I agree with the statement in the original post. Social anthropology not only attempts to uncover the function that religion served (and continues to serve) in societies, but the way people understood the world they lived in. Religion developed, I think, because people have a psychological need for it, and because socieites have a political and a cultural need for it. It can provide a moral underpinning for social norms. At the same time, it also leads to stratification, as people who can provide access to, or control the supernatural (shamans, priests, etc.) often emerge as elites.