Comparative Cultural Phylogenetics and the Transmission of Belief in an Oral Society

Cultural transmission typically results in a network of connections between cultural units (such as individuals or social groups), not the branching patterns of descent seen in genetic inheritance. As a consequence, the application of phylogenetic (or evolutionary clustering) methods to cultural history faces methodological problems. Most importantly, the history of relationships inferred through phylogenetic reconstruction, and manifested in the tree’s topology, cannot be trusted. In this paper, I suggest a novel use of phylogenetics which does not depend on the correct identification of ancestral relationships. In this method, alternative models of how information can be culturally transmitted are implemented on the same population, and the resulting trees compared. The model which better extracts “phylogenetic signal” or descent relations from the cultural data is preferred. The virtue of this method is that it relies only the general features of phylogenetic trees to make inferences about cultural history. An empirical case study concerning the social learning of food avoidances in a rural African population demonstrates that this comparative use of phylogenetics can effectively identify aspects of cultural inheritance. Such results could not be readily obtained using standard statistical procedures. Thus, by using phylogenetics comparatively, interesting things about cultural transmission can be learned.