When researchers look at the Denisovan ancestry in different modern populations — comparing the specific variants that are labeled “Denisovan” in different groups — they find that the Denisovan ancestry in Papuans and Australian Aboriginal people is most similar to the Denisova Cave genomes, while the Denisovan ancestry in Tibetans and some mainland Asian populations is less similar — consistent with derivation from a different, related but distinct Denisovan population.

This implies that there were at least two distinct Denisovan populations — perhaps separated for hundreds of thousands of years, perhaps as genetically diverse from each other as the most divergent modern human populations are today — that both interbred with modern humans at different points during the modern human expansion through Asia.

The geography of these two episodes of interbreeding is informative.

The interbreeding with the first Denisovan population (the one most similar to Altai Denisovans) apparently happened in Southeast Asia or the Pacific margin, as modern humans were moving toward Oceania.