University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2012 Dental Microwear Texture Analysis of Pliocene Bovids from Four Early Hominin Sites in Eastern Africa: Implications for Paleoenvironmental Dynamics and Human Evolution Jessica Renee Scott University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the African Studies Commons, Archaeological Anthropology Commons, and the Biological and Physical Anthropology Commons Recommended Citation Scott, Jessica Renee, "Dental Microwear Texture Analysis of Pliocene Bovids from Four Early Hominin Sites in Eastern Africa: Implications for Paleoenvironmental Dynamics and Human Evolution" (2012). Theses and Dissertations. 368. http://scholarworks.uark.edu/etd/368 This Dissertation is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. Dental Microwear Texture Analysis of Pliocene Bovids from Four Early Hominin Fossil Sites in Eastern Africa: Implications for Paleoenvironmental Dynamics and Human Evolution Dental Microwear Texture Analysis of Pliocene Bovids from Four Early Hominin Fossil Sites in Eastern Africa: Implications for Paleoenvironmental Dynamics and Human Evolution A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Dynamics By Jessica Renee Scott University of Arkansas at Little Rock Bachelor of Arts in Anthropology, 2005 University of Arkansas Master of Arts in Anthropology, 2007 May 2012 University of Arkansas ABSTRACT Many researchers have suggested that Pliocene climate change was a motive force for human evolution. The basic idea is that a shift toward drier, more open settings, led to adaptations for bipedality and the consumption of savanna resources, including large grazing mammals. However, more recent paleoenvironmental reconstructions suggest that Pliocene hominins occupied variable or mosaic habitats, including both open and closed settings. Many techniques have been used to refine our understanding of the paleoenvironments of eastern Africa; however these have not led to consensus reconstructions. At Kanapoi, ecological diversity analysis indicates that at least part of the site was composed of closed woodland forest; however, taxonomic uniformitarianism of bovid taxa suggests a dry, arid habitat. Similarly contradictory reconstructions exist for Allia Bay, with paleosol analysis and palynology suggesting a mosaic habitat dominated by savanna, and taxonomic uniformitarianism of faunal assemblages suggesting an environment composed of gallery forest, open woodland, floodplains and edaphic grasses. The Laetoli faunal assemblages have also led to varying reconstructions, with some suggesting habitats as disparate as open grassland and closed woodland. Hadar has been reconstructed as a shifting mosaic environment, with various proxies supporting different levels of habitat fluctuation. This dissertation aims to test these opposing hypotheses by bringing a new, independent dataset for the inference of diet, and by extension habitats of actual individuals in the days before death. I use dental microwear texture analysis to reconstruct ratios of graze to browse in the diet and therefore ecological contexts of fossil bovids from Kanapoi, Allia Bay, Laetoli and Hadar. This dissertation tests competing hypotheses concerning early hominin habitats at Kanapoi, Allia Bay, Laetoli and Hadar and how ecological settings may have changed over the temporal span of Australopithecus anamensis and A. afarensis . It also serves as an important test of the principle of taxonomic uniformitarianism, often applied to fossil fauna. High resolution casts of 220 fossil bovids from the four sites and 575 extant African bovids were scanned for dental microwear textures using a white-light confocal profiler. Four adjacent scans were collected from each specimen, resulting in a total work envelope of 204 x 276 µm. The scans were then analyzed using Toothfrax and Sfrax software packages and compared to a database of extant bovids with known diets. The extant bovids collected for use in this study include 25 extant African taxa, representing the full obligate grazer-browser-frugivore continuum. The extant bovids showed significant variation that separated the taxa predictably by known dietary category, with the exception of generalists and browser-grazer intermediates. Some variation was also noted within the dietary categories, suggesting seasonal and/or geographic variation. In general, browsing taxa had significantly higher values for complexity, heterogeneity and fill volume than grazing taxa, which evince higher values for anisotropy. The microwear textures of the fossil taxa were compared to the extant database and classified by diet. The Kanapoi and Allia Bay samples indicated that the bovids were primarily browsers or browser-grazers intermediates, suggesting the presence of more wooded habitats. The Laetoli sample is dominated by various levels of mixed feeding, although the presence of grazing taxa suggests a complex mosaic habitat at the site. Finally, the Hadar sample, divided into three hominin-bearing members, showed an increase in the number of grazing taxa over time. This suggests that there may have been gradual aridification at the site during the occupation of the australopiths. This dissertation is approved for Recommendation to the Graduate Council Dissertation Director: ____________________________________________________ Professor Peter S. Ungar, Ph.D. Dissertation Committee: ____________________________________________________ Professor Walter S. Manger, Ph.D. ____________________________________________________ Professor J. Michael Plavcan, Ph.D. ____________________________________________________ Professor René Bobe, Ph.D. ( ex officio) DISSERTATION DUPLICATION RELEASE I hereby authorize the University of Arkansas Libraries to duplicate this dissertation when needed for research and/or scholarship. Agreed ______________________________________________ Jessica R. Scott Refused ______________________________________________ Jessica R. Scott ACKNOWLEDGEMENTS Many people deserve thanks for their generous support of this project. First and foremost, I would like to sincerely thank Peter Ungar for being my mentor for the last seven years. Much of my success can be attributed to his unfailing support and encouragement, as well as his infectious enthusiasm for teeth! During my time in the Anthropology Department and the Environmental Dynamics program, Peter and I have enjoyed several firsts- my first trip to Africa, my first publication, my first conference presentation. And, how could I forget my first visit to the Bass Pro Shop, following a tradition set by my ENDY predecessors?Blaine, Francis- I’m proud to be part of the club, guys, but next time we set a tradition, could it possibly involve fewer creepy taxidermied animals? In all seriousness, Peter, I could not have asked for a better mentor. I have always been happy to be your graduate student, but I am truly honored to now call you my colleague and my friend. I have also had outstanding support from my committee and many other colleagues. I am eternally grateful to Justin Nolan and Mike Plavcan for many lively conversations and much needed help with statistical tests. I would also like to acknowledge the important contributions to this project made by Walt Manger, Dave Stahle, Dan Magoulick, Kim Smith, and René Bobe. Their suggestions helped me hone this project down from a swirling mass of ideas to a feasible and cohesive dissertation. Finally, no list of thanks would be complete without mention of Terry Harrison, Kaye Reed and Matt Sponheimer, who were invaluable during the initial discussions leading to the development of this project. Of course, without access to the extant and fossil specimens, this project would have remained in the planning phase. I would like to acknowledge the Office of the President of Kenya and the Ethiopian National Museum for granting me the research permissions necessary for this study. And of course, this dissertation would not have been possible without the cooperation of several museum curators who generously allowed me access to the specimens in their care. I would like to sincerely thank Emma Mbua and Francis Kirera (National Museums of Kenya); Mamitu Yilma, Yonas Beyanne and Chalachew Mesfin (Ethiopian National Museum); Emmanual Gillisen and Wim Wendelen (Royal Museum of Central Africa); Linda Gordon (National Museum of Natural History); Bruce Patterson and Bill Stanley (Field Museum); and Eileen Westwig (American Museum of Natural History) for their help and hospitality during my visits. Over the years, the group of scholars who I am lucky enough to call colleagues and mentors has grown beyond the University of Arkansas. They have supported me at especially important moments in my academic career and have been tremendous role models that I hope to live up to. A very sincere thank you to Bob Anemone, Frank Cuozzo, Larisa DeSantis, Kaye Reed,Michelle Sauther, Blaine Schubert, Mark Teaford, Alan Walker, Carol Ward, and Lars Weredelin. And no list of thanks would be complete without special acknowledgement of Rob Scott for spending many hours of his time teaching me how to study microwear. And, for pointing out that cracks and holes