Humans are the religious species: every human society has some form of religious belief. Evolutionary theory and religion may seem strange bedfellows. However, the ubiquity of religion suggests that it has played and continues to play an essential functional role in human societies. The last decade has seen substantial interest in religion’s role in human society. This high level of interest has led to the birth of an exciting new field of science – evolutionary religious studies. While provocative, these hypotheses have never been tested using the rigorous quantitative phylogenetic methods routinely used to test adaptive hypotheses in evolutionary biology. In this project we will use cutting-edge cultural phylogenetic methods to test three functional explanations for religion in human societies: 1. Do high gods help generate and maintain complex societies? 2. Do religious rituals give rise to complex society? 3. Does religion co-evolve with ecology? Our aim in this project is to bring together an inter-disciplinary group of researchers with expertise in both phylogenetic methods and cultural evolution, and religious studies. In this project we will leverage our existing databases of Pacific linguistic data, augment these with cultural and religious data from ethnographic sources, and use cutting-edge computational phylogenetic methods to test three hypotheses about the functional role that religion plays in societies. The results of these analyses will be published in leading scientific journals and the data will be made available in a highly-visible online database. This project will fundamentally illuminate the important role that religion plays in the emergence of complex societies and give a deeper insight into the evolution of human cooperation and altruism. In doing so we hope to make a major contribution to the exciting new field of science – evolutionary religious studies.