All anthropoid primates in nature lead highly sociable lives. In infancy and childhood this is characterized by stability and familiarity for both sexes; in adulthood either one or the other sex changes groups. The natal group provides a social network of matrilineal kinship; after sexual maturity incest avoidance and exogamy are the rule. Important differences exist across species and between the sexes in mating strategies. In most species, males emigrate, but in others females do so. Male sexual behavior is based on competition between peers; females exercise choice in selecting sexual partners. Normal development of sexual behavior and maternal caretaking requires contact with adults. According to one school of thought, the selection pressures of dynamic life in groups led to the evolution of "social intelligence." Such cognitive abilities are manifested in coalitions and reciprocity based on assessment of the predictability of others' behavior over time, i.e., on long-term relationships as well as short-term interactions. Another school of thought sees the evolutionary origins of cognitive capacities in the demands of subsistence. "Extractive" foraging requires varied techniques for the acquisition and skillful processing of foods. Optimal budgeting of daily activities such as ranging is facilitated by long-term memory and cognitive mapping. The absence of such social and environmental challenges may lead to pathological behavior.
McGrew, W.C. (1981). Social and cognitive capabilities of nonhuman primates: Lessons from the wild to captivity. International Journal for the Study of Animal Problems, 2(3), 138-149.