Most male and female primates, including human ancestors, show substantial differences (dimorphism) in the anatomy of the skull. The recognition of dimorphism is important for identifying species in the fossil record. Additionally, because dimorphism is strongly associated with variation in social behavior in living primates, it is used commonly to support claims about the social behavior of extinct species, especially human ancestors and their closest relatives. However, there is currently very little information documenting cranial dimorphism among living primates, and whether such dimorphism can be used to reconstruct the social behavior of extinct species. This study will gather data on a carefully selected set of living primates to document the magnitude and pattern of dimorphism in living primates and humans, and evaluate whether variation in samples of closely related fossils can be attributed to dimorphism, as opposed to variation that occurs between species. The study will also evaluate whether craniofacial dimorphism can be used to infer aspects of their social behavior. This study will provide a strong data base for evaluating the diversity of species in the human lineage, and for reconstructing the changes in behavior that occurred in the evolution of humans and their closest relatives.
