I don’t think you need to posit bicameralism to salvage parts of this theory. People developed language gradually, and I’m sure there was a period of time where

I don’t think you need to posit bicameralism to salvage parts of this theory. People developed language gradually, and I’m sure there was a period of time where it sat uneasily in the mind, and then a point in time where people had something like an internal monologue for the first time, and without having any theory of consciousness or souls or the brain or anything of the kind, it must have been a world shattering, all consuming miracle for the first people that experienced it. It makes sense to me that some people would have externalized the source of it and understood it to be spirits or gods or ancestors or whatever kind of disembodied force, and imagine being the first person who could understand it, and control it and help others achieve it — imagine the power and respect that gets you — unlocking a kind of consciousness or divinity in other people. You can see how priesthoods develop from it. Think about that and go back and read Genesis, and think about how it’s a story about naming things, and categorizing things, and learning about the world. And how it’s knowledge that drives people from a state of paradise, an enternal now where there is no passage of time, no thought, no awareness of ones own mortality.