I think that before speculating about the selection pressure leading to religion, we should ask whether religion arose as a grass-roots phenomenon, or was usually imposed (or suggested, like a fashion) from the top down. The former case would lead you to expect religion to provide a general selective advantage. The latter only requires religion to provide a selective advantage to the religious elites.
What made me think of this was discussions with a Catholic theologian, which uncovered 4 irreconcilable points between us. All of these points are argument...