When I was taking psych classes in the late 90s, it seemed every single psych prof had a copy of this on their shelves. I saw it cited in some of the text books as well so I grabbed a used copy to read.

It's an interesting hypothesis, but seems roughly as valid as Erich von Däniken's Chariots of the Gods?, that is, not valid at all. Were there any validity to the claim at all, we should be able to find supporting evidence in, say, the brain function of lower primates. It ain't there.