Evaluating The Hominin Scavenging Niche Through Analysis of the Carcass-Processing Abilities of the Carnivore Guild by Adam Hartstone-Rose Department of Biological Anthropology and Anatomy Duke University Date: July 27, 2008 Approved: ___________________________ Steven Churchill, Advisor ___________________________ Matt Cartmill ___________________________ Peter Lucas ___________________________ Louise Roth ___________________________ Christine Wall Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biological Anthropology and Anatomy in the Graduate School of Duke University 2008 ABSTRACT Evaluating The Hominin Scavenging Niche Through Analysis of the Carcass-Processing Abilities of the Carnivore Guild by Adam Hartstone-Rose Department of Biological Anthropology and Anatomy Duke University Date: July 27, 2008 Approved: ___________________________ Steven Churchill, Advisor ___________________________ Matt Cartmill ___________________________ Peter Lucas ___________________________ Louise Roth ___________________________ Christine Wall Abstract of Dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Biological Anthropology and Anatomy in the Graduate School of Duke University 2008 Copyright by Adam Hartstone-Rose 2008 Abstract Humans are more carnivorous than other hominoids. It has been hypothesized that, during the evolution of this increased carnivory, hominins transitioned through a scavenging niche made viable by certain carnivoran taxa (especially sabertooths) that may have lacked the morphology necessary to fully utilize all parts of carcasses (e.g., marrow), therefore leaving an open niche in the form of high-quality scavengable remains available for hominins. In this dissertation, I examine the postcanine dentition of modern carnivorans, using quantifications of occlusal radii-of-curvature and intercuspid notches, and study the correlation of this morphology with carcass-processing behavior. I use these correlations to deduce the carcass-processing capabilities of the Plio-Pleistocene carnivores of South Africa (a guild for which we have a good appreciation of taxonomic diversity, and that existed at an important time during the evolution of our lineage – possibly the time that we transitioned into that guild), and compare these results with those of previous studies that relied on more conventional morphological measures. Both radius-of-curvature and intercuspid notch data do a good job of separating taxa by dietary category, revealing subtle patterns including possible differences in the carcass-processing abilities of fossil and modern members of some extant species. Other strong trends confirm that the “hunting-hyena,” Chasmaporthetes, was probably a hypercarnivore, and not a durophage like its modern confamilial taxa. Somewhat surprisingly, results do not support the hypothesis that sabertooth felids were more hypercarnivorous than modern felids. Furthermore, though the sympatric hypercarnivorous taxa were more numerous, so too were the durophagous taxa, with one taxon, Pachycrocuta, probably exceeding the durophagous capabilities of modern durophages. iv As such, this dissertation shows no evidence that members of the paleo-carnivore guild were capable of producing higher quality scavengable carcasses than are modern carnivorans, and thus, based on these analyses of fossil carnivorans, it does not appear that high-quality scavengable remains were more available in the Plio-Pleistocene than there are today. Therefore, though there is clear evidence from other sources that hominins did scavenge at least occasionally, this dissertation does not support the hypothesis that there was an open niche consisting of high-quality scavengable remains. v Contents Abstract ........................................................................................................................................... iv List of Figures .................................................................................................................................. x Acknowledgements ....................................................................................................................... xiii CHAPTER 1: Introduction .............................................................................................................. 1 Background ............................................................................................................................... 3 Approach ................................................................................................................................... 5 Specific Aims and Hypotheses ................................................................................................ 10 Aim 1 (Evaluated in Chapter 4): ........................................................................................... 10 Aim 2 (Evaluated in Chapter 5): ........................................................................................... 11 Aim 3 (Evaluated in Chapter 6): ........................................................................................... 12 CHAPTER 2: A Brief Introduction to Carnivoran Dentitions ....................................................... 14 Carnivoran Dental Functional Regions ................................................................................... 15 Grasping Incisor Functional Region ........................................................................................ 17 Canine Killing Functional Region ........................................................................................... 23 Premolar Crushing or Slicing Functional Region ................................................................... 24 Sectorial Carnassial Region ..................................................................................................... 26 Grinding Molar Functional Region ......................................................................................... 28 CHAPTER 3: Materials and Methods ........................................................................................... 29 Fossil Sample .......................................................................................................................... 29 Extant Sample.......................................................................................................................... 31 Introduction to Taxa in the Study ............................................................................................ 31 Felids ..................................................................................................................................... 32 vi Canids ................................................................................................................................... 40 Hyaenids ................................................................................................................................ 41 Mustelids ............................................................................................................................... 44 Ursids .................................................................................................................................... 45 Marsupials ............................................................................................................................. 48 Other Carnivores ................................................................................................................... 50 Specimen Selection ................................................................................................................. 51 Variables .................................................................................................................................. 54 Measurement and Scoring ..................................................................................................... 57 Dietary Categorization .......................................................................................................... 57 Classification of Body Mass .................................................................................................. 61 Scoring of Tooth Wear .......................................................................................................... 66 Measurement of Radius-of-Curvature ................................................................................... 70 Scoring of Intercuspid Notches ............................................................................................. 74 Evaluations .............................................................................................................................. 76 Statistical Comparisons ........................................................................................................... 78 CHAPTER 4: General Results ....................................................................................................... 79 Basic Sample Statistics ............................................................................................................ 79 Validity of Measurements Based on Cast Specimens ............................................................ 79 Sexual Dimorphism ............................................................................................................... 82 Distribution of Wear Patterns ..............................................................................................