Something that everyone overlooks is that if an ancient ape were to give birth to a prehuman or a prehuman were to give birth to a human being, who would they have offspring with since there would be no one else of their kind. The prehuman would have to mate with an ancient ape but that would result in reverse evolution. The human being would have to mate with a prehuman but that, too, would result in reverse evolution. Reverse evolution means:

Evolution could never move forward.