Did Homo erectus and Denisovans mate? Tooth proteins hint at ancient trysts

Ancient proteins extracted from the teeth of Homo erectus individuals that lived in China suggest that the group might have interbred with Denisovans, another archaic human species. Researchers used enamel proteins from six H. erectus individuals and identified an amino-acid variant that’s previously been seen in Denisovans. The group also identified two amino-acid sequence variants shared by all six individuals that set H. erectus apart from humans and other human relatives — something that has proved hard to find in the past.