But there's absolutely no evidence for this at all, and a lot of evidence to the contrary.

Everyone knows someone who got a brain injury, or simply dementia from old age, which changed their personality completely.

I strongly recommend Dennett's 1991 book, "Consciousness Explained", which is both very solid, and an excellent read. (Dennett went on to later write the stunning "From Bacteria to Bach and Back" which goes on to discuss how evolution created consciousness, but that's a more general book.)