Extractive foraging and the evolution of primate intelligence

Abstract

One of the two major theories regarding the evolution of intelligence in primates is that feeding strategies determine mental development. Evidence for this theory is reviewed and related to extractive foraging, which is the act of locating and/or processing embedded foods such as underground roots and insects or hard-shelled nuts and fruits. It is shown that, although only cebus monkeys and chimpanzees in the wild use tools in extractive foraging, many other species of mammals (including primates) and birds are capable of extracting embedded foods without tools. Extractive foraging by primates is compared to extractive foraging by other mammals and birds to assess whether: 1) extractive foraging involves cognition, and 2) extractive foraging by primates is unique in a way that may mean it played a role in the development of intelligence among primates. This comparison reveals that some acts of extractive foraging by nonprimates are equally sophisticated as those of primates. It is suggested that extractive foraging played no significant role in the evolution of primate intelligence. Hypotheses for testing precise differences in extractive foraging ability across taxa are offered, and the roles of olfactory cues, manual dexterity, and strength in extractive foraging are evaluated. In conclusion, the hominization process is briefly reviewed in relation to foraging behavior. A «package» of traits that, in combination, is unique to hominids is discussed: tool-aided extractive foraging, division of labor by sex with food exchange, and feeding of juveniles.