DNA tracks mysterious Denisovans to Chinese cave, just before modern humans arrived nearby

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Tibet, Oct 31: For today’s Buddhist monks, Baishiya Karst Cave, 3200 meters high on the Tibetan Plateau, is holy. For ancient Denisovans, extinct hominins known only from DNA, teeth, and bits of bone found in another cave 2800 kilometers away in Siberia, it was a home, www.sciencemag.org reports said.

Last year, researchers proposed that a jawbone found long ago in the Tibetan cave was Denisovan, based on its ancient proteins. But archaeologist Dongju Zhang of Lanzhou University and her team wanted more definitive evidence, including DNA, the molecular gold standard. So in December 2018, they began to dig, after promising the monks they would excavate only at night and in winter to avoid disturbing worshippers.

After working from dusk to dawn while temperatures outside plunged to –18°C, then covering traces of their dig every morning, the scientists’ persistence paid off. Today in Science, Zhang’s team reports the first Denisovan ancient DNA found outside Denisova Cave: mitochondrial DNA (mtDNA) gleaned not from fossils but from the cave sediments themselves. Precise dates show the Denisovans took shelter in the cave 100,000 years and 60,000 years ago, and possibly as recently as 45,000 years ago when modern humans were flowing into eastern Asia.

The find shows that even though their bones are rare, “Denisovans were widespread in this hemisphere,” says University of Oxford geochronologist Tom Higham, who was not part of the study. It also ends a long quest for Denisovan DNA outside Siberia. “Every year, I’ve said we will find this,” says co-author Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology (EVA). “It’s been a decade.”

The presence of Denisovan DNA in the genomes of living people across Asia suggested these ancient humans were widespread. But the partial jaw from Baishiya Karst Cave was the first fossil evidence. Zhang and her colleagues identified the jaw as Denisovan based on a new method that relies on variation in a protein. Some researchers questioned the claim, however, because the method was new, and no one knew where in the cave the jaw had been…