Department of Anthropology, Rutgers, The State University of New Jersey
Friday Morning, Ballroom C
The relationship between jaw form and diet has long been of interest to anthropologists, but little is known about the factors that influence trabecular bone morphology in the mandibular condyles. The temporomandibular joint experiences loading during mastication, and it is thus reasonable to expect that its form and bone density may vary with diet and feeding parameters. We tested the hypothesis that the internal morphology of the mandibular condyle is driven by dietary ecology. The architecture of the mandibular condyle was examined using a sample (N=12) of extant primate mandibles. Mandibles were scanned using high-resolution X-ray computed tomography (HRXCT) and a 50-pixel cubic volume of interest from the center of the mandibular condyle was analyzed with ImageJ and Quant3D. Degree of anisotropy (DA) and trabecular bone volume fraction (BV/TV) were measured.
Daily percentage of time spent feeding was regressed against mean body mass for each species, and the ordinary least square residuals were calculated as a measure of feeding time relative to body mass. The relationship between DA and feeding time was not significant, but the correlation between BV/TV and feeding time was highly significant (p<0.001, R2=0.619). Primates that spend more time feeding than expected based on body size appear to have denser trabecular bone within the mandibular condyles. These data are important to further our understanding of the factors driving jaw form, and may enable us to predict the proportion of a daily activity budget spent on feeding for early hominins based on BV/TV in the mandibular condyles.
This study was funded by the Bigel Endowment, a Zelnick Research Award, and a Special Opportunity Award.