In 2008 a team of Russian archaeologists found something very unique in caves located in the Altai massif, in south-central Siberia, called Denisova caves, in honor of the 18th century hermit who lived there, Denis. Since 1980 it was known that it could be an important archaeological site, as remains dating back 180,000 years were found. What those experts found was not particularly striking: it was the fossil of a teenager’s finger in a geological stratum from 50,000 years ago. Subsequent excavations unearthed several teeth, the phalanx of a foot, and in 2012 a 2cm long piece of bone dated to 90,000 years was discovered. In total, the remains found, which corresponded to five individuals, would have fit comfortably in a medium matchbox. It wasn’t much, but enough to be able to do an analysis of the DNA preserved in the samples. And the results were quite a surprise.
The first Denisovan individual was identified in 2010 thanks to mitochondrial DNA extracted from the distal phalanx of the first found finger. Studies revealed that it was closely related to Neanderthals . But the bombshell came with the analysis of the bones found in 2012. The genetic material revealed that it had belonged to a thirteen-year-old girl, who was baptized with the name of Denny, and that her father had been a Denisovan and her mother a Neanderthal . This made it the first first-generation hybrid hominid ever discovered. The research, published in 2018, was the first direct evidence of what had long been suspected: that different species of Homo had interbred with each other more often than previously thought .
Denisovans had dark skin, eyes, and hair, and their build and facial features were probably similar to Neanderthals, however their molars were larger and reminiscent of those of archaic humans and australopithecines, from which Denisovans apparently descended. genus Homo .
In addition, they must have interbred regularly with modern humans and Neanderthals, since approximately 17% of the genome found in Denisova Cave is derived from them . However, one of the many mysteries that exists is that 4% of that genome comes from a very ancient and unknown human species that diverged from modern humans more than a million years ago.
In March 2019, two small skull fragments belonging to another specimen were found in the same cave, and shortly after a piece of jaw was found in the Baishiya cave, on the Tibetan plateau , a thousand kilometers from Denisova. At 160,000 years old and found at a height of 3 km above sea level, it tells us that Denisovans lived at high altitudes long before our species did. But the important thing is that this discovery solved another mystery: the origin of the EPAS1 gene of the Tibetans that alters the production of hemoglobin and helps them survive at high altitude. We now know that this is a gene inherited from the Denisovans .
In April 2019, Cell magazine gave a new twist to this story. Studying the genome of 161 people from Indonesia and Papua New Guinea found that about 5% of the DNA of Melanesians and Aboriginal Australians and 8% of Papuans is also derived from Denisovans. Moreover, introgression – this is the name given to the movement of genes from one species to another as a result of a hybridization process – into modern humans in New Guinea could have occurred just 30,000 years ago. If this were indeed the case, it would indicate that the Denisovans may have disappeared only fifteen millennia ago. What is most striking about this study is that the Denisovan DNA from Tibet differs from that of Papua, and both from Siberian. In fact, it does so from the others as well as from the Neanderthals, which suggests that we are dealing with a third lineage of archaic humans, which spread from Siberia to Southeast Asia.
