Denisovans, who lived during a time that overlapped with Neanderthals, are known only from a few fossils discovered in a Siberian cave. But they also left a genetic legacy that lives on today in the DNA of some Asian, Australian and Melanesian humans. A Denisovan genome was sequenced in 2012 and compared with that of modern humans, revealing the trait.
Tibetans and Sherpas have a genetic variant that helps them live in low oxygen at high altitudes, which can be traced back to Denisovans.
But before the discovery of this jawbone, researchers wondered why this genetic variant existed. Tiny, fragmented remains of Denisovans had only ever been found in Denisova Cave, which sits at an altitude of 2,296 feet.
Baishiya Karst Cave on the Tibetan Plateau, where the jawbone was found, has an altitude of 10,761 feet.
No DNA was preserved in the fossil, but the researchers were able to extract ancient proteins and analyze them, as well as conduct radioisotopic dating of the fossil. The study on their findings was published Wednesday in the journal Nature.
The jawbone was well-preserved and featured a primitive shape, as well as a few large molars that were still attached.
At 160,000 years old, the fossil predates other evidence of ancient humans at such a high altitude in the area, which was previously set at between 30,000 and 40,000 years ago.
The age and features of the fossil are also similar to those of the oldest known Denisovan fossils from Denisova Cave, which suggests that the populations were closely related.
The jawbone was found by a monk in 1980 and eventually made its way to Lanzhou University, where researchers have been studying the cave site since 2010. They began analyzing the jawbone in 2016.
"Archaic hominins occupied the Tibetan Plateau in the Middle Pleistocene and successfully adapted to high-altitude low-oxygen environments long before the regional arrival of modern Homo sapiens," said Dongju Zhang, study author and lecturer at Lanzhou University's Research School of Arid Environment and Climate Change, in a statement.
The discovery shows that Denisovans lived in East Asia and adapted to the conditions there.
"Our analyses pave the way towards a better understanding of the evolutionary history of hominins in East Asia," Jean-Jacques Hublin, study author and director of the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology, said in a statement.
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