Breeding and dispersal systems

Jim Moore

As an order, the Primates differ from most other vertebrates in that the majority of primate species live in stable social groups which usually contain representatives of all age-sex classes […]. This social organization has two consequences that are relevant here. First, dispersal is generally unambiguous; an indivivual either stays in her/his natal group or leaves it. Among most other mammals, defining and detecting philopatry involves repeated measures of dispersal distance, and sex-biased dispersal may exist only as statistical differences in mean dispersal distance […]. To the extent that group structure and mating system are correlated, this semi-closed feature of primate social organization simplifies research on primate inbreeding; if all adults males in a troop were born elsewhere, the possibility of close inbreeding is remote.

Second, the stable social environment either permits or requires elaborated relationships, which are themselves thought to promote the evolution of the apparent altruism, ‘social intelligence,’ and increased relative brain size that characterize the order […]. Although stable relationships themselves may favor the evolution of such traits for selfish reasons among nonrelatives […], most authors have emphasized the roles of reciprocal altruism and especially kin selection […]. Thus, our understanding of the evolutionary bases of several theoretically interesting behavior complexes depends to a great extent on a thorough knowledge of breeding and dispersal systems in primates […].

Fonte: Moore, J. 1993. In: Thornhill, NW, ed. The natural history of inbreeding and outbreeding. Chicago, UCP.