Paleoanthropology has generated a great deal of debate on the functional and structural significance of the circumorbital region, especially the browridge, in the evolution of primate and hominid skulls. Noone, however, has adequately tested models of browridge development. The researcher will test hypotheses relating to the adaptation of the circumorbital region to chewing stress and differential growth patterns in several primate species from both the Old and New World. He will generate much needed empirical data on interspecific variation using biomechanical and nonmechanical models. This research will help physical anthropologists develop a more comprehensive perspective on the evolutionary morphology of the primate skull. The data can then be used to generate more sophisticated models to explain hominid evolution.