Well, it's official. The most up-to-date DNA analyses have shown that everyone's a mongrel. All humans have the genes of Neanderthals or their recently-discovered cousins, the Denisovans, incorporated into their DNA. For a while, it looked like Africans had escaped the melange, but further research indicated some of the blended humans had returned to the dark continent and infected its stay-at-home inhabitants too.
In a way, it's sort of comforting, like learning that a rare, interesting species didn't die out after all. In fact, it's living within us.