The Cultural Evolution of Religion: A phylogenetic approach

Abstract

The costs and prevalence of religion present an explanatory challenge for evolutionary theorists. Costs include the opportunity costs of time spent praying, the reproductive costs of abstinent clergy, and the resource costs of sacrificial offerings. The question this raises is how natural selection could have allowed the majority of the global population today to become religious adherents. The emerging field of evolutionary religious studies seeks to explain the prevalence of religion by understanding its evolutionary origins and potential functions. In support of functional explanations, previous cross-cultural research has found that features of religion, such as belief in big gods, are associated with larger and more complex societies. However, this research is subject to Galton’s Problem and is based on the effects of modern world religions under conditions very different to most of our evolutionary history. Rigorous cross-cultural research is needed to test functions of religion in traditional cultures. In Chapter 1 I provide an overview of evolutionary religious studies and explain how phylogenetic comparative methods have the power to identify the co-evolution of religion and society in traditional Austronesian cultures. Phylogenetic methods can be used to reconstruct cultural history, address Galton’s Problem, and infer the direction of causality based on the order that traits tend to arise. Traditional Austronesian cultures had a diverse range of supernatural beliefs, practices and social structures, and can be linked to a language based genealogy. In Chapter 2 I present the Pulotu database which provides quantitative variables on the traditional religious and social systems of Austronesian cultures. I then use phylogenetic methods and the Pulotu database to test three prominent evolutionary theories of religion. In Chapter 3 I find evidence that belief in punishment by a broad range of supernatural agents helped build political complexity, but that big gods arose after political complexity in Austronesia. In Chapter 4 I find that human sacrifice functioned to help build and maintain social inequality in early human societies. In Chapter 5 I show that political systems facilitated the recent spread of Christianity. I finish in Chapter 6 by suggesting five directions for the future development of evolutionary religious studies.