The Denisovans, an archaic yet mysterious human group

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The Denisovans, whose genome has been deciphered thanks to the Swede Svante Pääbo, a pioneer in paleogenomics crowned Monday by the Nobel Prize in Medicine, are the representatives of a group of Asian humans cousins ​​of Neanderthals who left few traces of their passage. 

In 2008, a 40,000-year-old fragment was discovered in the Denisova Cave in Siberia: a little finger bone containing DNA remarkably well preserved thanks to favorable climatic conditions.

From this simple remnant, Svante Pääbo and his colleagues at the German Max-Planck Institute identify a new species of hominins (which designates all human lineages), whose DNA was hitherto unknown, baptized “Man of Denisova”. The discovery causes a stir.

The team then develops new techniques for DNA extraction and more sensitive analysis, which allow them to reconstruct a complete genome of the species, in 2012. Fine enough to understand that the Denisovans were cousins ​​of the Neanderthals with whom they shared a common ancestor, from whom they separated around 400,000 years ago.

The discovery of a fossilized remains of a young girl born of their union, in the same cave of Denisova, proved that these two archaic species had “hybridized”, according to the terms used by paleontologists.

But if we know that Neanderthal disappeared from the face of the Earth about 40,000 years ago, we do not know when Denisova died. Nor what it could have looked like, because it has left only rare fossil traces of its passage except those of the Siberian cave, and a mandible found on the Tibetan plateau in 2019.

However, Svante Pääbo's work has shed further light on the mystery, uncovering a 'gene flow' between Denisovans and Homo sapiens through comparisons with sequences from contemporary humans, the committee says Nobel in a press release.

In other words, before disappearing, Denisova also interbred with our species, bequeathing part of her DNA to current populations of Southeast Asia and Oceania: Negritos from the Philippines, Papuans from New Guinea and Australian Aborigines carry a large proportion of Denisovan genomes – up to 6%.

Scientists infer that the modern ancestors of these Melanesian populations were interbred with Denisovans who populated Southeast Asia — far from the cold mountains of e Siberia or Tibet. Proof of their presence in this part of the continent was missing, which a study published last May thinks it has found, in a cave in Laos.