I am an unapologetic atheist. Though, I phrase it that there is no evidence to believe there is a god, therefore I don't believe. I don't claim there is no god because that would impose on me a burden of proof I cannot meet. But there is no reason to believe in one, as yet.

Religion likely grew out of a few things. First, the need to "explain" things (e.g. why are there tornadoes?). Second, a need to unify a community. And third, as a way to power (i.e. he who speaks with god has power). Joseph Smith, for example, was a known conman. But he managed to convince people with his "tablets" and "seeing stones" that he had a direct line with god. Therefore, he had power over them, and moved to Utah (to avoid another jail term, since I'm sure he would have been arrested again had he stayed back east).

Just one modern example of things that have been going on for maybe 10000 years.