Genetic evidence puts Denisovans on the Tibetan Plateau from 100,000 to 60,000 years ago

Denisovan mitochondrial DNA extracted from sediment layers in Baishiya Karst Cave on the Tibetan Plateau indicates that these humanlike folk inhabited the high-altitude site roughly 100,000 years ago and again around 60,000 years ago, say geoarchaeologist Dongju Zhang of Lanzhou University, China, and her colleagues. These are the first examples of Denisovan DNA found outside of Siberia’s Denisova Cave (SN: 12/16/19).1 In that case, ancient humans new to the region’s thin air may have acquired advantageous genetic traits for that environment by mating with resident Denisovans. Present-day Tibetans carry a Denisovan gene variant that aids high-altitude survival (SN: 7/2/14), although it’s not clear if interbreeding occurred on the Tibetan Plateau.

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A second study in the same issue of Science supports that idea. Nuclear DNA extracted from fossils of two ancient Asian Homo sapiens — one dating to around 34,000 years ago in Mongolia and the other to roughly 40,000 years ago in China (SN: 1/21/13) — includes segments inherited from a specific line of Denisovans, says a team led by paleogeneticist Diyendo Massilani of the Max Planck Institute for Evolutionary Anthropology in Leipzig. Those genetic segments are found in present-day mainland Asians but are distinct from Denisovan DNA that modern Papuans and Aboriginal Australians apparently inherited from ancestors who interbred with another Denisovan population, the scientists report.

  • 1. Cave sediment possibly dating from 50,000 to 30,000 years ago also yielded Denisovan mitochondrial DNA, the scientists report in the Oct. 30 Science. If further research confirms that age estimate, it raises the likelihood that Denisovans survived on the Tibetan Plateau long enough to encounter the first humans to reach those heights as early as 40,000 years ago.
Inside a cave on the Tibetan Plateau, researchers collect sediment samples that were among those used to find remnants of Denisovan mitochondrial DNA from as early as 100,000 years ago.
Inside a cave on the Tibetan Plateau, researchers collect sediment samples that were among those used to find remnants of Denisovan mitochondrial DNA from as early as 100,000 years ago. © Yuanyuan Han, D. Zhang/Lanzhou Univ.

D. Zhang et al. Denisovan DNA in Late Pleistocene sediments from Baishiya Karst Cave on the Tibetan Plateau. Science. Vol. 370, October 30, 2020, p. 584. doi: 10.1126/science.abb6320.  

A late Middle Pleistocene mandible from Baishiya Karst Cave (BKC) on the Tibetan Plateau has been inferred to be from a Denisovan, an Asian hominin related to Neanderthals, on the basis of an amino acid subsitution in its collagen. Here we describe the stratigraphy, chronology, and mitochondrial DNA extracted from the sediments in BKC. We recover Denisovan mitochondrial DNA from sediments deposited ~100 thousand and ~60 thousand years ago (ka) and possibly as recently as ~45 ka. The long-term occupation of BKC by Denisovans suggests that they may have adapted to life at high altitudes and may have contributed such adaptations to modern humans on the Tibetan Plateau.

D. Massilani et al. Denisovan ancestry and population history of early East Asians. Science. Vol. 370, October 30, 2020, p. 579. doi: 10.1126/science.abc1166.

We present analyses of the genome of a ~34,000-year-old hominin skull cap discovered in the Salkhit Valley in northeastern Mongolia. We show that this individual was a female member of a modern human population that, following the split between East and West Eurasians, experienced substantial gene flow from West Eurasians. Both she and a 40,000-year-old individual from Tianyuan outside Beijing carried genomic segments of Denisovan ancestry. These segments derive from the same Denisovan admixture event(s) that contributed to present-day mainland Asians but are distinct from the Denisovan DNA segments in present-day Papuans and Aboriginal Australians.