Comment by DevX101

One of my favorite speculative hypotheses is Bicameral Mind Theory, which asserts that something like schizophrenia was relatively common until relatively recently, about 3000 BC. It argues that it was relatively normal for humans to hear voices in their head directing them. So when we read religious texts about the gods commanding so-and-so to do such-and-such, it wasn't just a spiritual metaphor, but an actual voice people heard in their heads and interpreted as higher powers.