Modern humans co-existed and interbred not only with Neanderthals, but also with another species of archaic humans, the mysterious Denisovans. While developing a new genome-analysis method for comparing whole genomes between modern human and Denisovan populations, researchers unexpectedly discovered two distinct episodes of Denisovan genetic intermixing, or admixing, between the two. This suggests a more diverse genetic history than previously thought between the Denisovans and modern humans.