Which was first: Atheism or Religion?

[fr0d0]

The cave man says "Ug! Show me the evidence!". He was unable to think beyond what he could sense.

*shrug* They clearly had a sense of an afterlife, based on some of the grave goods we've found.

I doubt very much that the inability of early humans to think beyond their senses is a tenable notion. If Oog drops a gourd full of water, he senses that the ground gets wet. It isn't much of a leap for him to 'think beyond his senses' and postulate that the Great Gourd Dropper In The Sky is responsible for rain. To a point, the more primitively minded one is, the more likely one is to postulate all sorts of loopy, unsubstantiated ideas. Atheism represents a positive evolutionary development of the ability to reason, not the other way round.

Boru

The term is a loose characterisation of course. What you're describing are the beginnings of rationalisation.