An ancient molar suggests an interbreeding between Homo sapiens and Denisovans in Asia

Tooth socket for a three-rooted molar (Image courtesy Christine Lee. All rights reserved)
Tooth socket for a three-rooted molar (Image courtesy Christine Lee. All rights reserved)

An article published in the journal “Proceedings of the National Academy of Sciences” reports the results of the analysis of a tooth belonging to a Denisovan that is part of a mandible discovered on the Tibetan plateau, dating back 160,000 years ago. It’s a three-rooted mandibular molar, a characteristic that today exists in a part of Asian modern humans and only rarely in Caucasian populations. That characteristic was considered the result of a mutation occurred in modern humans after the first migrations out of Africa but this discovery suggests that it’s instead the result of an interbreeding with the Denisovans.

An article published in May 2019 in the journal “Nature” reported the evidence that a 160,000 years old mandible discovered in the Baishiya Karst Cave, in the Xiahe Chinese region, on the Tibetan plateau, belonged to a Denisovan. There are very few remains belonging to these hominins and finding evidence of their presence in a place far from the Denisova Caves, in Siberia, was important. Among the researchers who collaborated in that study there were Shara Bailey, professor of anthropology at New York University (NYU), and Jean-Jacques Hublin of the Department of Human Evolution of the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig, in Germany, who, together with Susan Antón, another NYU anthropologist, have now focused their attention on the molar found together with the mandible.

In the species of the genus Homo, mandibular molars are generally two-rooted but there are some exceptions. In modern humans mandibular three-rooted molars are quite widespread and in some Asian populations over 40% of people can have them while it’s rare in non-Asian populations. For this reason, the discovery of a three-rooted mandibular molar belonging to a Denisovan is an important discovery as it suggests that today’s Asians inherited that characteristic from the Denisovans following interbreedings between the two species. This hypothesis contradicts the existing idea that that characteristic was the result of a mutation occurred after the first migrations of Homo sapiens from Africa spread above all among the Asian populations.

The availability of fragments of DNA from Denisovans allowed in the past to find traces of interbreedings with Homo sapiens in Asian populations. According to the authors of this research on the tooth discovered on the Tibetan plateau, the three-rooted molar is part of the characteristics inherited from these hominins. This adds further information on those ancient interbreedings and is important from the scientific point of view but also from the cultural point of view because for various Asian populations the continuity of the relationship between the population and the territory is important.

In the past, Chinese scientists tried to prove that the Homo erectus commonly known as Peking men were their direct ancestors but genetic studies showed a relationship with Siberian populations. In light of this research, this could be even truer in the sense that modern Chinese seem to be closely related not only with the Homo sapiens who lived in Siberia thousands of years ago but also with the Denisovans.

Leave a Reply

Your email address will not be published. Required fields are marked *