Jaynes makes an intriguing case that our sense of self emerged only after the left and right sides of the brain became integrated into a single thinking machine. Me, I think being self-aware emerges when you realize that there's someone other than you. For most of us, that happens at birth (but for an exception, see The World I Live In by one H Keller, also a five-star read). Anyway, Jaynes's theory is fascinating, but I can't think of a way to test it empirically, so I guess we'll never know if he was right ....