A team of international researchers have now confirmed the presence of a human lineage, the Denisovans, at the high altitudes of Tibet. In 2019, researchers had proposed that a jawbone found in the Baishiya Karst Cave, a Buddhist Sanctuary in Tibet, belongs to extinct hominins, known only from DNA, teeth, and bits of bone found in another cave—Denisova, 2800 km away in the Bashelaksky Range of the Altai mountains, Siberia, Russia (Long 2020).
However, researchers required more evidence to confirm that Tibet was the second home of Denisovans outside Siberia. Hence an international team of archaeologists, geologists and geneticists, including dating specialists Associate Professor Bo Li and Professor Zenobia Jacobs from the University of Wollongong, Australia, carried out further research, digging every night, to not disturb the worshipping Buddhists monks. Professor Dongju Zhang from Lanzhou University, China, led the excavation team.
They have now published their research results in the Science–‘Denisovan DNA in Late Pleistocene sediments from Baishiya Karst Cave on the Tibetan Plateau’. Although the researchers did not find any other Denisovan bones, yet Denisovan DNA was present in the soil. The new study supports the idea that Denisovans had a wide geographic distribution that was not limited only to Siberia.
Besides the mandible, dated to more than 160,000 years ago, stone artefacts recovered, were in all probably fashioned by the Denisovans. These artefacts can be dated to more than 190,000 years ago and to as recently as 45,000 years. Based on the mitochondrial DNA extracted from sediment layers in Baishiya Karst Cave, the study confirms that Denisovans humans, closely related to Neanderthals, occupied the cave from at least 100,000 years ago to 60,000 years ago, and probably as even as recently as 45,000 years ago.
The mandible (lower jawbone) discovered from Baishiya Karst Cave in 1980 by a Buddhist monk is so far the largest fossil of Denisovan, and also the only remains found outside Siberia (Zimmer 2019). Discovered on the Tibet Plateau, the proverbial ‘roof of the world’, 3280 m above sea level, researchers indicate that the modern Tibetan people may have inherited some of their genes that enable them to adapt to the high-altitude environment.
Denisovan humans DNA present in the genomes of living people across Asia suggested these ancient humans were widespread (Gibbons 2020). However, the jaw bone found in the Baishiya Karst Cave was the first fossil evidence to prove that theory. “We found firm evidence for the long-term presence of Denisovans in Baishiya Karst Cave and provided stratigraphic and chronological context for their occupation in the cave, confirming the occupation of Denisovans on the Tibetan Plateau”, says Professor Bo Li.
With this new evidence, it is clear that the Denisovans were remarkably hardy humans, able to endure harsh conditions on the Tibetan plateau at a high altitude. Scientists also suggest that up to 6 per cent of the genes now found in modern New Guineans and 3-5 per cent of the DNA of aboriginal Australians consists of Denisovan DNA (McKie 2018).
Denisovans humans, with an existence tethered on the few bones, have always puzzled researchers around the globe. Two years ago, researchers concluded that a bone fragment found in the Denisova Cave was that of a girl, whom they nicknamed Denny. Nevertheless, the surprising element in the research was that Denny’s descent was determined to be from a Neanderthal mother and Denisovan father, indicating the evidence of interbreeding. It proved that the Denisovans and the Neanderthals were living at the same place and at the same time. Scientific analysis of the fossils and DNA traces demonstrated Denisovans were present in the Denisova cave from at least 200,000 to 50,000 years ago, and Neanderthals were present there between 200,000 and 80,000 years ago (Dunhan 2019). Such studies mark the possibility of humans having a much more complex evolution that previously formulated.
Dunham W. 2019. Siberian cave findings shed light on enigmatic extinct human species, Reuters, available at https://www.reuters.com/article/us-science-denisovans-idUSKCN1PO2UG.
Gibbons A. 2020. DNA tracks mysterious Denisovans to Chinese cave, just before modern humans arrived nearby, Science. Available at https://www.sciencemag.org/news/2020/10/dna-tracks-mysterious-denisovans-chinese-cave-just-modern-humans-arrived-nearby.
Long B. 2020. Press Release-Study confirms Denisovan presence on ‘the roof of the world, University of Wollongong. Available at https://www.uow.edu.au/media/2020/study-confirms-denisovan-presence-on-the-roof-of-the-world.php#:~:text=Baishiya%20Karst%20Cave%2C%20a%20Buddhist,distribution%20not%20limited%20to%20Siberia.
McKie R. 2018. Meet Denny, the ancient mixed-heritage mystery girl, The Guardian, available at https://www.theguardian.com/science/2018/nov/24/denisovan-neanderthal-hybrid-denny-dna-finder-project.
Zimmer C. 2019. Denisovan Jawbone Discovered in a Cave in Tibet, New York Times, available at https://www.nytimes.com/2019/05/01/science/denisovans-tibet-jawbone-dna.html#:~:text=In%201980%2C%20a%20Buddhist%20monk,jawbone%2C%20studded%20with%20two%20teeth.