The origin of religious belief is something of a mystery, but in recent years scientists have started to make suggestions. One leading idea is that religion is an evolutionary adaptation that makes people more likely to survive and pass their genes onto the next generation. In this view, shared religious belief helped our ancestors form tightly knit groups that cooperated in hunting, foraging and childcare, enabling these groups to outcompete others. In this way, the theory goes, religion was selected for by evolution, and eventually permeated every human society.