Certainly the anthropological literature from early in the history of the field takes for granted that any new culture encountered will have some type of belief in divinity as core to its view of the world. I'm going to have to do some poking around in the history of atheist beliefs to satisfy my curiosity, I think. My gut feeling is that the World Wars probably had something to do with it; that seems (not surprisingly) to be a watershed time in terms of belief in what humanity is and isn't in terms of morals/religion/ethics.
Just some random uncorroborated thoughts on the nature of the universe, as per usual.