Despite numerous biomechanical investigations, the functional significance of the size and shape of the primate mandible remains obscure. The reason for this is not that the theoretical basis of biomechanical investigation is lacking, but that the limiting factor in previous studies has been in the choice of the models employed to demonstrate the mechanical behavior of the jaw. Nevertheless, past investigations have established that there is a relationship between mandibular form, masticatory stress, and diet in primates. The precise nature of this relationship, however, has yet to be elucidated. Analysis of cross-sectional morphology of hominoid jaws by computed tomography (CAT-scans) has revealed that the nature and extent of variation in the mechanical properties of the mandible cannot be known by consideration of external measurements alone. This study will use computed tomography to explore how compact bone distribution within the mandible contributes to its structural rigidity. The proposed research represents an important step in documenting the functional significance of size and shape variation in higher primate mandibles. Having established this relationship, this method may be applied to the fossil record, in order to infer directly the biomechanics of fossil jaws. In addition, the data will provide an independent line of evidence which may help to clarify the persistent debate over the nature of the diet in the fossil australopithecines.
