The Evolution of Conformist Transmission and the Emergence of Between-Group Differences

Unlike other animal species, much of the variation among human groups is cultural: genetically similar people living in similar environments exhibit strikingly different patterns of behavior because they have different, culturally acquired beliefs and values. Such cultural transmission is based on complex, derived psychological mechanisms that are likely to have been shaped by natural selection. It is important to understand the nature of these evolved psychological mechanisms because they determine which beliefs and values spread and persist in human groups. Boyd and Richerson showed that a tendency to acquire the most common behavior exhibited in a society was adaptive in a simple model of evolution in a spatially varying environment, because such a tendency increases the probability of acquiring adaptive beliefs and values. Here, we study the evolution of such "conformist transmission" in a more general model in which environments vary in both time and space. The analysis of this model indicates that conformist transmission is favored under a very broad range of conditions, broader in fact than the range of conditions that favor a substantial reliance on social learning. The analysis also suggests that there is a synergistic relationship between the evolution of imitation and the evolution of conformism. We conclude by examining the role of conformism in explaining the maintenance of cultural differences among groups.