I would guess that the seeds were sown once humans (or our primate ancestors) were able to consciously conceive of cause and effect, and learned how one can som

I would guess that the seeds were sown once humans (or our primate ancestors) were able to consciously conceive of cause and effect, and learned how one can sometimes, through one's own volition, bring about desired outcomes. From this, it does not seem an implausible leap to imagine that our environment is controlled by conscious entities, and once one is there, to seek out the language necessary to communicate one's own desires to those putative entities. Even more so, once one realizes that you can use language to persuade other people to act in a way that advances your own interests.