The dawn of civilization

[Angrboda]

There's a lot of evidence for religion, supernaturalism, and similar things, including the rituals, being an aspect of neurological and psychological mechanisms which evolved for other reasons, for example our dependence upon social behaviors as a species. Such things as agent detection, attribution, and projection, which are fundamental to a social species, and especially one with language, quite naturally give rise to concepts like ghosts, spirits, an afterlife, and gods. There are also neurological and psychological mechanisms related to religious behaviors, such as singing, dancing, raising one's hands to the sky, and even the effects of simple human touch (e.g. communal embrace, laying on of hands, etc.).

So religion and similar ideas have likely been with us for as long as we've been thinking, social animals. I'll let Gae handle the farming side, as he knows that and I don't.

Other than that, I'm not sure what needs to be explained.