Why would someone join an institution that removed the option of family life and required them to be celibate? Reproduction, after all, is at the very heart of the evolution that shaped us. Yet many religious institutions around the world require exactly this. The practice has led anthropologists to wonder how celibacy could have evolved in the first place. Some have suggested that practices that are costly to individuals, such as never having children, can still emerge when people blindly conform to norms that benefit a group – since cooperation is another cornerstone of human evolution. Othe…