Social Evolution in Primates: The Role of Ecological Factors and Male Behaviour

In order to explain the variation in primate social systems, socio-ecology has focussed on the role of ecological factors to explain female associations and relationships and on the spatio-temporal distribution of mating opportunities to explain male associations and relationships. While this approach has been quite successful, it ignores male-female associations and relationships and ignores the possibility that male behaviour modifies other aspects of the social system. In this paper, the ecological approach is complemented by consideration of a social factor found to limit fitness, namely infanticide by males. Infanticide risk is proposed to have selected for malefemale associations and relationships, and to have modified female-female relationships in some cases. It is also hypothesized to have selected for the unusual male bonding by species such as chimpanzees. Finally, its possible impact on between-group relations is examined. The findings suggest that infanticide is of equal importance to ecological factors, with which it may interact in sometimes complex ways, in shaping primate social systems.