The social organization of Neanderthal populations is not well understood. The latest research suggests that in Siberia at least, Neanderthals lived in groups of 10 to 20 people — similar to present-day mountain gorillas, which are an endangered species.
The study was carried out by a global team of scientists, including Svante Paabo, a Swedish geneticist who won the Nobel Prize for medicine this month for his work mapping our genetic ties to Neanderthals.
Nobel awarded to Swedish scientist who deciphered the Neanderthal genome
Unlike many archaeological sites, which contain fossils built up over long periods, genetic studies on 11 Neanderthals found in the Chagyrskaya Cave — in the Altai Mountains, near the Russian border with Kazakhstan, Mongolia and China — showed many of them were close relatives, suggesting they all lived around the same time.
“Chagyrskaya Cave is basically a moment in time 54,000 years ago when this community lived and died in this cave,” Richard G. Roberts, a scholar at the University of Wollongong in Australia and one of the co-authors of the study, said in an interview.
“Most archaeological sites, things accumulate slowly and tend to get chewed over by hyenas or something else like that,” he said. “You don’t really get sites that full of material. It was packed full of bones, Neanderthal bones, animal bones, artifacts. It’s a moment, literally frozen in time.”
The scientists used DNA extracted from fossils found in Chagyrskaya Cave and from two other Neanderthals found in a nearby cave to map out the relationships between the individuals and to search for clues on how they lived.
Chagyrskaya Cave is perched high on a hillside, overlooking a flood plain where herds of bison and other animals once probably grazed, Roberts said. The researchers found stone tools and bison bones buried in the cave alongside the remains.
Genetic data obtained from teeth and bone fragments showed that the individuals included a father and his daughter, along with a pair of second-degree relatives, possibly an aunt or an uncle, a niece or nephew, Roberts said. The father’s mitochondrial DNA — a set of genes passed from mothers to their children — was also similar to two of the other males in the cave, he said, indicating they probably had a common maternal ancestor.
“They’re so closely related, it’s like a clan really living in this cave,” he said. “The thought that they could go on for generations upon generations seems unlikely. I think probably they all died very closely in time. Maybe it was just a horrendous storm. They are in Siberia, after all.”
The study also revealed that the genetic diversity of Y chromosomes (which are passed down only through the male line) was a lot lower than that of the mitochondrial DNA in the individuals, which the authors said suggests that Neanderthal females were more likely to migrate than males. That pattern is also seen in many human societies, where women marry and move away with their husband’s family before they have children.
Previous work by Paabo, the Swedish geneticist, has shown that Neanderthals mixed with prehistoric humans after they migrated out of Africa, and the vestiges of those interactions live on in the genomes of many present-day people. During the pandemic, he found that a genetic risk factor associated with severe cases of covid-19 was passed down from Neanderthals, carried by about half of people in South Asia and about 1 in 6 in Europe.
The authors say the sample size of the latest study is small and may not be representative of the social lives of the entire Neanderthal population.
“If we could just reproduce [the study] in a couple of other places, then we’d really have a grasp on how Neanderthals ran their lives, maybe some indication as to why they went extinct and we didn’t,” said Roberts, the Australian scholar. “We’re so similar. So why are we the only ones left around on the planet?”