Hominid evolution and primate social cognition

Abstract

Selection for corticalization and complex language in later hominid evolution (genus Homo) indicates an adaptive context favouring increased capacity for mental-model representation (implicated in intentional action), and for social exchange and modification of such representations. Two current hypotheses for non-human primate encephalization are reviewed. Non-human primate grouping patterns and social systems are determined by three major factors: dietary characteristics, predation risk, and social competition. If social systems are determined by grouping patterns, and the latter by factors other than those of optimal foraging, then these two hypotheses for primate encephalization (foraging complexity and social cognition) refer to two distinct sources of selection pressures. Application of these hypotheses to the hominid case entails discriminating between the three possible determinants of hominid grouping patterns. Evidence for scavenging and for increased predation risk for early genus Homo groups suggests that optimal foraging models are not sufficient to predict later hominid social strategies. Increased social competition resulting from larger grouping patterns, the latter a response to predation risk, is hypothesized to have presented the dominant selection pressure for human social cognitive and socially manipulative group-living skills, and thus for hominid brain and language evolution.