The ancestral condition of primate social organization is a dispersed multi-male/multifemale system (= dispersed polygynandry). Within this system the ranges of adult males overlap the ranges of several adult females and vice versa, and males and females exhibit year-round social contacts, i.e., they live in social networks. This contrasts with other mammals that often have the same spatial system but differ from primates through the lack of social networks (= promiscuity). It is hypothesized that promiscuity is the ancestral condition of mammalian social organization and that a dispersed multimale/multife-male system arose from this system through the evolution of social networks in the earliest primates. Social networks are likely to have evolved through a prolongation of mother-infant relations.

The ubiquitous presence of social networks in primates is believed to be due to their primarily frugivorous diet. On the one hand, fruits are patchily distributed in space and time and, therefore, difficult to find, but on the other hand they are predictable and can be depended on once their location is known. Social networks are beneficial as they enable animals to share information about food sites with their offspring or siblings. Social networks are very likely to have been present in the last common ancestor of living primates, in conjunction with a diet that included large amounts of fruit.

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