I read it as a generalization that included the west, the far east, pretty much anywhere our extended group of cousins has been able to survive. And we are all

I read it as a generalization that included the west, the far east, pretty much anywhere our extended group of cousins has been able to survive. And we are all cousins. But apparently much like you shouldn't have a kid with your 1st cousin. It is for some reason very important to kill anyone further out than your 1000th or so. At least if they have something you want. Then our huge brains kick in and give us a good reason to do what we already wanted to. Often we write it in a book to make it more legitimate. Might be God told us, or we might come up with something scientific (interpreting data with a motive is super flexible) if we aren't feeling particularly religious.