It's a popular topic these days. Here's the manifesto of a new Website-cum-scholarly-project (The Evolution of Religion) that asks the question: are there selective advantages to believing in a supernatural deity?
Religious believers incur significant costs in terms of time, energy and resources that could be spent elsewhere. Religion therefore poses a major puzzle for disciplines that explain behavior on the basis of individual costs and benefits -- in particular economics and evolutionary biology … The aim of our project is to conduct a scientific examination of exactly the opposite hypothesis -- that religious beliefs and behavior confer adaptive advantages to individual believers, and were therefore favored by natural selection over human evolutionary history. In other words, religion may have evolved.