@Tuna,
Interesting thesis, and reminds me of a variation of that that's been percolating in my head about Dawkin's favorite theory.
I think it was a different but related thread but someone recently stated an oft-quoted 'truism' that "Evolution Explains Everything" [about life].
As you pointed out, religion, or belief in a God or gods, has been around for a long time in spite of repeated attempts to stamp it out. It would seem to place it's believers at a disadvantage in many ways. It would inhibit better understanding of the natural world, places non-productive demands on it's adherents, inhibits mating and 'gene spreading', demands sacrifices of valuable resources, etc. Given these evolutionary disadvantages, it should have gone extinct by now rather than spread. This is especially true in the post Darwin enlightened world.
So the question is, if 'Evolution Explains Everything':
What is the evolutionary benefit of belief in a God? Or if there isn't one, why does it persist?