Keywords: inclusive fitness kinship religious behaviour We describe and evaluate an integrative hypothesis for the origin and evolution of human religious cognition and behaviour, based on maximization of inclusive fitness. By this hypothesis, the concept of God is represented by one's circle of kin and social salience, such that serving God and serving this circle become synonymous. The theory is supported by data from anthropology, evolutionary theory, psychology, neuroscience, psychiatry, endocrinology and genetics. It is largely compatible with, yet can subsume, previous theories of religion that are also based on adaptation and natural selection. Ó 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. There is something sacred about kinship, as most social anthropologists who have studied its operation in the field are prepared to admit One human phenotype, religious behaviour, stands apart from all others with regard to its dominating emphasis on altruism and prosociality. This set of behaviours has yet to be analysed explicitly and comprehensively in the context of inclusive fitness theory, using the conceptual tools developed in Hamilton's wake for understanding its origins, maintenance and diversification. Like eusociality, or cooperative breeding, religion can be considered as a sociobehavioural system that has evolved in the contexts of genetic relatedness, parental manipulation (generalized here as asymmetries in control over phenotypes) and mutualism. In this article we describe and analyse an integrative theory, based on inclusive fitness maximization, for understanding the origin and evolution of religious behaviour and the concepts of God and supernatural agents. The theory is based mainly on works by Hamilton, Alexander, Trivers, Lahti, Coe, Palmer and Steadman, and it draws together evidence from anthropology, psychology, neuroscience, psychiatry, endocrinology and genetics into a unified, testable framework. The theory is novel specifically in its integrative, synthetic and reconciliatory nature, and its central emphasis on the roles of genetic relatedness and inclusive fitness in the evolution of religion. We first categorize and describe previous theories regarding the origins, bases and functions of the concept of God and other supernatural agents, and associated religious behaviour. Next, we present the theory, and discuss how it relates to, and can subsume, these earlier ideas without being strongly incompatible with any of them. We also discuss empirical evidence that bears upon the theory, and suggest opportunities for additional tests of its predictions. PREVIOUS THEORIES Previous ideas regarding the evolution of religion and concepts of God address diverse aspects of religious phenomena, at different levels of analysis, either proximate (dealing with mechanisms), or ultimate (dealing with selective pressures and other evolutionary causes). Moreover, studies of religion may focus on its supernatural components, its moralizing elements, or both in conjunction
