One of the most fundamental issues in the analysis of primate fossil samples is the determination of how many species they contain. Samples that contain differently-sized individuals of similar (but not identical) shape often incite debate among paleoanthropologists as to whether the sample is made up of two related species (one large, one small), or two sexes of a single species (large males, small females.) Theoretically, when two sexes differ significantly in size (as in baboons and gorillas), their limb joints may also differ slightly in shape. This is due to the fact that larger males will encounter relatively greater joint stress levels than females, thereby inducing differences in the surface area of the joints. Using video imaging and recent advances in computer analysis, this study will examine sex-related shape differences in the limb joint surfaces of a number of recent Old World primates, including monkeys and apes. This research will reveal exactly how the bones of males and females differ, as well as determine whether or not patterns of sex-related shape differences are similar across species, or depend upon factors such as how the animals move around. This examination of sex-based differences within modern primate taxa will provide a crucial background with which to evaluate current fossil assemblages.
