[AndrewC]

Survival and propogation. Everything comes down to this.

That is still ad hoc. How is the "survival" of the group determined? How is the group "propagated"?

[Junior]

Wouldn't that depend upon the group? Survival takes many forms, not just keeping its members alive. Christianity, as a group, survived by becoming the state religion of Rome. Propogation is also more than just simply having children. It also involves recruiting. Christianity adopted many of the trappings of contemporary pagan religions in order to win converts (Sunday worship comes to mind).