslin, P. A. S., Kuhn, C., Reed, D. R., Tharp, C. D., Slack, J. P., Kim, U.-K.,

Drayna, D. and Meyerhof, W. (2005) The molecular basis of individual

differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Current Biology 15, 322-327.

Byrne, R. W., Whiten, S. P., Henzi, S. P. and McCulloch, F. M. (1993) Nutritional

constraints on mountain baboons (Papio ursinus): implications for baboon

socioecology. Behavioral Ecology and Sociobiology 33, 233-246.

Caldwell, C. A. and Whiten, A. (2007) Social learning in monkeys and apes: Cultural

animals? In Primates in Perspective, pp. 652-677. Oxford University Press, New

York.

Carrai, V., Borgognini-Tarli, S., Huffman, M. and Bardi, M. (2003) Increase in tannin

consumption by sifaka (Propithecus verreauxi verreauxi) females during the birth

season: A case for self-medication in prosimians? Primates 44, 61-66.

Chalmeau, R., Visalberghi, E. and Gallo, A. (1997) Capuchin monkeys, Cebus apella fail

to understand a cooperative task. Animal Behaviour 54, 1215-1225.

Chang, W.-I., Chung, J.-W., Kim, Y.-K., Chung, S.-C. and Kho, H.-S. (2006) The

relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil

(PROP) taster status and taste thresholds for sucrose and quinine. Archives of

Oral Biology 51, 427-432. 283 Chapman, C. (1988) Patterns of foraging and range use by three species of neotropical

primates. Primates 29, 177-194.

Chivers, D. J. (1977) The feeding behaviour of saimang (Symphalangus syndactylus). In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 355-382. Academic Press, New York.

Clutton-Brock, T. H. (1977) Some aspects of intraspecific variation in feeding and

ranging behaviour in primates. In Primate Ecology: Studies of Feeding and

Ranging Behaviour in Lemurs, Monkeys and Apes, Clutton-Brock, T. H. ed, pp.

539-556. Academic Press, New York.

Cohen, J. (1988) Statistical Power Analyses for the Behavioral Sciences. Academic

Press, New York.

Cords, M. (1986) Interspecific and intraspecific variation in diet of two forest guenons,

Cercopithecus ascanius and C. mitis. Journal of Animal Ecology 55, 811-827.

Dasilva, G. (1992) The western black-and-white colobus as a low-energy strategist:

Activity budgets, energy expenditure and energy intake. The Journal of Animal

Ecology 61, 79-91. de Waal, F. B. M. (1989) Peacemaking Among Primates. Cambridge University Press,

Cambridge.

Delwiche, J. F., Buletic, Z. and Breslin, P. A. S. (2001) Relationship of papillae number

to bitter intensity of quinine and PROP within and between individuals.

Physiology & Behavior 74, 329-337.

284 Di Bitetti, M. S. and Janson, C. H. (2001) Reproductive socioecology of tufted capuchins

(Cebus apella nigritus) in Northeastern Argentina. International Journal of

Primatology 22, 127-142.

Dinehart, M. E., Hayes, J. E., Bartoshuk, L. M., Lanier, S. L. and Duffy, V. B. (2006)

Bitter taste markers explain variability in vegetable sweetness, bitterness, and

intake. Physiology & Behavior 87, 304-313.

Dominy, N., Lucas, P. W., Osorio, D. and Yamashita, N. (2001) The sensory ecology of

primate food perception. Evolutionary Anthropology 10, 171-186.

Doty, R. L., Bagla, R., Morgenson, M. and Mirza, N. (2001) NaCl thresholds:

Relationship to anterior tongue locus, area of stimulation, and number of

fungiform papillae. Physiology & Behavior 72, 373-378.

Drewnowski, A., Ahlstrom Henderson, S. and Barratt-Fornell, A. (1998) Genetic

sensitivity to 6-n-Propylthiouracil and sensory responses to sugar and fat

mixtures. Physiology & Behavior 63, 771-777.

Drewnowski, A., Ahlstrom Henderson, S., Levine, A. and Hann, C. (1999) Taste and

food preferences as predictors of dietary practices in young women. Public Health

Nutrition 2, 513–519.

Drewnowski, A., Henderson, S. A., Hann, C. S., Berg, W. A. and Ruffin, M. T. (2000)

Genetic taste markers and preferences for vegetables and fruit of female breast

care patients. Journal of the American Dietetic Association 100, 191-197.

285 Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1997)

Nontasters, tasters, and supertasters of 6-n-propylthiouracil (PROP) and hedonic

response to sweet. Physiology & Behavior 62, 649-655.

Duffy, V. B. and Bartoshuk, L. M. (2000) Food acceptance and genetic variation in taste.

Journal of the American Dietetic Association 100, 647-655.

Duffy, V. B., Bartoshuk, L. M., Striegel-Moore, R. and Rodin, J. (1998) Taste changes

across pregnancy. Annals of the New York Academy of Sciences 855, 805-809.

Duffy, V. B., Davidson, A. C., Kidd, J. R., Kidd, K. K., Speed, W. C., Pakstis, A. J.,

Reed, D. R., Snyder, D. J. and Bartoshuk, L. M. (2004) Bitter receptor gene

(TAS2R38), 6-n-Propylthiouracil (PROP) bitterness and alcohol intake.

Alcoholism: Clinical and Experimental Research 28, 1629-1637.

Dunbar, R. I. M. (1977) Feeding ecology of gelada baboons: A preliminary report. In

Primate Ecology, Clutton-Brock, T. H. ed, pp. 251-273. Academic Press, London.

Essick, G. K., Chopra, A., Guest, S. and McGlone, F. (2003) Lingual tactile acuity, taste

perception, and the density and diameter of fungiform papillae in female subjects.

Physiology & Behavior 80, 289-302.

Etter, L. (1999) Variation in taste perception across the menstrual cycle. In School of

Medicine, Vol. M.D. Yale Univeristy.

Fain, G. (2003) Sensory transduction. Sinauer Associates, Inc. Publishers, Sunderland,

Mass.

286 Fashing, P. (2001) Feeding ecology of guerezas in the Kakamenga Forest, Kenya: The

importance of Moraceae fruit in their diet. International Journal of Primatology

22, 579-609.

Fedigan, L. M. (1993) Sex differences and intersexual relations in adult white-faced

capuchins (Cebus capuchinus). International Journal of Primatology 14, 853-877.

Flaxman, S. M. and Sherman, P. W. (2000) Morning sickness: A mechanism for

protecting mother and embryo. The Quarterly Review of Biology 75, 113-148.

Fossey, D. and Harcourt, A. H. (1977) Feeding ecology of free-ranging mountain gorilla.

In Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs,

Monkeys and Apes, Clutton-Brock, T. H. ed, pp. 415-447. Academic Press, New

York.

Fragaszy, D. M. (1986) Time budgets and foraging behavior in wedged-capped capuchins

(Cebus olivaceus): Age and sex differences. In Current Perspecitives in Primate

Social Dynamics, Taub, D. M. and King, F. A. eds, pp. 159-174. van Nostrand

Reinhold, New York.

Fragaszy, D. M. and Bard, K. (1997) Comparison of development and life history in Pan

and Cebus. International Journal of Primatology 18, 683-701.

Fragaszy, D. M. and Boinski, S. (1995) Patterns of individual diet choice and efficiency

of foraging in wedge-capped capuchin monkeys (Cebus olivaceus). Journal of

Comparative Psychology 109, 339-348.

Fragaszy, D. M., Visalberghi, E. and Fedigan, L. (2004) The Complete Capuchin: The

Biology of the Genus Cebus. Cambridge University Press, Cambridge. 287 Freeland, W. J. and Janzen, D. H. (1974) Strategies in herbivory by mammals: The role

of plant secondary compounds. The American Naturalist 108, 269-289.

Freese, C. H. and Oppenheimer, J. R. (1981) The capuchin monkeys, Genus Cebus. In

Ecology and Behavior of Neotropical Primates, Vol. 1, Coimbra-Filho, A. F. and

Mittermeier, R. A. eds, pp. 331-390. Academia Brasileira de Ciências, Rio de

Janeiro.

Galdikas, B., M.F. and Teleki, G. (1981) Variations in subsistence activities of female

and male Pongids: New perspectives on the origins of hominid labor division.

Current Anthropology 33, 241-256.

Galetti, M. and Pedroni, F. (1994) Seasonal diet of capuchin monkeys (Cebus apella) in a

semideciduous forest in South-East Brazil. Journal of Tropical Ecology 10, 27-

39.

Gaulin, S. J. C. and Konner, M. (1977) On the natural diet of primates, including humans.

In Nutrition and the Brain, Vol. 1, Wurtman, R. J. and Wurtman, J. J. eds, pp. 1-

86. Raven Press, New York.

Gautier-Hion, A. (1980) Seasonal variations of diet related to species and sex in a

community of Cercopithecus monkeys. Journal of Animal Ecology 49, 237-269.

Gent, J. F. and Bartoshuk, L. M. (1983) Sweetness of sucrose neohesperidin

dihydrochalcone, and saccharin is related to genetic ability to taste 6-n-

propylthiouracil. Chemical Senses 7, 265-272.

Ghiglieri, M. P. (1984) Feeding ecology and sociality of chimpanzees in Kibale Forest,

Uganda. In Adaptations for Foraging in Nonhuman Primates: Contributions to an 288 Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 161-194. Columbia University Press, New York.

Gibson, K. R. (1986) Cognition, brain size and the extraction of embedded food

resources. In Primate ontongeny, cognition and social behavior, Vol. 3, Else, J.

G. and Lee, P. C. eds, pp. 93-103. Cambridge University Press, Cambridge.

Gittleman, J. L. and Thompson, S. D. (1988) Energy allocation in mammalian

reproduction. American Zoologist 28, 863-875

Glander, K. E. (1982) The impact of plant secondary compounds on primate feeding

behavior. Yearbook of Physical Anthropology 25, 1-18.

Glander, K. E., Fedigan, L. M., Fedigan, L. and Chapman, C. (1991) Field methods for

capture and measurement of three monkey species in Costa Rica. Folia

Primatologica 57, 70-82.

Goodall, J. (1963) Feeding behaviour of wild chimpanzees. Symposia of the Zoological

Society of London 10, 39-48.

Goodall, J. (1968) The behaviour of free-living chimpanzees of the Gombe stream area.

Animal Behavior Monographs 1, 161-311.

Goodall, J. (1986) The Chimpanzees of Gombe: Patterns of Behaviour. The Belknap

Press of Harvard University Press, Cambridge, Massachusetts.

Grassi, C. (2001) The behavioral ecology of Hapalemur griseus griseus: The influences

of microhabitat and population density on this small-bodied prosimian folivore.

Ph.D. Thesis, pp. 345. The University of Texas at Austin.

289 Grassi, C. (2002) Sex differences in feeding, height, and space use in Hapalemur griseus.

International Journal of Primatology 23.

Guo, S.-W. and Reed, D. R. (2001) The genetics of phenylthiocarbamide perception.

Annals of Human Biology 28, 111-142.

Hall, M. J., Bartoshuk, L. M., Cain, W. S. and Stevens, J. C. (1975) PTC taste blindness

and the taste of caffeine. Nature 253, 442-443.

Harrison, M. J. S. (1983) Age and sex differences in the diet and feeding strategies of the

green monkey, Cercopithecus sabaeus. Animal Behaviour 31, 969-977.

Hattori, Y., Kuroshima, H. and Fujita, K. (2005) Cooperative problem solving by tufted

capuchin monkeys (Cebus apella): Spontaneous division of labor,

communication, and reciprocal altruism. Journal of Comparative Psychology 119,

335–342.

Hayden, B. (1981) Subsistence and ecological adaptations of modern hunter/gatherers. In

Omnivorous Primates: Gathering and Hunting in Human Evolution, Harding, R.

S. O. and Teleki, G. eds. Columbia University Press, New York.

Hayes, J. E., Dinehart, M. E. and Duffy, V. B. (in press) Optimal liking of fat-sweet

mixtures varies with markers of bitter taste and anatomy. Appetite, 23.

Hemingway, C. A. (1999) Time budgets and foraging in a Malagasy primate: Do sex

differences reflect reproductive condition and female dominance? Behavioral

Ecology and Sociobiology 45, 311-322.

Hill, K. (1983) Adult male subsistence among Ache hunter-gatherers of Eastern

Paraguay. Ph.D. Thesis. Univeristy of Utah. 290 Hill, K., Hawkes, K., Hurtado, A. M. and Kaplan, H. (1984) Seasonal variance in diet of

Ache hunter-gatherers in eastern Paraguay. Human Ecology 12, 145-180.

Hladik, C. M. (1977) Chimpanzees of Gabon and chimpanzees of Gombe: Some

comparative data on the diet. In Primate Ecology: Studies of Feeding and

Ranging Behaviour in Lemurs, Monkeys, and Apes, Clutton-Brock, T. H. ed, pp.

481-501. Academic Press, London.

Hladik, C. M. and Simmen, B. (1996) Taste perception and feeding behavior in

nonhuman primates and human populations. Evolutionary Anthropology 5, 58-71.

Hosako-Naito, Y., Lucchina, L. A., Snyder, D. J., Boggiano, M. K., Duffy, V. B. and

Bartoshuk, L. M. (1996) Number of fungiform papillae in nontasters, medium

tasters, and supertasters of PROP (6-n-propylthiouracil). Chemical Senses 21,

616.

Hurtado, A. M. and Hill, K. (1986) Early dry season subsistence ecology of the Cuiva

(Hiwi) foragers if Venezuela. Human Ecology 15, 163-187.

Iaconelli, S. and Simmen, B. (2002) Taste thresholds and suprathreshold responses to

tannin-rich plant extracts and quinine in a primate species (Microcebus murinus).

Journal of Chemical Ecology 28, 2315-2326.

Isbell, L. A. (1998) Diet for a small primate: Insectivory and gummivory in the (large)

patas monkey (Erythrocebus patas pyrrhonotus) American Journal of

Primatology 45, 381-398.

291 Janjua, T. and Schwartz, S. (1997) unpublished data. In Duffy, V. B. and L. M.

Bartoshuk (2000) Food acceptance and genetic variation in taste. Journal of the

American Dietetic Association 100, 647-655.

Janson, C. H. and Chapman, C. A. (1999) Resources and primate community structure. In

Primate Communities, Fleagle, J. G., Janson, C. H. and Reed, K. E. eds, pp. 237-

267. Cambridge University Press, New York.

Jennions, M. D. and Moller, A. P. (2003) A survey of the statistical power of research in

behavioral ecology and animal behavior. Behavioral Ecology 14, 438-445.

Kaminski, L. C., Henderson, S. A. and Drewnowski, A. (2000) Young women's food

preferences and taste repsonsiveness to 6-n-porpylthiouracil (PROP). Physiology

& Behavior 68, 691-697.

Kaplan, H., Hill, K., Lancaster, J. and Hurtado, A. M. (2000) A theory of human life

history evolution: Diet, intelligence, and longevity. Evolutionary Anthropology:

Issues, News, and Reviews 9, 156-185.

Kappeler, P. M. and Pereira, M. E. (2002) Primate Life Histories and Socioecology.

Chicago University Press, Chicago.

Key, C. and Ross, C. (1999) Sex differences in energy expenditure in non-human

primates. Proceedings of the Royal Society B: Biological Sciences 266, 2479-

2485.

Kim, U.-K., Jorgenson, E., Coon, H., Leppert, M., Risch, N. and Drayna, D. (2003)

Positional cloning of the human quantitative trait locus underlying taste sensitivity

to phenlythiocarbamide. Science 299, 1221-1225. 292 Kinzey, W. G. (1977) Diet and feeding behaviour of Callicebus torquatus. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 127-151. Academic Press, New York.

Knott, C. D. (1998) Changes in orangutan caloric intake, energy balance, and ketones in

response to fluctuating fruit availability. International Journal of Primatology 19,

1061-1079.

Kool, K. (1993) The diet and feeding behavior of the silver leaf monkey (Trachypithecus

auratus sondaicus) in Indonesia. International Journal of Primatology 14, 667-

701.

Labov, J. B. (1977) Phytoestrogens and mammalian reproduction. Comparative

Biochemistry and Physiology 57A, 3-9.

Lambert, J. E. (1998) Primate digestion: Interactions among anatomy, physiology, and

feeding ecology. Evolutionary Anthropology 7, 8-20.

Leach, E. J. and Noble, A. C. (1986) Comparison of bitterness of caffeine and quinine by

a time-intensity procedure. Chemical Senses 11, 339-345.

Lenth, R. V. (2001) Some practical guidelines for effective sample size determination.

The American Statistician 55, 187-193.

Looy, H. and Weingarten, H. P. (1992) Facial expressions and genetic sensitivity to 6-n-

propylthiouracil predict hedonic response to sweet Physiology & Behavior 52, 75-

82.

293 Lucchina, L. A., Curtis, O. F., Putnam, P., Drewnowski, A., Prutkin, J. M. and Bartoshuk,

L. M. (1998) Psychophysical measurement of 6-n-propylthiouracil (PROP) taste

perception. Annals of the New York Academy of Sciences 855, 816-819.

Manson, J. H., Perry, S. and Parish, A. R. (1997) Nonconceptive sexual behavior in

bonobos and capuchins. International Journal of Primatology 18, 767-786.

Matsumoto-Odaa, A. and Hayashib, Y. (1999) Nutritional aspects of fruit choice by

chimpanzees. Folia Primatologica 70, 154-162.

McArthur, M. (1960) Food consumption and dietary levels of aborigines living on

naturally occurring foods. In Records of the American-Australian Scientific

expedition to Arnhem Land, Mountford, C. P. ed, pp. 90-135. Melbourne

Univeristy Press, Melbourne.

McCabe, G. and Fedigan, L. M. (2005) Eating for two: The effect of reproductive state

on the diet and nutrition of free-ranging female white-faced capuchins (Cebus

capuchinus) in Costa Rica. American Journal of Primatology 66, 112-113.

McGrew, W. C. (1979) Evolutionary implications of sex differences in chimpanzee

predation and tool-use. In The Great Apes, Hamburg, D. A. and McCown, E. R.

eds, pp. 441-463. Benjamin/Cummings, Menso Park, CA.

McGrew, W. C. and Marchant, L. F. (1997) Using tools at hand: Manual laterality and

elementary technology in Cebus spp. and Pan spp. International Journal of

Primatology 18, 787-810.

Meehan, B. (1982) Shell bed to shell midden. Australian Institute of Aboriginal Studies,

Canberra. 294 Miller, I. J. and Bartoshuk, L. M. (1991) Taste perception, taste bud distribution, and

spatial relationships. In Smell and Taste in Health and Disease, Getchell, T. V.,

Doty, R. L., Bartoshuk, L. M. and Snow, J. B. J. eds, pp. 205-233. Raven Press,

New York.

Miller, I. J. and Reedy, F. E. (1990a) Quantification of fungiform papillae and taste pores

in living human subjects. Chemical Senses 15, 281-294.

Miller, I. J. and Reedy, F. E. (1990b) Variations in human taste bud density and taste

intensity perception. Physiology & Behavior 47, 1213-1219.

Milton, K. (1980) The foraging strategy of howler monkeys. Columbia University Press,

New York.

Mistretta, C. M. (1991) Developmental neurobiology of the taste system. In Smell and

Taste in Health and Disease, Getchell, T. V., Doty, R. L., Bartoshuk, L. M. and

Snow, J. J. eds, pp. 35-64. Raven Press, New York.

Morland, H. S. (1991) Social organization and ecology of the black and white ruffed

lemurs (Varecia variegata) in lowland rain forest, Nosy Mangabe, Madagascar.

Yale University, New Haven, Connecticut.

Morland, H. S. (1992) Social organization and ecology of black and white ruffed lemurs

(Varecia variegata variegata) in lowland rainforest, Nosy Mangabe, Madagascar.

Ph.D. Thesis, pp. 419. Yale University.

National Academy of Sciences, Institute of Medicine (1990) Nutrition During

Pregnancy: Part I: Weight Gain, Part II: Nutrient Supplements National

Academy Press, Washington, D.C. 295 Nelson, G., Hoon, M. A., Chandrashekar, J., Zhang, Y., Ryba, N. J. P. and Zuker, C. S.

(2001) Mammalian sweet taste receptors. Cell 106, 381-390.

Nelson, R. J. (2000) An Inrtoduction to Behavioral Endocrinology. Sinauer Associates,

Inc., Sunderland, MA.

Newton, P. N. (1992) Feeding and ranging patterns of forest hanuman langurs (Presbytis

entellus). International Journal of Primatology 13, 245-285.

Nishida, T., Corp, N., Hamai, M., Hasegawa, T., Hiraiwa-Hasegawa, M., Hosaka, K.,

Hunt, K. D., Itoh, N., Kawanaka, K., Matsumoto-Oda, A., Mitani, J. C.,

Nakamura, M., Norikoshi, K., Sakamaki, T., Turner, L., Uehara, S. and Zamma,

K. (2003) Demography, female life history, and reproductive profiles among the

chimpanzees of Mahale. American Journal of Primatology 59, 99-121.

Nishida, T. and Uehara, S. (1983) Natural diet of chimpanzees (Pan troglodytes

schweunfurthii): Long-term records from the Mahalae Mountains, Tanzania.

African Study Monographs 3, 109-130.

O'Brien, T. G. and Kinnaird, M. F. (1997) Behavior, diet, and movements of the Sulawesi

crested black macaque (Macaca nigra). International Journal of Primatology 18,

321-351.

Ottoni, E. B. and Mannu, M. (2003) Spontaneous use of toolds by semifree-ranging

capuchin monkeys. In Animal Social Complexity: Intelligence, Culture, and

Individualized Societies, de Waal, F. B. M. and Tyack, P. L. eds, pp. 440-443.

Harvard Univeristy Press, Cambridge.

296 Overdorff, D. J. (1993) Ecological and reproductive correlates to range use in red-bellied

lemurs (Eulemur rubriventer) and roufous lemurs (Eulemur fulvus rufus). In

Lemur Social Systems and Their Ecological Basis, Kappeler, P. M. and Ganzhorn,

J. U. eds. Plenum Press, New York.

Pandolfi, S., Van Schaik, C. P. and Pusey, A. E. (2002) Sex differences in chimpanzee

and orangutan diet and the sexual division of labor in humans. American Journal

of Physical Anthropology Suppl. 34, 122.

Pandolfi, S. S., C.P., v. S. and Pusey, A. E. (2003) Sex differences in termite fishing

among Gombe chimpanzees. In Animal social complexity: Intelligence, culture,

and individualized societies. de Waal, F. B. M. and Tyack, P. L. eds, pp. 414-418.

Harvard University Press, Cambridge.

Pasquet, P., Oberti, B., El Ati, J. and Hladik, C. M. (2002) Relationships between

threshold-based PROP sensitivity and food preferences of Tunisians. Appetite 39,

167-173.

Pavelka, M. M. and Knopff, K. (2004) Diet and activity in black howler monkeys

(Alouatta pigra) in southern Belize: does degree of frugivory influence activity

level? Primates 45, 105-111.

Perry, S. (2003) Coalitionary Agression in white-faced capuchins. In Animal social

complexity: Intelligence, culture, and individualized societies. de Waal, F. B. M.

and Tyack, P. L. eds, pp. 111-114. Harvard University Press, Cambridge.

Perry, S. and Rose, L. (1994) Begging and transfer of coati meat by white-faced capuchin

monkeys, Cebus capucinus. Primates 35, 409-415. 297 Pickering, G. J., Simunkova, K. and DiBattista, D. (2004) Intensity of taste and

astringency sensations elicited by red wines is associated with sensitivity to PROP

(6-n-propylthiouracil). Food Quality and Preference 15, 147-154.

Politis, G. (1996) Nukak. Instituto Amazonico de Investigaciones Cientificas - SINCHI,

Columbia.

Pollock, J. I. (1977) The ecology and sociology of feeding in Indri indri. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 38-69. Academic Press, New York.

Portman, O. (1970) Nutritional requirements of non-human primates. In Feeding and

Nutrition of Non-human Primates, Harris, R. ed, pp. 87-116. Academic Press,

New York.

Prutkin, J., Duffy, V. B., Etter, L., Fast, K., Gardner, E., Lucchina, L. A., Snyder, D. J.,

Tie, K., Weiffenbach, J. and Bartoshuk, L. M. (2000) Genetic variation and

inferences about perceived taste intensity in mice and men. Physiology &

Behavior 69, 161-173.

Purves, D., Fitzpatric, D., Katz, L. C., LaMantia, A.-S. and McNamara, J. O. (1997)

Neuroscience. Sinaur Associates, Inc., Sunderland, MA.

Reedy, F. E., Bartoshuk, L. M., Miller, I. J., Duffy, V. B., Lucchina, L. A. and

Yanagisawa, K. (1993) Relationships among papillae, taste pores, and 6-n-

propythiouracil (PROP) suprathreshold taste sensitivity. Chemical Senses 18, 618-

619.

298 Remis, M. J. (2006) The role of taste in food selection by African apes: Implications for

niche separation and overlap in tropical forests Primates 47, 56-64.

Remis, M. J. and Kerr, M. E. (2002) Taste responses to fructose and tannic acid among

gorillas (Gorilla gorilla gorilla). International Journal of Primatology 23, 251-

261.

Richard, A. F. (1978) Variability in feeding behavior of a Malagasy prosimian,

Propithecus verreauxi: Lemuriformes. In The Ecology of Arboreal Folivores,

Montgomery, G. G. ed, pp. 519-533. Smithsonian Institution Press, Washington

DC.

Rodman, P. S. (1977) Feeding behavior of orangutans in the Kutai Reserve, East

Kalimantan. In Primate Ecology: Studies of Feeding and Ranging Behaviour in

Lemurs, Monkeys and Apes, pp. 383–413. Academic Press, London.

Rose, L. M. (1994) Sex differences in diet and foraging behavior in white-faced

capuchins (Cebus capucinus). International Journal of Primatology 15, 95-114.

Rose, L. M. (1997) Vertebrate predation and food-sharing in Cebus and Pan.

International Journal of Primatology 18, 727-765.

Ross, C. (2002) Life history, infant care strategies, and brain size in primates. In Primate

Life Histories and Socioecology, Kappeler, P. M. and Pereira, M. E. eds, pp. 266-

284. University of Chicago Press, Chicago.

Sampson, D. A. and Jansen, G. R. (1984) Protein and energy nutrition during lactation.

Annual Review of Nutrition 4, 43-67.

299 Schmidt, J. O. (1979) Ant venoms: A study of venom diversity. In Pesticide and Venom

Neurotoxicity, Shankland, D. L., Hollingworth, R. M. and Smyth, T. eds, pp. 247-

263. Plenum Press, New York.

Scott, T. R., Giza, B. K. and Yan, J. (1998) Electrophysiological respnses to bitter stimuli

in primate cortex. Annals of the New York Academy of Sciences 855, 498-501.

Simmen, B. and Charlot, S. (2003) A comparison of taste thresholds for sweet and

astringent-tasting compounds in great apes. Comptes Rendus Biologies 326, 449-

445.

Smith, C. C. (1977) Feeding behaviour and social organization in howling monkeys. In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 97-126. Academic Press, London.

Standford, C. B. (1996) The hunting ecology of wild chimpanzees: Implications for the

evolutionary ecology of pliocene hominids American Anthropologist, New Series

98, 96-113.

Standford, C. B. (1998) Predation and male bonds in primate societies. Behaviour 135,

513-533.

Stanford, C. B., Wallis, J., Mpongo, E. and Goodall, J. (1994) Hunting decisions in wild

chimpanzees. Behaviour 131, 1-20.

Stephan, H., Baron, G. and Frahm, H. (1988) Comparative size of brains and brain

components. In Comparative Primate Biology, Steklis, H. D. and Erwin, J. eds,

pp. 1-39. Liss, New York.

300 Takemoto, H. (2003) Phytochemical determination for leaf food choice by wild

chimpanzees in Guinea, Bossou. Journal of Chemical Ecology 29, 2551-2573.

Teleki, G. (1973) The Predatory Behavior of Wild Chimpanzees. Bucknell University

Press, Lewisburg, Pennsylvania.

Teleki, G. (1977) Spatial and temporal dimensions of routine activities performed by

chimpanzees in Gombe National Park, Tanzania: An ethological study of adaptive

strategy. Ph.D. Thesis. Pennsylvania State University.

Teleki, G. (1981) The omnivorous diet and eclectic feeding habits of chimpanzees in

Gombe National Park, Tanzania. In Omnivorous Primates: Gathering and

Hunting in Human Evolution, Harding, R. S. O. and Teleki, G. eds. Columbia

University Press, New York.

Tepper, B. (1998) 6-n-propylthiouracil: A genetic marker for taste with implications for

food preference and dietary habits. American Journal of Human Genetics 63,

1271-1276.

Tepper, B. J. (1999) Does genetic taste sensitivity to PROP influence food preferences

and body weight? Appetite 32, 422.

Tepper, B. J. and Nurse, R. J. (1997) Fat perception is related to PROP taster status.

Physiology & Behavior 61, 494-954.

Tepper, B. J. and Nurse, R. J. (1998) PROP taster status is related to fat perception and

preference. Annals of the New York Academy of Sciences 855, 802-804.

301 van Noordwijk, M. A. and van Schaik, C. P. (1999) The effects of dominance rank and

group size on female lifetime reproductive success in wild long-tailed macaques,

Macaca fascicularis. Primates 40, 105-130.

Van Schaik, C. P. and Deaner, R. O. (2003) Life history and cognitive evolution in

primates. In Animal Social Complexity: Intelligence, Culture, and Individualized

Societies, de Waal, F. B. M. and Tyack, P. L. eds, pp. 5-25. Harvard Univeristy

Press, Cambridge.

Vanderford, D. (2007) D.V.M., Duke University. Personal communication.

Visalberghi, E., Fragaszy, D. M. and Savage-Rumbaugh, S. (1995) Performance in a

Tool-using task by common chimpanzees (Pan troglodytes), bonobos (Pan

paniscus), an orangutan (Pongo pygmaeus), and capuchin monkeys (Cebus

apella). Journal of Comparative Psychology 109, 52-60.

Walker, R., Burger, O., Wagner, J. and Von Rueden, C. R. (2006) Evolution of brain size

and juvenile periods in primates. Journal of Human Evolution 51, 480.

Wasser, P. (1977) Feeding, ranging and group size in the Mangabe, Cercocebus albigena.

In Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs,

Monkeys and Apes, Clutton-Brock, T. H. ed, pp. 183-222. Academic Press, New

York.

Whissell-Beuchy (1990) Effects of age and sex on taste sensitivity to phenyltiocarbamide

(PTC) in the Berkley Guidance sample. Chemical Senses 15, 39-57.

302 Whiten, A. and van Schaik, C. P. (2007) The evolution of animal ‘cultures’ and social

intelligence. Philosophical Transactions of the Royal Society B: Biological

Sciences 362, 603-620.

Whitten, P. L. (1983) Diet and dominance among female vervet monkeys (Cercopithecus

aethiops). American Journal of Primatology 5, 139-159.

Wrangham, R. and van Zinnicq Bergmann Riss, E. (1990) Rates of predation on

mammals by gombe chimpanzees, 1972–1975. Primates 31, 157-170.

Wrangham, R. W. (2003) Ecological influences on chimpanzee hunting. American

Journal of Physical Anthropology Suppl. 36, 227-228.

Wrangham, R. W., Conklin-Brittain, N. L. and Hunt, D. M. (1998) Dietary responses of

chimpanzees and cercopithecines to seasonal variation in fruit abundance. I.

Antifeedants. International Journal of Primatology 19, 949-969.

Wrangham, R. W. and Waterman, P. G. (1981) Feeding behaviour of vervet monkeys on

Acacia tortilis and Acacia xanthophloea: With special reference to reproductive

strategies and tannin production. The Journal of Animal Ecology 50, 715-731.

Wynne-Edwards, K. E. (2001) Evolutionary biology of plant defenses against herbivory

and their predictive implications for endocrine disruptor susceptibility in

vertebrates. Environmental Health Perspectives 109, 443-448.

Yackinous, C. A. and Guinard, J.X. (2001) Relation between PROP taster status and fat

perception, touch, and olfaction. Physiology & Behavior 72, 427-437.

303 Yackinous, C. A. and Guinard, J. X. (2002) Relation between PROP (6-n-

propythiouracil) tater status, taste anatomy, and dietary intake measure for young

men and women. Appetite 38, 201-209.

304 Chapter 4: Phenylthiocarbamide (PTC) taste ability in chimpanzees: The T2R38 gene, fungiform papillae, and sex differences

ABSTRACT

Sensitivity to bitter tasting phenylthiocarbamide (PTC) and its close relative 6-n- propylthiouracil (PROP) are correlated with sensitivity to numerous other compounds found in food, many of which have toxic properties. Consequently, human PTC/PROP taste ability is associated with dietary intake and may therefore be related to health and reproductive success. The ability to detect PTC/PROP is influenced by both genetic and environmental factors. While some individuals are highly sensitive to PTC/PROP, others are unable to detect its presence at relatively high concentrations. Extensive research on PTC taste ability in humans worldwide has been ongoing for more than 75 years and, recently, the genetic basis for variation in PTC sensitivity was identified for both humans and chimpanzees. PTC sensitivity is largely controlled by alleles at the T2R38 locus, but the alleles are different in Homo and Pan. Therefore, the molecular basis for variation in PTC taste sensitivity evolved independently in humans and chimpanzees. Unlike PTC genotype, several patterns observed in human PTC gustatory ability have not been tested previously in chimpanzees. Among humans, one underlying cause of variability in PTC sensitivity is the density of lingual fungiform papillae (DFP). Furthermore, sex differences have been found in human PTC/PROP phenotype and DFP. Individuals highly sensitive to PTC/PROP tend to be female, and females tend to have greater DFPs compared with males. The purpose of this chapter is to test whether (1) DFP is correlated with PTC genotype and PTC phenotype and (2) whether sex differences in DFP and PTC phenotype are present in chimpanzees as they are in humans. Accordingly, T2R38 genotype was determined for 36 captive Pan troglodytes. PTC phenotype was determined

305 in 30 individuals using behavioral testing. PTC phenotype was based on whether or not the chimpanzees rejected or accepted a PTC-soaked apple slice. DFP was determined for each of the chimpanzees. The prediction of sex differences in DFP was supported, as females had significantly higher DFPs than males. Data did not support the other predictions. Contrary to expectations, no sex differences were found in PTC phenotype. However, sex differences were present in PTC genotype. A greater number of females had a taster genotype while a greater number of males had a non-taster genotype, although this difference was not statistically significant (p = 0.06). The fact that sex differences were found in T2R38 genotype and in lingual anatomy suggest that in both humans and chimpanzees high bitter taste sensitivity is more important for females than for males, possibly due to the nutritional requirements of gestation and lactation. The expectation that DFP would be associated with PTC phenotype was not supported by the chimpanzee data. There are several possible explanations for the discrepancy between the predictions based on human data and the results found here for chimpanzees. First, the chimpanzee sample may have been too small to reflect significant differences. Second, the use of sweet tasting apples as a vehicle for the PTC may have influenced the responses of some chimpanzees. Third, sex differences in human PTC/PROP sensitivity, and the relationship between PTC/PROP sensitivity and DFP, were found when PTC/PROP sensitivity was measured as perceived bitterness intensity at a specific concentration of PTC or PROP. In contrast, the tests of PTC phenotype used in the chimpanzees tested here tested acceptance or rejection at a specific concentration of PTC.

306 INTRODUCTION

Phenylthiocarbamide (PTC) taste ability in humans

Phenylthiocarbamide (PTC) is a bitter tasting, synthetic compound that is closely related to compounds found naturally in such vegetables as cabbage, broccoli, Brussels sprouts, turnips, and kale (Barnicot et al., 1951; Harris and Kalmus, 1949; Jerzsa-Latta et al., 1990; Tepper, 1998). The ability of humans to detect PTC is a phenotypic polymorphism, and since its discovery in 1931 tens of thousands of humans have been tested for PTC taste ability (Fox, 1932; Guo and Reed, 2001; Wooding, 2006). Depending on the population being tested, the percentage of individuals who are unable to detect PTC at a single test concentration (non-tasters) ranges from zero to 66.7% (Guo and Reed, 2001). Most of the psychophysical taste research related to PTC now uses another closely related synthetic compound, 6-n-propylthiouracil (PROP), because safety limits have been set for its use as a medication for hypothyroidism (Fischer and Griffin, 1959; Lawless, 1980). The ability to taste PROP is highly correlated with PTC taste ability, and the taste receptor for PTC (discussed below) also responds to PROP, although their responses are not identical (Barnicot et al., 1951; Bufe et al., 2005; Chang et al., 2006; Scott et al., 1998; Tepper, 1998).

Psychophysical measures of PTC/PROP taste ability

Taster/non-taster status and detection threshold PTC/PROP taste ability is determined using various methods. Originally, PTC sensitivity was tested with PTC crystals or filter paper (Blakeslee and Salmon, 1931; Fox, 1931; Snyder, 1931). The purpose of such tests was simply to identify tasters and non- 307 tasters using a single concentration of PTC. Non-tasters are insensitive to PTC/PROP at low concentrations. Subsequently, a more sensitive method was employed to test subjects using serial dilutions of PTC. This method was more informative because it identified detection thresholds, which are the lowest concentration of a test substance that can be distinguished from water (Kalmus, 1971; Miller and Bartoshuk, 1991). An individual with a relatively high threshold requires relatively more of the test substance in order to detect its presence. Therefore, the sensitivity of that individual to the test compound is considered low. Conversely, an individual with a relatively low threshold has relatively high sensitivity to the test compound. When PTC/PROP thresholds were investigated, a bimodal distribution of PTC/PROP non-tasters and tasters became apparent (Figure 4.1). This bimodal distribution is distinct from the Gaussian distribution of thresholds for other compounds such as quinine (Bartoshuk et al., 2004a; Fischer, 1967; Fischer and Griffen, 1961). In many of the current studies, individuals with PROP thresholds above 0.3mM are considered non-tasters and individuals with PROP thresholds of 0.1mM or below are considered taters (Bartoshuk et al., 1994). Thus, the term “non-taster” refers to individuals with low PTC/PROP sensitivity (high thresholds). Generally, non-tasters are able to detect PTC/PROP, but only at relatively high concentrations.

308

Figure 4.1: Illustration of the bimodal distribution of PTC/PROP thresholds of tasters and non-tasters. Low thresholds indicate high sensitivity. Figure based on Drewnowski et al., 1997.

Medium-tasters, high-sensitivity tasters, and suprathreshold intensity Later studies showed that measures of above threshold (i.e. suprathreshold) perception of PROP are not equivalent to measures of threshold (Bartoshuk, 1978; Miller and Bartoshuk, 1991). PROP threshold is negatively correlated with ratings of suprathreshold intensity (i.e. bitterness) (Drewnowski et al., 2000; Hayes et al., 2008). In other words, individuals that can detect PTC/PROP at very low concentrations will perceive the compound as being more intensely bitter. In 1994, Bartoshuk and colleages used suprathreshold intensity ratings to separate tasters into two groups: medium-tasters 309 and high-sensitivity tasters (which they called supertasters) (Bartoshuk et al., 1994; Kalmus, 1971; Tepper and Nurse, 1997). High-sensitivity tasters are generally able detect PROP at the lowest perceivable test concentrations and, once detected, find PROP to be the most intensely bitter (Bartoshuk et al., 1994; Yackinous and Guinard, 2002). In the United States, 25% of the population is estimated to be non-tasters, 50% to be medium- tasters, and 20% to be high-sensitivity tasters (Bartoshuk, 1993; Bartoshuk et al., 1994). It should be noted that PTC/PROP sensitivity is a continuous variable and there is considerable overlap between the PROP taste sensitivities of medium- and high- sensitivity tasters (Bartoshuk, 1979; Bartoshuk, 2000; Bartoshuk et al., 1994; Drewnowski et al., 1998b; Fischer et al., 1961; Fischer and Griffin, 1961; Fox, 1932; Hall et al., 1975; Kalmus, 1971; Pasquet et al., 2002; Reed et al., 1995; Snyder, 1931; Tepper et al., 2001). In order to standardize responses to suprathreshold concentrations of PROP across different subjects, a scaling method with ratio properties is used. Responses are measured in comparison to an unrelated response, such as the perceived saltiness of sodium chloride (NaCl). For instance, when identifying medium-tasters and high-sensitivity tasters, Bartoshuk and colleagues (1994) used the ratio [(0.001M PROP/0.32M NaCl)+(0.0032M PROP/1M NaCl)]/2, where PROP and NaCl refer to perceived intensity at the given concentration. For most non-tasters (PROP thresholds above 0.3mM), the response to PROP is clearly below that of NaCl. For tasters (PROP thresholds at or below 0.1mM), PROP function matches the NaCl function or exceeds it (Bartoshuk et al., 1994) (Figure 4.2). In other words, for non-tasters the perceived saltiness of NaCl is more intense than the perceived bitterness of PROP at any given concentration. For medium- tasters, the perceived saltiness of NaCl is similar to the perceived bitterness of PROP. For high-sensitivity tasters, the perceived bitterness of PROP is more intense than the 310 perceived saltiness of NaCl at a given concentration. However, cutoffs to distinguish high-sensitivity tasters from medium-tasters are somewhat arbitrary (Bartoshuk et al., 1994) (Figure 4.3). Furthermore, methods for determining PROP bitterness vary, and there is not a single, uniform criterion for categorizing non-tasters, medium-tasters, and high-sensitivity tasters among different studies (Rankin et al., 2004). Studies also vary in whether they treat medium- and high-sensitivity tasters separately, or as a single taster group.

Figure 4.2: Illustration of the relationship between PROP and NaCl sensitivity for non- tasters, medium-sensitivity tasters, and high-sensitivity tasters. PROP is indicated by the solid line and NaCl is indicated by the dashed line. Figure is based on Bartoshuk et al. (1994) and Tepper and Nurse (1997).

311

Figure 4.3: Illustration of hypothetical delineations among non-tasters, medium-tasters, and high-sensitivity tasters. Data points in grey squares are not used in analyses of taster groups. Medium- and high-sensitivity tasters are distinguished arbitrarily.

312 PTC/PROP taste ability and dietary intake

PTC/PROP taste ability is positively correlated with taste sensitivity to other compounds, including thresholds and preference ratings for fructose, sucrose, saccharine, quinine, and caffeine (fructose Pasquet et al., 2002; sucrose and saccharine Bartoshuk, 1979; Bartoshuk, 2000; Drewnowski et al., 1998a; Drewnowski et al., 1997; Duffy and Bartoshuk, 2000; Duffy et al., 2003; Gent and Bartoshuk, 1983; Looy and Weingarten, 1992; Lucchina et al., 1998; Miller and Reedy, 1990; Pasquet et al., 2002; quinine and caffeine Bartoshuk, 1979; Bartoshuk, 2000; Falconer, 1947; Gent and Bartoshuk, 1983; Hall et al., 1975; Kalmus, 1971; Leach and Noble, 1986). Taster status is also related to the intensity of oral sensations, such as astringency, fat, and heat (e.g., capsaicin) (Duffy et al., 2004; Pickering et al., 2004; Tepper, 1999; Tepper and Nurse, 1997, 1998). Consequently, it is recognized that those individuals with high PTC/PROP sensitivity, “have a different oral sensory world” from those who have lower PTC/PROP sensitivity (Duffy and Bartoshuk, 2000, p. 649). Because PTC/PROP taste ability is related to gustatory sensitivity to compounds found in food as well as to oral sensations, PTC/PROP ability is associated with food preferences and dietary intake in humans. The most consistent effect of PTC/PROP ability on food intake is seen in rates of consumption for bitter tasting foods and beverages. PTC/PROP tasters typically dislike the bitterness of cruciferous and green leafy vegetables (e.g. asparagus, broccoli, Brussels sprouts, cabbage, kale, and spinach) and bitter tasting beverages such as coffee, and therefore often consume less of them than non-tasters (Anliker et al., 1991; Dinehart et al., 2006; Drewnowski et al., 1999; Drewnowski et al., 2000; Drewnowski et al., 1998b; Kaminski et al., 2000; Keller et al., 2002; Ly and Drewnowski, 2001; Tepper and Steinmann, unpublished data in Tepper, 1998; Tepper, 1999). These findings are consistent with the expectation that detection of 313 bitter tasting compounds elicits an aversive response. Even neonates display a rejection response to bitter tasting compounds (Steiner et al., 2001). Bitter tasting compounds are most often found in immature fruits and seeds, tubers, and leaves (Glendinning, 1994). Leaves in particular are a rich source of both protein and other nutrients, but are also a source of secondary compounds that can be toxic, inhibit digestion, or disrupt reproduction, even at low levels (Glander, 1982; Janson and Chapman, 1999; Labov, 1977; Lambert, 1998; Milton, 1980; Wynne-Edwards, 2001). PTC, PROP, and closely related compounds that are found in cruciferous and green, leafy foods (e.g. isothiocyanates, thiocyanates and thioglycosides) are potent antithyroid agents which limit the amount of iodine available for thyroid metabolism (Barnicot et al., 1951; Harris and Kalmus, 1949; Jerzsa-Latta et al., 1990; Reed, 2004; Tepper, 1998). For instance, PTC sensitivity is almost perfectly correlated with taste sensitivity to goitrogenic l-5-vinyl-2-thio-oxazolidone (Boyd, 1950). Compounds related to PTC and PROP are probably produced by plants as chemical defense against herbivory. For example, toxic, bitter tasting isothiocyanates are produced in plants in response to tissue damage, such as that caused by herbivorous insects (Burow et al., 2007; Fenwick et al., 1983). Because of the relationship between PTC and other potentially detrimental compounds, and because of the ease of PTC phenotype testing, PTC status has been investigated as an indicator of numerous health conditions. Studies associating health conditions with PTC taster status range from investigations of body mass index, cardiovascular disease, cancer, and cystic fibrosis, among many others (Calle et al., 1999; Fischer and Griffen, 1964; Tepper and Ullrich, 2002). Taste discrimination is thought to be a critical variable in the process of food acquisition among non-human primates (Laska, 2001; Laska et al., 2000; Provenza, 1996). Detection of secondary compounds in immature fruits and seeds, and leaves in 314 particular, may be linked to bitter taste sensitivity (Glander, 1982; Janson and Chapman, 1999; Lambert, 1998; Milton, 1980). Accordingly, studies of PTC sensitivity may be informative for understanding intra- and interspecific variation in non-human primate feeding ecology. Among chimpanzees, specifically, leaves, pith, and stems make up about 20% of their diet (Wrangham et al., 1998) and chimpanzees are thought to use bitter taste to discriminate among plant species (Huffman, 2003; Koshimizu et al., 1994).

Anatomy of the mammalian gustatory system

Taste is the sensation produced when a chemical stimulus, or tastant, is applied to the taste cells inside taste buds (DeFazio et al., 2006; Finger, 2005; Lindemann, 1996; Purves et al., 1997). Taste buds are located in the soft palate, uvula, epiglottis, pharynx, larynx, esophagus, and tongue. On the tongue, taste buds are found in the lingual epithelium of gustatory papillae (Buck, 2000). There are four types of papillae on the superior surface of the primate tongue: circumvallate, foliate, fungiform, and filiform (Figure 4.4). Filiform papillae are located across the entire superior surface of the tongue, but do not contain taste buds (i.e., they are non-gustatory). Among the gustatory papillae, circumvallate papillae are located along the posterior edge of the tongue and foliate papillae are found along the posterolateral border of the tongue. Fungiform papillae (FP) are located on the anterior two-thirds of the tongue and are more densely concentrated toward the tip. The taste buds in fungiform papillae (anterior two-thirds) are innervated by the chorda tympani, a branch of the facial nerve (cranial nerve VII) (Buck, 2000; Møller, 2003; Scott and Plata-Salaman, 1999). Taste cells in foliate and circumvallate papillae (posterior third) are innervated by the greater petrosal nerve, which is a branch of

315 the glossopharyngeal nerve (cranial nerve IX) (Buck, 2000; Møller, 2003; Scott and Plata-Salaman, 1999). FP are the only structures on the anterior two-thirds of the tongue containing taste buds and are the first papillae to come in contact with food items entering the mouth (Buck, 2000; Purves et al., 1997). FP are formed early in gestation and remain intact throughout life (Janjua and Schwartz, 1997; Mistretta, 1991). FP that have been surgically removed regenerate in three to five weeks with functioning taste buds (Spielman and Brand unbuplished observation in Rossier et al., 2004). Fungiform papillae contain up to 22 taste buds, the pores of which are located on the superior surface of each papilla (Miller, 1986, 1987; Segovia et al., 2002). On circumvallate and foliate papillae taste pores are located laterally (Figure 4.4c) (Miller, 1986, 1987; Segovia et al., 2002). Because researchers can easily access FP and their taste pores, FP have been the focus of many psychophysical and electrophysiological studies of taste (Arvidson and Friberg, 1980).

316

Figure 4.4: Lingual gustatory papillae and taste buds. Illustration after Fain (2003).

317 PTC/PROP sensitivity and density of fungiform papillae

Studies of human subjects suggest that one underlying source of variation in PTC/PROP sensitivity is variation in the density of fungiform papillae. Specifically, the density of FP (DFP) on the anterior portion of the tongue is positively correlated with taster status or the perceived intensity of PTC or PROP bitterness (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yackinous and Guinard, 2001, 2002). For example, one study found that the average DFP of non-tasters was 54, while it was 73 for medium tasters and 98 for high- sensitivity tasters (Bartoshuk et al., 1994). Differences in DFP have not been tested in groups of tasters and non-tasters when status was determined by a single concentration of PTC or PROP. Among humans, DFP can vary by as much as six fold (Essick et al., 2003; Miller and Reedy, 1990b), and the DFP of an individual is positively correlated with the density of taste buds in their papillae (Bartoshuk et al., 1994; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Segovia et al., 2002). Thus, if an individual has a high DFP, on average he or she also has a relatively high density of taste buds on each papilla. Ostensibly, having a greater number of papillae and taste buds, and therefore a greater number of taste receptors, confers a greater sensitivity to tastants. The genetic control for DFP is still unknown (Duffy and Bartoshuk, 2000; Duffy et al., 2004).

Sex differences in PTC/PROP sensitivity and density of fungiform papillae

Although there is considerable overlap between the sexes, human females generally have higher PTC/PROP sensitivity and higher DFPs than do males. Earlier 318 studies using a single concentration of PTC to distinguish tasters from non-tasters showed that females tend to be tasters, whereas males were more often non-tasters (Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Fernberger, 1932; Patel, 1971; Simmons et al., 1956). Analyses of detection thresholds and perceived bitterness also show that the distribution of PTC/PROP sensitivity is skewed higher for females than it is for males (Bartoshuk et al., 1994; Falconer, 1947; Fernberger, 1932; Kim et al., 2003; Whissell- Beuchy, 1990). For instance, Bartoshuk et al. (1994) found that distributions of PROP thresholds were skewed significantly lower and intensity ratings were skewed significantly higher in females (thresholds χ2 = 16.28, p <0.001; intensity χ2 = 15.53, p <0.001). Likewise, human females have higher DFPs and higher densities of taste pores than males (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Duffy et al., 2004; Hayes et al., 2008; Tepper and Nurse, 1997). Tepper and Nurse (1997), for example, found that women had an average of 66.6±2.2 FP/cm2 while men had 55.6±2.1 FP/cm2 (F[1, 74] = 25.5, p < 0.0001).

Genetics of PTC taste sensitivity in humans

Bitter taste transduction is associated with the T2R (or TAS2R) family of taste receptors (Adler et al., 2000; Chandrashekar et al., 2000; Matsunami et al., 2000). T2R genes encode for seven-transmembrane domain G-protein coupled receptors (GPCRs) located in the apical microvilli of taste cells (Adler et al., 2000; Caicedo et al., 2002; Li et al., 2002; Nelson et al., 2002; Nelson et al., 2001; Zhang et al., 2003; Zhao et al., 2003). Twenty-five human T2R genes and eight pseudogenes have been identified, and are located on chromosomes 12, 7, and 5 (Go et al., 2005; Reed et al., 1999; Shi et al., 2003). Although the compounds (or ligands) detected by most T2R receptors are

319 unknown, the gene that encodes the PTC receptor was discovered by Kim et al. in 2003 (Kim et al., 2003). PTC taste ability is controlled by a single major locus on chromosome 7, designated hT2R38 (or hTAS2R38) (Bufe et al., 2005; Drayna et al., 2003; Kim et al., 2003). (This same gene has also been cited as T2R61 (Conte et al., 2002; Parry et al., 2004).) Kim et al., (2003) categorized subjects with PTC thresholds above 0.267mM PTC as non-tasters. They found that variation in hT2R38 is responsible for all of the bimodality (taster/non-taster designation) in PTC taste perception and 55-85% of observed variance in PTC thresholds (Kim et al., 2003). There are three important codon differences in taster and non-taster alleles (Kim et al., 2003). The taster allele most commonly found in humans codes for proline, alanine, and valine at these three amino acid sites and produces the PAV form of the receptor. The non-taster allele most commonly found in humans codes for alanine, valine, and isoleucine at those sites and produces the AVI form of the receptor (Kim et al., 2003). Five other rare alleles have also been identified in humans (mostly in sub-Saharan African populations), and they are presumed to be recombinants of the common taster and non-taster haplotypes (Wooding et al., 2004). Based on PTC thresholds, PAV homozygotes were the most sensitive to PTC, while PAV/AVI heterozygotes had slightly but significantly lower PTC sensitivity than PAV homozygotes. AVI homozygotes had the lowest mean PTC sensitivity. Thus, Kim and colleagues concluded that PAV form of the gene shows a heterozygote effect in which two copies confer greater PTC sensitivity than a single copy. Some of the remaining variance in PTC sensitivity also appears to be genetically determined, but specific genes explaining that variance have yet to be identified (Drayna, 2005; Kim et al., 2003; Reed, 2004). Additional variance in PTC sensitivity was also attributed to sex differences. Analysis of PTC taste thresholds indicated that females were more sensitive 320 than males to PTC (p = 0.003), but sex only explained 5.1% of the variance in thresholds (Kim et al., 2003, supplementary materials).

PTC genotype, phenotype, and density of fungiform papillae

To date, only two studies have investigated hT2R38 genotype, PROP phenotype, and DFP within the same group of subjects. The first investigation was published by Duffy and colleagues in 2004. In vivo and in vitro studies have shown that the receptor for PTC also responds to PROP, but these responses are not identical (Bufe et al., 2005). The hT2R38 receptor is two to three times more sensitive to PTC than to PROP, suggesting that PROP may be a suboptimal ligand to associate with this receptor (Bufe et al., 2005; Drayna, 2005; Miguet et al., 2006). However, the work of Duffy et al. showed that the mean PROP thresholds were significantly different in the three hT2R38 genotypes (AVI/AVI x = 0.58, PAV/AVI x = 0.038, PAV/PAV x = 0.003, p < 0.0001). Only one individual with the non-taster genotype (AVI/AVI) showed a taster phenotype (threshold was 0.0468mM PROP). Subjects who had the lowest 25% of the intensity ratings for 3.2mM PROP were categorized as non-tasters, the subjects with the highest 25% of the intensity ratings were categorized as high-sensitivity tasters, and the middle 50% were categorized as medium-tasters. Using these categories, there was a significant correspondence between genotype and phenotype such that the majority of AVI/AVI subjects were non-tasters, the majority of PAV/AVI subjects were medium-tastsers, and an equal number of PAV/PAV subjects were medium- and high-sensitivity taters (Duffy et al., 2004). The 2004 paper by Duffy and colleagues was the first to report analyses of T2R38 genotype and FP density. DFP was expressed as the number of FP in a 6mm diameter

321 circle on the right and left tongue tips. The average number of FP in each genotype group was not significantly different. The lack of association between number of FP and T2R38 genotype diverges from studies showing a correlation between DFP and PROP sensitivity (i.e. PROP phenotype) (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yackinous and Guinard, 2001, 2002). When only females were considered, there was a trend for homozygous tasters to have 25 papillae or more, whereas homozygous non-tasters tended to have fewer than 25 FP, although this result was not statistically significant (p = 0.08). Multiple regression analysis showed that genotype predicted most of the perceived bitterness of 3.2mM PROP, while FP number explained only 5% of the variance in perceived PROP bitterness. Sex was not a significant contributor to ratings of PROP bitterness. Duffy et al. concluded that the perceived bitterness of PROP probably results from a PROP-specific receptor, FP density, and other factors not related to genetic endowment (Duffy et al., 2004). In tests of sex differences, the average number of fungiform papillae was higher for females (26.48±0.96) than for males (22.60±1.05), as shown previously (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Tepper and Nurse, 1997). There were an unequal number of males and females represented in the data (53 females and 31 males), and tests for sex differences in genotype were not reported by Duffy and colleagues (2004). Accounting for the number of subjects of each sex, there was not a sex difference in hT2R38 genotypes. The greater number of females than males in the PAV homozygote group neared significance, however (AVI/AVI χ2 = 0.31, df = 1, ns, PAV/AVI χ2 = 0.64, df = 1, ns, PAV/PAV χ2 = 2.88, d.f. = 1, p = 0.09; Table 4.1).

322

Table 4.1: Distribution of males and females by PROP genotype in Duffy et al., (2004). Percent of N N N N total Females Predicted N Males Predicted Chi-square Genotype (F + M) (84 subjects) (53 total) Females (31 total) Males results χ2= 0.311, AVI/AVI 26 31 15 16.34 11 9.61 df = 1, p = 0.577 χ2= 0.639, PAV/AVI 37 44 21 23.32 16 13.64 df = 1, p = 0.424

χ2 = 2.88, PAV/PAV 21 25 17 13.25 4 7.75 df = 1, p = 0.090 Predicted numbers were calculated from data provided in the text. To illustrate, the AVI/AVI genotype has a total of 26 individuals which is 31% of total number of subjects (n = 84). The predicted number of 16.34 females in that genotype is 31% of the total number of females in the study (n = 53), while the actual number of females genotyped as AVI homozygotes was 15.

The second study of hT2R38 genotype, PROP phenotype, and DFP was published by Hayes and colleagues in 2008. Hayes et al. found that PROP threshold distinguished AVI homozygotes, but there was a great deal of overlap between the thresholds of heterozygotes and PAV homozygotes. There were significant differences in perceived PROP bitterness ratings among all the three of the genotype groups at higher concentrations of PROP (0.32, 1.0, and 3.2mM). PROP bitterness ratings were greatest for PAV homozygotes, less for heterozygotes, and the least for AVI homozygotes (Hayes et al., 2008). Differences in perceived PROP bitterness among the three genotype groups were not seen at two lower PROP concentrations (0.1 and 0.032mM). Hayes and colleagues used the General Labeled Magnitude Scale (gLMS) for determining bitterness intensity (Bartoshuk et al., 2004b). Subjects rated the intensity of samples from 1 (“no sensation”), to 100 (“the strongest imaginable sensation of any

323 kind”). High-sensitivity tasters were categorized as those with a bitterness rating over 51 for 2.3mM PROP, all of whom had a PROP threshold under 0.15mM. Although only two AVI homozygotes were categorized as high-sensitivity tasters, there was no distinction between heterozygotes and PAV homozygotes among high-sensitivity tasters. Thus, two copies of the PAV allele were not needed in order for subjects to rate 2.3mM PROP as very bitter (i.e. > 51 on the gLMS scale) (Hayes et al., 2008). With regard to lingual anatomy, DFP was measured as the number of FP per in a 6mm diameter circle, similar to Duffy et al., (2004). After controlling for sex, FP number was not significantly different among genotypes. FP number was a significant predictor of perceived bitterness of 3.2mM PROP among PAV and AVI homozygotes, but not for heterozygotes. Females had significantly greater numbers of fungiform papillae. However, there were no significant sex differences for PROP threshold or bitterness ratings (Hayes et al., 2008). Sex differences in genotype were not tested, but data reported by the authors have been summarized in Table 4.2. No sex differences were found in the hT2R38 genotypes reported by Hayes and colleagues (AVI/AVI χ2 = 0.25, df = 1, ns, PAV/AVI χ2 = 0.17, df = 1, ns, PAV/PAV χ2 = 0.45, df = 1, ns).

324 Table 4.2: Distribution of males and females by PROP genotype in Hayes et al., (2008).

Percent of N N N total N Females Predicted N Males Predicted Chi-square Genotype (F+M) (177 subjects) (117 total) Females (55 total) Males results χ2 = 0.250, AVI/AVI 52 29 31 33.93 16 15.95 df = 1, p = 0.615 χ2 = 0.171, PAV/AVI 75 42 50 49.14 25 23.10 df = 1, p = 0.679

χ2 = 0.448, PAV/PAV 50 28 36 32.76 14 15.40 df = 1, p = 0.503 Predicted numbers were calculated from data provided in the text. For example, the AVI/AVI genotype has a total of 52 individuals which is 29% of total number of subjects within the tree groups (n = 177). The predicted number of 33.93 females in that genotype is 29% of the total number of females in the study (n = 117), while the actual number of females genotyped as AVI homozygotes was 31.

Table 4.3 summarizes the findings from Duffy et al. (2004) and Hayes et al., (2008). In these two studies, DFP was associated with PROP phenotype (i.e. perceived bitterness) but not with PROP genotype. Previous studies showed that DFP is positively correlated with perceived PROP bitterness. For example, Reedy et al. (1993) showed that suprathreshold PROP “responsiveness” was correlated with DFP (Spearman rho = 0.64, p < 0.01) (Table 4.4). Soon after, Bartoshuk et al. (1994) showed that PROP bitterness (i.e. NaCl ratios) were significantly correlated with DFP (Spearman rho = 0.58, p < 0.0001). Essick et al. (2003) also reported that DFP was correlated with perceived PROP bitterness, r2 = 0.32, 0.54, and 0.74, (for 0.032mM, 0.32mM, and 3.2mM respectively, p < 0.0001). With the incorporation of genotype onto analyses, Hayes et al. (2008), reported that FP number was a significant predictor of 3.2mM PROP bitterness across the three genotypes, but relative to earlier studies, the reported contribution of DFP was not as 325 great (Spearman rho = 0.17, p = 0.027). FP number was a stronger predictor of bitterness in the two homozygous groups (Spearman rho = 0.33, p = 0.001, PAV/PAV Spearman rho = 0.30, P = 0.035, AVI/AVI Spearman rho = 0.32, P = 0.024) (no correlation was observed in the heterozygotes). The study by Duffy et al. (2004), which also factored genotype into the analyses, indicated that DFP may not contribute to perceived PROP bitterness as much as previously thought. Duffy et al. reported that FP number explained only 5% of the variance in perceived PROP bitterness. Previous studies of DFP showed that females have higher FP densities than males (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Tepper and Nurse, 1997). Those results were confirmed by Duffy et al. and Hayes et al., which found that females had significantly higher DFPs than males. Likewise, earlier studies of detection thresholds and perceived bitterness showed that the distribution of PTC/PROP sensitivity is skewed higher for females than for males (Bartoshuk et al., 1994; Falconer, 1947; Fernberger, 1932; Kim et al., 2003; Whissell-Beuchy, 1990). Sex also appears to influence the relationship between perceived PROP bitterness and DFP. Prutkin et al. (2000) found that the perceived bitterness of 3.2mM PROP was correlated with DFP among females (r = 0.27, p < 0.05), but not among males (r = 0.04, ns). Additionally, Yackinous et al. (2002) showed that the correlation between perceived PROP bitterness and DFP was higher among taster females than all males and females together or all tasters together (all subjects r = 0.42, p < 0.001, tasters only r = 0.38, p < 0.001 female tasters r = 0.47, p < 0.001). In contrast, neither Duffy et al. nor Hayes et al. found sex differences in PROP phenotype. The model generated by Duffy et al. to predict the perceived bitterness of 3.2mM PROP included genotype, FP number, sex, and age, but only genotype and FP number were significant predictors PROP bitterness. Similarly, Hayes and colleagues did

326 not find sex differences in PROP threshold or PROP bitterness, although genotype was not included in that analysis.

Table 4.3: Results of PTC/PROP analyses in humans and chimpanzees

Significant results

Humans Chimpanzees Previous Duffy et al., Hayes et al., Variables studies 2004 2008 This study Genotype, phenotype, & anatomy

PTC/PROP genotype & phenotype n/a YES YES YES

PTC/PROP genotype & DFP n/a NOa NO NO

PTC/PROP phenotype & DFP YESb n/ac YESd NOe

Sex differences

PTC/PROP genotype n/a NOf NOf NOg

PTC/PROP phenotype YESh NO NO NO

DFP YESi YES YES YES Results in bold differ between humans and chimpanzees. aAmong females only, homozygous tasters tended to have >25 FP and homozygous non-tasters had <25 FP in the circular area investigated (p = 0.08); bBartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yackinous and Guinard, 2001, 2002; cNumber of FP accounted for 5% of variance in perceived PROP bitterness; dNumber of FP predicted PROP bitterness; ePhenotype measured as acceptance or rejection of PTC; fCalculations were conducted using data from Duffy et al. (2004) and Hayes et al., (2008); gp = 0.06; Results in bold indicate differences between humans and chimpanzees; hBartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Falconer, 1947; Fernberger, 1932; Kim et al., 2003; Tepper and Nurse, 1997; Whissell-Beuchy, 1990; iBartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Tepper and Nurse, 1997.

327 Table 4.4: Previously reported DFPs and statistical tests for non-, medium-, and high- sensitivity tasters

Average DFP Statistical results High- Tasters & N N Non- Medium sens. Reported for all Non- Study females males tasters -tasters tasters three groups tastersa Spearman rho: χ2 = 7.49, Bartoshuk et al. 25 23 54 73 98 rs = 0.59, df = 1, (1994) p < 0.0001 p = 0.006

χ2 = 28.2, Essick et al. R2 = 0.74, 52 0 54 107 144 df = 1, (2003) p < 0.0001 p < 0.001

Spearman rho: χ2 = 6.60, Reedy et al. 10 8 61 78 106 rs = 0.64, df = 1, (1993) p < 0.01 p = 0.01

ANOVA: χ2 = 4.42, Tepper & Nurse 45 30 47 62 76 F(2,74) = 76.3, df = 1, (1997) p < 0.0001 p = 0.036

Yackinous & Fisher’s LSD: χ2 = 2.29, Guinard 92 55 124 130 167 F(2,144) = 39.27, df = 1, (2001) p < 0.001b p = 0.131

χ2 = 0.25, This study 14 14 53 50 n/a df = 1, p = 0.620 aChi-square tests performed on non-tasters compared with tasters (medium- and high- sensitivity tasters averaged). The expected number used was the average DFP of all three categories. bHigh-sensitivity tasters differed significantly from the other two categories.

328 PTC taste ability in non-human primates

Fisher et al., (1939) were the first to test PTC taste ability in non-human primates, beginning with Pan troglodytes. The chimpanzees were tested with 0.0427mM, 0.328mM, and 2.628mM PTC with 2% sucrose. The authors describe these solutions as tasting bitter at the lowest test concentration, but not unpalatable with the addition of sucrose. The latter two test concentrations would be increasingly bitter to human tasters, while non-tasters might find the 2.628mM solution slightly bitter. Among the chimpanzees, those classified as non-tasters continued to accept the 2.628mM solution, while those classified as tasters always rejected the 0.0427mM and 0.328mM solution. Some taster chimpanzees also rejected the lowest test concentration. Once the chimpanzees were classified as tasters and non-tasters, Fisher and colleagues found that 35% of the chimpanzees were non-tasters (n = 27). Later studies showed percentages of non-tasters between seven and 35% (Chiarelli, 1963, n = 70; Eaton and Gavin, 1965, n = 56; Polcari, 1971, n = 4). Tests of PTC thresholds in chimpanzees showed a bimodal distribution of PTC taster status similar to that in humans (Eaton and Gavin, 1965). PTC taster phenotype has been tested in numerous other non- human primate species. Together, Chiarelli (1963) and Polcari (1971) tested 78 primate species from a wide range of taxa. In almost every species tested, both PTC tasters and non-tasters have been identified (when n ≥ 10) (Chiarelli, 1963, n = 70; Eaton and Gavin, 1965, n = 56; Fisher et al., 1939; Polcari, 1971, n = 44). Although numerous primate taxa have been tested for PTC phenotype, sample sizes are usually very small and detection thresholds have rarely been determined (Chiarelli, 1959, 1963; Eaton and Gavin, 1965; Fisher et al., 1939; Polcari, 1971; Smith et al., 1981).

329 Genetics of PTC taste sensitivity in chimpanzees

Of the five non-human primates tested (Pan, Gorilla, Pongo, Macaca, and Ateles), all are homozygous for the PAV form of T2R38, indicating that the AVI form seen in humans arose after the divergence of humans from the nearest common primate ancestor (Kim et al., 2003). In fact, Wooding and colleagues (2006) discovered that the non-taster allele did arise independently in humans and chimpanzees. The genetic basis for PTC taste ability in chimpanzees is predominantly controlled by two T2R38 alleles, neither of which are shared with humans (Wooding et al., 2006). Wooding et al.’s sequencing of the chT2R38 orthologue in 37 wild born chimpanzees (P. troglodytes troglodytes, P. t. verus, and P. t. schweinfurthii), showed that a site in the second position of the initiation codon is responsible for PTC polymorphism in Pan. The substitution at this site changes the codon from ATG to AGG, resulting in a different downstream start codon and production of a truncated receptor that does not respond to PTC in vitro.

Accordingly, the ATG → AGG mutation either severely reduces or eliminates production of a functional PTC receptor (Wooding, 2006 #1201). In order to confirm the identification of chT2R38(AGG) as the PTC non-taster allele, Wooding and colleagues tested for an association between chT2R38 genotype and PTC phenotype in 39 unrelated captive chimpanzees. Chimpanzees were offered apples soaked in 4.0mM PTC and their responses were scored on a five-point scale, ranging from “readily accept” to “strongly reject.” Given the bitter taste of PTC, individuals who accepted the PTC should presumably be non-tasters, while those who reject it should be tasters. The chimpanzees regularly accept apples during routine enrichment and control trials using water soaked apples instead of PTC. Preliminary analysis of the genotype groups showed that the heterozygote group behaved similarly to the ATG homozygote group. Accordingly, ATG/ATG and ATG/AGG individuals were categorized as tasters 330 while AGG/AGG individuals were categorized as non-tasters. The results showed that 18 out of 30 ATG/ATG and ATG/AGG individuals displayed a taster PTC phenotype, while all nine AGG/AGG individuals showed a non-taster PTC phenotype. Statistical tests showed a significant association between chT2R38 genotype and behavioral responses to PTC (p < 0.01). Thus, Wooding et al. conclude that chT2R38 genotype is highly predictive of PTC taste ability in chimpanzees.

Objective and predictions

PTC/PROP taste ability has been the subject of considerable research concerning human taste ability, genetics, dietary preferences, and health. Studies in humans have shown that DFP is significantly correlated with measures of the perceived PROP bitterness (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako- Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yackinous and Guinard, 2001, 2002). However, a more recent study taking genetics into account, indicates that the contribution of DFP to perceived PROP bitterness may not be as substantial as once thought (Duffy et al., 2004). Human studies have also shown that DFP is not correlated with T2R38 genotype (Duffy et al., 2004; Hayes et al., 2008). A number of investigations have also reported sex differences with regard to DFP and PROP taste ability. Human females tend to have greater DFPs than males, and show greater PTC/PROP sensitivity (Bartoshuk et al., 1994; Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Duffy and Bartoshuk, 2000; Duffy et al., 2004; Falconer, 1947; Fernberger, 1932; Hayes et al., 2008; Kim et al., 2003; Patel, 1971; Simmons et al., 1956; Tepper and Nurse, 1997; Whissell-Beuchy, 1990). When humans have been

331 categorized as tasters and non-tasters using a single test concentration of PTC, females were more often tasters and males were more often non-tasters (Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Fernberger, 1932; Patel, 1971; Simmons et al., 1956). Furthermore, in analyses of detection thresholds and perceived PROP bitterness, females show greater sensitivity to PROP than males (Bartoshuk et al., 1994; Falconer, 1947; Fernberger, 1932; Kim et al., 2003; Whissell-Beuchy, 1990). Some studies have also found that DFP and perceived PROP bitterness are more highly correlated among females than among males (Prutkin et al., 2000; Yackinous and Guinard, 2002). In contrast, analyses of data from Duffy et al. (2004) and Hayes et al. (2008) showed no significant sex differences among the three main T2R38 genotypes. Recent work on the genetics of PTC taste ability in humans and chimpanzees has shown that a PTC non-taster allele evolved independently in these two genera (Wooding et al., 2006). Compared with humans, very little is known about the taste ability of non- human primates, including chimpanzees. Although PTC genotype and phenotype have been investigated previously, neither DFP nor sex differences in PTC taster status have been investigated in chimpanzees. Accordingly, the purpose of this chapter is to explore whether chimpanzees are similar to humans with regard to (1) the relationship between lingual anatomy (DFP) and PTC taste ability, and (2) sex differences in DFP, PTC taste ability, and T2R38 genotype. To this end, the following predictions will be tested in Pan troglodytes: (a) Individuals with a PTC taster phenotype have higher DFPs compared with phenotypic non-tasters, (b) DFP does not differ significantly among the three chT2R38 genotypes, (c) females have greater DFPs than males, (d) more phenotypic PTC tasters are female than male, and (e) there are no sex differences in PTC genotype.

332 METHODS

Sample

Data were collected on 36 unrelated, adult Pan troglodytes, including 18 females and 20 males, at the Southwest Foundation for Biomedical Research in San Antonio, Texas. chT2R38 genotype and DFP data were collected on all 36 animals. PTC phenotype was measured on 30 individuals in the dataset.

Functional assay for chT2R38 genotype

Genotyping was conducted by the Bamshad Lab in the Department of Pediatrics at the University of Washington in Seattle. Genotyping of the chimp T→G polymorphism in the initiation codon of chT2R38 was performed by resequencing. Specifically, the 5’ regions and exon 1 of chT2R38 was PCR amplified and sequenced. Sequence trace files were evaluated using the Sequencher, and polymorphisms were verified by manual evaluation of the individual sequence traces. For most polymorphisms, it was possible to evaluate both the forward and the reverse sequences.

Behavioral testing for PTC phenotype

PTC phenotype was measured by presenting individuals with PTC-soaked apples. Each individual underwent four test sessions including two control trials and two PTC trials, starting with a control trial and then alternating to a PTC trial, control trial, and a final PTC trial. All four trials were performed on separate days between April 2, 2007 and May 8, 2007 with at least 48 hours between trials.

333 To prepare the PTC-laced apples for trial sessions, apples were first cored and then sliced in to 14 sections. They were then soaked overnight (12 – 18 hours) in two liters of 0.4mM PTC in water. To prepare for control trials, the apples were prepared in different work areas using separate equipment in order to insure that PTC did not contaminate the control solution. Apples were sliced and soaked in 0.35g of vitamin C in one gallon water for one to two hours before testing. The purpose of the vitamin C in the control solution was to prevent fruit browning. PTC prevents browning and test apples appeared crisp and fresh even after overnight soaking. To prevent browning and softening in the control apples, soaking was limited to 1-2 hours in the vitamin C solution, which is an antioxidant without the bitter taste properties associated with PTC. Maribel Vazquez, the director of behavioral enrichment at the Foundation, had consistent contact with the animals and conducted all tests. Ms. Vazquez was blind to the genotype of the animals. Apples are a regular enrichment food for these chimpanzees and the soaked apple slices were presented to the chimpanzees in the same manner that enrichment is typically administered. When the soaked apple slice was presented, the observer scored the chimpanzee’s response on a five-point scale (1 = readily accept, 2 = accept, 3 = unclear, 4 = reject, and 5 = strongly reject). Behavioral indicators included whether or not the slice was consumed, the time taken to consume the apple slice, presence of excess salivation, and the presence and extent of facial grimacing. Perception of the bitter taste of quinine is known to produce a grimace in chimpanzees (Steiner et al., 2001). A dried apricot without PTC was provided to each subject immediately following both control and PTC testing.

334 Calculating the density of fungiform papillae

The methods for identifying and counting fungiform papillae followed the procedural protocol established for cadavers by Miller and Reedy (1990). In live, sedated animals, a dental prop was placed between the maxillary and mandibular canines to keep the mouth open during data collection. The tongue was then wiped clean with gauze and 0.5% methylene blue biological stain (Fischer Scientific) was applied to the superior surface of the tongue using a disposable pipette. Unabsorbed methylene blue was wiped off with Kim Wipes® (Fischer Scientific). Methylene blue adheres to all papillae except fungiform, permitting visual identification of this papilla type (Figure 4.5). Histological verification in rabbits has found this method to provide accurate identification of fungiform papillae (Miller and Reedy, 1990a). After dyeing, a high-resolution digital photograph was taken of the tongue using the macro function of a Canon A80 camera. A scale was included in each image for size reference. Papillae were counted manually using Adobe Photoshop® software. Using the scale in each image, a 0.5cm line was drawn on the image. This 0.5cm line was then moved to the medial line of the tongue so that the line began at the anterior-most point at the tip of the tongue and measured 0.5cm back. Next, a square was drawn starting at the posterior edge (top) of the 0.5cm line. The left vertical edge of the square was aligned along the vertical 0.5cm line, providing a right angle from the vertical line. The horizontal (top) edge of the square, placed 0.5cm from the tip of the tongue, provided a guide to draw a horizontal line across the right side of the tongue exactly 0.5cm posterior to the tip. This procedure, using the square as a right angle to the 0.5cm vertical line, was repeated on the left side of the tongue. Once a continuous horizontal line was drawn across the tongue 0.5cm posterior to the tip, the vertical 0.5cm line was removed so that it did not obscure vision of the FP underneath (Figure 4.5). Subsequently, all FP anterior to 335 the horizontal line were counted. If a papilla was only partially visible below the line it was included in the count. Each counted papilla was marked with a colored dot in order to avoid counting any papilla more than once. NIH ImageJ® software was used to determine the area of the anterior 0.5cm of the tongue. The area of the tongue tip was measured three times, and the average of the three measurements was used in analyses. Body mass was measured for each individual at the time of data collection.

Figure 4.5: Tongue of captive Pan troglodytes stained with methylene blue. Light structures are fungiform papillae.

336 Capture and anesthetization procedures

All procedures were approved by the IACUCs at the University of Texas at Austin and the Southwest Foundation for Biomedical Research. Data were collected during routine physical examinations. Capture, anesthetization, and monitoring of vital signs were conducted by the staff and Melissa de la Garza, D.V.M., and followed a pre- established procedural protocol determined by the Foundation.

Statistical analysis

Data were analyzed using SAS JMP software version 5.0.1.2. Due to small sample sizes non-parametric tests were used, including Wilcoxon rank sum tests, chi- squared tests, and Fisher’s Exact tests. Wooding et al. (2006) categorized heterozygotes as tasters based on preliminary association analyses comparing the phenotypes of the ATG/ATG and ATG/AGG animals. Therefore, statistical tests on genotype were conducted using (1) the three genotypes ATG/ATG, ATG/AGG, and AGG/AGG, and (2) two genotype categories including (a) all ATG/ATG and ATG/AGG individuals together (ATG_tasters), and (b) all AGG/AGG individuals (AGG_non-tasters). Scores for each individual’s PTC phenotype were averaged over the two trials, and each individual was categorized as a taster or non-taster based on their average score. Individuals with scores of 1, 1.5, and 2 accepted the PTC and were designated phenotypic non-tasters. Individuals with scores of 4, 4.5, and 5 rejected the PTC and were designated phenotypic tasters. When testing for sex differences in anatomy, sexual dimorphism may be a confounding variable. If females are significantly smaller within a species and also have smaller tongues, this could influence DFP. For example, if females and males have the 337 same number of fungiform papillae, but females have smaller tongues, FP density would be higher in females as a result of differences in body mass. To address the potential influence of body mass, and therefore sexual dimorphism, tests were conducted using two different values for papillae density: DFP, and the ratio of DFP to the cube root of body mass (DFP ratio).

RESULTS

PTC genotype and phenotype

All individuals accepted the apple slice during control trials. The majority of chimpanzees readily accepted the control apples (were scored a 1 on the scale). Five individuals accepted control apples (were scored a 2) one time over the course of both control trials. Data from two individuals were excluded from analyses because their responses to the behavioral testing were unclear. Ambiguous results in these individuals were due to uncooperative behavior, such as knocking the apple away and not tasting it, in addition to showing conflicting behavior. For instance, one individual readily accepted PTC-laced apple on one trial and strongly rejected it on another. All of the phenotypic data that were used in analyses were from individuals who were consistent in their behavioral response to the PTC, either scoring a 1 or 2 during both PTC trials, or a 4 or 5 during both PTC trials (n = 28). The distribution of phenotypes for each genotype is shown in Table 4.5 and Figure 4.6. When PTC genotypes were categorized as ATG_tasters (ATG/ATG and ATG/AGG) and AGG_non-tasters (AGG/AGG), ATG_tasters rejected the PTC-laced apples significantly more often than did non-tasters (Wilcoxon rank sum, z = -2.90, df = 1, p < 0.01). When all three PTC genotypes were tested for a relationship with PTC 338 phenotype (accept or reject) there was also a significant difference among the three genotypes (χ2 = 8.08, df = 2, p < 0.05) (Figure 4.7). Post hoc analyses showed that ATG/ATG and AGG/AGG were significantly different from one another (Fisher’s Exact test, one-tailed p = 0.01). There was also a significant difference between the phenotypes of ATG/AGG and AGG/AGG, indicating that heterozygous tasters were significantly more likely to reject PTC than homozygous non-tasters (Fisher’s Exact test, one-tailed p = 0.05). The phenotypes of ATG/ATG and ATG/AGG individuals were not significantly different from one another (Fisher’s Exact test, one-tailed ns).

Table 4.5: PTC phenotype, DFP, and sex of individuals in each genotype.

Number of phenotyped individuals that Total number of accepted/rejected PTC Average DFP individuals of each Genotype (phenotype) (±StDev) sex (F/M)

ATG/ATG 1/5 48.18±8.90 5/2 ATG/AGG 6/7 50.63±14.18 9/8 AGG/AGG 8/1 52.03±13.00 3/9

339

Figure 4.6: Histogram of the distribution of genotypes within each phenotype rating. 1 = readily accept, 2 = accept, 4 = reject, and 5 = strongly reject.

340 ** *

Figure 4.7: Histogram of the percent of PTC phenotypes in each genotype category. Among chimpanzees who are homozygous non-tasters (AGG/AGG), one rejected the PTC-laced apple slices. Among chimpanzees who are homozygous tasters (ATG/ATG), one individual accepted the PTC-laced apple. There are significant differences between homozygous non-tasters (AGG/AGG) and the other two genotypes, but not between homozygous and heterozygous tasters (* p < 0.05, ** p < 0.01).

341 DFP and PTC genotype and phenotype

The average DFP of each genotype is shown in Table 4.5. DFP was not significantly associated with PTC genotype or genotype categories (Wilcoxon rank sum, ATG/ATG-ATG/AGG z = -0.83, df = 1, ns; ATG/AGG-AGG/AGG z = 0.51, df = 1, ns; ATG/ATG-AGG/AGG z = -1.14, df = 1, ns; ATG_taster and AGG_non-taster z = 0.85, df = 1, ns) (Figure 4.8). Similarly, DFP ratio was not significantly associated with PTC genotype or genotype categories (Wilcoxon rank sum, ATG/ATG-ATG/AGG z = -0.76, df = 1, ns; ATG/AGG-AGG/AGG z = 0.73, df = 1, ns; ATG/ATG-AGG/AGG z = -1.39, df = 1, ns; ATG_taster and AGG_non-taster z = 1.12, df = 1, ns). DFP and DFP ratio were not significantly associated with PTC phenotype (Wilcoxon rank sum, DFP z = - 0.81, df = 1, ns; DFP ratio z = -.92, df = 1, ns) (Table 4.6, Figure 4.9).

Table 4.6: PTC phenotype, DFP, and sex of individuals in each genotype

Average DFP Average DFP ratio Phenotype N (±StDev) (±StDev)

Reject (tasters) 13 50.34±12.14 12.49±3.25 Accept (non-tasters) 15 54.67±10.68 13.61±2.89

342

(n = 12) (n = 17) (n = 7)

Figure 4.8: Box plot of the distribution of DFPs in each genotype. DFPs were not significantly different in each group (Wilcoxon rank sum, ATG/ATG- ATG/AGG z = -0.83, df = 1, ns; ATG/AGG-AGG/AGG z = 0.51, df = 1, ns; ATG/ATG-AGG/AGG z = -1.14, df = 1, ns; taster and non-taster genotype categories z = 0.85, df = 1, ns).

343

(Non-tasters) (Tasters) (n = 15) (n = 13)

Figure 4.9: Box plot of the distribution of DFPs in each phenotype. DFPs were not significantly different in each group (Wilcoxon rank sum, DFP z = -0.81, df = 1, ns; DFP ratio z = -.92, df = 1, ns).

344 Sex differences

An analysis of PTC genotype categories showed that ATG tasters are more often female than male. The relationship between sex and PTC genotype category approached significance (Fisher’s Exact test, one tailed p = 0.06) (Figure 4.10). Sex differences across the three genotypes were not statistically significant (χ2 = 4.24, df = 2, p = 0.12) (Figure 4.11). A comparison of sex differences among homozygote tasters (ATG/ATG) and homozygote non-tasters (AGG/AGG) approached significance (Fisher’s Exact test, one tailed p = 0.07). Sex differences between heterozygotes (ATG/AGG) and taster homozygotes (ATG/ATG) or non-taster homozygotes (AGG/AGG) were not significant. There was no sex difference in PTC phenotype (Fisher’s Exact test, one tailed ns). However there was a sex difference in DFP with females having higher DFPs and higher DFP ratios (Wilcoxon rank sum, DFP z = 2.06, df = 1, p < 0.05; DFP ratio z = 2.15, df = 1, p < 0.05) (Figure 4.12).

345

Figure 4.10: Histogram of sex differences in PTC AGG_non-taster (AGG/AGG) and ATG_taster (ATG/ATG and ATG/AGG) genotype categories. More ATG_tasters are female, whereas more AGG_non-tasters are male (Fisher’s Exact test, one tailed p = 0.06).

346

Figure 4.11: Histogram of sex differences in PTC genotypes. More homozygote tasters (ATG/ATG) are female while more homozygote non-tasters (AGG/AGG) are male. This relationship was not significant when all three genotypes were tested. Sex differences between homozygous tasters (ATG/ATG) and non-tasters (AGG/AGG) neared significance (Fisher’s Exact test, one tailed p = 0.07).

347

(n = 17) (n = 19)

Figure 4.12: Box plot of sex differences in DFP. Females (F) had significantly higher densities of FP than males (M) (Wilcoxon rank sum, z = 2.06, df = 1, p < 0.05).

348 DISCUSSION

PTC genotype and phenotype

The results shown here corroborate the findings of Wooding et al. (2006) who found that the phenotypes of individuals with ATG/ATG and ATG/AGG genotypes did not differ significantly. Notably, the amount of PTC used in the current study (0.4mM) was ten times lower than the amount used in the original 2006 study (4.0mM), yet produced similar results. When ATG/ATG and ATG/AGG genotypes were grouped as ATG_tasters, they rejected PTC soaked apples significantly more often than individuals with the homozygous non-taster genotype (AGG/AGG). Given that only five individuals had the ATG/ATG genotype, the lack of significant difference between the ATG/ATG and ATG/AGG genotypes may have been due to a lack of statistical power. The data presented here show that only one individual with a homozygote taster (ATG/ATG) genotype still accepted PTC and only one homozygous non-taster (AGG/AGG) rejected the PTC-laced apple. Heterozygotes (ATG/AGG), on the other hand, were almost evenly split between accepting and rejecting the PTC (Table 4.5; Figure 4.7). Thus, it appears that the heterozygous form may confer varying levels of PTC taste sensitivity. Among humans, the perceived bitter taste intensity of PTC and PROP is greatest for homozygous tasters, and significantly reduced in heterozygotes (Duffy, 2004; Kim et al., 2003). Among a sample of unrelated human subjects, Kim et al. (2003) found a great deal of overlap between PAV/PAV and PAV/AVI individuals in their PTC thresholds, but very little over lap with AVI/AVI individuals, who had the lowest PTC sensitivity. Likewise, a test of human PROP sensitivity and hT2R38 showed substantial overlap in perceived bitterness of PROP between PAV/PAV and PAV/AVI individuals and very

349 little overlap between those two genotypes and the perceived PROP bitterness of AVI/AVI individuals (Duffy et al., 2004). If there is a similar relationship between genotype and perceived PTC intensity in chimpanzees, heterozygous individuals may have the ability to detect PTC, but not perceive the compound as intensely bitter. In addition, the intensity and quality of taste stimuli are modified when combined with other tastants (Keast and Breslin, 2002). Thus, the sweet tasting compounds in the apple slice may affect the perceived unpleasantness of the PTC. An example of this among primates is the tolerance for tannic acid. Alone, the astringency of tannic acid serves as a deterrent. However, combined with sweet tasting sugars, tolerance for tannins increases substantially (Remis and Kerr, 2002; Simmen, 1994). Accordingly, the perception of the bitter tasting PTC may not dissuade taster individuals with lower sensitivity from consuming a sweet tasting apple. Additionally, Wooding and colleagues (2006) suggested that some individuals with taster genotypes have PTC detection thresholds above the 4.0mM PTC used in their study, or that some chimpanzees did perceive the PTC sample, but did not have an aversion to it in terms of preference. The same may be true for the heterozygous tasters analyzed here, in which case some individuals may be tasters but have detection thresholds above 0.4mM PTC.

DFP and PTC genotype and phenotype

Neither DFP nor DFP ratio were associated with PTC genotype in the chimpanzees (Figure 4.8). This result was expected given the absence of a significant association between DFP and PTC genotype in humans (Duffy et al., 2004; Hayes et al., 2008). In contrast, it was hypothesized that chimpanzees with PTC taster phenotype would have significantly higher DFPs. Surprisingly, PTC phenotype in the chimpanzees

350 was not associated with DFP or DFP ratio. In fact, if there is any trend at all, it is in the opposite direction from what was expected, with chimpanzees that rejected the PTC- laced apples (tasters) having lower DFPs (Figure 4.9). This result contrasts with patterns in the human data. Among humans, there is much evidence for a positive association between DFP and perceived PTC/PROP bitterness (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yackinous and Guinard, 2001, 2002). Table 4.4 shows the reported DFPs of non-tasters, medium-tasters, and high-sensitivity tasters for several previous studies. Taster categories in these studies were always based on reports of perceived PROP bitterness (or ratios with NaCl response). However, in most cases, PROP thresholds do tend to separate tasters (medium and high-sensitivity) from non- tasters. For example, in Bartoshuk et al.’s 1994 study, non-tasters all had PROP thresholds above 0.3mM and medium- and high-sensitivity tasters all had thresholds below at or below 0.1mM. Essick et al. (2003) used the same classifications as Bartoshuk et al., as did Tepper and Nurse (1997). Accordingly, combining medium- and high- sensitivity tasters does not give same distributions as the use of thresholds alone, but does approximate group designations based on thresholds. With these approximations of taster and non-taster designations, the differences in DFP are still highly significant for the human data in all but one case (Yackinous and Guinard, 2001) (Table 4.5). In contrast, the mean DFPs of chimpanzee tasters and non-tasters (rejecters and acceptors, respectively) were essentially the same. Still, the lack of association between DFP and PTC phenotype in chimpanzees may be due to the method of PTC behavioral testing that was employed. Using a “reject” or “accept” criteria to categorize tasters and non-tasters is clearly not equivalent to using 351 thresholds, and is much different from reports of perceived bitterness. In their model predicting perceived bitterness of PROP, Duffy and colleagues (2004) found that DFP accounted for only 5% of PROP bitterness. If that is the case in chimpanzees as well, more sophisticated methods of data collection and analysis may be required to fully assess the effect of DFP on PTC perception in chimpanzees. Other factors may also have contributed to the lack of association between DFP and PTC phenotype. First, as mentioned earlier, the sweet taste of the apple slices may affect the perceived unpleasantness of the PTC in some individuals. Second, sample sizes in the current study may be too small to detect phenotypic differences in DFP. Third, different compounds were tested in humans (PROP) and chimpanzees (PTC). Although the hT2R38 receptor for PTC also responds to PROP, the responses of PTC and PROP are not identical (Bufe et al., 2005). Tests of PROP phenotype in chimpanzees might help to clarify whether the difference in test stimuli is affecting research outcomes. Given these considerations, the results reported here should be considered preliminary. However, current evidence from this study suggests that DFP may not contribute to PTC sensitivity in chimpanzees. In this regard, the chimpanzee gustatory system may differ substantially from the gustatory system of humans.

Sex differences

When PTC genotype categories (ATG_tasters and AGG_non-tasters) were analyzed, ATG_tasters were more often female than male, a pattern that neared statistical significance (Fisher’s Exact test, one tailed p = 0.06). Given that PTC genotype and phenotype are correlated, it was surprising to find no significant sex difference in PTC phenotype. However, as mentioned above, the binary measure used here (accept and

352 reject) may not be sensitive enough to show sex differences in phenotype. A measure of detection threshold may be more appropriate in this case. Additionally, there was a sex difference in DFP with females having higher DFPs, even when correcting for differences in body mass. Again, this was unexpected since DFP was not correlated with PTC phenotype. Duffy et al. (1998) argued that greater bitter taste intensity in females might serve to support healthy pregnancy outcomes by protecting against the ingestion of poisons. The avoidance of toxins is especially critical for reproductive females, as some compounds can be detrimental to a growing fetus (Flaxman and Sherman, 2000; Gaulin and Konner, 1977). Evidence suggests that detecting and avoiding bitter tasting compounds may be especially critical during the first trimester of pregnancy. Bitter taste sensitivity and intensity ratings for bitter tasting quinine hydrochloride increase significantly in the first trimester of pregnancy (Bhatia and Puri, 1991; Duffy et al., 1998). PTC/PROP tasters have a greater dislike of green, leafy foods, and therefore do not ingest them as often as PTC/PROP non-tasters (Anliker et al., 1991; Dinehart et al., 2006; Drewnowski et al., 1999; Drewnowski et al., 2000; Drewnowski et al., 1998; Kaminski et al., 2000; Keller et al., 2002; Ly and Drewnowski, 2001; Tepper and Steinmann, unpublished data in Tepper, 1998; Tepper, 1999). Given that numerous, bitter tasting toxic compounds are found in leaves (Glander, 1982; Janson and Chapman, 1999; Labov, 1977; Lambert, 1998; Milton, 1980; Wynne-Edwards, 2001), a dislike of green, leafy foods in the first trimester could have beneficial consequences for fetal development. Therefore, genetic sex differences in PTC sensitivity, as well as sex differences in lingual anatomy, might reflect a selective advantage for females to have to have more sensitive gustatory systems. In this way, females might improve reproductive

353 success by avoiding the secondary compounds in leaves, particularly during gestation and lactation.

Selection for PTC polymorphism

The PTC non-taster allele evolved independently in humans and chimpanzees (Wooding et al., 2006). The fact that a convergent non-taster allele has been maintained in both Homo and Pan suggests that either the non-taster or the heterozygous taster phenotype, (or both), are beneficial. PTC sensitivity is associated with sensitivity to other bitter tasting compounds (Bartoshuk, 1979; Bartoshuk, 2000; Falconer, 1947; Gent and Bartoshuk, 1983; Hall et al., 1975; Kalmus, 1971; Leach and Noble, 1986). In the context of food item selection, PTC taste ability can be considered an indication of bitter taste sensitivity in general. PTC is related to bitter tasting compounds found naturally in cruciferous and green leafy vegetables (Barnicot et al., 1951; Harris and Kalmus, 1949; Jerzsa-Latta et al., 1990; Tepper, 1998) and the bitter taste of green leafy foods can indicate the presence of potentially toxic compounds (Glander, 1982; Milton, 1979, 1984; Waterman and Kool, 1994). Because some bitter compounds can be toxic at high levels, it would seem beneficial to have high bitter taste sensitivity in order to detect them (Boyd, 1950; Drewnowski and Rock, 1995). Another selective advantage to high bitter taste sensitivity might be the identification of medicinal plants. While toxic at higher levels, bitter tasting plant secondary compounds are useful for their medicinal properties, such as antibiotic and antiparasitic effects (Huffman, 2003). Both humans and chimpanzees use plants medicinally. Humans are known to identify medicinal plants by their bitter taste (Etkin and Ross, 1982; Heinrich et al., 1992; Pieroni et al., 2007). Chimpanzees are also thought

354 to use bitter taste as a signal when selecting plants for medicinal use, and for controlling intake of those medicinal substances (Huffman, 2003; Koshimizu et al., 1994). In these contexts of toxin avoidance and medicinal use, high sensitivity to bitter tasting compounds would provide a selective advantage. Assuming a correlation between PTC genotype and sensitivity to bitter compounds generally, toxin avoidance and medicinal use may account for the persistence of the PTC taster allele (Drewnowski and Rock, 1995). Individuals who can identify the toxic and medicinal properties of plants should be at a fitness advantage. It is not clear, though, what advantage is provided by the non- taster allele (Guo and Reed, 2001). Wooding et al. (2004) proposed that the non-taster allele in humans might encode for a receptor that is associated with a different bitter substance. The non-taster allele might then be maintained because sensitivity to this unidentified, bitter compound is a selective force. In addition, heterozygote tasters might be at an advantage if the non-taster allele confers sensitivity to another compound or compounds. In this case, heterozygotes could regulate intake of a wider range of bitter compounds, and that might lead to a fitness advantage over homozygotes (Wooding, 2006; Wooding et al., 2004). Alternatively, if heterozygote tasters have an intermediate bitter taste sensitivity, as seen for PTC sensitivity in humans (Duffy, 2004), this may be more advantageous than homozygote taster or non-taster status. Human high-sensitivity PTC tasters usually experience the compound as intensely bitter (Bartoshuk et al., 1994; Yackinous and Guinard, 2002). Bitter taste is an important determinant of food item rejection (Dinehart et al., 2006; Drewnowski et al., 2000; Kaminski et al., 2000). Among the chimpanzees in this study, all but one of the homozygous tasters clearly rejected the PTC-laced apples. On the other hand, homozygous non-tasters are probably not able to detect relatively low levels of potentially toxic or medicinally useful secondary compounds. Heterozygotes, 355 however, might be able to identify the presence of bitter tasting compounds, but have a greater ability than homozygote tasters to control their innate rejection response (Steiner et al., 2001; Ueno et al., 2004). As a result, heterozygous taster status may be more advantageous in the identification and use of plants, which might explain the persistence of the non-taster allele.

SUMMARY

Much research has been conducted on the human gustatory system, food preferences, and diet. This research on a non-human primate species closely related to humans supports previous taste research by providing an evolutionary context. Unlike PTC genotype, several patterns observed in human PTC gustatory ability have not been tested previously in chimpanzees. Among humans, PTC/PROP phenotype is correlated with the DFP on the anterior of the tongue (Bartoshuk et al., 1994; Delwiche et al., 2001; Essick et al., 2003; Hayes et al., 2008; Hosako-Naito et al., 1996; Miller and Bartoshuk, 1991; Miller and Reedy, 1990b; Prutkin et al., 2000; Reedy et al., 1993; Tepper, 1999; Tepper and Nurse, 1997, 1998; Yackinous and Guinard, 2001, 2002). Conversely, DFP is not associated with PTC genotype in humans (Duffy et al., 2004; Hayes et al., 2008). Whether a relationship between PTC phenotype or genotype and DFP is also present in chimpanzees was previously untested. In addition, sex differences in PTC genotype, PTC phenotype, and DFP have been observed in humans (Bartoshuk et al., 1994; Duffy and Bartoshuk, 2000; Duffy et al., 2004; Tepper and Nurse, 1997). Evidence of a similar relationship between DFP and PTC phenotype in chimpanzees would support the idea that there is a functional advantage for females to have higher bitter taste sensitivity.

356 The results presented here show several similarities in the PTC taste abilities of humans and chimpanzees. Neither species showed a correlation between PTC genotype and DFP. In both species, there was a sex difference in DFP in which females had higher DFPs than males. Humans and chimpanzees differed with regard to tests for PTC phenotype. Among humans, PTC phenotype is correlated with DFP, but this was not the case for chimpanzees. Likewise, there is a sex difference in PTC phenotype among humans, whereas there was not among chimpanzees. Although the tests for PTC phenotype did not show the expected patterns in chimpanzees, it is possible that significant relationships were obscured by the methods of phenotypic testing that were used. Whereas PTC testing in humans uses precise methods to determine detection thresholds and perceived intensity, the chimpanzees tested here were only categorized as tasters or non-tasters, depending on their response to a single concentration of PTC. Additional data on chimpanzee lingual anatomy, such as taste bud and receptor densities, in addition to more precise data on detection thresholds for PTC, will be necessary to more fully understand the relationship between DFP and PTC sensitivity in Pan. Given the sex differences found in genotype and DFP among chimpanzees it is possible that, on average, female chimpanzees have greater PTC sensitivity similar to humans.

357 REFERENCES Adler, E., Hoon, M. A., Mueller, K. L., Chandrashekar, J., Ryba, N. J. P. and Zuker, C. S.

(2000) A novel family of mammalian taste receptors. Cell 100, 693-702.

Arvidson, K. and Friberg, U. (1980) Human taste: Response and taste bud number in

fungiform papillae. Science 209, 807-808.

Barnicot, N. A., Harris, H. and Kalmus, H. (1951) Taste thresholds of further eighteen

compounds and their correlation with PTC thresholds. Annals of Eugenics,

London 16, 119-128.

Bartoshuk, L. (1979) Bitter taste of saccharin related to the genetic ability to taste the

bitter substance 6-n-propylthiouracil. Science 205, 934-935.

Bartoshuk, L., Fast, K., Snyder, D. J. and Duffy, V. B. (2004a) Genetic differences in

human oral perception: Advanced methods reveal basic problems in intensity

scaling. In Genetic Variation in Taste Sensitivity, Prescott, J. and Tepper, B. J.

eds, pp. 1-41. Marcel Dekker, Inc., New York.

Bartoshuk, L. M. (1978) The psychophysics of taste. American Journal of Clinical

Nutrition 31, 1068-1077.

Bartoshuk, L. M. (1993) The biological basis of food perception and acceptance. Food

Quality and Preference 4, 21-32.

Bartoshuk, L. M. (2000) Comparing sensory experiences accross individuals: Recent

psychophysical advances illuminate genetic variation in taste perception.

Chemical Senses 25, 447-460.

358 Bartoshuk, L. M., Duffy, V. B., Green, B. G., Hoffmann, J. N., Ko, C. W., Lucchina, L.

A., Marks, L. E. and Snyder, D. J. (2004b) Valid across-group comparisons with

labeled scales: The gLMS versus magnitude matching. Physiology & Behavior

82, 109-114.

Bartoshuk, L. M., Duffy, V. B., Lucchina, L. A., Prutkin, J. and Fast, K. (1998) PROP (6-

n-propylthiouracil) supertasters and saltiness of NaCl. Annals of the New York

Academy of Sciences 855, 793-796.

Bartoshuk, L. M., Duffy, V. B. and Miller, I. J. (1994) PTC/PROP tasting: Anatomy,

psychophysics, and sex effects. Physiology & Behavior 56, 1165-1171.

Bhatia, S. and Puri, R. (1991) Taste sensitivity in pregnancy. Indian Journal of

Physiology and Pharmacology 35, 121-124.

Blakeslee, A. F. and Salmon, M. R. (1931) Odor and taste blindness. Eugenical News 16,

105-109.

Boyd, W. (1950) Taste reactions to antithyroid substances. Science 112, 153 (letter).

Boyd, W. C. and Boyd, L. G. (1936) New racial blood group studies in Europe and

Egypt. Science 84, 328-329.

Boyd, W. C. and Boyd, L. G. (1937) Sexual and racial variations in ability to taste

phenylthiocarbamide, with some data in the inheritance. Annals of Eugenics,

London 8, 46-51.

Buck, L. M. (2000) Smell and taste: The chemical senses. In Principals of Neural

Sciance, Kandel, E. R., Schwartz, J. H. and Jessell, T. M. eds, pp. 625-647.

McGraw-Hill, New York. 359 Bufe, B., Breslin, P. A. S., Kuhn, C., Reed, D. R., Tharp, C. D., Slack, J. P., Kim, U.-K.,

Drayna, D. and Meyerhof, W. (2005) The molecular basis of individual

differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Current Biology 15, 322-327.

Burow, M., Bergner, A., Gershenzon, J. and Wittstock, U. (2007) Glucosinolate

hydrolysis in Lepidium sativum - identification of the thiocyanate-forming

protein. Plant Molecular Biology 63, 49-61.

Caicedo, A., Kim, K.-N. and Roper, S. D. (2002) Individual mouse taste cells respond to

multiple chemical stimuli. The Journal of Physiology Online 544, 501-509.

Calle, E. E., Thun, M. J., Petrelli, J. M., Rodriguez, C. and Heath, C. W. (1999) Body

mass index and mortality in a prospective cohort of U.S. adults. The New England

Journal of Medicine 341, 1097-1105.

Chandrashekar, J., Mueller, K. L., Hoon, M. A., Adler, E., Feng, L., Guo, W., Zuker, C.

S. and Ryba, N. J. P. (2000) T2Rs function as bitter taste receptors. Cell 100, 703-

711.

Chang, W.I., Chung, J.W., Kim, Y.K., Chung, S.C. and Kho, H.S. (2006) The

relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil

(PROP) taster status and taste thresholds for sucrose and quinine. Archives of

Oral Biology 51, 427-432.

Chiarelli, B. (1959) Sensitivity to phenyl-thio-carbamide (P.T.C.) in some monkeys (data

collected at Italian zoological gardens). Archivio per l'antropologia e la etnologia

89, 1-9. 360 Chiarelli, B. (1963) Sensitivity to P.T.C. (phenyl-thio-carbamide) in primates. Folia

Primatologica 1, 88-94.

Conte, C., Ebeling, M., Marcuz, A., Nef, P. and Andres-Barquin, P. J. (2002)

Identification and characterization of human taste receptor genes belonging to the

TAS2R family. Cytogenetic and Genomic Research 98, 45-53.

DeFazio, R. A., Dvoryanchikov, G., Maruyama, Y., Kim, J. W., Pereira, E., Roper, S. D.

and Chaudhari, N. (2006) Separate Populations of Receptor Cells and Presynaptic

Cells in Mouse Taste Buds. Journal of Neuroscience 26, 3971-3980.

Delwiche, J. F., Buletic, Z. and Breslin, P. A. S. (2001) Relationship of papillae number

to bitter intensity of quinine and PROP within and between individuals.

Physiology & Behavior 74, 329-337.

Dinehart, M. E., Hayes, J. E., Bartoshuk, L. M., Lanier, S. L. and Duffy, V. B. (2006)

Bitter taste markers explain variability in vegetable sweetness, bitterness, and

intake. Physiology & Behavior 87, 304-313.

Drayna, D. (2005) Human taste genetics. Annual Review of Genomics and Human

Genetics 6, 217-235.

Drayna, D., Coon, H., Kim, U.-K., Elsner, T., Cromer, K., Otterud, B., Baird, L., Peiffer,

A. P. and Leppert, M. (2003) Genetic analysis of a complex trait in the Utah

Genetic Reference Project: A major locus for PTC taste ability on chromosome 7q

and a secondary locus on chromosome 16p. Human Genetics 112, 567-572.

361 Drewnowski, A., Ahlstrom Henderson, S. and Barratt-Fornell, A. (1998a) Genetic

sensitivity to 6-n-Propylthiouracil and sensory responses to sugar and fat

mixtures. Physiology & Behavior 63, 771-777.

Drewnowski, A., Henderson, S. A., Hann, C. S., Berg, W. A. and Ruffin, M. T. (2000)

Genetic taste markers and preferences for vegetables and fruit of female breast

care patients. Journal of the American Dietetic Association 100, 191-197.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1997)

Nontasters, tasters, and supertasters of 6-n-propylthiouracil (PROP) and hedonic

response to sweet. Physiology & Behavior 62, 649-655.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1998b) Sensory

responses to 6-n-propylthiouracil (PROP) or sucrose solutions and food

preferences in young women. Annals of the New York Academy of Sciences 855,

797-801.

Drewnowski, A. and Rock, C. L. (1995) The influence of genetic taste markers on food

acceptance. American Journal of Clinical Nutrition 62, 506-511.

Duffy, V. B. (2004) Associations between oral sensation, dietary behaviors and risk of

cardiovascular disease (CVD). Appetite 43, 5-9.

Duffy, V. B. and Bartoshuk, L. M. (2000) Food acceptance and genetic variation in taste.

Journal of the American Dietetic Association 100, 647-655.

Duffy, V. B., Bartoshuk, L. M., Striegel-Moore, R. and Rodin, J. (1998) Taste changes

across pregnancy. Annals of the New York Academy of Sciences 855, 805-809.

362 Duffy, V. B., Davidson, A. C., Kidd, J. R., Kidd, K. K., Speed, W. C., Pakstis, A. J.,

Reed, D. R., Snyder, D. J. and Bartoshuk, L. M. (2004) Bitter receptor gene

(TAS2R38), 6-n-propylthiouracil (PROP) bitterness and alcohol intake.

Alcoholism: Clinical and Experimental Research 28, 1629-1637.

Duffy, V. B., Peterson, J. M., Dinehart, M. E. and Bartoshuk, L. (2003) Genetic and

environmental variation in taste: Associations with sweet intensity, preference,

and intake. Topics in Clinical Nutrition 18, 209-220.

Eaton, J. W. and Gavin, J. A. (1965) Sensitivity to P-T-C among primates. American

Journal of Physical Anthropology 23, 381-388.

Essick, G. K., Chopra, A., Guest, S. and McGlone, F. (2003) Lingual tactile acuity, taste

perception, and the density and diameter of fungiform papillae in female subjects.

Physiology & Behavior 80, 289-302.

Etkin, N. L. and Ross, P. J. (1982) Food as medicine and medicine as food: An adaptive

framework for the interpretation of plant utilization among the Hausa of northern

Nigeria. Social Science & Medicine 16, 1559-1573.

Fain, G. (2003) Sensory transduction. Sinauer Associates, Inc. Publishers, Sunderland,

Mass.

Falconer, D. S. (1947) Sensory thresholds for solutions of phenylthiocarbamide. Results

of tests on a large sample, made by R. A. Fisher. Annals of Eugenics, London 13,

211-222.

363 Fenwick, G. R., Heaney, R. K. and Mulling, W. J. (1983) Glucosinolates and their

breakdown products in food and food plants. Critical reviews in food science and

nutrition 18, 123 – 201.

Fernberger, S. W. (1932) A preliminary study of taste deficiency. Journal of Psychology

44, 322-326.

Finger, T. E. (2005) Cell types and lineages in taste buds. Chemical Senses 30, i54 - i55.

Fischer, R. (1967) Genetics and gustatory chemoreception in man and other primates. In

The Chemical Senses and Nutrition, Kare, M. R. and Maller, O. eds, pp. 621-681.

John Hopkins Press, Baltimore.

Fischer, R. and Griffen, F. (1961) Quinine dimorphism among “non-tasters” of 6-n-

propylthiouracil. Experientia 17, 36-38.

Fischer, R. and Griffen, F. (1964) Pharmacogenic aspects of gustation. Arzneimittel-

Forschung 14, 673-686.

Fischer, R., Griffen, F., England, S. and Garn, S. M. (1961) Taste thresholds and food

dislikes. Nature 191, 1328.

Fischer, R. and Griffin, F. (1959) On factors involved in the mechanism of taste

blindness. Experientia 15, 447-448.

Fischer, R. and Griffin, F. (1961) Taste blindness and variations in taste-threshold in

relation to thyroid metabolism. Journal of Neuropsychiatry 3, 98-104.

Fisher, R. A., Ford, E. B. and Huxley, J. (1939) Taste-testing the anthropoid apes. Nature

114, 750.

364 Flaxman, S. M. and Sherman, P. W. (2000) Morning sickness: A mechanism for

protecting mother and embryo. The Quarterly Review of Biology 75, 113-148.

Fox, A. L. (1931) Six in ten "tasteblind" to bitter chemical. Science News Letters 9, 249.

Fox, A. L. (1932) The relationship between chemical constitution and taste. Proceedings

of the National Academy of Sciences of the United States of America 18, 115-120.

Gaulin, S. J. C. and Konner, M. (1977) On the natural diet of primates, including humans.

In Nutrition and the Brain, Vol. 1, Wurtman, R. J. and Wurtman, J. J. eds, pp. 1-

86. Raven Press, New York.

Gent, J. F. and Bartoshuk, L. M. (1983) Sweetness of sucrose neohesperidin

dihydrochalcone, and saccharin is related to genetic ability to taste 6-n-

propylthiouracil. Chemical Senses 7, 265-272.

Glander, K. E. (1982) The impact of plant secondary compounds on primate feeding

behavior. Yearbook of Physical Anthropology 25, 1-18.

Glendinning, J. I. (1994) Is the bitter rejection response always adaptive? Physiology &

Behavior 56, 1217-1227.

Go, Y., Satta, Y., Takenaka, O. and Takahashi, N. (2005) Lineage-specific loss of

function of bitter taste receptor genes in humans and nonhuman primates.

Genetics 170, 313-326.

Guo, S.-W. and Reed, D. R. (2001) The genetics of phenylthiocarbamide perception.

Annals of Human Biology 28, 111-142.

Hall, M. J., Bartoshuk, L. M., Cain, W. S. and Stevens, J. C. (1975) PTC taste blindnes

and the taste of caffeine. Nature 253, 442-443. 365 Harris, H. and Kalmus, H. (1949) The measurement of taste sensitivity to phenylthiourea

(PTC). Annals of Eugenics, London 15, 32-45.

Hayes, J. E., Bartoshuk, L., Kidd, J. R. and Duffy, V. B. (2008) Supertasting and PROP

bitterness depends on more than the TAS2R38 gene Chemical Senses 33, 255-265.

Heinrich, M., Rimpler, H. and Barrera, N. A. (1992) Indigenous phytotherapy of

gastrointestinal disorders in a lowland Mixe community (Oaxaca, Mexico):

Ethnopharmacologic evaluation. Journal of Ethnopharmacology 36, 63-80.

Hosako-Naito, Y., Lucchina, L. A., Snyder, D. J., Boggiano, M. K., Duffy, V. B. and

Bartoshuk, L. M. (1996) Number of fungiform papillae in nontasters, medium

tasters, and supertasters of PROP (6-n-propylthiouracil). Chemical Senses 21,

616.

Huffman, M. (2003) Animal self-medication and ethno-medicine: Exploration and

exploitation of the medicinal properties of plants. Proceedings of the Nutrition

Society 62, 371-381.

Janjua, T. and Schwartz, S. (1997) unpublished data. In Duffy, V. B. and L. M.

Bartoshuk (2000) Food acceptance and genetic variation in taste. Journal of the

American Dietetic Association 100, 647-655.

Janson, C. H. and Chapman, C. A. (1999) Resources and primate community structure. In

Primate Communities, Fleagle, J. G., Janson, C. H. and Reed, K. E. eds, pp. 237-

267. Cambridge University Press, New York.

366 Jerzsa-Latta, M., Krondl, M. and Coleman, P. (1990) Use and perceived attributes of

cruciferous vegetables in terms of genetically-mediated taste sensitivity. Appetite

15, 127-134.

Kalmus, H. (1971) Genetics of taste. In Taste, Vol. 4, Chemical Senses, Part 2, Beidler,

L. M. ed, pp. 165-179. Springer-Verlag Berlin, Heidelberg.

Kaminski, L. C., Henderson, S. A. and Drewnowski, A. (2000) Young women's food

preferences and taste repsonsiveness to 6-n-porpylthiouracil (PROP). Physiology

& Behavior 68, 691-697.

Keast, R. S. J. and Breslin, P. A. S. (2002) An overview of binary taste–taste interactions

Food Quality and Preference 14, 111–124

Kim, U.-k., Jorgenson, E., Coon, H., Leppert, M., Risch, N. and Drayna, D. (2003)

Positional cloning of the human quantitative trait locus underlying taste sensitivity

to phenlythiocarbamide. Science 299, 1221-1225.

Koshimizu, K., Ohigashi, H. and Huffman, M. A. (1994) Use of Vernonia amygdalina by

wild chimpanzee: Possible roles of its bitter and related constituents. Physiology

& Behavior 56, 1209-1216.

Labov, J. B. (1977) Phytoestrogens and mammalian reproduction. Comparative

Biochemistry and Physiology 57A, 3-9.

Lambert, J. E. (1998) Primate digestion: Interactions among anatomy, physiology, and

feeding ecology. Evolutionary Anthropology 7, 8-20.

367 Laska, M. (2001) A comparison of food preferences and nutrient composition in captive

squirrel monkeys, Saimiri sciureus, and pigtail macaques, Macaca nemestrina.

Physiology & Behavior 73, 111-120.

Laska, M., Hernandez Salazar, L. T. and Rodriguez Luna, E. (2000) Food preferences

and nutrient composition in captive spider monkeys, Ateles geoffroyi.

International Journal of Primatology 21, 671-683.

Lawless, H. (1980) A comparison of different methods used to assess sensitivity to the

taste of phenylthiocarbamide (PTC). Chemical Senses 5, 247-256.

Leach, E. J. and Noble, A. C. (1986) Comparison of bitterness of caffiene and quinine by

a time-intensity procedure. Chemical Senses 11, 339-345.

Li, X., Staszewski, L., Xu, H., Durick, K., Zoller, M. and Adler, E. (2002) Human

receptors for sweet and umami taste. Proceedings of the National Academy of

Sciences of the United States of America 99, 4692-4696.

Lindemann, B. (1996) Taste reception. Physiological Reviews 76, 719-766.

Looy, H. and Weingarten, H. P. (1992) Facial expressions and genetic sensitivity to 6-n-

Propylthiouracil predict hedonic response to sweet. Physiology & Behavior 52,

75-82.

Lucchina, L. A., Curtis, O. F., Putnam, P., Drewnowski, A., Prutkin, J. M. and Bartoshuk,

L. M. (1998) Psychophysical measurement of 6-n-propylthiouracil (PROP) taste

perception. Annals of the New York Academy of Sciences 855, 816-819.

Matsunami, H., Montmayeur, J.-P. and Buck, L. B. (2000) A family of candidate taste

receptors in human and mouse. Nature 404, 601-604. 368 Miguet, L., Zhang, Z. and Grigorov, M. G. (2006) Computational studies of ligand-

receptor interactions in bitter taste receptors. Journal of Receptors and Signal

Transduction 26, 611-630.

Miller, I. J. (1986) Variation in human taste bud densities among regions and subjects.

The Anatomical Record 216, 474-482.

Miller, I. J. (1987) Human fungiform taste bud density and distribution. Annals of the

New York Academy of Sciences 510, 501.

Miller, I. J. and Bartoshuk, L. M. (1991) Taste perception, taste bud distribution, and

spatial relationships. In Smell and Taste in Health and Disease, Getchell, T. V.,

Doty, R. L., Bartoshuk, L. M. and Snow, J. B. J. eds, pp. 205-233. Raven Press,

New York.

Miller, I. J. and Reedy, F. E. (1990a) Quantification of fungiform papillae and taste pores

in living human subjects. Chemical Senses 15, 281-294.

Miller, I. J. and Reedy, F. E. (1990b) Variations in human taste bud density and taste

intensity perception. Physiology & Behavior 47, 1213-1219.

Milton, K. (1979) Factors influencing leaf choice by howler monkeys: A test of some

hypotheses of food selection by generalost herbivores American Naturalist 114,

362-378.

Milton, K. (1980) The foraging strategy of howler monkeys. Columbia University Press,

New York.

Milton, K. (1984) The role of food-processing factors in primate food choice. In

Adaptations for Foraging in Nonhuman Primates: Contributions to an 369 Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 249-279. Columbia University Press, New York.

Mistretta, C. M. (1991) Developmental neurobiology of the taste system. In Smell and

Taste in Health and Disease, Getchell, T. V., Doty, R. L., Bartoshuk, L. M. and

Snow, J. J. eds, pp. 35-64. Raven Press, New York.

Møller, A. R. (2003) Sensory Systems: Anatomy and Physiology. Academic Press,

London.

Nelson, G., Chandrashekar, J., Hoon, M. A., Feng, L., Zhao, G., Ryba, N. J. P. and

Zuker, C. S. (2002) An amino acid taste receptor. Nature 416, 199-202.

Nelson, G., Hoon, M. A., Chandrashekar, J., Zhang, Y., Ryba, N. J. P. and Zuker, C. S.

(2001) Mammalian sweet taste receptors. Cell 106, 381-390.

Parry, C. M., Erkner, A. and le Coutre, J. (2004) Divergence of T2R chemosensory

receptor families in humans, bonobos, and chimpanzees. Proceedings of the

National Academy of Sciences of the United States of America 101, 14830-14834.

Pasquet, P., Oberti, B., El Ati, J. and Hladik, C. M. (2002) Relationships between

threshold-based PROP sensitivity and food preferences of Tunisians. Appetite 39,

167-173.

Patel, S. (1971) ABO blood groups, PTC tasting and derrnatoglyphics of Tibetans at

Chandragiri, Orissa American Journal of Physical Anthropology 35, 149-150.

Pickering, G. J., Simunkova, K. and DiBattista, D. (2004) Intensity of taste and

astringency sensations elicited by red wines is associated with sensitivity to PROP

(6-n-propylthiouracil). Food Quality and Preference 15, 147-154. 370 Pieroni, A., Houlihan, L., Ansari, N., Hussain, B. and Aslam, S. (2007) Medicinal

perceptions of vegetables traditionally consumed by South-Asian migrants living

in Bradford, Northern England. Journal of Ethnopharmacology 113, 100-110.

Polcari, R. (1971) De nouvelles données sur la sensibilité à la phenil-thio-carbamide chez

les primates. Paper presented at the Proceeding of the Third International

Congress of Primatology, Zurich, 1971.

Provenza, F. D. (1996) Acquired aversions as the basis for varied diets of ruminants

foraging on rangelands. Journal of Animal Science 74, 2010-220.

Prutkin, J., Duffy, V. B., Etter, L., Fast, K., Gardner, E., Lucchina, L. A., Snyder, D. J.,

Tie, K., Weiffenbach, J. and Bartoshuk, L. M. (2000) Genetic variation and

inferences about perceived taste intensity in mice and men. Physiology &

Behavior 69, 161-173.

Purves, D., Fitzpatric, D., Katz, L. C., LaMantia, A.-S. and McNamara, J. O. (1997)

Neuroscience. Sinaur Associates, Inc., Sunderland, MA.

Rankin, K. M., Godinot, N., Christensen, C. M., Tepper, B. J. and Kirkmeyer, S. V.

(2004) Assessment of different methods for 6-n-propylthiouracil status

classification. In Genetic Variation in Taste Sensitivity, Prescott, J. and Tepper, B.

J. eds, pp. 63-88. Marcel Dekker, Inc., New York.

Reed, D. R. (2004) Progress in human bitter phenylthiocarbomide genetics. In Genetic

Variation in Taste Sensitivity, Prescott, J. and Tepper, B. J. eds, pp. 43-61. Marcel

Dekker, Inc., New York.

371 Reed, D. R., Bartoshuk, L. M., Duffy, V. B., Marino, S. and Price, A. (1995)

Propylthiouracil tasting: Determination of underlying threshold distributions

using maximum liklihood. Chemical Senses 20, 529-533.

Reed, D. R., Nanthakumar, E., North, M., Bell, C., Bartoshuk, L. M. and Price, R. A.

(1999) Localization of a gene for bitter taster perception to human chromosome

5p15. American Journal of Human Genetics 64, 1478-1480.

Reedy, F. E., Bartoshuk, L. M., Miller, I. J., Duffy, V. B., Lucchina, L. A. and

Yanagisawa, K. (1993) Relationships among papillae, taste pores, and 6-n-

propythiouracil (PROP) suprathreshold taste sensitivity. Chemical Senses 18, 618-

619.

Remis, M. J. and Kerr, M. E. (2002) Taste responses to fructose and tannic acid among

gorillas (Gorilla gorilla gorilla). International Journal of Primatology 23, 251-

261.

Rossier, O., Cao, J., Huque, T., Spielman, A. I., Feldman, R. S., Medrano, J. F., Brand, J.

G. and le Coutre, J. (2004) Analysis of human fungiform papillae cDNA library

and identification of taste-related genes. Chemical Senses 29, 13-23.

Scott, T. R., Giza, B. K. and Yan, J. (1998) Electrophysiological respnses to bitter stimuli

in primate cortex. Annals of the New York Academy of Sciences 855, 498-501.

Scott, T. R. and Plata-Salaman, C. R. (1999) Taste in the monkey cortex. Physiology &

Behavior 76, 489-511.

372 Segovia, C., Hutchinson, I., Laing, D. G. and Jinks, A. L. (2002) A quantitative study of

fungiform papillae and taste pore density in adults and children. Developmental

Brain Research 138, 135-146.

Shi, P., Zhang, J., Yang, H. and Zhang, Y.-p. (2003) Adaptive diversification of bitter

taste receptor genes in mammalian evolution. Molecular Biology and Evolution

20, 805-814.

Simmen, B. (1994) Taste discrimination and diet differentiation among New World

primates. In The Digestive System of Mammals: Food, Form, and Function,

Chivers, D. J. and Langer, P. eds, pp. 150-165. Cambridge University Press,

Cambridge.

Simmons, R. T., Graydon, J. J., Semple, N. M. and Swindlwer, D. R. (1956) A blood

group genetical survey in West Nakanai, New Britian. 14, 275-286.

Smith, D. G., Lorey, F. W. and Small, M. (1981) Taste sensitivity to phenylthiourea

(PTC) in the rhesus monkey (Macaca mulatta). Primates 22, 404-408.

Snyder, L. H. (1931) Inherited taste deficiency. Science 74, 151-152.

Steiner, J. E., Glaser, D., Hawilo, M. E. and Berridge, K. C. (2001) Comparative

expression of hedonic impact: affective reactions to taste by human infants and

other primates. Neuroscience and Biobehavioral Reviews 25, 53-74.

Tepper, B. (1998) 6-n-propylthiouracil: A genetic marker for taste with implications for

food preference and dietary habits. American Journal of Human Genetics 63,

1271-1276.

373 Tepper, B. J. (1999) Does genetic taste sensitivity to PROP influence food preferences

and body weight? Appetite 32, 422.

Tepper, B. J., Christensen, C. M. and Cao, J. (2001) Development of brief methods to

classify individuals by PROP taster status. Physiology & Behavior 73, 571-577.

Tepper, B. J. and Nurse, R. J. (1997) Fat perception is related to PROP taster status.

Physiology & Behavior 61, 494-954.

Tepper, B. J. and Nurse, R. J. (1998) PROP taster status is related to fat perception and

preference. Annals of the New York Academy of Sciences 855, 802-804.

Tepper, B. J. and Ullrich, N. (2002) Influence of genetic taste sensitivity to 6-n-

propylthiouracil (PROP), dietary restraint and disinhibition on body mass index in

middle-aged women. Physiology & Behavior 75, 305-312.

Ueno, A., Ueno, Y. and Tomonaga, M. (2004) Facial response to four basic tastes in

newborn rhesus macaques (Macaca mulatta) and chimpanzees (Pan troglodytes).

Behavioural Brain Research 154, 261-271.

Waterman, P. G. and Kool, K. (1994) Colobine food selection and plant chemistry. In

Colobine Monkeys: Their Ecology, Behavior, and Evolution, Davies, A. G. and

Oates, J. F. eds, pp. 251-284. Cambridge University Press, Cambridge.

Whissell-Beuchy (1990) Effects of age and sex on taste sensitivity to phenyltiocarbamide

(PTC) in the Berkley Guidance sample. Chemical Senses 15, 39-57.

Wooding, S. (2006) Phenylthiocarbamide: A 75-year adventure in genetics and natural

selection Genetics 172, 2015-2023.

374 Wooding, S., Bufe, B., Grassi, C., Howard, M. T., Stone, A. C., Vazquez, M., Dunn, D.

M., Meyerhof, W., Weiss, R. B. and Bamshad, M. J. (2006) Independent

evolution of bitter-taste sensitivity in humans and chimpanzees. Nature 440, 930-

934

Wooding, S., Kim, U.-k., Bamshad, M. J., Larsen, J., Jorde, L. B. and Drayna, D. (2004)

Natural selection and molecular evolution in PTC, a bitter-taste receptor gene.

American Journal of Human Genetics 74, 637-646.

Wrangham, R. W., Conklin-Brittain, N. L. and Hunt, D. M. (1998) Dietary responses of

chimpanzees and cercopithecines to seasonal variation in fruit abundance. I.

Antifeedants. International Journal of Primatology 19, 949-969.

Wynne-Edwards, K. E. (2001) Evolutionary biology of plant defenses against herbivory

and their predictive implications for endocrine disruptor susceptibility in

vertebrates. Environmental Health Perspectives 109, 443-448.

Yackinous, C. A. and Guinard, J.X. (2001) Relation between PROP taster status and fat

perception, touch, and olfaction. Physiology & Behavior 72, 427-437.

Yackinous, C. A. and Guinard, J.X. (2002) Relation between PROP (6-n-propythiouracil)

tater status, taste anatomy, and dietary intake measure for young men and women.

Appetite 38, 201-209.

Zhang, Y., Hoon, M. A., Chandrashekar, J., Mueller, K. L., Cook, B., Wu, D., Zuker, C.

S. and Ryba, N. J. P. (2003) Coding of sweet, bitter, and umami tastes: Different

receptor cells sharing similar signaling pathways. Cell 112, 293-301.

375 Zhao, G., Zhang, Y., Hoon, M. A., Chandrashekar, J., Erienbach, I., Ryba, N. J. P. and

Zuker, C. S. (2003) The receptors for mammalian sweet and umami taste. Cell

115, 255-266.

376 Chapter 5: Conclusions

The dietary niche of a primate plays a key role in the evolution of its biology (Lee-Thorp, 2002) and social behavior (Dunbar, 2002; Isbell, 1991; Janson, 1988; Kappeler and Van Schaik, 2002; Sterck et al., 1997; van Schaik, 1989; Wrangham, 1980). Foraging and feeding behavior have been proposed to have shaped many primate adaptations (Marshall and Wrangham, 2007) including cognitive ability (Clutton-Brock and Harvey, 1980; Milton, 1988), biomechanics (Feagle, 1984; Pontzer and Wrangham, 2004), digestive anatomy (Chivers and Hladik, 1980, 1984; Lambert, 1998), reproductive endocrinology (Lee and Hauser), and body size (Clutton-Brock and Harvey, 1977; Janson and Chapman, 1999). In addition, feeding behavior is also thought to have shaped the evolution of the special senses (vision Dominy, 2004a; Dulai et al., 1999; Regan et al., 2001; olfaction Dudley, 2002; Dudley, 2004; touch Hoffmann et al., 2004). Although the sense of taste is arguably the most important sense for the discrimination of food contents, few studies have addressed the role of dietary niche in the evolution of the primate gustatory system, especially from a broad, comparative perspective. The purpose of this dissertation was to provide insight into the evolution of the primate gustatory system through a comparative analysis of lingual fungiform papillae. Investigations fell into three categories: the effects of body mass on FP anatomy and taste sensitivity, the relationship between taste sensitivity and diet, and sex differences. Each of these categories will be discussed below.

EFFECTS OF BODY MASS

Body mass is an important consideration for broad interspecific analyses (Martin, 1990). Accordingly, the first part of this investigation was concerned with the 377 relationships among lingual anatomy and body mass. Analyses showed that body mass was positively correlated with the surface area of the dorsal tongue and with the area (i.e. size) of fungiform papillae. Conversely, body mass was negatively correlated with density of FP (Chapter 2). Both sweet taste sensitivity and diet are also correlated with body mass (Clutton-Brock and Harvey, 1977; Hladik and Simmen, 1996; Simmen and Hladik, 1998). Given the relationships of lingual anatomy, sweet taste sensitivity, and diet to body mass, subsequent analyses should take body mass into consideration. The approach used here to correct for body mass was to analyze ratios (diving by 3√body mass) and the residuals of DFP, or papilla area, and body mass. Results sometimes differed between ratios and residuals. For instance, sucrose threshold was correlated with DFP ratio, but not DFP residual. In other cases, significant results were found for residuals, but not ratios. Consequently, testing all three measures (uncorrected, ratio, and residual) would appear to be preferable to choosing just one of these measures. Significant results were also sometimes found when using an uncorrected measure of DFP or papilla area, while ratio and residual data did not yield significant results. For example, among all taxa together, papilla area was positively correlated with the percent of leaves in the diet, but results for papilla area ratio and residual were not significant. Such results suggest that body mass contributes considerably to the relationship among papilla area and leaf-eating. It does not, however, negate the biological or functional relevance of the relationship between papilla area and leaf-eating. Although both of these variables are related to body mass, papilla area (and therefore taste sensitivity) may still be an important factor in determining leaf feeding behavior.

378 TASTE SENSITIVITY AND DIET

After investigating the role of body mass, the relationships among FP anatomy, taste sensitivity, and diet were considered. While investigations of the non-human primate gustatory system are in their infancy, a large body of human research on this topic has been amassed. As a result, the patterns observed in humans were used to establish many of the expectations for what would be observed among the non-human primates in this research. These expectations included the predictions that, among non- human primates, taste sensitivity would be positively correlated with DFP and negatively correlated with fungiform papilla area. In contrast to these predictions, the exact opposite was found. Sucrose and fructose sensitivity were negatively correlated with DFP and positively correlated with papilla area (Chapter 2). Since most of the data on taste sensitivity was available for platyrrhines and strepsirrhines, these results should be interpreted only for to those two groups. Among platyrrhines and strepsirrnies, it appears that within a narrow size range (such as one species), a greater density of smaller papillae may confer greater sweet taste sensitivity. However, when comparing species of different sizes, even a relatively high density of smaller papillae (which are found in smaller species) does not confer greater sweet taste sensitivity compared with species that have a smaller density of larger papillae. In smaller species, with smaller papillae, there may be limited space for taste buds and the taste cells contained within them. Data from circumvallate papillae show that papillae of larger primate species tend to have more taste buds than the papillae of primates with smaller body sizes (Machida et al., 1967). This may be the case for fungiform papillae as well. In an attempt to understand the relationship between taste sensitivity and diet, DFP and papilla area were used as a proxy for sweet taste sensitivity in several analyses within Chapter 2. These analyses revealed clear phylogenetic differences. Strepsirrhines, 379 platyrrhines, and catarrhines each showed distinctive relationships between FP anatomy and dietary patterns. Other data showed phylogenetic differences as well. FP size was significantly smaller in strepsirrhines compared with haplorhines. Furthermore, significant correlations between FP and sucrose thresholds were not significant when analyzing independent contrasts. Like the effects of body mass, the results from phylogenetic analyses can be difficult to interpret when one variable is highly confounded with phylogeny (Garland et al., 2005). Diet, in particular, shows strong phylogenetic patterns (Garland et al., 2005). Accordingly, it is premature to rule out causal relationships among lingual anatomy, taste sensitivity, and diet at this time. It is clear, however, that phylogeny must be considered in future analyses of the primate guatatory system and it is suggested that comparisons of distantly related species be viewed with caution. For instance, Laska (2001) published a comparison of food preferences in Saimiri sciureus and Macaca nemestrina. Future research should focus more narrowly on closely related species, for instance those in the same family or subfamily.

SEX DIFFERENCES

The second group of predictions that were based on findings from human research related to sex differences in lingual anatomy and taste sensitivity. On average, human females have significantly higher DFPs and greater taste sensitivity than do males (Bartoshuk et al., 1994; Blakeslee and Salmon, 1931; Boyd and Boyd, 1936, 1937; Duffy and Bartoshuk, 2000; Falconer, 1947; Fernberger, 1932; Kim et al., 2003; Patel, 1971; Simmons et al., 1956; Tepper and Nurse, 1997; Whissell-Beuchy, 1990). Accordingly, non-human primate females were expected to have higher DFPs and greater taste

380 sensitivity than males. These expectations were investigated in Chapters 3 and 4. In Chapter 3, sex differences in DFP were investigated among five primate species. The results from this investigation showed a trend for females to have higher papillae densities in all five species. However, this sex differences was only significant in C. apella and P. troglodytes. The relevance of this sex difference among chimpanzees was further supported with data from Chapter 4, which showed that females are significantly more likely to have the genetic predisposition for greater taste sensitivity. On the other hand, three of the species tested did not show significant sex differences in DFP. An explanation for the difference in results for various species was offered. Capuchins, chimpanzees, and humans share large relative brain sizes and relatively extended life history variables, such as long gestation periods, that make each offspring costly in comparison to the other species tested (Chalmeau et al., 1997; Fragaszy and Bard, 1997; Gibson, 1986; Ross, 2002; Stephan et al., 1988; Van Schaik and Deaner, 2003; Walker et al., 2006). As a result, greater taste sensitivity may have been particularly valuable for females in these three species as they acquire the necessary nutrients and avoid toxins during gestation and lactation. Testing this hypothesis, however, will require data from many additional primate species.

SEX DIFFERENCES AND THE EVOLUTION OF THE HUMAN GUSTATORY SYSTEM

With relatively larger brain sizes and long periods of infant dependency, I have argued that more k-selected species should show relatively greater sex differences in gustatory anatomy and function. This relationship between infant dependency and gustatory sex differences would be particularly true for humans. The high maternal investment during gestation, lactation, and altricial childhood development would

381 ostensibly select for an especially keen gustatory ability among human females. More specifically, the ability to detect bitter tasting toxins would be essential for health and reproductive success. While detection of compounds that are sour, salty, umami, or sweet tasting is clearly important in the food selection process, it is arguable that detection of bitter tasting compounds is more critical to survival and health. The adverse effects of ingesting toxins are numerous, including disrupted reproduction (Profet, 1995, Wynne- Edwards, 2001). Conversely, unknowing ingestion of a sweet tasting compound would not have dire health consequences for most individuals or their reproductive capacity. Instead, it is probably adaptive to have a conservative warning system in place to regulate the risk of ingesting potentially harmful, bitter tasting substances. Interestingly, in contrast to the discriminatory ability for sweet taste, there is limited functional discrimination among different bitter tasting compounds (Adler et al., 2000). As a result, the gustatory system can recognize the presence of a bitter stimulus, but does not allow for conscious determination of which particular stimulus is present. Genetic evidence also points to the importance of the human ability to detect bitter tasting compounds. T1R sweet receptor genes appear to evolve slowly in comparison with T2R bitter taste receptor genes (Shi and Zhang, 2006; Shi et al., 2003). On the other hand, investigations of the quantity and relatively rapid rate of pseudogenization consistently show that the primate T2R gene family is under relaxed constraints, especially in humans (Fischer et al., 2005; Go et al., 2005; Parry et al., 2004; Wang et al., 2004). Variability in T2R genes could indicate that humans rely relatively less on their sensitivity to bitter tasting compounds compared with non-human primates, or that humans’ bitter taste ability has adapted rapidly to detect different bitter tasting compounds found in local environments (Go et al., 2005; Kim et al., 2005; Parry et al., 2004; Wang et al., 2004; Wooding et al., 2004). 382 There are several means by which primates avoid ingesting high levels of toxins. Dietary diversification, for example, allows some toxins to be ingested but at relatively low levels (Provenza et al., 2003). Food processing is also a common method of toxin avoidance. For instance, toxins are often localized in a plant part that can be removed (e.g. seeds). Several methods of food processing are unique to humans, including soaking, grinding, fermenting, and heating (Profet, 1995). Cooking can serve to detoxify many plants that would otherwise need to be avoided (Stahl et al., 1984). The ability to cook foods must have had enormous consequences for the dietary repertoire of hominids once they gained control of fire as early as 790,000 years ago (Goren-Inbar et al., 2004; Harris, 1992; Wang et al., 2004). In fact, the ability to cook food items may be related to changes in T2R genes (Goren-Inbar et al., 2004; Harris, 1992; Wang et al., 2004). It is possible that the use of fire could have relaxed selection for bitter taste receptors, but this is unlikely in my opinion. Even human processes of detoxification do not preclude the initial need for identifying the presence of toxins to determine whether the item requires processing in the first place. Initially detecting the presence of toxins almost assuredly requires the sense of taste. If toxins are not detected by the gustatory system and are ingested in too great a concentration, the regurgitation response is one last line of defense against toxicosis. Unlike primates, many rodents and lagomorphs, such as rats, mice, guinea pigs, hamsters, and rabbits are incapable of vomiting (Andrews and Horn, 2006). Instead, non-vomiting species probably avoid toxicosis by acquiring learned aversions quite rapidly (Andrews and Horn, 2006). Interestingly, non-vomiting species are also much more r-selected than primates. An investigation of a link between rapid learning of toxin identification and rapid reproduction would be of great interest. Perhaps it is because k-selected species have a longer learning process that they require the ability to vomit. Furthermore, as one 383 of the most k-selected primates (see chapter 3), it is possible that the ability and propensity of human females to vomit during pregnancy (i.e. pregnancy sickness) is a particularly critical method of avoiding toxicosis for mother and fetus. Even without significantly affecting the mother, many toxins increase an embryo’s risk of birth defects (Profet, 1995). In a highly k-selected species such as humans, birth defects could be devastating to a female’s reproductive success. In addition to being more sensitive to bitter tasting compounds generally, women are also more susceptible to nausea than men (Profet, 1995). Furthermore, human females are known to become even more sensitive to bitter tasting compounds in the first trimester of pregnancy (Duffy et al., 1998), the time at which time nausea and vomiting is also most likely to occur. Even if pregnancy sickness is assumed to protect the mother and fetus from toxins during pregnancy, however, evidence is lacking as to whether this is a uniquely human phenomenon. Research on pregnancy sickness in non-human primates has yet to be conducted and would be of interest in this case. Additionally, the presence or increased frequency of geophagy during non-human primate pregnancy could be telling. Human females of some cultures are known to consume clay only during pregnancy, and it has been hypothesized that this behavior serves to mitigate the detrimental effects of toxins in the diet (Wiley and Solomon, 1998).

FURTHER INVESTIGATION

One benefit of this dissertation was the identification of areas requiring further research. Additional data on detection thresholds would help to resolve our understanding of the interspecific relationships between taste sensitivity and FP anatomy. Our understanding of within-species relationships between taste sensitivity and FP anatomy

384 would benefit from data on taste thresholds as well. The methods for Chapter 4 included testing chimpanzees for acceptance or rejection of a single concentration of PTC, in which case DFP was not correlated with behavioral responses to the bitter stimulus. It is likely that taste thresholds are correlated with DFP in chimpanzees, as they are in humans. Two-bottle testing is required to obtain thresholds, however, rather than testing at a single concentration. Unfortunately, data on detection thresholds are difficult to obtain in adequate numbers. Consequently, if a clear relationship could be established between FP anatomy and gustatory sensitivity, a great deal of research could be conducted using anatomical measures as a proxy. This is beneficial in several ways, including the ability to collect data on wild animals, which can then be observed for data on feeding behavior. Notably, the data on humans are usually collected using bitter tasting stimuli (PROP), whereas the majority of non-human primate data are derived from tests using sweet tasting stimuli. Currently, more data on primate taste thresholds are available for sweet taste thresholds (e.g. fructose and sucrose) than for bitter taste thresholds (e.g. quinine hydrochloride). Given the wealth of data on PTC and PROP sensitivity in humans, additional investigations of PTC sensitivity in non-human primates would be provide noteworthy material for comparisons with the human data. In addition to taste thresholds, histological investigations will help to clarify anatomical differences among species, such as the number of taste cells within fungiform papillae. Data are also needed on the genetics of the receptors responsible for the detection of various compounds, and data on which receptors are expressed in the FP of various primate species. Finally, precise dietary data would aid in deciphering the role of taste in primate food selections. The chemical composition of primate foods should be

385 known. In addition to data on consumed foods, data on plant species that are never eaten and those that are taste-tested and rejected (Glander, 1982) would be beneficial.

386 REFERENCES Andrews, P. L. R. and Horn, C. C. (2006) Signals for nausea and emesis: Implications for

models of upper gastrointestinal diseases. Autonomic Neuroscience 125, 100-115.

Bartoshuk, L. M., Duffy, V. B. and Miller, I. J. (1994) PTC/PROP tasting: anatomy,

psychophysics, and sex effects. Physiology & Behavior 56, 1165-1171.

Blakeslee, A. F. and Salmon, M. R. (1931) Odor and taste blindness. Eugenical News 16,

105-109.

Boyd, W. C. and Boyd, L. G. (1936) New racial blood group studies in Europe and

Egypt. Science 84, 328-329.

Boyd, W. C. and Boyd, L. G. (1937) Sexual and racial variations in ability to taste

phenylthiocarbamide, with some data in the inheritance. Annals of Eugenics,

London 8, 46-51.

Chalmeau, R., Visalberghi, E. and Gallo, A. (1997) Capuchin monkeys, Cebus apella fail

to understand a cooperative task. Animal Behaviour 54, 1215-1225.

Chivers, D. J. and Hladik, C. M. (1980) Morphology of the gastrointestinal tract in

primates: Comparisons with other mammals in relation to diet. Journal of

Morphology 166, 337-386.

Chivers, D. J. and Hladik, C. M. (1984) Diet and gut morphology in primates. In Food

acquisition and processing in primates, Chivers, D. J., Wood, B. A. and

Bilsborough, A. eds, pp. 213-230. Plenum Press, New York.

Clutton-Brock, T. H. and Harvey, P. H. (1977) Species differences in feeding and ranging

behavior in primates. In Primate Ecology: Studies of Feeding and Ranging 387 Behavior in Lemurs,Monkeys, and Apes, Clutton-Brock, T. H. and Harvey, P. H.

eds, pp. 557-584. Academic Press, London.

Clutton-Brock, T. H. and Harvey, P. H. (1980) Primates, brains and ecology. Journal of

Zoology, London 190, 309-323.

Dominy, N. (2004) Color as an indicator of food quality to anthropoid primates:

Ecological evidence and an evolutionary scenario. In Anthropoid Origins: New

Visions, Ross, C. F. and Kay, R. F. eds, pp. 615-644. Kluwer Academic, New

York.

Dudley, R. (2002) Fermenting fruit and the historical ecology of ethanol ingestion: Is

alcoholism in modern humans an evolutionary hangover? Addiction 97, 381-388.

Dudley, R. (2004) Ethanol, fruit ripening, and the historical origins of human alcoholism

in primate frugivory. Integrated and Comparative Biology 44, 315-323.

Duffy, V. B. and Bartoshuk, L. M. (2000) Food acceptance and genetic variation in taste.

Journal of the American Dietetic Association 100, 647-655.

Dulai, K. S., von Dornum, M., Mollon, J. D. and Hunt, D. M. (1999) The evolution of

trichromatic color vision by opsin gene duplication in new world and old world

primates Genome Research 9?, 629-638.

Dunbar, R. I. M. (2002) Modeling primate behavioral ecology. International Journal of

Primatology 23, 785-819.

Falconer, D. S. (1947) Sensory thresholds for solutions of phenylthiocarbamide. Results

of tests on a large sample, made by R. A. Fisher. Annals of Eugenics, London 13,

211-222. 388 Feagle, J. G. (1984) Primate locomotion and diet. In Food acquisition and processing in

primates, Chivers, D. J., Wood, B. A. and Bilsborough, A. eds, pp. 105-117.

Plenum Press, New York.

Fernberger, S. W. (1932) A preliminary study of taste deficiency. Journal of Psychology

44, 322-326.

Fischer, A., Gilad, Y., Man, O. and Paabo, S. (2005) Evolution of bitter taste receptors in

humans and apes. Molecular and Biology and Evolution 22, 432-436.

Fragaszy, D. M. and Bard, K. (1997) Comparison of Development and Life History in

Pan and Cebus. International Journal of Primatology 18, 683-701.

Garland, T., Bennett, A. F. and Rezende, E. L. (2005) Phylogenetic approaches in

comparative physiology. The Journal of Experimental Biology 208, 3015-3035

Gibson, K. R. (1986) Cognition, brain size and the extraction of embedded food

resources. In Primate ontongeny, cognition and social behavior, Vol. 3, Else, J.

G. and Lee, P. C. eds, pp. 93-103. Cambridge University Press, Cambridge.

Glander, K. E. (1982) The impact of plant secondary compounds on primate feeding

behavior. Yearbook of Physical Anthropology 25, 1-18.

Go, Y., Satta, Y., Takenaka, O. and Takahashi, N. (2005) Lineage-specific loss of

function of bitter taste receptor genes in humans and nonhuman primates.

Genetics 170, 313-326.

Goren-Inbar, N., Alperson, N., Kislev, M. E., Simchoni, O., Melamed, Y., Ben-Nun, A.

and Werker, E. (2004) Evidence of hominin control of fire at Gesher Benot

Ya`aqov, Israel. Science 304, 725 - 727. 389 Harris, D. R. (1992) Human diet and subsistence. In: The Cambridge encyclopedia of

human evolution, Jones, S., Martin, R. and Pilbeam, D. eds, pp. 69-74. Cambridge

University Press.

Hladik, C. M. and Simmen, B. (1996) Taste perception and feeding behavior in

nonhuman primates and human populations. Evolutionary Anthropology 5, 58-71.

Hoffmann, J. N., Montag, A. G. and Dominy, N. (2004) Meissner corpuscles and

somatosensory acuity: The prehensile appendages of primates and elephants. The

Anatomical Record Part A 281A, 1138-1147.

Isbell, L. (1991) Contest and scramble competition: patterns of female aggression and

ranging behavior among primates. Behavioral Ecology 2, 143-155.

Janson, C. H. (1988) Intraspecific food competition and primate social structure: a

synthesis. Behaviour 105, 1-17.

Janson, C. H. and Chapman, C. A. (1999) Resources and primate community structure. In

Primate Communities, Fleagle, J. G., Janson, C. H. and Reed, K. E. eds, pp. 237-

267. Cambridge University Press, New York.

Kappeler, P. M. and Van Schaik, C. P. (2002) Evolution of primate social systems.

International Journal of Primatology 23, 707-740.

Kim, U.-k., Jorgenson, E., Coon, H., Leppert, M., Risch, N. and Drayna, D. (2003)

Positional cloning of the human quantitative trait locus underlying taste sensitivity

to phenlythiocarbamide. Science 299, 1221-1225.

390 Kim, U., Wooding, S., Ricci, D., Jorde, L. B. and Drayna, D. (2005) Worldwide

haplotype diversity and coding sequence variation at human bitter taste receptor

loci. Human Mutation 26, 199-204.

Lambert, J. E. (1998) Primate digestion: Interactions among anatomy, physiology, and

feeding ecology. Evolutionary Anthropology 7, 8-20.

Lee, P. C. and Hauser, M. D. Long-term consequences of changes in territory quality on

feeding and reproductive strategies of vervet monkeys. The Journal of Animal

Ecology 67, 347-358.

Lee-Thorp, J. (2002) Hominid dietary niches from proxy chemical indicators in fossils:

The Swartkrans example. In Human Diet: Its Origins and Evolution, Ungar, P. S.

and Teaford, M. F. eds. Bergin and Garvey, Westport, Connecticut.

Machida, H., Perkins, E. and Giacommetti, L. (1967) The anatomical and histochemical

properties of the tongue of primates. Folia Primatologica 5, 264-279.

Marshall, A. and Wrangham, R. (2007) Evolutionary Consequences of Fallback Foods.

International Journal of Primatology 28, 1219-1235.

Martin, R. D. (1990) Primate Origins and Evolution: A Phylogenetic Reconstruction.

Princeton University Press, Princeton.

Milton, K. (1988) Foraging behavior and the evolution of priamte intelligence. In

Machiavellian Intelligence: Social Expertise and the Evolution of Intellect in

Monkeys, Apes, and Humans, Byrne, R. W. and Whiten, A. eds, pp. 285-305.

Clarendon Press, Oxford.

391 Parry, C. M., Erkner, A. and le Coutre, J. (2004) Divergence of T2R chemosensory

receptor families in humans, bonobos, and chimpanzees. Proceedings of the

National Academy of Sciences of the United States of America 101, 14830-14834.

Patel, S. (1971) ABO blood groups, PTC tasting and derrnatoglyphics of Tibetans at

Chandragiri, Orissa American Journal of Physical Anthropology 35, 149-150.

Pontzer, H. and Wrangham, R. W. (2004) Climbing and the daily energy cost of

locomotion in wild chimpanzees: implications for hominoid locomotor evolution.

Journal of Human Evolution 46, 315-335.

Profet, M. (1995) Pregnancy sickness: Using your body's natural defenses to protect your

baby-to-be. Addison-Wesley Publishing Group, Reading, MA.

Provenza, F. D., Villalba, J. J., Dziba, L. E., Atwood, S. B. and Banner, R. E. (2003)

Linking herbivore experience, varied diets, and plant biochemical diversity. Small

Ruminant Research 49, 257-274.

Regan, B. C., Julliot, C., Simmen, B., Vienot, F., Charles-Dominique, P. and J.D., M.

(2001) Fruits, foliage and the evolution of primate colour vision. Philosophical

Transactions of the Royal Society of London. Series B: Biological Sciences 356,

229-283.

Ross, C. (2002) Life history, infant care strategies, and brain size in primates. In Primate

Life Histories and Socioecology, Kappeler, P. M. and Pereira, M. E. eds, pp. 266-

284. University of Chicago Press, Chicago.

392 Shi, P. and Zhang, J. (2006) Contrasting modes of evolution between vertebrate

sweet/umami receptor genes and bitter receptor genes. Molecular Biology and

Evolution 23, 292-300.

Shi, P., Zhang, J., Yang, H. and Zhang, Y.-p. (2003) Adaptive diversification of bitter

taste receptor genes in mammalian evolution. Molecular Biology and Evolution

20, 805-814.

Simmen, B. and Hladik, C. M. (1998) Sweet and bitter taste discrimination in primates:

Scaling effects across species. Folia Primatologica 69, 129-138.

Simmons, R. T., Graydon, J. J., Semple, N. M. and Swindlwer, D. R. (1956) A blood

group genetical survey in West Nakanai, New Britian. 14, 275-286.

Stahl, A. B., Dunbar, R. I. M., Homewood, K., Ikawa-Smith, F., Kortlandt, A., McGrew,

W. C., Milton, K., Paterson, J. D., Poirier, F. E., Sugardjito, J., Tanner, N. M. and

Wrangham, R. W. (1984) Hominid dietary selection before fire. Current

Anthropology 25, 151-168.

Stephan, H., Baron, G. and Frahm, H. (1988) Comparative size of brains and brain

components. In Comparative Primate Biology, Steklis, H. D. and Erwin, J. eds,

pp. 1-39. Liss, New York.

Sterck, E. H. M., Watts, D. P. and van-Schaik, C. P. (1997) The evolution of female

social relationships in nonhuman primates. Behavioral ecology and sociobiology

41, 291-311.

Tepper, B. J. and Nurse, R. J. (1997) Fat perception is related to PROP taster status.

Physiology & Behavior 61, 494-954. 393 van Schaik, C. P. (1989) The ecology of social relationships amongst female primates. In

Comparative Socioecology: The behavioral ecology of humans and other

mammals, Standen, V. and Foley, R. A. eds, pp. 195 - 218. Blackwell Scientific

Publications, Oxford.

Van Schaik, C. P. and Deaner, R. O. (2003) Life history and cognitive evolution in

primates. In Animal Social Complexity: Intelligence, Culture, and Individualized

Societies, de Waal, F. B. M. and Tyack, P. L. eds, pp. 5-25. Harvard Univeristy

Press, Cambridge.

Walker, R., Burger, O., Wagner, J. and Von Rueden, C. R. (2006) Evolution of brain size

and juvenile periods in primates. Journal of Human Evolution 51, 480.

Wang, X., Thomas, S. D. and Zhang, J. (2004) Relaxation of selective constraint and loss

of function in the evolution of human bitter taste receptor genes. Human

Molecular Genetics 13, 2671-2678.

Whissell-Beuchy (1990) Effects of age and sex on taste sensitivity to phenyltiocarbamide

(PTC) in the Berkley Guidance sample. Chemical Senses 15, 39-57.

Wiley, A. S. and Solomon, H. K. (1998) Geophagy in pregnancy: A test of a hypothesis.

Current Anthropology 39, 532-545.

Wooding, S., Kim, U.-k., Bamshad, M. J., Larsen, J., Jorde, L. B. and Drayna, D. (2004)

Natural selection and molecular evolution in PTC, a bitter-taste receptor gene.

American Journal of Human Genetics 74, 637-646.

Wrangham, R. W. (1980) An ecological model of female-bonded primate groups.

Behaviour 75, 262-299. 394

Appendix: Data for individual samples

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Alouatta palliata — 18 27.91 — — — F 4.10 L Alouatta palliata — 17 38.37 — — — F 5.00 L Alouatta palliata — 14 22.69 — — — F 4.20 L Alouatta palliata — 14 21.08 — — — F 4.90 L Alouatta palliata — — 19.14 — — — F 3.95 L Alouatta palliata 1.980 15 20.55 — — — F 4.50 L Alouatta palliata 2.442 10 21.13 — — — F 4.50 L Alouatta palliata — 7 12.48 — — — F 4.75 L Alouatta palliata 2.245 31 42.82 — — — F 5.25 L Alouatta palliata — 13 16.35 — — — M 6.00 L Alouatta palliata 0.791 21 31.38 — — — M 4.50 L Alouatta palliata — — 16.70 — — — M 6.90 L Alouatta palliata — 12 18.30 — — — M 4.25 L Alouatta palliata — 8 10.47 — — — M 6.25 L Aotus trivirgatus 1.437 41 83.67 — — — M — C Aotus trivirgatus 1.444 38 78.03 — — — M — C Aotus trivirgatus 1.293 45 87.55 — — — x — C Aotus vociferans — 41 82.16 — — — F — C Aotus vociferans — 50 106.84 — — — F — C Aotus vociferans 0.689 37 77.73 — — — M — C Aotus vociferans 1.415 40 93.68 — — — M — C Aotus vociferans 1.165 31 68.43 — — — M — C Ateles geoffroyi 2.237 30 51.19 — — — F 8.50 L Ateles geoffroyi 3.667 20 29.41 — — — F 7.60 L Ateles geoffroyi 1.655 30 57.69 5.210 68 13.05 x — C

395 Ateles geoffroyi — 31 52.45 6.434 120 18.65 x — C

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Ateles geoffroyi 2.453 27 53.05 6.143 x — C Ateles paniscus — — — 6.869 63 9.17 x — C Ateles paniscus — 40 82.82 5.627 99 17.59 x — C Ateles paniscus 1.800 41 76.49 7.194 137 19.04 x — C Callithrix jacchus — 56 235.29 1.551 107 68.99 F — C Callithrix jacchus 0.569 49 232.23 — — — F — C Callithrix jacchus — 47 173.43 — — — F — C Callithrix jacchus — 44 280.25 — — — F — C Callithrix jacchus — 49 213.04 — — — M — C Callithrix jacchus 0.494 64 249.03 — — — x — C Callithrix jacchus 0.468 55 212.36 — — — x — C Callithrix jacchus — 60 270.27 — — — x — C Callithrix jacchus — 41 168.03 — — — x — C Callithrix jacchus — 64 221.45 — — — x — C Callithrix jaccus — — — 1.779 125 70.26 M — C Cebuella pygmea 0.350 71 327.19 1.072 91 84.89 F 0.12 C Cebuella pygmea 0.292 — — 0.776 125 161.08 M — C Cebus apella 1.313 48 112.41 — — — F 2.28 C Cebus apella 2.600 71 95.17 — — — F 2.65 C Cebus apella 1.352 48 84.81 — — — F 3.25 C Cebus apella — 69 126.61 — — — F 2.31 C Cebus apella — 54 73.87 — — — M 4.06 C Cebus apella — 37 58.27 — — — M 4.21 C Cebus apella — 38 53.07 — — — M 3.22 C Cebus apella — 55 104.76 — — — M 4.59 C Cebus apella — 43 69.47 — — — M 3.96 C Cebus apella — 60 90.77 — — — M 3.50 C Cebus apella — 33 58.20 — — — M 3.50 C 396 Cebus apella — 61 94.14 — — — M 3.26 C

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Cercopithecus aethiops — 57 91.35 7.117 105 14.75 F — C Cercopithecus aethiops — 52 74.82 — — — F — C Cercopithecus aethiops — 84 168.67 — — — F 2.50 L Cercopithecus aethiops — 78 168.10 — — — F 3.00 L Cercopithecus aethiops — — 86.45 — — — F 3.50 L Cercopithecus aethiops — 47 90.36 — — — F 3.80 L Cercopithecus aethiops — 80 175.05 — — — F 4.00 L Cercopithecus aethiops — 70 125.08 — — — F 5.10 L Cercopithecus aethiops — — 175.76 — — — F 3.50 L Cercopithecus aethiops — 60 129.68 — — — F 3.75 L Cercopithecus aethiops — — 75.67 — — — F 3.25 L Cercopithecus aethiops 4.600 50 93.28 — — — M — C Cercopithecus aethiops 2.413 71 77.09 — — — M — C Cercopithecus aethiops — 70 142.86 — — — M — C Cercopithecus aethiops — — 156.03 — — — M 3.75 L Cercopithecus aethiops — — 174.07 — — — M 3.00 L Cercopithecus aethiops — 68 116.24 — — — M 2.70 L Cercopithecus aethiops — 54 129.07 — — — M 4.50 L Cercopithecus aethiops — 75 170.05 — — — M 2.50 L Cercopithecus aethiops — — 120.90 — — — M 2.00 L Cercopithecus aethiops — — 90.09 — — — M 7.00 L Cercopithecus aethiops 1.235 42 81.21 — — — M 5.50 L Cercopithecus aethiops 2.200 59 107.33 — — — M 3.00 L Cercopithecus ascanius — — — 5.659 96 16.96 F — C Cercopithecus ascanius — — — 6.826 116 16.99 M — C Cercopithecus diana — — — 7.897 51 6.46 M — C Cercopithecus neglectus — — — 6.463 179 27.70 F — C Cercopithecus neglectus — — — 8.557 — — M — C 397 Cercopithecus petaurista — — — 10.537 48 4.56 F — C

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Cercopithecus petaurista — — — 9.455 45 4.76 M — C Cheirogaleus major 0.540 31 102.65 — — — M — C Chierogaleus major — — — — 111 — M — C Colobus guereza 3.795 37 27.75 — — — F 11.70 L Colobus guereza 3.400 28 18.54 — — — F 9.30 L Colobus polykomos — 32 60.49 6.397 135 21.10 F — C Colobus polykomos — 25 31.49 11.086 154 13.89 F — C Colobus polykomos 4.282 32 48.93 13.108 184 14.04 M — C Daubentonia 1.289 — — — — — F 2.50 L madagascariensis D. madagascariensis 1.600 30 53.76 — — — M 2.78 L Eulemur fulvus colaris 0.842 34 58.72 — — — F 2.18 L Eulemur fulvus colaris — 28 58.21 — — — F 2.30 L Eulemur fulvus colaris 0.728 28 59.45 — — — M 2.08 L Eulemur fulvus colaris 0.830 35 78.83 — — — M 2.08 L Eulemur fulvus colaris — 34 67.19 — — — M 2.32 L Eulemur macaco macaco — 33 74.32 — — — F 2.19 C Eulemur macaco macaco 0.914 27 57.20 — — — F 2.02 L Eulemur macaco macaco 0.770 26 58.96 — — — F 2.60 L Eulemur macaco macaco 1.216 9 32.97 — — — M 2.34 L Eulemur mongoz 0.395 38 99.74 — — — F 1.21 C Hapalemur griseus 0.461 37 130.28 — — — F 0.80 C griseus H. g. griseus 0.532 38 137.18 — — — F 0.88 C H. g. griseus 0.387 45 142.86 — — — F 0.64 C Hylobates lar — — — 6.347 112 17.65 F — C Hylobates lar 2.292 37 44.21 — — — F 6.39 L Hylobates lar 2.800 26 29.61 — — — M 8.90 L Lemur catta 0.403 36 100.28 — 261 — F 2.21 C

398 Lemur catta 0.972 24 53.10 — — — M 2.38 C

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Lemur catta 0.448 33 60.11 — — — M 2.53 C Macaca fascicularis 1.364 90 130.81 — — — x — C Macaca fascicularis 2.400 77 126.64 — — — x — C Macaca fascicularis 2.448 68 129.52 — — — x — C Macaca mulatta 1.309 50 103.31 14.199 82 5.78 F — C Macaca mulatta 2.200 39 60.47 18.897 256 13.55 F 8.80 C Macaca mulatta — 40 75.76 10.950 F — C Macaca mulatta — 29 88.41 11.816 222 18.79 M — C Macaca mulatta 1.976 71 100.14 — — — M — C Microcebus murinus 0.122 72 473.68 — — — F 0.06 C Otolemur crassicaudatus 0.136 26 119.82 — — — F — C Otolemur crassicaudatus 0.551 39 112.07 — — — F — C Otolemur crassicaudatus 0.823 25 73.75 — — — F — C Otolemur crassicaudatus — — — 7.317 91 12.44 M — C Otolemur garnetti 0.440 34 100.59 8.297 — — M — C Otolemur garnetti 0.394 60 189.87 — — — x — C Otolemur garnetti 0.326 58 196.61 — — — x — C Pan troglodytes — 59 41.87 — — — F 71.90 L Pan troglodytes 3.449 63 56.20 — — — F 69.60 L Pan troglodytes — 66 46.87 — — — F 58.90 L Pan troglodytes — 49 47.41 — — — F 56.40 L Pan troglodytes — 68 61.43 — — — F 54.70 L Pan troglodytes — 47 49.32 — — — F 68.50 L Pan troglodytes 6.489 67 62.21 — — — F 54.30 L Pan troglodytes — 61 44.02 — — — F 70.50 L Pan troglodytes — 66 43.42 — — — F 61.70 L Pan troglodytes — 51 52.65 — — — F 72.50 L Pan troglodytes 3.770 93 72.66 — — — F 63.90 L 399 Pan troglodytes — 78 53.35 — — — F 82.90 L

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Pan troglodytes — 88 68.63 — — — F 50.90 L Pan troglodytes — 81 52.94 — — — F 69.80 L Pan troglodytes — 80 65.04 — — — F 59.30 L Pan troglodytes — 60 50.17 — — — F 84.20 L Pan troglodytes — 75 54.47 — — — F 64.50 L Pan troglodytes — 74 50.34 — — — F 47.80 L Pan troglodytes — 62 54.87 — — — F 69.70 L Pan troglodytes — 70 57.55 — — — F 62.80 L Pan troglodytes — 80 62.35 — — — F 63.50 L Pan troglodytes — 78 67.71 — — — F 49.70 L Pan troglodytes — 44 40.57 — — — M 73.00 L Pan troglodytes — 66 46.20 — — — M 67.40 L Pan troglodytes 6.871 52 31.71 — — — M 61.00 L Pan troglodytes — 51 51.57 — — — M 70.60 L Pan troglodytes — 74 48.16 — — — M 58.20 L Pan troglodytes — 64 33.38 — — — M 50.00 L Pan troglodytes — 101 75.04 — — — M 64.40 L Pan troglodytes — 86 65.19 — — — M 78.60 L Pan troglodytes — 52 42.87 — — — M 61.90 L Pan troglodytes — 78 58.21 — — — M 58.80 L Pan troglodytes — 46 27.62 — — — M 64.60 L Pan troglodytes — 48 39.23 — — — M 65.60 L Pan troglodytes — 61 58.37 — — — M 71.10 L Pan troglodytes — 68 46.52 — — — M 69.20 L Pan troglodytes — 73 29.76 — — — M 54.70 L Pan troglodytes — 31 19.81 — — — M 61.30 L Pan troglodytes — 54 37.32 — — — M 70.40 L Pan troglodytes — 75 64.88 — — — M 59.40 L 400 Pan troglodytes — 63 51.81 — — — M 64.60 L

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Pan troglodytes — 69 42.88 — — — M 74.60 L Pan troglodytes — 53 39.23 — — — M 71.00 L Pan troglodytes — 64 60.15 — — — M 72.00 L Pan troglodytes — 65 51.51 — — — M 77.40 L Pan troglodytes — 48 32.63 — — — M 68.00 L Papio anubis — 73 99.05 — — — F — C Papio cynocephalus 1.466 119 166.43 28.476 519 18.23 F — C anubis P. c. anubis 1.967 80 102.17 33.402 447 13.38 F — C P. c. anubis 1.754 84 99.06 39.876 579 14.52 M — C P. c. anubis — 75 96.65 42.500 482 11.34 M — — Piliocolobus badius 1.242 50 93.28 6.129 — — F — C Pongo pygmaeus 3.075 48 32.97 — — — F 103* L pygmaeus Presbytis fransoisi 3.092 76 83.89 — — — x — C Propithecus coquereli — 38 73.08 — — — F 4.16 C Propithecus coquereli 0.824 53 96.72 — — — F 3.94 L Propithecus coquereli 0.720 54 94.57 — — — M 4.18 L Propithecus coquereli 0.960 60 108.89 — — — M 3.64 L Propithecus edwardsi 0.881 26 59.63 — — — F 5.70 L Propithecus edwardsi — 29 70.22 — — — F 5.13 L Propithecus edwardsi — 36 73.47 — — — F 5.85 L Propithecus edwardsi 1.228 34 65.38 — — — F 6.23 L Propithecus edwardsi 0.523 45 63.11 — — — M 5.35 L Propithecus edwardsi — 37 72.41 — — — M 5.07 L Propithecus tattersali 0.637 23 92.37 — — — F 4.30 C Propithecus tattersali 0.744 66 168.80 — — — M 2.98 C Saguinus oedipus 0.950 36 145.75 — — — F — C Saguinus oedipus 0.812 46 165.47 — — — M — C

401 Saimiri sciureus — 39 103.17 — — — F — C

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Saimiri sciureus — 14 36.65 — — — F — C Saimiri sciureus 0.684 5 26.74 — — — F — C Saimiri sciureus 1.002 21 47.19 — — — F — C Saimiri sciureus 0.884 22 60.61 — — — F — C Saimiri sciureus — 17 39.17 — — — M — C Saimiri sciureus — 14 93.33 — — — M — C Saimiri spp. — — — 2.422 — — F — C Saimiri spp. — — — 1.414 — — M — C Saimiri spp. — — — 1.765 — — M — C Saimiri spp. — — — 1.945 30 15.42 M — C Theropithecus gelada 0.916 23 26.68 27.136 346 12.75 M — C Trachypithecus 1.757 60 93.46 7.007 — — F — C christatus Varecia rubra 0.886 — — — — — F — L Varecia rubra 1.026 — — — — — F — L Varecia rubra 0.915 30 53.76 — — — F 3.30 L Varecia variegata — 38 77.08 — — — F — C Varecia variegata — 35 77.95 — — — F 4.05 L Varecia variegata — 26 54.05 — — — F 4.00 L Varecia variegata 0.782 43 87.40 — — — F 3.90 L Varecia variegata — 15 45.32 — — — F 4.30 L Varecia variegata 0.917 26 42.90 — — — F 3.80 L Varecia variegata — 27 50.19 — — — F 4.60 L Varecia variegata — 22 47.93 — — — F 4.60 L Varecia variegata — 17 71.43 — — — M 3.60 L Varecia variegata — 17 70.25 — — — M 3.70 L Varecia variegata 1.576 29 58.35 — — — M 3.40 L Varecia variegata — 18 41.00 — — — M 3.50 L

402 Varecia variegata — 11 44.53 — — — M 3.80 L

Papilla Surface area area of Body (cm2 x N tongue mass Spec. Species 1000) FP DFP (cm2) tNFP tDFP Sex (kg) type Varecia variegata — 16 61.07 — — — M 3.60 L Varecia variegata — 28 65.27 — — — M 3.70 L Varecia variegata — 33 76.21 — — — M 3.60 L Varecia variegata — 24 54.42 — — — M 3.80 L Varecia variegata — 21 43.48 — — — M 3.50 L

NON-PRIMATES: Cynocephalus variegatus — — — 6.988 — — F — C Cynocephalus variegatus — — — 4.768 — — M — C Tupaia belangeri 1.413 33 130.95 — — — F — C Tupaia belangeri 0.280 31 118.77 — — — M — C Tupaia belangeri 0.543 21 74.73 — — — M — C Tupaia belangeri — 32 155.34 — — — M — C Tupaia belangeri — 38 115.50 — — — M — C Tupaia belangeri — 24 108.60 — — — M — C

Papilla area = the average area (outline in orthogonal view) of 10 individual fungiform papillae (FP) on the 0.5cm tip of the tongue; NFP = number of FP on the anterior 0.5cm of the tongue; DFP = density of FP per square cenitmeter on the anterior 0.5cm of the tongue; tNFP = number of FP on entire dorsal tongue; tDFP = density of FP on entire dorsal tongue; M = male, F = female, x = sex unknown; Spec. type = live or cadaveric specimen type, L = live, C = cadaveric; Body mass data are provided for those specimens measured during this study; *This individual was quite obese (per the observation of the attending veterinarians), so data were also analyzed using published data on body mass in wild animals.

403 Bibliography

Adler, E., Hoon, M. A., Mueller, K. L., Chandrashekar, J., Ryba, N. J. P. and Zuker, C. S.

(2000) A novel family of mammalian taste receptors. Cell 100, 693-702.

Aiello, L. C. (1997) Brains and guts in human evolution: The expensive tissue

hypothesis. Brazilian Journal of Genetics 20, 141-148.

Aiello, L. C. and Wheeler, P. (1995) The expensive tissue hypothesis: The brain and the

digestive system in human and primate evolution. Current Anthropology 36, 199-

211.

Akabas, M. H., Dodd, J. and Al-Awqati, Q. (1988) A bitter substance induces a rise in

intracellular calcium in a subpopulation of rat taste cells. Science 242, 1047-1050.

Altmann, J. (1980) Baboon Mothers and Infants. Harvard University Press, Cambridge.

Anderson, J. R. (1996) Chimpanzees and capuchin monkeys: Comparative cognition. In

Reaching Into Thought: The Minds of the Great Apes, Russon, A. E., Bard, K. A.

and Parker, S. T. eds, pp. 23-56. Cambridge University Press, Cambridge.

Andrews, P. L. R. and Horn, C. C. (2006) Signals for nausea and emesis: Implications for

models of upper gastrointestinal diseases. Autonomic Neuroscience 125, 100-115.

Anliker, J. A., Bartoshuk, L., Ferris, A. M. and Hooks, L. D. (1991) Children's food

preferences and genetic sensitivity to the bitter taste of 6-n-propylthiouracil

(PROP). American Journal of Clinical Nutrition 54, 316-320.

404 Arbisi, P. A., Billington, C. J. and Levine, A. S. The effect of naltrexone on taste

detection and recognition threshold. Appetite 32, 241-249.

Amrine-Madsen, H., Koepfli, K.-P., Wayne, R. K. and Springera, M. S. (2003) A new

phylogenetic marker, apolipoprotein B, provides compelling evidence for

eutherian relationships. Molecular Phylogenetics and Evolution 28, 225–240.

Arvidson, K. and Friberg, U. (1980) Human taste: Response and taste bud number in

fungiform papillae. Science 209, 807-808.

Aschoff, J., Günther, B. and Kramer, K. (1971) Energiehaushalt und

Temperaturregulation. Urban and Schwarzenberg, Munich.

Avenet, P., Hofmann, F. and Lindemann, B. (1988) Transduction in taste receptor cells

requires cAMP protein kinase. Nature 331, 351-354.

Balko, E. A. (1998) A behaviorally plastic response to forest composition and logging

disturbance by Varecia variegata variegata in Ranomafana National Park,

Madagascar. Ph.D. Thesis, pp. 3145. State University of New York, Syracuse.

Barnicot, N. A., Harris, H. and Kalmus, H. (1951) Taste thresholds of further eighteen

compounds and their correlation with PTC thresholds. Annals of Eugenics,

London 16, 119-128.

Barton, R. A. (1989) Foraging strategies, diet and competition in olive baboons. Ph.D.

Thesis. University of St. Andrews.

Bartoshuk, L. (1979) Bitter taste of saccharin related to the genetic ability to taste the

bitter substance 6-n-propylthiouracil. Science 205, 934-935.

405 Bartoshuk, L. M. (1978) History of taste research. In Handbook of Perception, Vol. VIA,

Tasting and Smelling, Carterette, E. C. and Friedman, M. P. eds, pp. 3-18.

Academic Press, New York.

Bartoshuk, L. M. (1978) The psychophysics of taste. American Journal of Clinical

Nutrition 31, 1068-1077.

Bartoshuk, L. M. (1993) The biological basis of food perception and acceptance. Food

Quality and Preference 4, 21-32.

Bartoshuk, L. M. (2000) Comparing sensory experiences accross individuals: Recent

psychophysical advances illuminate genetic variation in taste perception.

Chemical Senses 25, 447-460.

Bartoshuk, L. M. and Beauchamp, G. K. (1994) Chemical senses. Annual Review of

Psychology 45, 419-449.

Bartoshuk, L. M., Duffy, V. B. and Miller, I. J. (1994) PTC/PROP tasting: Anatomy,

psychophysics, and sex effects. Physiology & Behavior 56, 1165-1171.

Bartoshuk, L. M., Duffy, V. B., Green, B. G., Hoffmann, J. N., Ko, C. W., Lucchina, L.

A., Marks, L. E. and Snyder, D. J. (2004b) Valid across-group comparisons with

labeled scales: The gLMS versus magnitude matching. Physiology & Behavior

82, 109-114.

Bartoshuk, L. M., Duffy, V. B., Lucchina, L. A., Prutkin, J. and Fast, K. (1998) PROP (6-

n-propylthiouracil) supertasters and saltiness of NaCl. Annals of the New York

Academy of Sciences 855, 793-796.

406 Bartoshuk, L. M., Fast, K., Karrer, T. A., Marino, S., Price, R. A. and Reed, D. A. (1992)

PROP supertatsters and the perception of sweetness and bitterness. Chemical

Senses 17, 594.

Bartoshuk, L., Fast, K., Snyder, D. J. and Duffy, V. B. (2004a) Genetic differences in

human oral perception: Advanced methods reveal basic problems in intensity

scaling. In Genetic Variation in Taste Sensitivity, Prescott, J. and Tepper, B. J.

eds, pp. 1-41. Marcel Dekker, Inc., New York.

Bartoshuk, L., Marino, S. E. and Snyder, D. J. (2007) Age and hormonal effects of sweet

taste and preference. Appetite 49, 277.

Beare, J. I. (1906) Greek theories of elementary cognition from Alcmaeon to Aristotle.

Clarendon Press, Oxford.

Beosch, C. and Boesch, H. (1989) Hunting behavior of wild chimpanzees in the Taï

National Park. American Journal of Physical Anthropology 78, 547-573.

Bernhardt, S. J., Naim, M., Zehavi, U. and Lindemann, B. (1996) Changes in IP3 and

cytosolic Ca2+ in response to sugars and non-sugar sweeteners in transduction of

sweet taste in the rat Journal of Physiology 490, 325-336

Bhatia, S. and Puri, R. (1991) Taste sensitivity in pregnancy. Indian Journal of

Physiology and Pharmacology 35, 121-124.

Birch, L. L. (1992) Children's preferences for high-fat foods. Nutrition Reviews 50, 249-

255.

Birch, L. L. (1999) Development of food preferences. Annual Review of Nutrition 19, 41-

62. 407 Birch, L. L., McPhee, L., Steinberg, L. and Sullivan, S. (1990) Conditioned flavor

preferences in young children. Physiology & Behavior 47, 501-505.

Birkinshaw, C. R. (1995) The importance of the black lemur 'Eulemur macaco'

(Lemuridae, primates), for seed dispersal Lokobe Forest, Madagascar. Vol. PhD.

University College London, London.

Blakeslee, A. F. (1932) Genetics of sensity thresholds: Taste for phenyl thio carbamide.

Proceedings of the National Academy of Sciences of the United States of America

18, 120-130.

Blakeslee, A. F. and Salmon, M. R. (1931) Odor and taste blindness. Eugenical News 16,

105-109.

Boesch, C. (2003) Complex cooperation among Taï chimpanzees. In Animal Social

Complexity: Intelligence, Culture, and Individualized Societies, de Waal, F. B. M.

and Tyack, P. L. eds, pp. 93-110. Harvard Univeristy Press, Cambridge.

Boesch, C. and Boesch, H. (1990) Tool use and tool making in wild chimpanzees. Folia

Primatologica 54, 86-99.

Boinski, S. (1988) Sex differences in the foraging behavior of squirrel monkeys in a

seasonal habitat. Behavioral Ecology and Sociobiology 23, 177-186.

Bolton, K. A., Campbell, V. M. and Burton, F. D. (1998) Chemical analysis of soils of

Kowloon (Hong Kong) eaten by hybrid macaques. Journal of Chemical Ecology

24, 195-205.

Bonnaire, L. and Simmen, B. (1994) Taste perception if fructose solutions and diet in

lemuridae. Folia Primatalogica 63, 171-176. 408 Bose, S. (1964) Economy of the Onge of Little Andaman. Man in India 44, 298-310.

Boyd, W. (1950) Taste reactions to antithyroid substances. Science 112, 153 (letter).

Boyd, W. C. and Boyd, L. G. (1936) New racial blood group studies in Europe and

Egypt. Science 84, 328-329.

Boyd, W. C. and Boyd, L. G. (1937) Sexual and racial variations in ability to taste

phenylthiocarbamide, with some data in the inheritance. Annals of Eugenics,

London 8, 46-51.

Bradshaw, J. W. S. (2006) The evolutionary basis for the feeding behavior of domestic

dogs (Canis familiaris) and cats (Felis catus). Journal of Nutrition 136, 1927S-

1931.

Brett, F. L., Turner, T. R., Jolly, C. J. and Cauble, R. (1982) Trapping baboons and vervet

monkeys from wild, free-ranging populations. Journal of Wildlife Management

46, 164-174.

Britt, A. (2000) Diet and feeding behaviour of the black-and-white ruffed lemur (Varecia

variegata variegata) in the Betampona Reserve, Eastern Madagascar. Folia

Primatologica 71, 133-141.

Brosnan, F. H. (1985) Mammalian reproduction: An ecological perspective. Biology of

Reproduction 32, 1-26.

Buck, L. M. (2000) Smell and taste: The chemical senses. In Principals of Neural

Sciance, Kandel, E. R., Schwartz, J. H. and Jessell, T. M. eds, pp. 625-647.

McGraw-Hill, New York.

409 Bufe, B., Breslin, P. A. S., Kuhn, C., Reed, D. R., Tharp, C. D., Slack, J. P., Kim, U.-K.,

Drayna, D. and Meyerhof, W. (2005) The molecular basis of individual

differences in phenylthiocarbamide and propylthiouracil bitterness perception.

Current Biology 15, 322-327.

Bufe, B., Hofmann, T., Krauttwurst, D., Raguse, J. D. and Meyerhof, W. (2002) The

human TAS2R16 receptor mediates bitter taste in response to β-glucopyranosides

Nature Genetics 32, 397-401.

Burow, M., Bergner, A., Gershenzon, J. and Wittstock, U. (2007) Glucosinolate

hydrolysis in Lepidium sativum - identification of the thiocyanate-forming

protein. Plant Molecular Biology 63, 49-61.

Byrne, R. W., Whiten, S. P., Henzi, S. P. and McCulloch, F. M. (1993) Nutritional

constraints on mountain baboons (Papio ursinus): Implications for baboon

socioecology. Behavioral Ecology and Sociobiology 33, 233-246.

Byrne, R. W., Whiten, S. P., Henzi, S. P. and McCulloch, F. M. (1993) Nutritional

constraints on mountain baboons (Papio ursinus): implications for baboon

socioecology. Behavioral Ecology and Sociobiology 33, 233-246.

Caicedo, A., Kim, K.-N. and Roper, S. D. (2002) Individual mouse taste cells respond to

multiple chemical stimuli. The Journal of Physiology Online 544, 501-509.

Caldwell, C. A. and Whiten, A. (2007) Social learning in monkeys and apes: Cultural

animals? In Primates in Perspective, pp. 652-677. Oxford University Press, New

York.

410 Calle, E. E., Thun, M. J., Petrelli, J. M., Rodriguez, C. and Heath, C. W. (1999) Body

mass index and mortality in a prospective cohort of U.S. adults. The New England

Journal of Medicine 341, 1097-1105.

Campbell, C. J. (2000) The Reproductive Biology of Black-Handed Spider Monkeys

(Ateles geoffroyi): Integrating Behavior and Endocrinology. Ph.D. Thesis, pp.

183. University of California, Berkeley.

Carrai, V., Borgognini-Tarli, S., Huffman, M. and Bardi, M. (2003) Increase in tannin

consumption by sifaka (Propithecus verreauxi verreauxi) females during the birth

season: a case for self-medication in prosimians? Primates 44, 61-66.

Chalmeau, R., Visalberghi, E. and Gallo, A. (1997) Capuchin monkeys, Cebus apella fail

to understand a cooperative task. Animal Behaviour 54, 1215-1225.

Chandrashekar, J., Mueller, K. L., Hoon, M. A., Adler, E., Feng, L., Guo, W., Zuker, C.

S. and Ryba, N. J. P. (2000) T2Rs function as bitter taste receptors. Cell 100, 703-

711.

Chang, W.-I., Chung, J.-W., Kim, Y.-K., Chung, S.-C. and Kho, H.-S. (2006) The

relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil

(PROP) taster status and taste thresholds for sucrose and quinine. Archives of

Oral Biology 51, 427-432.

Chang, W.-I., Chung, J.-W., Kim, Y.-K., Chung, S.-C. and Kho, H.-S. (2006) The

relationship between phenylthiocarbamide (PTC) and 6-n-propylthiouracil

(PROP) taster status and taste thresholds for sucrose and quinine. Archives of

Oral Biology 51, 427-432. 411 Chapman, C. (1988) Patterns of foraging and range use by three species of neotropical

primates. Primates 29, 177-194.

Charles-Dominique, P. ( 1977 ) Ecology and Behavior of Nocturnal Primates. Duckworth

Press London.

Chen, M. C., Wu, S. V., Reeve, J. R. and Rozengurt, E. (2006) Bitter stimuli induce Ca2+

signaling and CCK release in enteroendocrine STC-1 cells: Role of L-type

voltage-sensitive Ca2+ channels American Journal of Cell Physiology 291, C726-

C739.

Chiarelli, B. (1959) Sensitivity to phenyl-thio-carbamide (P.T.C.) in some monkeys (data

collected at Italian zoological gardens). Archivio per l'antropologia e la etnologia

89, 1-9.

Chiarelli, B. (1963) Sensitivity to P.T.C. (phenyl-thio-carbamide) in primates. Folia

Primatologica 1, 88-94.

Chivers, D. J. (1977) The feeding behaviour of Saimang (Symphalangus syndactylus). In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 355-382. Academic Press, New York.

Chivers, D. J. and Hladik, C. M. (1980) Morphology of the gastrointestinal tract in

primates: Comparisons with other mammals in relation to diet. Journal of

Morphology 166, 337-386.

Chivers, D. J. and Hladik, C. M. (1984) Diet and gut morphology in primates. In Food

acquisition and processing in primates, Chivers, D. J., Wood, B. A. and

Bilsborough, A. eds, pp. 213-230. Plenum Press, New York. 412 Cipollini, M. L. and Levey, D. J. (1997) Secondary metabolites of fleshy vertebrate-

dispersed fruits: Adaptive hypotheses and implications for seed dispersal.

American Naturalist 150, 346-372.

Clapp, T. R., Stone, L. M., Margolskee, R. F. and Kinnamon, S. C. (2001)

Immunocytochemical evidence for co-expression of Type III IP3 receptor with

signaling components of bitter taste transduction. BMC Neuroscience 2, 6-14.

Clapp, T. R., Yang, R., Stoick, C. L., Kinnamon, S. C. and Kinnamon, J. C. (2004)

Morphologic characterization of rat taste receptor cells that express components

of the phospholipase C signaling pathway. Journal of Comparative Neurology

468, 311–321

Clutton-Brock, T. H. (1977) Some aspects of intraspecific variation in feeding and

ranging behaviour in primates. In Primate Ecology: Studies of Feeding and

Ranging Behaviour in Lemurs, Monkeys and Apes, Clutton-Brock, T. H. ed, pp.

539-556. Academic Press, New York.

Clutton-Brock, T. H. and Harvey, P. H. (1977) Species differences in feeding and ranging

behavior in primates. In Primate Ecology: Studies of Feeding and Ranging

Behavior in Lemurs,Monkeys, and Apes, Clutton-Brock, T. H. and Harvey, P. H.

eds, pp. 557-584. Academic Press, London.

Clutton-Brock, T. H. and Harvey, P. H. (1980) Primates, brains and ecology. Journal of

Zoology, London 190, 309-323.

Cohen, J. (1988) Statistical Power Analyses for the Behavioral Sciences. Academic

Press, New York. 413 Conklin-Brittain, N. L., Wrangham, R. W. and Hunt, K. D. (1998) Dietary response of

chimpanzees and cercopithecines to seasonal variation in fruit abundance. II.

Macronutrients. International Journal of Primatology 19, 971-332.

Conte, C., Ebeling, M., Marcuz, A., Nef, P. and Andres-Barquin, P. J. (2002)

Identification and characterization of human taste receptor genes belonging to the

TAS2R family. Cytogenetic and Genomic Research 98, 45-53.

Conte, C., Ebeling, M., Marcuz, A., Nef, P. and Andres-Barquin, P. J. (2003)

Evolutionary relationships of the TAS2R receptor gene families in mouse and

human. Physiological Genomics 14, 73-82.

Cords, M. (1986) Interspecific and intraspecific variation in diet of two forest guenons,

Cercopithecus ascanius and C. mitis. Journal of Animal Ecology 55, 811-827.

Critchley, H. D. and Rolls, E. T. (1996a) Hunger and satiety modify the responses of

olfactory and visual neurons in the primate orbitofrontal cortex. Journal of

Neurophysiology 75, 1673-1686.

Critchley, H. D. and Rolls, E. T. (1996b) Resposnes of primate taste cortex neurons to the

astringent tastant tannic acid. Chemical Senses 21, 135-145.

Curtis, D. J. (1997) The mongoose lemur (Eulemur mongoz): A Study of behaviour and

ecology. Ph.D. Thesis, pp. 178. Universität of Zürich.

Damak, S., Rong, M., Yasumatsu, K., Kokrashvili, Z., Pérez, C. A., Shigemura, N.,

Yoshida, R., Jr., B. M., Glendinning, J. I., Ninomiya, Y. and Margolskee, R. F.

(2006) TRPM5 null mice respond to bitter, sweet, and umami compounds

Chemical Senses 31, 253–264. 414 Danilova, V. and Hellekant, G. (2003) Comparison of the responses of the chorda

tympani and glossopharyngeal nerves to taste stimuli in C57BL/6J mice. BMC

Neuroscience 4, 5.

Danish, L., Chapman, C. A., Hall, M. B., Rode, K. D. and Worman, C. O. D. (2006) The

role of sugar in diet selectin in redtail and red colobus monkeys. In Feeding

Ecology in Apes and Other Primates, Hohman, G., Robbins, M. M. and Boesch,

C. eds, pp. 473-487. Cambridge University Press, Cambridge.

Das, S. (1958) Inheritance of the PTC taste characeter in man: An analysis of 126 Rarhi

Brahmin families of West Bengal. Annals of Human Genetics 22, 200-212.

Dasilva, G. (1992) The western black-and-white colobus as a low-energy strategist:

Activity budgets, energy expenditure and energy intake. The Journal of Animal

Ecology 61, 79-91.

Davies, A. G., Oates, J. F. and Dasilva, G. (1999) Patterns of frugivory in three west

African colobine monkeys. International Journal of Primatology 20, 327-357. de Waal, F. B. M. (1989) Peacemaking Among Primates. Cambridge University Press,

Cambridge.

DeFazio, R. A., Dvoryanchikov, G., Maruyama, Y., Kim, J. W., Pereira, E., Roper, S. D.

and Chaudhari, N. (2006) Separate Populations of Receptor Cells and Presynaptic

Cells in Mouse Taste Buds. Journal of Neuroscience 26, 3971-3980.

Delwiche, J. F., Buletic, Z. and Breslin, P. A. S. (2001) Relationship of papillae number

to bitter intensity of quinine and PROP within and between individuals.

Physiology & Behavior 74, 329-337. 415 Dennys, V. (1991) Approche du rôle de la perception gustative dans la différenciation et

la régulation du comportement alimentaire des lémuriens. Ph.D. Thesis.

Université Paris - XIII, Villetaneuse.

Depew, L. A. (1983) Ecology and behaviour of baboons (Papio anubis) in the Shai Hills

Game Production Reserve, Ghana. . Vol. M.Sc. Cape Coast University.

Di Bitetti, M. S. and Janson, C. H. (2001) Reproductive socioecology of tufted capuchins

(Cebus apella nigritus) in Northeastern Argentina. International Journal of

Primatology 22, 127-142.

Dinehart, M. E., Hayes, J. E., Bartoshuk, L. M., Lanier, S. L. and Duffy, V. B. (2006)

Bitter taste markers explain variability in vegetable sweetness, bitterness, and

intake. Physiology & Behavior 87, 304-313.

Dominy, N. (2004) Color as an indicator of food quality to anthropoid primates:

Ecological evidence and an evolutionary scenario. In Anthropoid Origins: New

Visions, Ross, C. F. and Kay, R. F. eds, pp. 615-644. Kluwer Academic, New

York.

Dominy, N. (2004) Fruits, fingers, and fermentation: The sensory cues available to

foraging primates Integrated and Comparative Biology 44, 295-303.

Dominy, N. and Lucas, P. W. (2001) Ecological importance of trichromatic vision to

primates. Nature 410, 363-366.

Dominy, N. and Lucas, P. W. (2004) Significance of color, calories, and climate to the

visual ecology of catarrhines. American Journal of Primatology 62, 189-207.

416 Dominy, N. and Lucas, P. W. (2006) Primate sensory systems and foraging behavior. In

Feeding Ecology in Apes and Other Primates, Hohmann, G., Robbins, M. M. and

Boesch, C. eds, pp. 489-509. Cambridge University Press, Cambridge.

Dominy, N., Lucas, P. W., Osorio, D. and Yamashita, N. (2001) The sensory ecology of

primate food perception. Evolutionary Anthropology 10, 171-186.

Donati, G., Bollen, A., Borgognini-Tarli, S. M. and Ganzhorn, J. U. (2007) Feeding over

the 24-h cycle: dietary flexibility of cathemeral collared lemurs (Eulemur collaris)

Behavioral Ecology and Sociobiology in press.

Dotson, C. D., Roper, S. D. and Spector, A. C. (2005) PLCβ2-independent behavioral

avoidance of prototypical bitter-tasting ligands Chemical Senses 30, 593–600.

Doty, R. L., Bagla, R., Morgenson, M. and Mirza, N. (2001) NaCl thresholds:

relationship to anterior tongue locus, area of stimulation, and number of

fungiform papillae. Physiology & Behavior 72, 373-378.

Drayna, D. (2005) Human taste genetics. Annual Review of Genomics and Human

Genetics 6, 217-235.

Drayna, D., Coon, H., Kim, U.-K., Elsner, T., Cromer, K., Otterud, B., Baird, L., Peiffer,

A. P. and Leppert, M. (2003) Genetic analysis of a complex trait in the Utah

Genetic Reference Project: a major locus for PTC taste ability on chromosome 7q

and a secondary locus on chromosome 16p. Human Genetics 112, 567-572.

Drewnowski, A. (1986) Sweetness and obesity. In Sweetness (ILSI Human Nutritions

Reviews), Dobbing, J. ed, pp. 177-192. Springer, Berlin.

417 Drewnowski, A. (1997) Taste preferences and food intake. Annual Review of Nutrition

17, 237-253.

Drewnowski, A. and Rock, C. L. (1995) The influence of genetic taste markers on food

acceptance. American Journal of Clinical Nutrition 62, 506-511.

Drewnowski, A., Ahlstrom Henderson, S. and Barratt-Fornell, A. (1998) Genetic

sensitivity to 6-n-Propylthiouracil and sensory responses to sugar and fat

mixtures. Physiology & Behavior 63, 771-777.

Drewnowski, A., Ahlstrom Henderson, S. and Shore, A. B. (1997) Genetic sensitivity to

6-n-propylthiouracil (PROP) and hedonic responses to bitter and sweet tastes.

Chemical Senses 22, 27-37.

Drewnowski, A., Ahlstrom Henderson, S., Levine, A. and Hann, C. (1999) Taste and

food preferences as predictors of dietary practices in young women. Public Health

Nutrition 2, 513–519.

Drewnowski, A., Brunzell, J. D., Sande, K., Iverius, P. H. and Greenwood, M. R. C.

(1985) Sweet tooth reconsidered: Taste responsiveness in human obesity.

Physiology & Behavior 35, 617-622.

Drewnowski, A., Henderson, S. A., Hann, C. S., Berg, W. A. and Ruffin, M. T. (2000)

Genetic taste markers and preferences for vegetables and fruit of female breast

care patients. Journal of the American Dietetic Association 100, 191-197.

Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1997)

Nontasters, tasters, and supertasters of 6-n-propylthiouracil (PROP) and hedonic

response to sweet. Physiology & Behavior 62, 649-655. 418 Drewnowski, A., Henderson, S. A., Shore, A. B. and Barratt-Fornell, A. (1998) Sensory

responses to 6-n-propylthiouracil (PROP) or sucrose solutions and food

preferences in young women. Annals of the New York Academy of Sciences 855,

797-801.

Dudley, R. (2002) Fermenting fruit and the historical ecology of ethanol ingestion: Is

alcoholism in modern humans an evolutionary hangover? Addiction 97, 381-388.

Dudley, R. (2004) Ethanol, fruit ripening, and the historical origins of human alcoholism

in primate frugivory. Integrated and Comparative Biology 44, 315-323.

Duffy, V. B. (2004) Associations between oral sensation, dietary behaviors and risk of

cardiovascular disease (CVD). Appetite 43, 5-9.

Duffy, V. B. and Bartoshuk, L. M. (2000) Food acceptance and genetic variation in taste.

Journal of the American Dietetic Association 100, 647-655.

Duffy, V. B., Bartoshuk, L. M., Striegel-Moore, R. and Rodin, J. (1998) Taste changes

across pregnancy. Annals of the New York Academy of Sciences 855, 805-809.

Duffy, V. B., Davidson, A. C., Kidd, J. R., Kidd, K. K., Speed, W. C., Pakstis, A. J.,

Reed, D. R., Snyder, D. J. and Bartoshuk, L. M. (2004) Bitter receptor gene

(TAS2R38), 6-n-Propylthiouracil (PROP) bitterness and alcohol intake.

Alcoholism: Clinical and Experimental Research 28, 1629-1637.

Duffy, V. B., Hayes, J. E. and Dinehart, M. E. (2006) Genetic differences in sweet taste

perception. In Optimising sweet taste in foods, Spillane, W. J. ed, pp. 30-53.

Woodhead Publishing, Cambridge.

419 Duffy, V. B., Peterson, J. M., Dinehart, M. E. and Bartoshuk, L. (2003) Genetic and

environmental variation in taste: Associations with sweet intensity, preference,

and intake. Topics in Clinical Nutrition 18, 209-220.

Dulai, K. S., von Dornum, M., Mollon, J. D. and Hunt, D. M. (1999) The evolution of

trichromatic color vision by opsin gene duplication in new world and old world

primates. Genome Research 9, 629-638.

Dunbar, R. I. M. (1977) Feeding ecology of gelada baboons: A preliminary report. In

Primate Ecology, Clutton-Brock, T. H. ed, pp. 251-273. Academic Press, London.

Dunbar, R. I. M. (2002) Modeling primate behavioral ecology. International Journal of

Primatology 23, 785-819.

Dunbar, R. I. M. and Dunbar, P. (1974) Ecological relations and niche separation

between sympatric terrestrial primates in Ethiopia. Folia Primatologica 21, 36–

60.

Eaton, J. W. and Gavin, J. A. (1965) Sensitivity to P-T-C among primates. American

Journal of Physical Anthropology 23, 381-388.

Emmons, L. H. (2000) Tupai: A field study of Bornean Tree Shrews. University of

California Press, Berkely.

Emura, S., Hayakawa, D., Chen, H. and Shoumura, S. (2002) Morphology of the dorsal

lingual papillae in the Japanese macaque and savanna monkey. Anatomia,

Histologia, Embryologia: Journal of Veterinary Medicine Series C 31, 313-316.

420 Essick, G. K., Chopra, A., Guest, S. and McGlone, F. (2003) Lingual tactile acuity, taste

perception, and the density and diameter of fungiform papillae in female subjects.

Physiology & Behavior 80, 289-302.

Etkin, N. L. and Ross, P. J. (1982) Food as medicine and medicine as food: An adaptive

framework for the interpretation of plant utilization among the Hausa of northern

Nigeria. Social Science & Medicine 16, 1559-1573.

Etter, L. (1999) Variation in taste perception across the menstrual cycle. In School of

Medicine, Vol. M.D. Yale Univeristy.

Fain, G. (2003) Sensory transduction. Sinauer Associates, Inc. Publishers, Sunderland,

Mass.

Falconer, D. S. (1947) Sensory thresholds for solutions of phenylthiocarbamide. Results

of tests on a large sample, made by R. A. Fisher. Annals of Eugenics, London 13,

211-222.

Falconer, D. S. (1947) Sensory thresholds for solutions of phenylthiocarbamide. Results

of tests on a large sample, made by R. A. Fisher. Annals of Eugenics, London 13,

211-222.

Fashing, P. (2001) Feeding ecology of guerezas in the Kakamenga Forest, Kenya: The

importance of Moraceae fruit in their diet. International Journal of Primatology

22, 579-609.

Feagle, J. G. (1984) Primate locomotion and diet. In Food acquisition and processing in

primates, Chivers, D. J., Wood, B. A. and Bilsborough, A. eds, pp. 105-117.

Plenum Press, New York. 421 Fedigan, L. M. (1993) Sex differences and intersexual relations in adult white-faced

capuchins (Cebus capuchinus). International Journal of Primatology 14, 853-877.

Feldman, G. M., Mogyorosi, A., Heck, G. L., DeSimone, J. A., Santos, C. R., Clary, R.

A. and Lyall, V. (2003) Salt-evoked lingual surface potential in humans. Journal

of Neurophysiology 90, 2060–2064.

Fenwick, G. R., Heaney, R. K. and Mulling, W. J. (1983) Glucosinolates and their

breakdown products in food and food plants. Critical reviews in food science and

nutrition 18, 123 – 201.

Fernberger, S. W. (1932) A preliminary study of taste deficiency. Journal of Psychology

44, 322-326.

Ferrell, F. (1984) Preference for sugars and nonnutritive sweeteners in young beagles.

Neuroscience & Biobehavioral Reviews 8, 199-203.

Finger, T. E. (2005) Cell types and lineages in taste buds. Chemical Senses 30, i54 - i55.

Finger, T. E., Danilova, V., Barrows, J., Bartel, D. L., Vigers, A. J., Stone, L., Hellekant,

G. and Kinnamon, S. C. (2005) ATP signaling is crucial for communication from

taste buds to gustatory nerves 310, 1495-1499.

Fischer, A., Gilad, Y., Man, O. and Paabo, S. (2005) Evolution of bitter taste receptors in

humans and apes. Molecular and Biology and Evolution 22, 432-436.

Fischer, R. (1967) Genetics and gustatory chemoreception in man and other primates. In

The Chemical Senses and Nutrition, Kare, M. R. and Maller, O. eds, pp. 621-681.

John Hopkins Press, Baltimore.

422 Fischer, R. and Griffen, F. (1961) Quinine dimorphism among “non-tasters” of 6-n-

propylthiouracil. Experientia 17, 36-38.

Fischer, R. and Griffen, F. (1964) Pharmacogenic aspects of gustation. Arzneimittel-

Forschung 14, 673-686.

Fischer, R. and Griffin, F. (1959) On factors involved in the mechanism of taste

blindness. Experientia 15, 447-448.

Fischer, R. and Griffin, F. (1961) Taste blindness and variations in taste-threshold in

relation to thyroid metabolism. Journal of Neuropsychiatry 3, 98-104.

Fischer, R. and Kaelbling, R. (1966) Increase in taste acuity with sympatric stimulation:

The relation of just-noticeable taste difference to a systemic psychotropic drug

use. Recent Advances in Biological Psychiatry 9, 183-195.

Fischer, R., Griffen, F., England, S. and Garn, S. M. (1961) Taste thresholds and food

dislikes. Nature 191, 1328.

Fisher, R. A., Ford, E. B. and Huxley, J. (1939) Taste-testing the anthropoid apes. Nature

114, 750.

Flaxman, S. M. and Sherman, P. W. (2000) Morning sickness: A mechanism for

protecting mother and embryo. The Quarterly Review of Biology 75, 113-148.

Fossey, D. and Harcourt, A. H. (1977) Feeding ecology of free-ranging mountain gorilla.

In Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs,

Monkeys and Apes, Clutton-Brock, T. H. ed, pp. 415-447. Academic Press, New

York.

Fox, A. L. (1931) Six in ten "tasteblind" to bitter chemical. Science News Letters 9, 249. 423 Fox, A. L. (1932) The relationship between chemical constitution and taste. Proceedings

of the National Academy of Sciences of the United States of America 18, 115-120.

Fragaszy, D. M. (1986) Time budgets and foraging behavior in wedged-capped capuchins

(Cebus olivaceus): Age and sex differences. In Current Perspecitives in Primate

Social Dynamics, Taub, D. M. and King, F. A. eds, pp. 159-174. Van Nostrand

Reinhold, New York.

Fragaszy, D. M. and Bard, K. (1997) Comparison of Development and Life History in

Pan and Cebus. International Journal of Primatology 18, 683-701.

Fragaszy, D. M. and Boinski, S. (1995) Patterns of individual diet choice and efficiency

of foraging in wedge-capped capuchin monkeys (Cebus olivaceus). Journal of

Comparative Psychology 109, 339-348.

Fragaszy, D. M., Visalberghi, E. and Fedigan, L. (2004) The Complete Capuchin: The

Biology of the Genus Cebus. Cambridge University Press, Cambridge.

Freeland, W. J. and Janzen, D. H. (1974) Strategies in herbivory by mammals: The role

of plant secondary compounds. The American Naturalist 108, 269-289.

Freese, C. H. and Oppenheimer, J. R. (1981) The capuchin monkeys, Genus Cebus. In

Ecology and Behavior of Neotropical Primates, Vol. 1, Coimbra-Filho, A. F. and

Mittermeier, R. A. eds, pp. 331-390. Academia Brasileira de Ciências, Rio de

Janeiro.

Furuichi, T., Hashimoto, C. and Tashiro, Y. (2001) Fruit availability and habitat use by

chimpanzees in the Kalinzu Forest, Uganda: Examination of fallback foods.

International Journal of Primatology 22, 929-945. 424 Galdikas, B., M.F. and Teleki, G. (1981) Variations in susistence activities of female and

male Pongids: New perspectives on the origins of hominid labor division. Current

Anthropology 33, 241-256.

Galef, B. G. (1996) Food selection: Problems in understanding how we choose foods to

eat. Neuroscience and Biobehavioral Reviews 20, 67-73.

Galetti, M. and Pedroni, F. (1994) Seasonal diet of capuchin monkeys (Cebus apella) in a

semideciduous forest in South-East Brazil. Journal of Tropical Ecology 10, 27-

39.

Ganzhorn, J. (1989) Primate species separation in relation to secondary plant chemicals.

Human Evolution 4, 125.

Ganzhorn, J. U. (1988) Food partitioning among Malagasy primates. Oecologica (Berlin)

75, 436-450.

Ganzhorn, J. U. and Wright, P. C. (1994) Temporal patterns in primate leaf eating: The

possible role of leaf chemistry. Folia Primatologica 63, 203-208.

Garber, P. A. (1987) Foraging strategies among living primates. Annual Review of

Anthropology 16, 339-364.

Garland, T., Bennett, A. F. and Rezende, E. L. (2005) Phylogenetic approaches in

comparative physiology. The Journal of Experimental Biology 208, 3015-3035.

Gaulin, S. J. C. and Konner, M. (1977) On the natural diet of primates, including humans.

In Nutrition and the Brain, Vol. 1, Wurtman, R. J. and Wurtman, J. J. eds, pp. 1-

86. Raven Press, New York.

425 Gaulin, S. J. C. and Sailer, L. D. (1985) Are females the ecological sex? American

Anthropologist 87, 111-119.

Gautier-Hion, A. (1980) Seasonal variations of diet related to species and sex in a

community of cercopithecus monkeys. Journal of Animal Ecology 49, 237-269.

Gent, J. F. and Bartoshuk, L. M. (1983) Sweetness of sucrose neohesperidin

dihydrochalcone, and saccharin is related to genetic ability to taste 6-n-

propylthiouracil. Chemical Senses 7, 265-272.

Ghiglieri, M. P. (1984) Feeding ecology and sociality of chimpanzees in Kibale Forest,

Uganda. In Adaptations for Foraging in Nonhuman Primates: Contributions to an

Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 161-194. Columbia University Press, New York.

Gibson, K. R. (1986) Cognition, brain size and the extraction of embedded food

resources. In Primate ontongeny, cognition and social behavior, Vol. 3, Else, J.

G. and Lee, P. C. eds, pp. 93-103. Cambridge University Press, Cambridge.

Gilad, Y., Man, O. and Glusman, G. (2005) A comparison of the human and chimpanzee

olfactory receptor gene repertoires. Genome Research 15, 224-230.

Gilad, Y., Man, O., Paabo, S. and Lancet, D. (2003) Human specific loss of olfactory

receptor genes. Proceedings of the National Academy of Sciences of the United

States of America 100, 3324-3327.

Gilbertson, T. A., Damak, S. and Margolskee, R. F. (2000) The molecular physiology of

taste transduction. Current opinion in Neurobiology 10, 519-527.

426 Gittleman, J. L. and Thompson, S. D. (1988) Energy allocation in mammalian

reproduction. American Zoologist 28, 863-875

Glander, K. E. (1975) Habitat and resource utilization: An ecological view of social

organization in mantled howling monkeys. Ph.D. Thesis. University of Chicago.

Glander, K. E. (1978) Howling monkey feeding behavior and plant secondary

compounds: A study of strategies. In The Ecology of Arboreal Folivores,

Montgomery, G. G. ed, pp. 561-574. Smithsonian Institution Press, Washington

DC.

Glander, K. E. (1982) The impact of plant secondary compounds on primate feeding

behavior. Yearbook of Physical Anthropology 25, 1-18.

Glander, K. E., Fedigan, L. M., Fedigan, L. and Chapman, C. (1991) Field methods for

capture and measurement of three monkey species in Costa Rica. Folia

Primatologica 57, 70-82.

Glanville, E. V. and Kaplan, A. R. (1965) Food preferences and sensitivity of taste for

bitter compounds. Nature 205, 851-853.

Glaser, D. (1980) Die leistugen des geschmacksorgans beim menschen im vergleich zu

nichtmenschlichen primaten. Lebensm.-Wiss u. -Technol. 13, 276-282.

Glaser, D. (2002) Experimental studies of primate sensory capacity. Evolutionary

Anthropology Supp 1, 136-139.

Glaser, D. (2002) Specialization and phyletic trends of sweetness reception in animals.

Pure and Applied Chemistry 74, 1153-1158.

427 Glaser, D. and Hellekant, G. (1977) Verhaltens- und electrophysiologische experimente

über den geschmackssinn bei Saguinus midas tamarin (Callitrichidae). Folia

Primatologica 28, 43-51.

Glaser, D., Tinti, J.-M. and Nofre, C. (1996) Gustatory repsonses of non-human primates

to dipeptide deratives or analogues, sweet in man. Food Chemistry 56, 313-321.

Glaser, D., Tinti, J.-M. and Nofre, C. (1997) Taste preference in nonhuman primates to

compounds sweet in man. Chemical Senses 22, 687.

Glendinning, J. I. (1994) Is the bitter rejection response always adaptive? Physiology &

Behavior 56, 1217-1227.

Go, Y., Satta, Y., Takenaka, O. and Takahashi, N. (2005) Lineage-specific loss of

function of bitter taste receptor genes in humans and nonhuman primates.

Genetics 170, 313-326.

Goldstein, G. L., Daun, H. and Tepper, B. J. (2007) Influence of PROP taster status and

maternal variables on energy intake and body weight of pre-adolescents.

Physiology & Behavior 90, 809-817.

Goldstein, S. J. and Richard, A. F. (1989) Ecology of rhesus macaques (Macaca mulatta)

in northwest Pakistan. International Journal of Primatology 10, 531-567.

Goodall, J. (1963) Feeding behaviour of wild chimpanzees. Symposia of the Zoological

Society of London 10, 39-48.

Goodall, J. (1968) The behaviour of free-living chimpanzees of the Gombe stream area.

Animal Behavior Monographs 1, 161-311.

428 Goodall, J. (1986) The Chimpanzees of Gombe: Patterns of Behaviour. The Belknap

Press of Harvard University Press, Cambridge, Massachusetts.

Goren-Inbar, N., Alperson, N., Kislev, M. E., Simchoni, O., Melamed, Y., Ben-Nun, A.

and Werker, E. (2004) Evidence of hominin control of fire at Gesher Benot

Ya`aqov, Israel. Science 304, 725 - 727.

Grassi, C. (2001) The behavioral ecology of Hapalemur griseus griseus: The influences

of microhabitat and population density on this small-bodied prosimian folivore.

Ph.D. Thesis, pp. 345. The University of Texas at Austin.

Grassi, C. (2002) Sex differences in feeding, height, and space use in Hapalemur griseus.

International Journal of Primatology 23.

Grinker, J. A., Price, J. M. and Greenwood, M. R. C. (1976) Studies of taste in childhood

obesity. In Hunger: Basic mechanisms and clinical applications, Novin, D.,

Wyrwicka, W. and Bray, G. A. eds, pp. 441-457. Raven, New York.

Guo, S.-W. and Reed, D. R. (2001) The genetics of phenylthiocarbamide perception.

Annals of Human Biology 28, 111-142.

Haefeli, R. J., Solms, J. and Glaser, D. (1998) Taste responses to amino acids in common

marmosets (Callithrix jacchus jacchus, Callitrichidae) a non-human primate in

comparison to humans. Lebensm.-Wiss u. -Technol. 31, 371-376.

Hall, M. J., Bartoshuk, L. M., Cain, W. S. and Stevens, J. C. (1975) PTC taste blindnes

and the taste of caffiene. Nature 253, 442-443.

Hänig, D. P. (1901) Zur psychophysik des geschmackssinnes. Philosophische Studien 17,

576-623. 429 Harding, R. S. O. (1976) Ranging patterns of a group of baboons (Papio anubis) in

Kenya. Folia Primatologica 25, 143-185.

Harris, D. R. (1992) Human diet and subsistence. In The Cambridge encyclopedia of

human evolution, Jones, S., Martin, R. and Pilbeam, D. eds, pp. 69-74. Cambridge

University Press.

Harris, T. R. and Chapman, C. A. (2007) Variation in diet and ranging of black and white

colobus monkeys in Kibale National Park, Uganda. Primates 48, 208-221.

Harris, H. and Kalmus, H. (1949) The measurement of taste sensitivity to phenylthiourea

(PTC). Annals of Eugenics, London 15, 32-45.

Harrison, M. J. S. (1983) Age and sex differences in the diet and feeding strategies of the

green monkey, Cercopithecus sabaeus. Animal Behaviour 31, 969-977.

Hattori, Y., Kuroshima, H. and Fujita, K. (2005) Cooperative problem solving by tufted

capuchin monkeys (Cebus apella): Spontaneous division of labor,

communication, and reciprocal altruism. Journal of Comparative Psychology 119,

335–342.

Hayden, B. (1981) Subsistence and ecological adaptations of modern hunter/gatherers. In

Omnivorous Primates: Gathering and Hunting in Human Evolution, Harding, R.

S. O. and Teleki, G. eds. Columbia University Press, New York.

Hayes, J. E., Bartoshuk, L., Kidd, J. R. and Duffy, V. B. (2008) Supertasting and PROP

bitterness depends on more than the TAS2R38 gene. Chemical Senses 33, 255-

265.

430 Hayes, J. E., Dinehart, M. E. and Duffy, V. B. (in press) Optimal liking of fat-sweet

mixtures varies with markers of bitter taste and anatomy. Appetite, 23.

Heck, G. L., Mierson, S. and DeSimone, J. D. (1984) Salt taste transduction occurs

through an amiloride-sensitive sodium transport pathway. Science 223, 403-405.

Heck, G. L., Persuand, K. C. and DeSimone, J. A. (1989) Direct measurement of

translingual epithelial NaCl and Kcl currents during the chorda tympani taste

response. Biophysical Journal 55, 843-857.

Heinrich, M., Rimpler, H. and Barrera, N. A. (1992) Indigenous phytotherapy of

gastrointestinal disorders in a lowland Mixe community (Oaxaca, Mexico):

Ethnopharmacologic evaluation. Journal of Ethnopharmacology 36, 63-80.

Hellekant, G. and Danilova, V. (1996) Species differences toward sweeteners. Food

Chemistry 56, 323-328.

Hemingway, C. A. (1998) Selectivity and variability in the diet of Milne-Edwards’

sifakas (Propithecus diadema edwardsi): Implications for folivory and seed-

eating. International Journal of Primatology 19, 355-377.

Hemingway, C. A. (1999) Time budgets and foraging in a Malagasy primate: do sex

differences reflect reproductive condition and female dominance? Behavioral

Ecology and Sociobiology 45, 311-322.

Herness, M. S. and Gilbertson, T. A. (1999) Cellular mechanisms of taste transduction.

Annual Review of Physiology 61, 873-900.

Hill, K. (1983) Adult male subsistence among Ache hunter-gatherers of Eastern

Paraguay. Ph.D. Thesis. Univeristy of Utah. 431 Hill, K., Hawkes, K., Hurtado, A. M. and Kaplan, H. (1984) Seasonal variance in diet of

Ache hunterpgatherers in eastern Paraguay. Human Ecology 12, 145-180.

Hladik, C. M. (1977) Chimpanzees of Gabon and chimpanzees of Gombe: Some

comparative data on the diet. In Primate Ecology: Studies of Feeding and

Ranging Behaviour in Lemurs, Monkeys, and Apes, Clutton-Brock, T. H. ed, pp.

481-501. Academic Press, London.

Hladik, C. M. (1978) Adaptive strategies of primates in relation to leaf-eating. In The

Ecology of Arboreal Folivores, Montgomery, G. G. ed, pp. 373-395. Smithsonian

Institution Press, Washington DC.

Hladik, C. M. (1979) Diet and ecology of prosimians. In The Study of Prosimian

Behavior, Doyle, G. A. and Martin, R. D. eds, pp. 307-357. Academic Press, New

York.

Hladik, C. M. (1981) Diet and the evolution of feeding strategies anong forest primates.

In Omnivorous Primates: Gathering and Hunting in Human Evolution, Harding,

R. S. O. and Teleki, G. eds. Columbia University Press, New York.

Hladik, C. M., Charles-Dominique, P. and Petter, J. J. (1980) Feeding strategies of five

nocturnal prosimians in the dry forest of the West coast of Madagascar. In

Nocturnal Malagasy Primates: Ecology, Physiology, and Behavior, Charles-

Dominique, P., Cooper, H. M., Hladik, A., Hladik, C. M., Pages, E., Pariente, G.

F., Petter-Rousseaux, A., Petter, J. J. and Schilling, A. eds, pp. 41-73. Academic

Press, New York.

432 Hladik, C. M. and Simmen, B. (1996) Taste perception and feeding behavior in

nonhuman primates and human populations. Evolutionary Anthropology 5, 58-71.

Hladik, C. M., Pasquet, P. and Simmen, B. (2002) New perspectives on taste and primate

evolution: The dichotomy in gustatory coding for perception of beneficent versus

noxious substances as supported by correlations among human thresholds.

American Journal of Physical Anthropology 117, 342-348.

Hoffmann, J. N., Montag, A. G. and Dominy, N. (2004) Meissner corpuscles and

somatosensory acuity: The prehensile appendages of primates and elephants. The

Anatomical Record Part A 281A, 1138-1147.

Hofmann, T., Chubanov, V., Gudermann, T. and Montell, C. (2003) TRPM5 Is a voltage-

modulated and Ca2+-activated monovalent selective cation channel Current

Biology 13, 1153–1158.

Holt, S. H. A., Cobiac, L., Beaumont-Smith, N. E., Easton, K. and Best, D. J. (2000)

Dietary habits and the perception and liking of sweetness among Australian and

Malaysian students: A cross-cultural study. Food Quality and Preference 11, 299-

312.

Hoon, M. A., Adler, E., Lindemeier, J., Battey, J. F., Ryba, N. J. P. and Zuker, C. S.

(1999) Putative mammalian taste receptors: A class of taste-specific GPCRs with

distinct topographic selectivity. Cell 96, 541–551.

Hosako-Naito, Y., Lucchina, L. A., Snyder, D. J., Boggiano, M. K., Duffy, V. B. and

Bartoshuk, L. M. (1996) Number of fungiform papillae in nontasters, medium

433 tasters, and supertasters of PROP (6-n-propylthiouracil). Chemical Senses 21,

616.

Hosako-Naito, Y., Lucchina, L. A., Snyder, D. J., Boggiano, M. K., Duffy, V. B. and

Bartoshuk, L. M. (1996) Number of fungiform papillae in nontasters, medium

tasters, and supertasters of PROP (6-n-propylthiouracil). Chemical Senses 21,

616.

Houle, A., Chapman, C. and Vickery, W. (2007) Intratree variation in fruit production

and implications for primate foraging. International Journal of Primatology 28,

1197-1217.

Huang, L., Shanker, Y. G., Dubauskaite, J., Zheng, J. Z., Yan, W., Rosenzweig, S.,

Spielman, A. I., Max, M. and Margolskee, R. F. (1999) Gγ13 colocalizes with

gustducin in taste receptor cells and mediates IP3 responses to bitter denatonium

Nature Neuroscience 12, 1055-1062.

Huang, Y.-J., Maruyama, Y., Lu, K.-S., Pereira, E., Plonsky, I., Baur, J. E., Wu, D. and

Roper, S. D. (2005) Mouse taste buds use serotonin as a neurotransmitter. The

Journal of Neuroscience 25, 843– 847.

Hubener, F. and Laska, M. (1998) Assessing olfactory performance in an Old World

primate, Macaca nemistrina. Physiology & Behavior 64, 521-527.

Huffman, M. (2003) Animal self-medication and ethno-medicine: Exploration and

exploitation of the medicinal properties of plants. Proceedings of the Nutrition

Society 62, 371-381.

434 Huque, T., Lischka, F. W., Bresliin, P. A., Feldman, R. S., Spielman, A. I. and Brand, J.

G. (in press) Expression of GPR4, a aproton sensing GPCR, in human fungiform

papillae. Chemical Senses.

Hurtado, A. M. and Hill, K. (1986) Early dry season subsistence ecology of hte Cuiva

(Hiwi) foragers if Venezuela. Human Ecology 15, 163-187.

Hyde, R. J. and Feller, R. P. (1981) Age and sex effects on taste of sucrose, NaCl, citric

acid and caffeine. Neurobiology of Aging 2, 315-318.

Iaconelli, S. and Simmen, B. (2002) Taste thresholds and suprathreshold responses to

tannin-rich plant extracts and quinine in a primate species (Microcebus murinus).

Journal of Chemical Ecology 28, 2315-2326.

Inoue, M., Beauchamp, G. K. and Bachmanov, A. A. (2004) Gustatory neural responses

to umami taste stimuli in C57BL/6ByJ and 129P3/J Mice. Chemical Senses 29,

789-795.

Isbell, L. (1991) Contest and scramble competition: patterns of female aggression and

ranging behavior among primates. Behavioral Ecology 2, 143-155.

Isbell, L. A. (1998) Diet for a small primate: Insectivory and gummivory in the (large)

patas monkey (Erythrocebus patas pyrrhonotus) American Journal of

Primatology 45, 381-398.

Iwamoto (1979) Feeding Ecology. In Ecological and Social Studies of the Gelada

Baboon, Kawai, M. ed, pp. 279-330. Kodansha, Tokyo.

Jacobs, G. H. (1996) Primate photopigments and primate color vision. Proceedings of the

National Academy of Sciences of the USA 93, 577-581. 435 Jacobs, G. H. and Deegan II, J. F. (1993) Photopigments underlying colorvision in

ringtail lemurs (Lemur catta) and brown lemurs (Eulemur fulvus). American

Journal of Primatology 30, 243-256.

James, C. E., Laing, D. G. and Oram, N. (1997) A comparison of the ability of 8–9-year-

old children and adults to detect taste stimuli. Physiology & Behavior 62, 193-

197.

Janjua, T. and Schwartz, S. (1997) unpublished data. In Duffy, V. B. and L. M.

Bartoshuk (2000) Food acceptance and genetic variation in taste. Journal of the

American Dietetic Association 100, 647-655.

Janson, C. H. (1988) Intraspecific food competition and primate social structure: A

synthesis. Behaviour 105, 1-17.

Janson, C. H. and Chapman, C. A. (1999) Resources and primate community structure. In

Primate Communities, Fleagle, J. G., Janson, C. H. and Reed, K. E. eds, pp. 237-

267. Cambridge University Press, New York.

Janzen, D. H. (1983) Dispersal of seeds by vertebrate guts. In Coevolution, Futuyma, D.

J. and Slatkin, M. eds, pp. 232-262. Sinauer, Sunderland, Mass.

Jennions, M. D. and Moller, A. P. (2003) A survey of the statistical power of research in

behavioral ecology and animal behavior. Behavioral Ecology 14, 438-445.

Jerzsa-Latta, M., Krondl, M. and Coleman, P. (1990) Use and perceived attributes of

cruciferous vegetables in terms of genetically-mediated taste sensitivity. Appetite

15, 127-134.

436 Johns, T. (1999) The Chemical Ecology of Human Ingestive Behaviors. Annual Review

of Anthropology 28, 27-50.

Kalmus, H. (1958) Improvements in the classification of the taster genotypes. Annals of

Human Genetics 22, 222-230.

Kalmus, H. (1971) Genetics of taste. In Taste, Vol. 4, Chemical Senses, Part 2, Beidler,

L. M. ed, pp. 165-179. Springer-Verlag Berlin, Heidelberg.

Kaminski, L. C., Henderson, S. A. and Drewnowski, A. (2000) Young women's food

preferences and taste repsonsiveness to 6-n-porpylthiouracil (PROP). Physiology

& Behavior 68, 691-697.

Kaplan, H., Hill, K., Lancaster, J. and Hurtado, A. M. (2000) A theory of human life

history evolution: Diet, intelligence, and longevity. Evolutionary Anthropology:

Issues, News, and Reviews 9, 156-185.

Kappeler, P. M. and Pereira, M. E. (2002) Primate Life Histories and Socioecology.

Chicago University Press, Chicago.

Kappeler, P. M. and Van Schaik, C. P. (2002) Evolution of primate social systems.

International Journal of Primatology 23, 707-740.

Kay, R. F. (1984) On the use of anatomical features to infer foraging behavior in extinct

primates. In Adaptations for Foraging in Nonhuman Primates: Contributions to

Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 21-53. Columbia University Press, New York.

437 Kay, R. F. and Scheine, W. S. (1979) On the relationship between chitin particle size and

digestibility in the primate Galago senagalensis. American Journal of Physical

Anthropology 50, 301-308.

Keast, R. S. J. and Breslin, P. A. S. (2002) An overview of binary taste–taste interactions

Food Quality and Preference 14, 111–124.

Keller, K. L., Steinmann, L., Nurse, R. J. and Tepper, B. J. (2002) Genetic taste

sensitivity to 6-n-propylthiouracil influences food preference and reported intake

in preschool children. Appetite 38, 3-12.

Key, C. and Ross, C. (1999) Sex differences in energy expenditure in non-human

primates. Proceedings of the Royal Society B: Biological Sciences 266, 2479-

2485.

Kim, U., Jorgenson, E., Coon, H., Leppert, M., Risch, N. and Drayna, D. (2003)

Positional cloning of the human quantitative trait locus underlying taste sensitivity

to phenlythiocarbamide. Science 299, 1221-1225.

Kim, U., Wooding, S., Ricci, D., Jorde, L. B. and Drayna, D. (2005) Worldwide

haplotype diversity and coding sequence variation at human bitter taste receptor

loci. Human Mutation 26, 199-204.

Kinnamon, S. C. and Margolskee, R. F. (1996) Mechanisms of taste transduction.

Current opinion in Neurobiology 6, 506-513.

Kinzey, W. G. (1977) Diet and feeding behaviour of Callicebus torquatus. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 127-151. Academic Press, New York. 438 Knott, C. D. (1998) Changes in orangutan caloric intake, energy balance, and ketones in

response to fluctuating fruit availability. International Journal of Primatology 19,

1061-1079.

Kobayashi, K. (1992) Stereo architecture of the interface of the epithelial cell layer and

connective tissue core of the foliate papilla in the rabbit tongue. Acta Anatomica

143, 109-117.

Kobayashi, K., Kumakura, M., Yoshimura, K., Takahashi, M., Zeng, J. H., Kageyama, I.,

Kobayashi, K. and Hama, N. (2004) Comparative morphological studies on the

stereo structure of the lingual papillae of selected primates using scanning

electron microscopy. Annals of Anatomy - Anatomischer Anzeiger 186, 525-530.

Kool, K. (1993) The diet and feeding behavior of the silver leaf monkey (Trachypithecus

auratus sondaicus) in Indonesia. International Journal of Primatology 14, 667-

701.

Koshimizu, K., Ohigashi, H. and Huffman, M. A. (1994) Use of Vernonia amygdalina by

wild chimpanzee: Possible roles of its bitter and related constituents. Physiology

& Behavior 56, 1209-1216.

Kumar, S. and Hedges, S. B. (1998) A molecular timescale for vertebrate evolution.

Nature 392, 917-920.

Kurihara, K. and Kashiwayanagi, M. (1998) Introductory remarks on umami taste.

Annals of the New York Academy of Sciences 855.

Labov, J. B. (1977) Phytoestrogens and mammalian reproduction. Comparative

Biochemistry and Physiology 57A, 3-9. 439 Lahann, P. (2007) Feeding ecology and seed dispersal of sympatric cheirogaleid lemurs

(Microcebus murinus, Cheirogaleus medius, Cheirogaleus major) in the littoral

rainforest of south-east Madagascar. Journal of Zoology 271, 88-98.

Lambert, J. E. (1998) Primate digestion: Interactions among anatomy, physiology, and

feeding ecology. Evolutionary Anthropology 7, 8-20.

Laska, M. (1996) Taste preference thresholds for food-associated sugars in the squirrel

monkey (Saimiri sciureus). Primates 37, 91-95.

Laska, M. (1999) Taste responsiveness to food-associated acids in the squirrel monkey

(Saimiri sciureus). Journal of Chemical Ecology 25, 1623-1631.

Laska, M. (2000) Gustatory responsiveness to food-associated sugars and acids in pigtail

macaques, Macaca menestrina. Physiology & Behavior 70, 495-504.

Laska, M. (2001) A comparison of food preferences and nutrient composition in captive

squirrel monkeys, Saimiri sciureus, and pigtail macaques, Macaca nemestrina.

Physiology & Behavior 73, 111-120.

Laska, M., Carrera Sanchez, E. and Rodriguez Luna, E. (1996) Gustatory thresholds for

food associated sugars in the spider monkey (Ateles geoffroyi). American Journal

of Primatology.

Laska, M., Carrera Sanchez, E. and Rodriguez Luna, E. (1998) Taste preferences for

food-associated sugars in the spider monkey (Ateles geoffroyi). Primates 39, 91-

96.

440 Laska, M., Freist, P. and Krause, S. (2007) Which senses play a role in nonhuman

primate food selection? A comparison between squirrel monkeys and spider

monkeys. American Journal of Primatology 69, 282–294.

Laska, M., Hernandez Salazar, L. T. and Rodriguez Luna, E. (2000) Food preferences

and nutrient composition in captive spider monkeys, Ateles geoffroyi.

International Journal of Primatology 21, 671-683.

Laska, M., Scheuber, H.P., Carrera Sanchez, E. and Rodriguez Luna, E. (1999) Taste

difference thresholds for sucrose in two species of nonhuman primates. American

Journal of Primatology 48, 153-160.

Laska, M., Schull, E. and Scheuber, H.P. (1999) Taste preference thresholds for food

associated sugars in baboons (Papio hamadryas anubis). International Journal of

Primatology 20, 25-34.

Lawless, H. (1980) A comparison of different methods used to assess sensitivity to the

taste of phenylthiocarbamide (PTC) Chemical Senses 5, 247-256.

Leach, E. J. and Noble, A. C. (1986) Comparison of bitterness of caffiene and quinine by

a time-intensity procedure. Chemical Senses 11, 339-345.

Lee-Thorp, J. (2002) Hominid dietary niches from proxy chemical indicators in fossils:

The Swartkrans example. In Human Diet: Its Origins and Evolution, Ungar, P. S.

and Teaford, M. F. eds. Bergin and Garvey, Westport, Connecticut.

Lee, P. C. and Hauser, M. D. Long-term consequences of changes in territory quality on

feeding and reproductive strategies of vervet monkeys. The Journal of Animal

Ecology 67, 347-358. 441 Lenth, R. V. (2001) Some Practical Guidelines for Effective Sample Size Determination.

The American Statistician 55, 187-193.

Levit, S. G. and Soboleva, G. V. (1935) Comparative intrapair correlations of fraternal

twins and siblings. Journal of Genetics 30, 389-396.

Li, X., Li, W., Mascioli, K. J., Bachmanov, A. A., Tordoff, M. G., Epple, G.,

Beauchamp, G. K. and Reed, D. R. (2003) Comparative analysis of the T1R taste

receptor genes in primates. Chemical Senses 28, 296.

Li, X., Li, W., Wang, H., Cao, J., Maehashi, K., Huang, L., Bachmanov, A. A., Reed, D.

R., Legrand-Defretin, V., Beauchamp, G. K. and Brand, J. G. (2005)

Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward

sugar. PLoS Biology 1, 27-35.

Li, X., Staszewski, L., Xu, H., Durick, K., Zoller, M. and Adler, E. (2002) Human

receptors for sweet and umami taste. Proceedings of the National Academy of

Sciences of the United States of America 99, 4692-4696.

Lima, E. M. and Ferrari, S. F. (2003) Diet of a Free-Ranging Group of Squirrel Monkeys

(Saimiri sciureus) in Eastern Brazilian Amazonia. Folia Primatologica 74, 150-

158.

Lin, W., Finger, T. E., Rossier, B. C. and Kinnamon, S. C. (1999) Epithelial Na+channel

subunits in rat taste cells: Localization and regulation by aldosterone Journal of

Comparative Neurology 405, 406–420.

Lindburg, D. G. (1977) Feeding behavior and diet of Rhesus monkeys (Macaca mulatta)

in Siwalik Forest in North India. In Primate Ecology: Studies of Feeding and 442 Ranging Behavior in Lemurs, Monkeys and Apes, Clutton-Brock, T. H. and

Harvey, P. H. eds, pp. 223-249. Academic Press, London.

Lindemann, B. (1996) Taste reception. Physiological Reviews 76, 719-766.

Lindemann, B. (2001) Receptors and transduction in taste. Nature 413, 219-225.

2+ Liu, D. and Liman, E. R. (2003) Intracellular Ca and the phospholipid PIP2 regulate the

taste transduction ion channel TRPM5. Proceedings of the National Academy of

Sciences of the United States of America 100, 15160-15165.

Looy, H. and Weingarten, H. P. (1992) Facial expressions and genetic sensitivity to 6-n-

Propylthiouracil predict hedonic response to sweet Physiology & Behavior 52, 75-

82.

Lucchina, L. A., Curtis, O. F., Putnam, P., Drewnowski, A., Prutkin, J. M. and Bartoshuk,

L. M. (1998) Psychophysical measurement of 6-n-propylthiouracil (PROP) taste

perception. Annals of the New York Academy of Sciences 855, 816-819.

Ludwig, M.-G., Vanek, M., Guerini, D., Gasser, J. A., Jones, C. E., Junker, U.,

Hofstetter, H., Wolf, R. M. and Seuwen, K. (2003) Proton-sensing G-protein-

coupled receptors. Nature 425, 93-98.

Lundy, R. F., Jr. and Contreras, R. J. (1999) Gustatory neuron types in rat geniculate

ganglion. J Neurophysiol 82, 2970-2988.

Ly, A. and Drewnowski, A. (2001) PROP (6-n-propylthiouracil) tasting and sensory

responses to caffeine, sucrose, neohesperidin dihydrochalcone and chocolate.

Chemical Senses 26, 41-47.

443 Lyall, V., Alam, R. I., Phan, D. Q., Ereso, G. L., Phan, T.-H. T., Malik, S. A., Montrose,

M. H., Chu, S., Heck, G. L., Feldman, G. M. and Desimone, A. J. A. (2001)

Decrease in rat taste receptor cell intracellular pH is the proximate stimulus in

sour taste transduction. American Journal of Physiology: Cell Physiology 281,

C1005 – C1013.

Lyall, V., Heck, G. L., Vinnikove, A. K., Ghosh, S., Phan, T. T., Alam, R. I., Russell, O.

F., Malik, S. A., Bigbee, J. W. and DeSimone, J. A. (2004) The mammalian

amiloride-insensitive non-specific taste receptor a vanilloid receptor-1 variant.

Journal of Physiology 558, 147-159.

Machida, H., Perkins, E. and Giacommetti, L. (1967) The anatomical and histochemical

properties of the tongue of primates. Folia Primatologica 5, 264-279.

MacKinnon, J. (1974) The behaviour and ecology of wild orang-utans (Pongo

pygmaeus). Animal Behaviour 22, 3-74.

MacKinnon, J. R. and MacKinnon, K. C. (1978) Comparative feeding ecology of six

sympatric primates in West Malaysia. In Recent Advances in Primatology, Vol. 1:

Behavior, Chivers, D. J. and Herbert, J. eds, pp. 305-321. Academic Press,

London.

Maddison, W. P. and Maddison, D. R. (2006) Mesquite: a modular system for

evolutionary analysis. Version 1.12 http://mesquiteproject.org.

Manson, J. H., Perry, S. and Parish, A. R. (1997) Nonconceptive sexual behavior in

bonobos and capuchins. International Journal of Primatology 18, 767-786.

444 Marshall, A. and Wrangham, R. (2007) Evolutionary consequences of fallback foods.

International Journal of Primatology 28, 1219-1235.

Martin, N. G. (1975) Phenylthiocarbamide tasting in a sample of twins. Annals of Human

Genetics 38, 321-326.

Martin, R. D. (1990) Primate Origins and Evolution: A Phylogenetic Reconstruction.

Princeton University Press, Princeton.

Maruyama, Y., Pereira, E., Margolskee, R. F., Chaudhari, N. and Roper, S. D. (2006)

Umami Responses in Mouse Taste Cells Indicate More than One Receptor.

Journal of Neuroscience 26, 2227.

Matsumoto-Odaa, A. and Hayashib, Y. (1999) Nutritional aspects of fruit choice by

chimpanzees. Folia Primatologica 70, 154-162.

Matsunami, H., Montmayeur, J.-P. and Buck, L. B. (2000) A family of candidate taste

receptors in human and mouse. Nature 404, 601-604.

McArthur, M. (1960) Food consumption and dietary levels of aborigines living on

naturally occurring foods. In Records of the American-Australian Scientific

expedition to Arnhem Land, Mountford, C. P. ed, pp. 90-135. Melbourne

Univeristy Press, Melbourne.

McCabe, G. and Fedigan, L. M. (2005) Eating for two: The effect of reproductive state

on the diet and nutrition of free-ranging female white-faced capuchins (Cebus

capuchinus) in Costa Rica. American Journal of Primatology 66, 112-113.

445 McGrew, W. C. (1979) Evolutionary implications of sex differences in chimpanzee

predation and tool-use. In The Great Apes, Hamburg, D. A. and McCown, E. R.

eds, pp. 441-463. Benjamin/Cummings, Menso Park, CA.

McGrew, W. C. and Marchant, L. F. (1997) Using tools at Hand: Manual laterality and

elementary technology in Cebus spp. and Pan spp. International Journal of

Primatology 18, 787-810.

McLaughlin, S. K., McKinnon, P. J. and Margolskee, R. F. (1992) Gustducin is a taste-

cell-specific G protein closely related to transducins. Nature 357, 563-569.

Meehan, B. (1982) Shell bed to shell midden. Australian Institute of Aboriginal Studies,

Canberra.

Merton, B. (1958) Taste sensitivity to PTC in 60 Norwegian families with 176 children.

Acta Genetica et Statistica Medica 8, 114-128.

Midford, P. E., Garland Jr., T. and Maddison, W. P. (2005) PDAP Package of Mesquite.

Version 1.07.

Miguet, L., Zhang, Z. and Grigorov, M. G. (2006) Computational studies of ligand-

receptor interactions in bitter taste receptors. Journal of Receptors and Signal

Transduction 26, 611-630.

Miller, I. J. (1986) Variation in human taste bud densities among regions and subjects.

The Anatomical Record 216, 474-482.

Miller, I. J. (1987) Human fungiform taste bud density and distribution. Annals of the

New York Academy of Sciences 510, 501.

446 Miller, I. J. and Bartoshuk, L. M. (1991) Taste perception, taste bud distribution, and

spatial relationships. In Smell and Taste in Health and Disease, Getchell, T. V.,

Doty, R. L., Bartoshuk, L. M. and Snow, J. B. J. eds, pp. 205-233. Raven Press,

New York.

Miller, I. J. and Reedy, F. E. (1990) Quantification of fungiform papillae and taste pores

in living human subjects. Chemical Senses 15, 281-294.

Miller, I. J. and Reedy, F. E. (1990) Variations in human taste bud density and taste

intensity perception. Physiology & Behavior 47, 1213-1219.

Miller, I. J. and Whitney, G. (1989) Sucrose octaacetate-taster mice have more vallate

taste buds than non-tasters. Neuroscience Letters 100, 271-275.

Milton, K. (1979) Factors influencing leaf choice by howler monkeys: A test of some

hypotheses of food selection by generalost herbivores American Naturalist 114,

362-378.

Milton, K. (1980) The foraging strategy of howler monkeys. Columbia University Press,

New York.

Milton, K. (1984) The role of food-processing factors in primate food choice. In

Adaptations for Foraging in Nonhuman Primates: Contributions to an

Organismal Biology of Prosimians, Monkeys, and Apes, Rodman, P. S. and Cant,

J. G. H. eds, pp. 249-279. Columbia University Press, New York.

Milton, K. (1988) Foraging behavior and the evolution of priamte intelligence. In

Machiavellian Intelligence: Social Expertise and the Evolution of Intellect in

447 Monkeys, Apes, and Humans, Byrne, R. W. and Whiten, A. eds, pp. 285-305.

Clarendon Press, Oxford.

Milton, K. (2003) The Critical Role Played by Animal Source Foods in Human (Homo)

Evolution. Journal of Nutrition 133, 3886S-3892S.

Milton, K. and May, M. L. (1976) Body weight, diet and home range area in primates.

Nature 259, 459-462.

Ming, D., Ninomiya, Y. and Margolskee, R. F. (1999) Blocking taste receptor activation

of gustducin inhibits gustatory responses to bitter compounds. Proceedings of the

National Academy of Sciences of the United States of America 96, 9903–9908.

Ming, D., Ruiz-Avila, L. and Margolskee, R. F. (1998) Characterization and

solubilization of bitter-responsive receptors that couple to gustducin. Proceedings

of the National Academy of Sciences of the United States of America 95, 8933–

8938.

Mistretta, C. M. (1991) Developmental neurobiology of the taste system. In Smell and

Taste in Health and Disease, Getchell, T. V., Doty, R. L., Bartoshuk, L. M. and

Snow, J. J. eds, pp. 35-64. Raven Press, New York.

Møller, A. R. (2003) Sensory Systems: Anatomy and Physiology. Academic Press,

London.

Mombaerts, P. (2004) Genes and ligands for ororant, vomeronasal and taste receptors.

Nature Reviews: Neuroscience 5, 263-278.

Montmayeur, J.P., Liberles, S. D., Matsunami, H. and Buck, L. B. (2001) A candidate

taste receptor gene near a sweet taste locus. Nature Neuroscience 5, 492 - 498. 448 Morland, H. S. (1991) Social organization and ecology of the black and white ruffed

lemurs (Varecia variegata) in lowland rain forest, Nosy Mangabe, Madagascar.

Yale University, New Haven, Connecticut.

Morland, H. S. (1992) Social organization and ecology of black and white ruffed lemurs

(Varecia variegata variegata) in lowland rainforest, Nosy Mangabe, Madagascar.

Ph.D. Thesis, pp. 419. Yale University.

National Academy of Sciences, Institute of Medicine (1990) Nutrition During

Pregnancy: Part I: Weight Gain, Part II: Nutrient Supplements National

Academy Press, Washington, D.C.

Nelson, G., Chandrashekar, J., Hoon, M. A., Feng, L., Zhao, G., Ryba, N. J. P. and

Zuker, C. S. (2002) An amino acid taste receptor. Nature 416, 199-202.

Nelson, G., Hoon, M. A., Chandrashekar, J., Zhang, Y., Ryba, N. J. P. and Zuker, C. S.

(2001) Mammalian sweet taste receptors. Cell 106, 381-390.

Nelson, R. J. (2000) An Inrtoduction to Behavioral Endocrinology. Sinauer Associates,

Inc/, Sunderland, MA.

Newton, P. N. (1992) Feeding and ranging patterns of forest hanuman langurs (Presbytis

entellus). International Journal of Primatology 13, 245-285.

Ninomiya, Y., Kajiura, H. and Mochizuki, K. (1993) Differential taste responses of

mouse chorda tympani and glossopharyngeal nerves to sugars and amino acids.

Neuroscience Letters 163, 197-200.

449 Nishida, T. and Uehara, S. (1983) Natural diet of chimpanzees (Pan troglodytes

schweunfurthii): Long-term record from the Mahalae Mountains, Tanzania.

African Study Monographs 3, 109-130.

Nishida, T., Corp, N., Hamai, M., Hasegawa, T., Hiraiwa-Hasegawa, M., Hosaka, K.,

Hunt, K. D., Itoh, N., Kawanaka, K., Matsumoto-Oda, A., Mitani, J. C.,

Nakamura, M., Norikoshi, K., Sakamaki, T., Turner, L., Uehara, S. and Zamma,

K. (2003) Demography, female life history, and reproductive profiles among the

chimpanzees of Mahale. American Journal of Primatology 59, 99-121.

Nofre, C., Tinti, J. M. and Glaser, D. (1996) Evolution of the sweetness receptor in

primates. II. Gustatory responses of non-human primates to nine compounds

known to be sweet in man. Chemical Senses 21, 747-762.

Norgren, R. (1984) Central neural mechanisms of taste. In Handbook of Physiology: The

Nervous System, Sensory Processes., Vol. III, pp. 1087–1128. American

Physiological Society, Washington, D.C.

Northcutt, G. R. (2004) Taste buds: Development and evolution. Brain, Behavior and

Evolution 64, 198-206.

O'Brien, T. G. and Kinnaird, M. F. (1997) Behavior, diet, and movements of the Sulawesi

crested black macaque (Macaca nigra). International Journal of Primatology 18,

321-351.

O’Driscoll Worman, C. and Chapman, C. (2005) Seasonal variation in the quality of a

tropical ripe fruit and the response of three frugivores. Journal of Tropical

Ecology 21, 689–697. 450 Oates, J. F. (1977) The guereza and its food. In Primate Ecology: Studies of Feeding and

Ranging Behavior in Lemurs, Monkeys, and Apes, Clutton-Brock, T. H. ed, pp.

275-321. Academic Press, New York.

Oates, J. F. and Davies, A. G. (1994) What are the colobines? In Colobine Monkeys:

Their Ecology, Behavior, and Evolution, Davies, A. G. and Oates, J. F. eds, pp. 1-

9. Cambridge University Press, Cambridge.

Oftedal, O. T. (1991) The nutritional consequences of foraging in primates: The

relationship of nutrient intakes to nutrient requirements. Philosophical

Transactions of the Royal Society B: Biological Sciences 334, 161–170.

Ottoni, E. B. and Mannu, M. (2003) Spontaneous use of toolds by semifree-ranging

capuchin monkeys. In Animal Social Complexity: Intelligence, Culture, and

Individualized Societies, de Waal, F. B. M. and Tyack, P. L. eds, pp. 440-443.

Harvard Univeristy Press, Cambridge.

Overdorff, D. J. (1993) Ecological and reproductive correlates to range use in red-bellied

lemurs (Eulemur rubriventer) and roufous lemurs (Eulemur fulvus rufus). In

Lemur Social Systems and Their Ecological Basis, Kappeler, P. M. and Ganzhorn,

J. U. eds. Plenum Press, New York.

Palmer, R. K. (2007) The pharmacaology and signaling of bitter, sweet, and umami taste

sensing. Molecular Interventions 7, 87-98.

Palombit, R. A. (1997) Inter- and intraspecific variation in the diets of sympatric siamang

(Hylobates syndactylus) and Lar Gibbon (Hylobates lar). Folia Primatologica 68,

321-337. 451 Pandolfi, S. S., Van Schaik, C. P. and Pusey, A. E. (2003) Sex differences in termite

fishing among Gombe chimpanzees. In Animal social complexity: Intelligence,

culture, and individualized societies. de Waal, F. B. M. and Tyack, P. L. eds, pp.

414-418. Harvard University Press, Cambridge.

Pandolfi, S., Van Schaik, C. P. and Pusey, A. E. (2002) Sex differences in chimpanzee

and orangutan diet and the sexual division of labor in humans. American Journal

of Physical Anthropology Suppl. 34, 122.

Parra, R. (1978) Comparison of foregut and hindgut fermentation in herbivores. In The

Ecology of Arboreal Folivores, Montgomery, G. G. ed, pp. 205-229. Smithsonian

Institution Press, Washington DC.

Parry, C. M., Erkner, A. and le Coutre, J. (2004) Divergence of T2R chemosensory

receptor families in humans, bonobos, and chimpanzees. Proceedings of the

National Academy of Sciences of the United States of America 101, 14830-14834.

Pasquet, P., Oberti, B., El Ati, J. and Hladik, C. M. (2002) Relationships between

threshold-based PROP sensitivity and food preferences of Tunisians. Appetite 39,

167-173.

Patel, S. (1971) ABO blood groups, PTC tasting and derrnatoglyphics of Tibetans at

Chandragiri, Orissa American Journal of Physical Anthropology 35, 149-150.

Pavelka, M. M. and Knopff, K. (2004) Diet and activity in black howler monkeys

(Alouatta pigra) in southern Belize: Does degree of frugivory influence activity

level? Primates 45, 105-111.

452 Penfield, W. and Faulk, M. E. (1955) The insula: Further observations on its function.

Brain 78, 445-470.

Pérez, C. A., Huang, L., Rong, M., Kozak, J. A., Preuss, A. K., Zhan, H., Max, M. and

Margolskee, R. F. (2002) A transient receptor potential channel in taste receptor

cells. Nature Neuroscience 5, 1169-1176.

Perry, S. (2003) Coalitionary Agression in white-faced capuchins. In Animal social

complexity: Intelligence, culture, and individualized societies. de Waal, F. B. M.

and Tyack, P. L. eds, pp. 111-114. Harvard University Press, Cambridge.

Perry, S. and Rose, L. (1994) Begging and transfer of coati meat by white-faced capuchin

monkeys, Cebus capucinus. Primates 35, 409-415.

Peterson, J. M., Bartoshuk, L. M. and Duffy, V. B. (1999) Intensity and preference for

sweetness is influenced by genetic taste variation. Journal of the American

Dietetic Association 99, A28-A28.

Pfaffmann, C. (1941) Gustatory afferent impulses. Journal of Cellular and Comparative

Physiology 17, 243-258.

Pickering, G. J., Simunkova, K. and DiBattista, D. (2004) Intensity of taste and

astringency sensations elicited by red wines is associated with sensitivity to PROP

(6-n-propylthiouracil). Food Quality and Preference 15, 147-154.

Pieroni, A., Houlihan, L., Ansari, N., Hussain, B. and Aslam, S. (2007) Medicinal

perceptions of vegetables traditionally consumed by South-Asian migrants living

in Bradford, Northern England. Journal of Ethnopharmacology 113, 100-110.

453 Pochron, S. and Wright, P. C. (in review) Diet competition in a female-dominant

prosimian primate, the Milne-Edwards' sifaka (Propithecus edwardsi). Primates.

Polcari, R. (1971) De nouvelles données sur la sensibilité à la phenil-thio-carbamide chez

les primates. Paper presented at the Proceeding of the Third International

Congress of Primatology, Zurich, 1971.

Politis, G. (1996) Nukak. Instituto Amazonico de Investigaciones Cientificas - SINCHI,

Columbia.

Pollock, J. I. (1977) The ecology and sociology of feeding in Indri indri. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 38-69. Academic Press, New York.

Pontzer, H. and Wrangham, R. W. (2004) Climbing and the daily energy cost of

locomotion in wild chimpanzees: Implications for hominoid locomotor evolution.

Journal of Human Evolution 46, 315-335.

Popp, J. L. (1978) Male baboons and evolutionary principles. Ph.D. Thesis. Harvard

University.

Portman, O. (1970) Nutritional requirements of non-human primates. In Feeding and

Nutrition of Non-human Primates, Harris, R. ed, pp. 87-116. Academic Press,

New York.

Prawitt, D., Monteilh-Zoller, M. K., Brixel, L., Spangenberg, C., Zabel, B., Fleig, A. and

Penner, R. (2003) TRPM5 is a transient Ca2+-activated cation channel responding

2+ to rapid changes in [Ca ]i. Proceedings of the National Academy of Sciences of

the United States of America 100, 15166 –15171. 454 Pritchard, T. C., Hamilton, R. B. and Norgren, R. (1989) Neural coding of gustatory

information in the thalamus of Macaca mulatta. Journal of Neurophysiology 61,

1-14.

Pritchard, T. C., Macaluso, D. A. and Eslinger, P. J. (1999) Taste perception in patients

with insular cortex lesions. Behavioral Neuroscience 113, 663-671.

Pritchard, T. C., Reilly, S., Hamilton, R. B. and Norgren, R. (1994) Taste preference of

Old World monkeys: I. A single-bottle preference test. Physiology & Behavior 55,

447-481.

Prodi, D. A., Drayna, D., Forabosco, P., Palmas, M. A., Maestrale, G. B., Piras, D. and

Angius, A. (2004) Bitter taste study in a Sardinian genetic isolate supports the

association of phenylthiocarbamide sensitivity to the TAS2R38 bitter receptor

gene. Chemical Senses 29, 697-702.

Profet, M. (1995) Pregnancy sickness: Using your body's natural defenses to protect your

baby-to-be. Addison-Wesley Publishing Group, Reading, MA.

Provenza, F. D. (1996) Acquired aversions as the basis for varied diets of ruminants

foraging on rangelands. Journal of Animal Science 74, 2010-220.

Provenza, F. D., Villalba, J. J., Dziba, L. E., Atwood, S. B. and Banner, R. E. (2003)

Linking herbivore experience, varied diets, and plant biochemical diversity. Small

Ruminant Research 49, 257-274.

Prutkin, J., Duffy, V. B., Etter, L., Fast, K., Gardner, E., Lucchina, L. A., Snyder, D. J.,

Tie, K., Weiffenbach, J. and Bartoshuk, L. M. (2000) Genetic variation and

455 inferences about perceived taste intensity in mice and men. Physiology &

Behavior 69, 161-173.

Puertas, P. E., Aquino, R. and Encarnación, F. (1992) Uso de alimentos y competición

entre el mono nocturno Aotus vociferans y otros mamíferos, Loreto, Perú. Folia

Amazonia 4, 135–144.

Purves, D., Fitzpatric, D., Katz, L. C., LaMantia, A.-S. and McNamara, J. O. (1997)

Neuroscience. Sinaur Associates, Inc., Sunderland, MA.

Raemaekers, J. J. (1979) Ecology of sympatric gibbons. Folia Primatologica 31, 227-

245.

Ramirez, I. (1990) Why do sugars taste good? Neuroscience & Biobehavioral Reviews

14, 125-134.

Ramirez, M. F., Freese, C. H. and Revilla C., J. (1977) Feeding ecology of the pygmy

marmoset, Cebuella pygmaea, in Northeastern Peru. In Biology and conservation

of the callitrichidae, Kleiman, D. G. ed, pp. 91-104. Smithsonian Institution

Press, Washington D.C.

Rankin, K. M., Godinot, N., Christensen, C. M., Tepper, B. J. and Kirkmeyer, S. V.

(2004) Assessment of different methods for 6-n-propylthiouracil status

classification. In Genetic Variation in Taste Sensitivity, Prescott, J. and Tepper, B.

J. eds, pp. 63-88. Marcel Dekker, Inc., New York.

Ray, D. A., Xinga, J., Hedgesa, D. J., Halla, M. A., Labordea, M. E., Anders, B. A.,

Whitea, B. R., Stoilovaa, N., Fowlkesa, J. D., Landry, K. E., Chemnickb, L. G.,

456 Ryderb, O. A. and Batzera, M. A. (2005) Alu insertion loci and platyrrhine

primate phylogeny. Molecular Phylogenetics and Evolution 35, 117–126.

Reed, D. R. (2004) Progress in human bitter phenylthiocarbomide genetics. In Genetic

Variation in Taste Sensitivity, Prescott, J. and Tepper, B. J. eds, pp. 43-61. Marcel

Dekker, Inc., New York.

Reed, D. R., Bachmanov, A. A., Beauchamp, G. K., Tordoff, M. and Price, R. A. (1997)

Heritable variation in food preference and their contribution to obesity. Behavior

Genetics 27, 373-387.

Reed, D. R., Bartoshuk, L. M., Duffy, V. B., Marino, S. and Price, A. (1995)

Propylthiouracil tasting: Determination of underlying threshold distributions

using maximum liklihood. Chemical Senses 20, 529-533.

Reed, D. R., Nanthakumar, E., North, M., Bell, C., Bartoshuk, L. M. and Price, R. A.

(1999) Localization of a gene for bitter taster perception to human chromosome

5p15. American Journal of Human Genetics 64, 1478-1480.

Reedy, F. E., Bartoshuk, L. M., Miller, I. J., Duffy, V. B., Lucchina, L. A. and

Yanagisawa, K. (1993) Relationships among papillae, taste pores, and 6-n-

propythiouracil (PROP) suprathreshold taste sensitivity. Chemical Senses 18, 618-

619.

Regan, B. C., Julliot, C., Simmen, B., Vienot, F., Charles-Dominique, P. and Mollen, J.

D. (2001) Fruits, foliage and the evolution of primate colour vision. Philosophical

Transactions of the Royal Society of London. Series B: Biological Sciences 356,

229-283. 457 Remis, M. J. (2006) The role of taste in food selection by African apes: Implications for

niche separation and overlap in tropical forests Primates 47, 56-64.

Remis, M. J. and Kerr, M. E. (2002) Taste responses to fructose and tannic acid among

gorillas (Gorilla gorilla gorilla). International Journal of Primatology 23, 251-

261.

Reynolds, V., Plumptre, A. J., Greenham, J. and Harborne, J. (1998) Condensed tannins

and sugars in the diet of chimpanzees (Pan troglodytes schweinfurthii) in the

Budongo Forest, Uganda. Oecologia 115, 331-336.

Riba-Hernández, P., Stoner, K. E. and Lucas, P. W. (2003) The sugar composition of

fruits in the diet of spider monkeys (Ateles geoffroyi) in tropical humid forest in

Costa Rica. Journal of Tropical Ecology 19, 709-716.

Richard, A. (1985) Primates in Nature. W.H. Freeman and Company, New York.

Richard, A. F. (1978) Variability in feeding behavior of a Malagasy prosimian,

Propithecus verreauxi: Lemuriformes. In The Ecology of Arboreal Folivores,

Montgomery, G. G. ed, pp. 519-533. Smithsonian Institution Press, Washington

DC.

Richter, T. A., Caicedo, A. and Roper, S. D. (2003) Sour taste stimuli evoke Ca2+ and pH

responses in mouse taste cells. The Journal of Physiology Online 547, 475-483.

Robinson, P. P. and Winkles, P. A. (1990) Quantitative study of fungiform papillae and

taste buds on the cat's tongue. The Anatomical Record 226, 108-111.

458 Rodman, P. S. (1977) Feeding behavior of orangutans in the Kutai Reserve, East

Kalimantan. In Primate Ecology: Studies of Feeding and Ranging Behaviour in

Lemurs, Monkeys and Apes, pp. 383–413. Academic Press, London.

Rolls, B. J., Rowe, E. A., Rolls, E. T., Kingston, B., Megson, A. and Gunary, R. (1981)

Variety in a meal enhances food intake in man. Physiology & Behavior 26, 215-

221.

Rolls, E. T. (1999) The Brain and Emotion. Oxford University Press, Oxford.

Rolls, E. T. (2005) Taste, olfactory, and food texture processing in the brain, and the

control of food intake. Physiology & Behavior 85, 45-56.

Rolls, E. T. and Baylis, L. L. (1994) Gustatory, olfactory, and visual convergence within

the primate orbitofrontal cortex. Journal of Neuroscience 14, 5437-5452.

Rolls, E. T., Rolls, B. J. and Rowe, E. A. (1983) Sensory-specific and motivation-specific

satiety for the sight and taste of food and water in man. Physiology & Behavior

30, 185-192.

Rolls, E. T., Scott, T. R., Sienkiewicz, Z. J. and Yaxley, S. (1988) The responsiveness of

neurones in the frontal opercular gustatory cortex of the macaque monkey is

independent of hunger. Journal of Physiology 397, 1-12.

Romanov, R. A., Rogachevskaja, O. A., Bystrova, M. F., Jiang, P., Margolskee, R. F. and

Kolesnikov, S. S. (2007) Afferent neurotransmission mediated by hemichannels

in mammalian taste cells. The EMBO Journal 26, 657-667.

459 Roos, C., Schmitz, J. and Zischler, H. (2004) Primate jumping genes elucidate

strepsirrhine phylogeny. Proceedings of the National Academy of Sciences of the

United States of America 101, 10650–10654.

Roper, S. D. (2006) Cell communication in taste buds. Cellular and Molecular Life

Sciences 63, 1494-1500.

Roper, S. D. (2007) Signal transduction and information processing. Pflugers Archiv.

European Journal of Physiology 454, 759-776.

Rose, L. M. (1994) Sex differences in diet and foraging behavior in white-faced

capuchins (Cebus capucinus). International Journal of Primatology 15, 95-114.

Rose, L. M. (1997) Vertebrate predation and food-sharing in Cebus and Pan.

International Journal of Primatology 18, 727-765.

Ross, C. (2002) Life history, infant care strategies, and brain size in primates. In Primate

Life Histories and Socioecology, Kappeler, P. M. and Pereira, M. E. eds, pp. 266-

284. University of Chicago Press, Chicago.

Rossier, O., Cao, J., Huque, T., Spielman, A. I., Feldman, R. S., Medrano, J. F., Brand, J.

G. and le Coutre, J. (2004) Analysis of human fungiform papillae cDNA library

and identification of taste-related genes. Chemical Senses 29, 13-23.

Rozin, P. and Vollmecke, T. A. (1986) Food likes and dislikes. Annual Review of

Nutrition 6, 433-456.

Rudolphi, K. A. (1823) Grundriss der Physiologie. Ferdinand Dümmler, Berlin.

460 Rui-Liin, N., Tanaka, T., Zhou, J. and Tanaka, O. (1982) Phlorizin and trilobatin, sweet

dihydrochalcone-glucosides from leaves of Lithocarpus litseifolius (Hance) Rehd.

(Fagaceae). Agricultural and Biological Chemistry, 1933–1934.

Ruiz-Avila, L., McLaughlin, S. K., Wildman, D., McKinnon, P. J., Robichon, A.,

Spickofsky, N. and Margolskee, R. F. (1995) Coupling of bitter receptor to

phosphodiesterase through transducin in taste receptor cells. Nature 376, 80-85.

Ruiz-Avila, L., Wong, G. T., Damak, S. and Margolskee, R. F. (2001) Dominant loss of

responsiveness to sweet and bitter compounds caused by a single mutation in α-

gustducin. Proceedings of the National Academy of Sciences of the United States

of America 98, 8868 – 8873.

Salem, A.-H., Ray, D. A., Xing, J., Callinan, P. A., Myers, J. S., Hedges, D. J., Garber, R.

K., Witherspoon, D. J., Jorde, L. B. and Batzer, M. A. (2003) Alu elements and

hominid phylogenetics. Proceedings of the National Academy of Sciences of the

United States of America 100, 12787–12791.

Sampson, D. A. and Jansen, G. R. (1984) Protein and energy nutrition during lactation.

Annual Review of Nutrition 4, 43-67.

Schiffman, S. (1980) Magnitude estimation of amino acids for young and elderly

subjects. In Olfaction and Taste, Vol. 7, Van der Starre, H. ed, pp. 379–383. IRL

Press, London.

Schilling, A., Danilova, V. and Hellekant, G. (2004) Behavioral study in the gray mouse

lemur (Microcebus murinus) using compounds considered sweet by humans.

American Journal of Primatology 62, 43-48. 461 Schmidt, J. O. (1979) Ant venoms: A study of venom diversity. In Pesticide and Venom

Neurotoxicity, Shankland, D. L., Hollingworth, R. M. and Smyth, T. eds, pp. 247-

263. Plenum Press, New York.

Scott, T. R. and Plata-Salaman, C. R. (1999) Taste in the monkey cortex. Physiology &

Behavior 76, 489-511.

Scott, T. R., Giza, B. K. and Yan, J. (1998) Electrophysiological respnses to bitter stimuli

in primate cortex. Annals of the New York Academy of Sciences 855, 498-501.

Segovia, C., Hutchinson, I., Laing, D. G. and Jinks, A. L. (2002) A quantitative study of

fungiform papillae and taste pore density in adults and children Developmental

Brain Research 138, 135-146.

Shedlock, A. M. and Okada, N. (2000) SINE insertions: Powerful toods for molecular

systematics. Bioessays 22, 148-160.

Shi, P. and Zhang, J. (2006) Contrasting modes of evolution between vertebrate

sweet/umami receptor genes and bitter receptor genes. Molecular Biology and

Evolution 23, 292-300.

Shi, P., Zhang, J., Yang, H. and Zhang, Y.-p. (2003) Adaptive diversification of bitter

taste receptor genes in mammalian evolution. Molecular Biology and Evolution

20, 805-814.

Simmen, B. (1991) Stratégies alimentaires des primates néotropiceaux en fonction de la

perception des produits de l'environment. Ph.D. Thesis. Université Paris - XIII,

Villetaneuse.

462 Simmen, B. (1992) Seuil de discrimination et réponses supraliminaires à des solution de

fructose en function du régime alimentaire des Primates Callithricidae. Comptes

Rendus de l'Académie des Sciences 315, 151-157.

Simmen, B. (1994) Taste discrimination and diet differentiation among New World

primates. In The Digestive System of Mammals: Food, Form, and Function,

Chivers, D. J. and Langer, P. eds, pp. 150-165. Cambridge University Press,

Cambridge.

Simmen, B. and Charlot, S. (2003) A comparison of taste thresholds for sweet and

astringent-tasting compounds in great apes. Comptes Rendus Biologies 326, 449-

445.

Simmen, B. and Hladik, C. M. (1998) Sweet and bitter taste discrimination in primates:

Scaling effects across species. Folia Primatologica 69, 129-138.

Simmen, B., Hladik, A. and Ramasiarisoa, P. (2003) Food intake and dietary overlap in

native Lemur catta and Propithecus verreauxi and introduced Eulemur fulvus at

Berenty, Southern Madagascar International Journal of Primatology 24, 949-968.

Simmen, B., Hladik, A., Ramasiarisoa, P., Iaconelli, S. and Hladik, C. M. (1999) Taste

discrimination in lemurs and other primates, and the relationships to distribution

of plant allelochemicals in different habitats of Madagascar. In New Directions in

Lemur Studies, Rakotosamimanana, B., Rasamimanana, H., Ganzhorn, J. U. and

Goodman, S. M. eds, pp. 201-219. Plenum Publishers, New York.

Simmons, R. T., Graydon, J. J., Semple, N. M. and Swindlwer, D. R. (1956) A blood

group genetical survey in West Nakanai, New Britian. 14, 275-286. 463 Singer, S. S., Schmitz, J., Schwiegk, C. and Zischler, H. (2003) Molecular cladistic

markers in New World monkey phylogeny (Platyrrhini, Primates). Molecular

Phylogenetics and Evolution 26, 490–501.

Smith, C. C. (1977) Feeding behaviour and social organization in howling monkeys. In

Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys

and Apes, Clutton-Brock, T. H. ed, pp. 97-126. Academic Press, London.

Smith, D. G., Lorey, F. W. and Small, M. (1981) Taste sensitivity to phenylthiourea

(PTC) in the rhesus monkey (Macaca mulatta). Primates 22, 404-408.

Smith, D. V. (1971) Taste intenstiy as a function of areas and concentration:

Differentiation between compounds. Journal of Experimental Psychology 87,

163-171.

Smith, D. V. and Margolis, F. L. (1999) Taste processing: Whetting our appetites.

Current Biology 9, R453-R455.

Smith, R. J. and Jungers, W. L. (1997) Body mass in comparative primatology. Journal

of Human Evolution 32, 523-559.

Snyder, L. H. (1931) Inherited taste deficiency. Science 74, 151-152.

Soranzo, N., Bufe, B., Sabeti, P. C., Wilson, J. F., Weale, M. E., Marguerie, R.,

Meyerhof, W. and Goldstein, D. B. (2005) Positive selection on a high-sensitivity

allele of the human bitter-taste receptor TAS2R16. Current Biology 15, 1257-

1265.

Stahl, A. B., Dunbar, R. I. M., Homewood, K., Ikawa-Smith, F., Kortlandt, A., McGrew,

W. C., Milton, K., Paterson, J. D., Poirier, F. E., Sugardjito, J., Tanner, N. M. and 464 Wrangham, R. W. (1984) Hominid dietary selection before fire. Current

Anthropology 25, 151-168.

Standford, C. B. (1996) The hunting ecology of wild chimpanzees: Implications for the

evolutionary ecology of pliocene hominids American Anthropologist, New Series

98, 96-113.

Standford, C. B. (1998) Predation and male bonds in primate societies. Behaviour 135,

513-533.

Stanford, C. B., Wallis, J., Mpongo, E. and Goodall, J. (1994) Hunting Decisions in Wild

Chimpanzees. Behaviour 131, 1-20.

Steiner, J. E., Glaser, D., Hawilo, M. E. and Berridge, K. C. (2001) Comparative

expression of hedonic impact: Affective reactions to taste by human infants and

other primates. Neuroscience and Biobehavioral Reviews 25, 53-74.

Stephan, H., Baron, G. and Frahm, H. (1988) Comparative size of brains and brain

components. In Comparative Primate Biology, Steklis, H. D. and Erwin, J. eds,

pp. 1-39. Liss, New York.

Sterck, E. H. M., Watts, D. P. and van-Schaik, C. P. (1997) The evolution of female

social relationships in nonhuman primates. Behavioral ecology and sociobiology

41, 291-311.

Stevens, D. R., Seifert, R., Bufe, B., Müller, F., Kremmer, E., Gauss, R., Meyerhof, W.,

Kaupp, U. B. and Lindemann, B. (2001) Hyperpolarization-activated channels

HCN1 and HCN4 mediate responses to sour stimuli. Nature 413, 631-635.

465 Sugita, M. (2006) Taste perception and conding in the periphery. Cellular and Molecular

Life Sciences 63, 2000-2015.

Sussman, R. W. (1977) Feeding behaviour of Lemur catta and Lemur fulvus. In Primate

Ecology: Studies of Feeding and Ranging Behaviour in Lemurs, Monkeys and

Apes, Clutton-Brock, T. H. ed, pp. 1-36. Academic Press, London.

Takemoto, H. (2003) Phytochemical determination for leaf food choice by wild

chimpanzees in Guinea, Bossou. Journal of Chemical Ecology 29, 2551-2573.

Tan, Y. and Li, W.-H. (1999) Trichromatic vision in prosimians. Nature 402, 36.

Teaford, M. F., Lucas, P. W., Ungar, P. S. and Glander, K. E. (2006) Mechanical

defenses in leaves eaten by Costa Rican howling monkeys (Alouatta palliata).

American Journal of Physical Anthropology 129, 99-104.

Teleki, G. (1973) The Predatory Behavior of Wild Chimpanzees. Bucknell University

Press, Lewisburg, Pennsylvania.

Teleki, G. (1977) Spatial and temporal dimensions of routine activities performed by

chimpanzees in Gombe National Park, Tanzania: An ethological study of adaptive

strategy. Ph.D. Thesis. Pennsylvania State University.

Teleki, G. (1981) The omnivorous diet and eclectic feeding habits of chimpanzees in

Gombe National Park, Tanzania. In Omnivorous Primates: Gathering and

Hunting in Human Evolution, Harding, R. S. O. and Teleki, G. eds. Columbia

University Press, New York.

466 Tepper, B. (1998) 6-n-propylthiouracil: A genetic marker for taste with implications for

food preference and dietary habits. American Journal of Human Genetics 63,

1271-1276.

Tepper, B. J. (1999) Does genetic taste sensitivity to PROP influence food preferences

and body weight? Appetite 32, 422.

Tepper, B. J. and Nurse, R. J. (1997) Fat perception is related to PROP taster status.

Physiology & Behavior 61, 494-954.

Tepper, B. J. and Nurse, R. J. (1998) PROP taster status is related to fat perception and

preference. Annals of the New York Academy of Sciences 855, 802-804.

Tepper, B. J. and Ullrich, N. (2002) Influence of genetic taste sensitivity to 6-n-

propylthiouracil (PROP), dietary restraint and disinhibition on body mass index in

middle-aged women. Physiology & Behavior 75, 305-312.

Tepper, B. J., Christensen, C. M. and Cao, J. (2001) Development of brief methods to

classify individuals by PROP taster status. Physiology & Behavior 73, 571-577.

Thompson, D. A., Moskowitz, H. R. and Campbell, R. (1976) Effects of body weight and

food intake on pleasantness ratings for sweet stimuli. Journal of Applied

Psychology 41, 77-83.

Tonosaki, K. and Funakoshi, M. (1988) Cyclic mucleotides mediate taste transduction.

Nature 331, 354-356.

Trubey, K. R., Culpepper, S., Maruyama, Y., Kinnamon, S. C. and Chaudhari, N. (2006)

Tastants evoke cAMP signal in taste buds that is independent of calcium

signaling. American Journal of Cell Physiology 291, C237-244. 467 Turnbull, B. and Matisoo-Smith, E. (2002) Taste sensitivity to 6-n-propylthiouracil

predicts acceptance of bitter-tasting spinach in 3-6-y-old children. American

Journal of Clinical Nutrition 76, 1101-1105.

Ueno, A., Ueno, Y. and Tomonaga, M. (2004) Facial response to four basic tastes in

newborn rhesus macaques (Macaca mulatta) and chimpanzees (Pan troglodytes).

Behavioural Brain Research 154, 261-271.

Ungar, P. S. (1995) Fruit preferences of four sympatric primate species at Ketambe,

Nothern Sumatra, Indonesia. International Journal of Primatology 16, 221-245.

Valentin, G. A. (1853) A textbook of physiology. Henry Renshaw, London. van Noordwijk, M. A. and van Schaik, C. P. (1999) The affects of dominance rank and

group size on female lifetime reproductive success in wild long-tailed macaques,

Macaca fascicularis. Primates 40, 105-130. van Roosmalen, M. G. M. and Klein, L. L. (1988) The spider monkeys: Genus Ateles. In

Ecology and Behavior of Neotropical Primates, Vol. 2, Mittermeier, R. A.,

Coimbra-Filho, A. F. and da Fonseca, G. A. B. eds, pp. 455-537. World Wildlife

Fund, Washington D.C. van Schaik, C. P. (1989) The ecology of social relationships amongst female primates. In

Comparative Socioecology: The behavioral ecology of humans and other

mammals, Standen, V. and Foley, R. A. eds, pp. 195 - 218. Blackwell Scientific

Publications, Oxford. van Schaik, C. P. and Deaner, R. O. (2003) Life history and cognitive evolution in

primates. In Animal Social Complexity: Intelligence, Culture, and Individualized 468 Societies, de Waal, F. B. M. and Tyack, P. L. eds, pp. 5-25. Harvard Univeristy

Press, Cambridge.

Vanderford, D. (2007) D.V.M., Duke University. Personal communication.

Vasey, N. (2000) Niche Separation in Varecia variegata rubra and Eulemur fulvus

albifrons: I. Interspecific Patterns. American Journal of Physical Anthropology

112, 411-431.

Verhagen, J. V., Kadohisa, M. and Rolls, E. T. (2004) Primate insular/opercular taste

cortex: Neuronal representations of the viscosity, fat texture, grittiness,

temperature, and taste of foods. Journal of Neurophysiology 92, 1685–1699.

Vij, S. (1976) Observations on the comparative anatomy of the tongues of some South

East Asian primates. Journal of the Singapore National Academy of Sciences 5,

31-35.

Visalberghi, E., Fragaszy, D. M. and Savage-Rumbaugh, S. (1995) Performance in a tool-

using task by common chimpanzees (Pan troglodytes), bonobos (Pan paniscus),

an orangutan (Pongo pygmaeus), and capuchin monkeys (Cebus apella). Journal

of Comparative Psychology 109, 52-60.

Visalberghi, E., Sabbatini, G., Stammati, M. and Addessi, E. (2003) Preferences towards

novel foods in Cebus apella: The role of nutrients and social influences.

Physiology & Behavior 80, 341-349.

Walker, R., Burger, O., Wagner, J. and Von Rueden, C. R. (2006) Evolution of brain size

and juvenile periods in primates. Journal of Human Evolution 51, 480.

469 Wang, X., Thomas, S. D. and Zhang, J. (2004) Relaxation of selective constraint and loss

of function in the evolution of human bitter taste receptor genes. Human

Molecular Genetics 13, 2671-2678.

Wasser, P. (1977) Feeding, ranging and group size in the Mangabe, Cercocebus albigena.

In Primate Ecology: Studies of Feeding and Ranging Behaviour in Lemurs,

Monkeys and Apes, Clutton-Brock, T. H. ed, pp. 183-222. Academic Press, New

York.

Waterman, P. G. and Kool, K. (1994) Colobine food selection and plant chemistry. In

Colobine Monkeys: Their Ecology, Behavior, and Evolution, Davies, A. G. and

Oates, J. F. eds, pp. 251-284. Cambridge University Press, Cambridge.

Wheatley (1980) Feeding and ranging of Eastern Bornean Macaca fascicularis. In The

Macaques: Studies in Ecology, Behavior, and Evolution, Lindburg, D. G. ed, pp.

215-246. Van Nostrand Reinhold Co., New York.

Whissell-Beuchy (1990) Effects of age and sex on taste sensitivity to phenyltiocarbamide

(PTC) in the Berkley Guidance sample. Chemical Senses 15, 39-57.

Wiley, A. S. and Solomon, H. K. (1998) Geophagy in pregnancy: A test of a hypothesis.

Current Anthropology 39, 532-545.

Whiten, A. and van Schaik, C. P. (2007) The evolution of animal ‘cultures’ and social

intelligence. Philosophical Transactions of the Royal Society B: Biological

Sciences 362, 603-620.

Whitten, P. L. (1982) Female Reproductive Strategies Among Ververt Monkeys.

Department of Anthropology, pp. 292. Harvard University, Cambridge. 470 Whitten, P. L. (1983) Diet and dominance among female vervet monkeys (Cercopithecus

aethiops). American Journal of Primatology 5, 139-159.

Witherly, S. A., Pangborn, R. M. and Stern, J. S. (1980) Gustatory responses and eating

duration of obease and lean adults. Appetite 1, 52-63.

Wong, G., Gannon, K. S. and Margolskee, R. F. (1996) Transduction of bitter and sweet

taste by gustducin. Nature 381, 796-800.

Wooding, S. (2006) Phenylthiocarbamide: A 75-year adventure in genetics and natural

selection Genetics 172, 2015-2023.

Wooding, S., Bufe, B., Grassi, C., Howard, M. T., Stone, A. C., Vazquez, M., Dunn, D.

M., Meyerhof, W., Weiss, R. B. and Bamshad, M. J. (2006) Independent

evolution of bitter-taste sensitivity in humans and chimpanzees. Nature 440, 930-

934.

Wooding, S., Kim, U.-k., Bamshad, M. J., Larsen, J., Jorde, L. B. and Drayna, D. (2004)

Natural selection and molecular evolution in PTC, a bitter-taste receptor gene.

American Journal of Human Genetics 74, 637-646.

Wrangham, R. W. (1980) An ecological model of female-bonded primate groups.

Behaviour 75, 262-299.

Wrangham, R. W. (2003) Ecologica influences on chimpanzee hunting. American

Journal of Physical Anthropology Suppl. 36, 227-228.

Wrangham, R. W. and van Zinnicq Bergmann Riss, E. (1990) Rates of predation on

mammals by gombe chimpanzees, 1972–1975. Primates 31, 157-170.

471 Wrangham, R. W. and Waterman, P. G. (1981) Feeding behaviour of vervet monkeys on

Acacia tortilis and Acacia xanthophloea: With special reference to reproductive

strategies and tannin production. The Journal of Animal Ecology 50, 715-731.

Wrangham, R. W., Conklin-Brittain, N. L. and Hunt, D. M. (1998) Dietary responses of

chimpanzees and cercopithecines to seasonal variation in fruit abundance. I.

Antifeedants. International Journal of Primatology 19, 949-969.

Wrangham, R., Conklin-Brittain, N. L., Chapman, C. A. and Hunt, K. D. (1991) The

significance of fibrous foods for Kibale Forest chimpanzees. Philosophical

Transactions of the Royal Society B: Biological Sciences 334, 171-178.

Wright, P. C. (1985) The costs and benefits of nocturnality for Aotus trivirgatus (the

night monkey). Ph.D. Thesis, pp. 315. City University of New York, New York.

Wynne-Edwards, K. E. (2001) Evolutionary biology of plant defenses against herbivory

and their predictive implications for endocrine disruptor susceptibility in

vertebrates. Environmental Health Perspectives 109, 443-448.

Xing, J., Wanga, H., Hana, K., Raya, D. A., Huanga, C. H., Chemnick, L. G., Stewartc,

C.-B., Disotelld, T. R., Ryderb, O. A. and Batzer, M. A. (2005) A mobile element

based phylogeny of Old World monkeys. Molecular Phylogenetics and Evolution

37, 872–880.

Yackinous, C. A. and Guinard, J. X. (2001) Relation between PROP taster status and fat

perception, touch, and olfaction. Physiology & Behavior 72, 427-437.

472 Yackinous, C. A. and Guinard, J. X. (2002) Relation between PROP (6-n-

propythiouracil) tater status, taste anatomy, and dietary intake measure for young

men and women. Appetite 38, 201-209.

Yang, R., Crowley, H. H., Rock, M. E. and Kinnamon, J. C. (2000) Taste cells with

synapses in rat circumvallate papillae display SNAP-25like immunoreactivity The

Journal of Comparative Neurology 424, 205–215.

Yaxley, S., Rolls, E. T. and Sienkiewicz, Z. J. (1988) The responsiveness of neurons in

the insular gustatory cortex of the macaque monkey is independent of hunger.

Physiology & Behavior 42, 223-229.

Yaxley, S., Rolls, E. T., Sienkiewicz, Z. J. and Scott, T. R. (1985) Satiety does not affect

gustatory activity in the nucleus of the solitary tract of the alert monkey. Brain

Research 347, 85-93.

Ye, Q., Heck, G. L. and DeSimone, J. A. (1994) Effects of voltage perturbation of the

lingual receptive field on chorda tympani responses to Na + and K + salts in the

rat: Implications for gustatory transduction Journal of General Physiology 104,

885-907.

Yeager, C. P. (1996) The feeding ecology of the long-tailed macaque (Macaca

fascicularis) in Kalimantan Tengah, Indonesia. International Journal of

Primatology 17, 51-62.

Yoshida, R., Shigemura, N., Sanematsu, K., Yasumatsu, K., Ishizuka, S. and Ninomiya,

Y. (2006) Taste responsiveness of fungiform taste cells with action potentials.

Journal of Neurophysiology 96, 3088-3095. 473 Zhang, Y., Hoon, M. A., Chandrashekar, J., Mueller, K. L., Cook, B., Wu, D., Zuker, C.

S. and Ryba, N. J. P. (2003) Coding of sweet, bitter, and umami tastes: Different

receptor cells sharing similar signaling pathways. Cell 112, 293-301.

Zhao, G., Zhang, Y., Hoon, M. A., Chandrashekar, J., Erienbach, I., Ryba, N. J. P. and

Zuker, C. S. (2003) The receptors for mammalian sweet and umami taste. Cell

115, 255-266.

474 Vita

Laura Jean Alport was born February 18th, 1974 in Skokie, Illinois to Elizabeth and Howard Alport. She earned her B.F.A. at Washington University in St. Louis in 1997 and began her graduate studies in anthropology at the University of Texas at Austin in 1998. Current publications include “Comparative analysis of the role of olfaction and the neocortex in primate intrasexual competition” (Anatomical Record 2004).

This dissertation was typed by the author.