The Atheist Perspective

Because humans have evolved the capacity and inclination to build mental models of their world (both their physical world and their social world), and the simplest model to build (integrating both the physical and the social world) is what we call a religion. But models are only true insofar as they survive only valid tests. We did not learn which tests those were until the Scientific Revolution and we have only recently begun applying those tests in the proper way to the components of religious worldviews. And most people aren't even applying those tests at all, but preferring instead what's simple and easy to believe, to what's actually true.

Evolutionary Origin of Religions