Optimal Foraging and Hominid Evolution: Labor and Reciprocity

Abstract

We argue that cooperative foraging incorporating information exchange may have preceded tool use during the course of hominid evolution. In moving to the savanna, early hominids must have faced increasingly dispersed but sometimes more profitable food sources. The problem is finding such foods. Search costs can be reduced for each individual if a number of foragers cooperate by ranging over different parts of the habitat and by exchanging information about encountered food items. Given the probability of encountering a given food item and the return per individual for that item, it is possible to specify the optimal group size. Thus, in the patchy savanna environment, selection would have favored increased gregariousness and cooperation on the part of early hominids, setting the stage for the emergence of reciprocal exchanges of information and resources. However, such a system of reciprocity is open to manipulation. Outside the foraging context, the tension between reciprocity and manipulation would shape other social interactions. Communication and information exchange may have been more critical than labor and technology in evolving hominids from hominoids. Human sociality may find its origins in a shift in primate foraging tactics.