Welcome to Denisova Cave, a rocky refuge nestled in the Anui Mountains in Altai, southern Siberia. It is here that researchers extracted DNA from a bone fragment belonging to a Neanderthal man who lived 110,000 years ago. By comparing her genetic code to that of a woman who occupied the place 10,000 years earlier, scientists made a touching discovery: they were related. Not directly, but like members of the same lineage who have passed down the keys to the house over hundreds of generations.
For Diyendo Massilani, professor of genetics at Yale and first author of the study, it is very likely that “Denisova Cave was part of a larger landscape used repeatedly by these Neanderthal populations over time“. It was not a quick passage, but a real installation in this territory, over several millennia.
This loyalty to home perhaps hides a darker reality, that of isolation. The study, published in the journal Proceedings of the National Academy of Sciences (PNAS), reveals that these groups were generally tiny. We are talking about clans of less than 50 individuals, living so far from each other that encounters almost never happened. Result? Record inbreeding which was obviously bad for the tribe. Analyzes show that the Altai man’s parents shared large segments of identical DNA, a sign that they were probably as close as first cousins.
Dangerous inbreeding
According to Live Science, this genetic loneliness has created abysmal differences between populations. In just 50,000 years, the Neanderthals of Siberia and those of Europe became as different from each other as human populations separated by 300,000 years of history are today. “What is striking about our results is how differentiated these populations could become», adds Diyendo Massilani.
For paleogeneticists, these results change our view of the end of the Neanderthals. We have long looked for an external culprit such as a supervolcano, an epidemic or the arrival of Homo sapiens. But the answer may already be in their genes. By remaining cooped up in their small family bubbles for too long, they have lost the flexibility necessary to adapt to changes in the climate.
Léo Planche, population geneticist at Paris-Saclay University, who did not participate in the study, is enthusiastic about this new clarification: “We are starting to have enough Neanderthal genomes to be able to really say things about their population structure“. The more data we accumulate, the more the portrait of this cousin emerges from the caricature of the thick brute to become that of a more sensitive, but tragically isolated human.
Neanderthals survived for millennia in extreme conditions, but their social model, based on very closed clans, eventually reached its limits. Today, each new bone fragment found in Denisova is another piece to add to the great puzzle of our origins. By studying these missing cousins, we also discover a little of ourselves.
