They unexpectedly discovered the oldest human genome to date – that of a Denisovan who lived 200,000 years ago.
Although rumors had been swirling around the halls of the annual meeting of the Society for Molecular Biology and Evolution, held this year in Puerto Vallarta, Mexico, for several days, the intervention of population geneticist Stéphane Peyrenees of the Max … Planck of Evolutionary Anthropology made everyone sit down in the packed room: “I am pleased to inform you,” Peyrenees said, “of a new Denisovan genome from a man who lived 200,000 years ago.”
The interest and surprise of those present were more than justified, because this genome is the oldest of those obtained to date and surpasses the previous record no more and no less than the previous record, the genetic load of a Neanderthal who lived about 120,000 years ago.
So, this is an impressive scientific milestone. However, one that has not yet been published, but which, as Peyrenee assures, will soon be published in a peer-reviewed scientific journal. This result, the second genome we have from a Denisovan, comes after more than a decade of trying to find fossils of this still mysterious species, a “cousin” of the Neanderthals, the first news of which appeared only 14 years ago thanks to the analysis of DNA extracted in the Denisova Cave in Siberia from a single tiny fragment of the little finger of a girl who lived between 60,000 and 80,000 years ago.
According to Peyren, the analysis conducted with his colleagues shows that this man comes from an early population of Denisovans, who interbred several times with a group of Neanderthals and whose population has not been discovered until now. In short, despite the fact that the article comes with all the data, it seems that we have stumbled upon a new and powerful source of information about this enigmatic human species.
Mysterious view
The Denisovans are known not only from their fossils, but also from their DNA. So far, researchers have had the girl’s genome, as well as some DNA fragments from common fossils (teeth, toe bones…) of seven other individuals, all found in the same Denisova Cave.
Later, scientists also found traces of Denisovan DNA in modern populations such as the Papuans and Chinese, demonstrating that, at least in Asia, this ancient population interbred with our own species. However, although scientists have worked hard to figure out what they looked like, no one really knows what the Denisovans looked like.
As Peyrenheu explained, his achievement is linked to the genetic analysis of a 200,000-year-old molar found in a deep layer of Denisova Cave by Russian archaeologist Maxim Kozlikin, who decided to send it to the Max Planck Institute in Germany. There, Peyrenheu and his colleagues were able to extract an exceptional amount of DNA, which they later compared with the DNA of other Denisovans, as well as Neanderthals and modern humans.
Other population
The analysis showed that the Denisovan male inherited 5% of his genome from a previously unknown Neanderthal population. The individual, labeled “Denisova 25,” came from a different population than the girl known as “Denisova 3,” as well as from other Denisovans who lived in the cave.
All of this, Peyrenees explained in his talk, suggests that the ancient population to which the male belonged was replaced in the cave by more modern Denisovans. The data also suggests that this ancient Denisovan population interbred several times with Neanderthals, who eventually (around 120,000 years ago) displaced the Denisovans from the cave.
But about 60,000 years ago, as evidenced by the girl’s little finger, the Denisovans were back in the cave. And it’s even possible that the two groups were aligned: DNA from a bone fragment from a woman who lived more than 50,000 years ago actually shows that she had a Neanderthal mother and a Denisovan father.
Later, both DNA and fossils indicate that modern humans occupied the cave, and the Denisovans and Neanderthals disappeared. The region was clearly a crossroads for different types of people, Peyrenees said.
Although Denisovans and Neanderthals interbred repeatedly, the scientist continued, their lineages are distinct, and they diverged from a common ancestor at least 400,000 years ago. The ancestors of the Neanderthals spread across Europe and the Middle East, while the Denisovans headed further east into Asia, where they evolved separately, acquiring some 300,000 genetic changes that, as the new genome shows, separated them forever from the Neanderthals.
Since then, Neanderthals and Denisovans have remained separate groups that only intermingled at the edges of their geographic ranges. Now Peyrenue only needs to publish his work so that the scientific community can learn much more about this mysterious human species.