Were Denisova the first Tibetans?

Mandible fragment is the oldest fossil of a human being in the highlands of Tibet

The Xiahe Mandible is the first fossil of a Denisova human outside of Siberia. © Dongju Zhang / Lanzhou University
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It is a spectacular find: for the first time, researchers have discovered the fossil of a Denisova man outside of Siberia. The well-preserved part of a mandible from a cave in Tibet is around 160, 000 years old and in its anatomical features resembles the findings from the famous Denisova Cave. The bones provide solid evidence of the spread of these early humans in East Asia. And they suggest that the mysterious hominins may have been the very first humans in the Tibetan highlands.

The enigmatic Denisova people have immortalized themselves in the genome of many populations living today. Traces of this sister group of Neanderthals can be found in the genome of Australians, Melanesians and Asians. The Tibetans even owe their height adjustment to a gene that probably comes from the Denisova. "The traces of Denisova DNA in the genetic material of today's populations indicate that this human form could once have been widespread, " explains Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology in Leipzig.

However, tangible evidence of the existence of the Denisova people is scarce. So far, they have confined themselves to a few fragments of bones and teeth that researchers found in a cave in the Siberian Altai Mountains. All the more spectacular, therefore, is what has been revealed by the analysis of a human lower jaw part from the highlands of Tibet: the fossil is the first concrete proof of the spread of Denisova people outside of Siberia.

The site, Baishiya Karst Cave, is located at an altitude of some 3, 000 meters in the Tibetan Plateau. Dongju Zhang / Lanzhou University

Fossil from lofty height

A monk had originally found the bones as early as 1980 in the Baishiya Karst Cave in Xiahe at 3, 280 meters. But only now could the lower jaw, of which only the right half is preserved, undergo a thorough scientific analysis. To whom did the bones once belong? Because the scientists around Fahu Chen of the Chinese Academy of Sciences in Beijing were unable to isolate useful DNA from the fossil, they used proteins from a molar tooth to answer that question.

It turned out: The bones are probably from a Denisova man. "Our protein analysis revealed that the Xiahe mandible belonged to a population closely related to the Denisova cave people, " says co-author Frido Welker of the University of Copenhagen. The anatomical features also support an assignment of the fossil to the Denisova family, as the researchers report. Because both the primitive shape of the lower jaw and the very large molars are characteristics that are also found in the fossil fragments from the Denisova cave. display

At least 160, 000 years old

Using the uranium-thorium datings, the lower jaw was also able to elicit the secret of its age: according to the results, the fossil is at least 160, 000 years old - and thus as old as the oldest finds from the Denisova-H cave. "This suggests that Denisova people or closely related populations have deep roots in Central East Asia, " the team writes. But not only that: his old age also makes the lower jaw the oldest known fossil of a hominin in the highlands of Tibet. "It is at least 120, 000 years older than the oldest paleolithic sites in the region, " say Chen and his colleagues.

This means that the Denisova man may have been the first human form in the highlands of Tibet - and explains why this early human developed genetic adaptations to a high-altitude life he achieved through prehistoric infidelity inherited Tibetans living today. "The ancient people successfully adapted to the high-oxygen, low-oxygen environment long before the arrival of Homo sapiens in the region, " said co-author Dongju Zhang of Lanzhou University in China.

Similarities of the Xiahe mandible with other fossils from China also suggest, according to the researchers, that these bones may also be attributed to Denisova humans. "Our analyzes are now paving the way for a better understanding of hominid evolutionary history during the Middle Pleistocene in East Asia, " concludes Jean-Jacques Hublin. (Nature, 2019; doi: 10.1038 / s41586-019-1139-x)

Source: Nature Press / Max Planck Society

- Daniel Albat