1Institute of Human Origins, Arizona State University, Tempe, AZ, USA, 2Rwanda Development Board - Tourism and Conservation, Rwanda, 3Departments of Biomaterials and Basic Sciences, New York University College of Dentistry, NY, USA, 4Mountain Gorilla Veterinary Project, University of California Davis, USA, 5Dian Fossey Gorilla Fund International, Atlanta, GA, USA, 6Department of Anthropology and Center for the Advanced Study of Hominid Paleobiology, The George Washington University, Washington, DC, USA
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Teeth are at the interface between an animal and its environment. Consequently, aspects of dental size, shape, development, and wear inform research on the ecology, life history, and dietary demands of extinct and extant primates. Teasing apart influences on tooth wear (unworn morphology, food/tooth material properties, etc.) can be difficult even in living primates, and to date has relied on samples lacking critical chronological and ecological data. The mountain gorilla skeletal collection from Volcanoes National Park, Rwanda provides an excellent case study for relating dental ecology to dental wear as this sample represents a breeding population, with known ages, life histories, diets, and ranging patterns.
An emerging view is that as teeth wear, their occlusal surfaces alter in a way that maintains or enhances their complex topography. We tested this by employing dental topographic analyses of occlusal slope, angularity, and relief index (RFI) on a cross-sectional sample (n=17; ~4-43 yrs.) of wild G. beringei beringei for M1-2. Slope (r=-0.76, -0.81) and angularity (r=-0.72, -0.75) are negatively correlated with age (for M1 and M2, respectively; p<0.05). RFI and age are not linearly related, but sample size prohibited alternative curve fitting. It was observed that M1 RFI initially decreases with age, but rises at >20 yrs., with the opposite pattern for M2s. This complex relationship between RFI and age suggests that selection may shape tooth anatomy to maintain occlusal relief. This may be advantageous for the lifelong mastication of tough fibrous foods. Results are discussed within the context of population life history.
Funding was provided by the Institute of Human Origins Graduate Fellowship to HG, and by the Leakey Foundation, National Geographic Society, and NSF BCS 0852866 and 0964944 to the Mountain Gorilla Skeletal Project.