There's been a few studies/books... Just google it.
Genes contribute to religious inclination - being-human - 16 March 2005 - New Scientist
and a book called "the God gene" or something.
None of which I've actually read because I frankly couldn't give a damn what one scientist says and the next refutes. What one minute is FACT before the next minute is absoloute crap. What they want the people to believe, the vast majority will believe regardless of how certain it actually is.
I just find it interesting that you can't Insult gay's because sexuality is genetic (look at all the studies!) but religious people are just brainwashed (Ignore the sudies!).