By comparing DNA sequences, Nobel Prize winner Svante Paabo and his team found a ‘gene flow’ between both Denisovans and Neanderthals, and between Denisovans and modern humans.
Little is known of the mysterious Denisovans. These distant relatives of the Neanderthals roamed eastern and southern Eurasia, but left little trace of their time on Earth.
“Hominin Denisova” was discovered by Swedish paleogeneticist Svante Paabo, the winner of this year’s Nobel Prize in medicine.
In 2012, Paabo and his team sequenced the DNA of a well-preserved fragment of bone that was 40,000 years old and found four years earlier in the Denisova Cave in southern Siberia.
The result was astounding: They had come across an entirely novel hominin, distinct from Neanderthals and even more from modern humans.
The Denisovans shared a common ancestor with the Neanderthals until their populations diverged 380,000 to 470,000 years ago.
This was much later than the split between modern humans and Neanderthals/Denisovans, which occurred between 550,000 and 760,000 years ago.
In the same cave, paleontologists later discovered the fossil of a girl who was part Neanderthal and part Denisovan, proving that these two species interbred.
We know the Neanderthals disappeared about 40,000 years ago, but we have little idea when our other closest evolutionary relative went extinct.
Little is known about what the Denisovans looked like because they left few fossilised traces of their time on Earth other than the fragments found in Siberia and a jawbone discovered on the Tibetan Plateau in 2019. In 2019, researchers in Israel said they had reconstructed a prehistoric Denisovan skeleton – claiming 85 percent accuracy – using DNA found in the pinky bone of a 13-year-old girl who died tens of thousands of years ago.
The work of Paabo and his team at the Max Planck Institute in Leipzig, Germany has nonetheless shed some light on our mysterious ancestor.
By comparing DNA sequences, they found a “gene flow” between both Denisovans and Neanderthals, and between Denisovans and modern humans.
In other words, before they went extinct, Denisovans also interbred with our species.
Up to six percent of Denisovan DNA is still found in present-day humans in the Asia-Pacific and Southeast Asia, such as the Indigenous people of Australia, Melanesia and the Philippines. This suggests our far-distant relative roamed over a vast swathe of eastern and southern Eurasia.
Neanderthals, by contrast, lived in western Eurasia.
Scientists believe the ancient ancestors of today’s Melanesians interbred with Denisovans from Southeast Asia, far from the frozen mountains of Siberia and Tibet.
Proof that the Denisovans had spread as far as the tropics of Asia was lacking until a missing link – a child’s tooth at least 130,000 years old – was discovered in a cave in Laos in 2018.
One of the biggest remaining mysteries is why modern humans were so successful in their expansion and why the Denisovans and Neanderthals went extinct after having adapted to a Eurasian environment for several hundred thousand years.