Abstract: | Interest in phylogeny is increasing in many areas of evolutionary biology. One area of evolutionary anthropology that has not yet fully embraced this growth in phylogenetic thinking, however, is the study of primate behavior and ecology.1 The predominant framework for behavioral studies of primates over the last three decades has been socioecological. The goals have been to identify broad correlations between species' behaviors and current environmental conditions. As such, the socioecological approach has been largely nonhistorical, taking little account of phylogeny. In contrast, phylogenetic approaches view the behavior of contemporary taxa within an explicitly historical framework. Although socioecology has proven extremely productive, there are many reasons to think that research in primatology could be profitably supplemented by a phylogenetic perspective.2,3 |