Protein in Homo erectus teeth suggests Denisovans gave us some of their DNA

Humanity's ancestry has grown far clearer thanks to our ability to obtain ancient DNA. We now know that, as humans left Africa, they interbred with the groups they met there, Neanderthals and Denisovans. Evidence from the Denisovan genome also suggests that this was nothing new; the Denisovans had apparently interbred with an even earlier group.