Yeah, I don't understand it much either, but the big thing to realize, is that, for the most part they don't actually look at the evidence, they don't see the fossil progression of hominoid skulls as a progression towards humanity, they either see a sharp line somewhere, and everything before that is not human, and everything after is human, but where that line varies from person to person, with most of them willfully unaware of the dozens, even hundreds of different organisms that show a relatively smooth progression of humanness over time, the gap where there line fits seems pretty large.