According to Wade, a New York Times science writer, religions are machines for manufacturing social solidarity. They bind us into groups. Long ago, codes requiring altruistic behavior, and the gods who enforced them, helped human society expand from families to bands of people who were not necessarily related. We didn’t become religious creatures because we became social; we became social creatures because we became religious. Or, to put it in Darwinian terms, being willing to live and die for their coreligionists gave our ancestors an advantage in the struggle for resources.The wrong-headedness of this utterly un-original "explanation" makes me crazy. The problems:
1) If the point of religion is to unite us, why does it so spectacularly fail to do so? Christians have been in conflict with other Christians since Jesus died, sometimes very bloody conflicts.
2) You don't need a common religion to get people to work together, as the Roman, Chinese and Mongol empires all show. If you actually talk to people who belong to violent tribes, like Napoleon Chagnon did with the Yanomamo, you find out that they don't speak in religious terms about their identities. Their solidarity is tribal, not religious. And in fact their religion is so similar to the religions of all their traditional enemies that it would make no sense to see their conflicts in those terms.
3) If the point of religion is social solidarity, why does it include so much else that has nothing to do with society, from abstruse theology to origin myths to systems of divination?
4) On a more epistemological note, how does this "explanation" explain anything? If dancing together for the same god really makes people more willing to fight and die together, why is that so? To say that religion developed because shared rituals enhance solidarity is not really a biological or neuroscientific explanation, it simply changes the question to "how did we evolve a tendency to express or develop shared identities through rituals?"
Religion is not just a social system, it is first and foremost a psychological system. It exists inside people's heads. People believe in God because it makes them feel better to do so. Religion is a response to psychic events. I reviewed a book by anthropologist Weston La Barre that makes this perfectly clear here. As La Barre says,
Man lives in two worlds, a matter-of-fact one of common public experience, the other of mysteriously “supernatural” and compelling private dream or trance. More precisely, these two “worlds” of man are really two modes of psychic experience in the individual.... Thus material culture, technology and science are adaptations to the outside world; religion, to the inner world of man, his unsolved problems and unmet needs.
We have minds and we live to a great extent within them. What we think and feel matters. Any "evolutionary" explanation that fails to recognize the importance to us of completely mental events cannot explain anything about the way we think, including our religions.