Why does religion even exist? Lots of people are happy to offer answers to this question, but as Scott Atran points out in his book In Gods We Trust, those answers are really no better than just-so stories. They have no scientific basis.
Whenever we see a behavior pattern that’s exhibited around the world by long-separated populations of a single species, it’s a reasonable inference that evolution has selected for that behavior. Atran tries to construct an evolutionary view of religion. This is difficult to do, because our evidence about the mental habits of our species across the past few million years is, frankly, all but nonexistent. But the attempt is worth making. His book is densely written, but it’s worth tackling.
Religion exhibits a few definite characteristics, wherever it’s found.
First, it’s an activity of social groups. An individual who had never been exposed to such a thing (if there were ever such an individual) could be said to have mystical leanings or mystical experiences, but such an individual could not be said to have a religion.
Second, religion encourages or requires people to make what Atran calls counter-factual statements. I’d be more inclined to call them statements of fantasy. They’re statements for which there is no physical evidence. (The writings in old books do not count as evidence.) Those who are in a religious group are expected to believe that these counter-factual statements are true, and quite possibly to believe that they’re objectively verifiable.
The individuals making the statements may or may not actually believe them. We’ve all read stories about preachers who were privately atheists, but who perhaps didn’t want to have to find a new career or believed that the statements they made in public had some value in terms of guiding other people toward good behavior. Nonetheless, it’s clear that the majority of religious people do in fact believe that the counter-factual statements that are part of their religion are true.
Third, religions teach about the existence of invisible beings (ghosts, demons, gods, saints, and so on) who are aware of human activities and are involved in those activities in some way, either by directly interfering (for good or ill) and/or by providing instructions on how humans are to behave. Instruction on behavior is almost always part of a religion. Also, it’s possible to communicate with and possibly influence these invisible beings in some manner, perhaps through private prayer or perhaps through public ritual.
Patriotism is, of course, a form of religion. It differs from other religions only in that it has no teachings about invisible beings.
Fourth, religions typically demand personal sacrifice. This can range from the trivial (spending an hour on Sunday morning sitting quietly in a room when you would rather be doing something else) to the devastating — lifelong celibacy, for example, or significant financial donations, or even death in a Crusade. Devoting massive amounts of money and labor to building pyramids and cathedrals is a waste of resources, and resources are sometimes in short supply.
A personal sacrifice is a hard-to-fake demonstration to one’s religious community that one is a believer. This is why Abraham’s decision to kill his son makes sense in religious terms. It’s insane, but his willingness to do it is a hard-to-fake demonstration of his belief in the tenets of his religion.
Fifth, in many cases religious communities persecute non-believers. Not all religions do this, but it’s more the norm than the exception. Persecution can take various forms, from forbidding a non-believer to marry a believer to imprisonment and death.
All of this behavior is quite bizarre, if you stop to think about it. You’d think that evolution would have selected against religious belief, if only because belief causes people to waste precious resources, up to and including their own lives. Also, believing things that aren’t true is not, in evolutionary terms, a good survival strategy.
I haven’t finished reading Atran’s book, so I don’t know what sort of explanation he has up his sleeve. But it’s quite clear that a science-based explanation is needed. Stephen Jay Gould’s idea that science and religion are separate “magisteria,” and that in consequence religion ought to remain beyond the bounds of scientific deconstruction, is just hogwash. Very thin hogwash, if it comes to that.