A fossil jaw discovered on the Tibetan plateau belonged to a Denisovan

An article published in the journal “Nature” reports evidence that a jaw discovered in Baishiya Karst Cave, in the Xiahe Chinese region, on the ibetan plateau, dated from about 160,000-year ago, belonged to a Denisovan. A team of researchers coordinated by the Max Planck Institute for Evolutionary Anthropology (MPI-EVA), Germany, and by the Lanzhou University, China, extracted proteins from the mandible and one of the molars that are specific to determine the relationship of that individual with the Denisovas whose remains were discovered in Siberia.

The Denisova Cave on the Altai Mountains in Siberia are an important paleoanthropological site because the first fossils of a species of hominins that as a result were named Denisovans were found there. Very few other fossils of this species were found in the following years but advances in genetic techniques allowed to extract DNA fragments from some bone fragments belonging to this species and other hominins opening the doors to research on the relationships among the various species and on interbreedings between Homo sapiens, Neanderthals and Denisovans.

The Tibetan mandible, shown in the image (Courtesy Dongju Zhang, Lanzhou University. All rights reserved) was discovered in 1980 and after some time was donated to the Lanzhou University, where an initial examination indicated that it probably belonged to a hominin who lived in the middle Pleistocene who had some features in common with the Neanderthals and Denisovans. A carbonate crust attached to the jaw allowed an indirect dating which indicates that the bone is at least 160,000 years old.

At Lanzhou University, researchers Fahu Chen and Dongju Zhang studied the area around Baishiya Karst Cave, finding tools and animal bones that indicate that the Denisovans probably lived there for some time. In 2016, the researchers began a collaboration with the Department of Human Evolution at the MPI-EVA in Leipzig which led to in-depth fossil analysis. The search for DNA fragments was not successful but the researchers were able to extract from the bone and a molar’s dentin various proteins that are still useful for the analysis because a part of them is specific for each species. Their analysis showed a relationship with the Siberian Denisovans.

The presence of Denisovans in Tibet indicates that they had spread far beyond Siberia and the fact that the remains of one of them were found in Baishiya Karst Cave, at an altitude of about 3,300 meters (almost 11,000 feet) above sea level, suggests that they they had adapted to live at those altitudes, where there’s a significantly lower amount of oxygen than at sea level. There’s no genetic evidence for that adaptation but previous research already suggested that the genes present in today’s Tibetans that allow them to live in those conditions were passed on to them by Denisovans. It could therefore be another proof of interbreedings between Homo sapiens and Denisovans after other genetic traces found in modern Asian and Australian populations.

Jean-Jacques Hublin, director of the Department of Human Evolution at the MPI-EVA and one of the authors of this study, pointed out similarities with other fossils discovered in China that could belong to other Denisovans. Research on the Tibetan plateau is difficult due to environmental conditions so it’s possible that there are many others somewhere in the area. New examinations of Chinese hominin fossils and more discoveries could be crucial to reconstruct the history of a species that is still mysterious in many ways and of its interbreedings with Homo sapiens.

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