| Previous work by Lucas and others has investigated the relationship between food mechanical properties and tooth form. However, less has been done to examine how these same properties affect skull shape. This project investigates whether, and in what way, the fracture resistance of foods influences the hard tissues of the primate masticatory system. A comparative study was designed to test the hypothesis that the taxa that eat the most fracture resistant foods all feature similar trends in masticatory morphology related to either increasing the mechanical advantage of the masticatory system or decreasing the stress on that system. The face and jaws of capuchins, macaques, baboons, and apes were compared in three dimensions using geometric morphometrics and biomechanical models. The taxa from each clade that are reported to eat the most fracture resistant foods all showed similar morphological trends in their masticatory systems relative to the other members of their clade, and these trends are biomechanically consistent with being adaptive for the oral processing of fracture resistant foods. Similar patterns were found in bears. The fact that these morphological trends exist in New World monkeys, Old World monkeys, apes, and even bears suggests that the influence of food mechanical properties on masticatory form may be widespread in mammals. This observation not only has the potential to increase our understanding of mammalian dietary adaptation, but could also be valuable in interpreting homoplasy in both living and fossil primates. |
