This article examines three anthropological theories explaining how religion has evolved and continues to evolve. They are: commitment theory, which postulates that religion is a system of costly signaling that reduces deception and creates cooperation within groups; cognitive theory, which postulates that religion is the manifestation of mental modules that have evolved for other purposes; and ecological regulation theory, which postulates that religion is a master control system regulating the interaction of human groups with their environments. An assessment of the success of the theories is offered. The idea that the biological evolution of the capacity for religion is based on the group selection rather than individual selection is rejected as unnecessary. The relationship between adaptive systems and culturally transmitted sacred values is examined cross-culturally, and the three theories are integrated into an overall gene-culture view of religion that includes both the biological evolution and the cultural evolution of behavioral systems.