The first Neanderthal draft genome was published in 2010. Since then, researchers from the Max Planck Institute for Evolutionary Anthropology have sequenced 18 more genomes from 14 different archaeological sites across Eurasia.
While these genomes have provided insight into the broader movements of Neanderthal history, we still know very little about individual Neanderthal populations.
To explore the social structure of Neanderthals, researchers turned their attention to southern Siberia, a region that had previously been very fruitful for ancient DNA research, including the discovery of Denisova hominin remains in the famous Denisova Cave.
From the work done in that region, we know that Neanderthals and Denisovans lived there for thousands of years, and that Neanderthals and Denisovans interacted with each other. The finding of a child with a Denisovan father and a Neanderthal mother supports this.
The first Neanderthal community
In the new study, published in Nature, researchers focused on Neanderthal remains in Chagyrskaya and Okladnikov Caves, located 100 kilometers from Denisova Cave.
Neanderthals occupied these sites for short periods around 54,000 years ago, and a large number of potentially contemporaneous Neanderthal remains have been recovered from their deposits.
The researchers successfully extracted DNA from 17 Neanderthal remains. This was the largest Neanderthal remains ever sequenced in a single study.
Chagyrskaya Cave was excavated over the past 14 years by researchers from the Institute of Archaeology and Ethnography of the Russian Academy of Sciences. In addition to several hundred thousand stone tools and animal bones, the researchers recovered more than 80 fragments of bones and teeth, one of the largest collections of Neanderthals not only in the region but in the world.
The Neanderthals at Chagyrskaya and Okladnikov hunted chamois, horses, bison and other animals that migrated through the river valleys overlooked by the caves. They gathered raw material for their stone tools from tens of kilometers away, and the discovery of the same raw material in both Chagyrskaya and Okladnikov Caves supports genetic evidence that the groups living in these regions were closely linked.
Previous work on a toe fossil from Denisova cave showed that Neanderthals also lived in the Altai mountains quite early, around 120,000 years ago. Genetic data show that the Neanderthals from Chagyrskaya and Okladnikov Caves are not descended from these ancient groups, but are more closely related to European Neanderthals. This is also supported by archaeological material: The stone tools from Chagyrskaya Cave most closely resemble the Micoquian culture known from Germany and Eastern Europe.
The 17 remains belonged to 13 Neanderthal individuals, 7 males and 6 females, of which 8 were adults and 5 were children and young adolescents. In their mitochondrial DNA, the researchers found several heteroplasmies shared between the individuals. Heteroplasmies are a special type of genetic variant that persists for only a small number of generations.
The easternmost Neanderthals
Among these remains were those of a Neanderthal father and his young daughter. The researchers also found a pair of second-degree relatives: a young male and an adult female, perhaps a cousin, aunt or grandmother.
The combination of heteroplasmies and related individuals strongly suggests that the Neanderthals in Chagyrskaya Cave must have lived and died at the same time.
Laurits Skov, first author of the study, said: “It’s very exciting that they lived at the same time. This means they probably came from the same social community. So, for the first time we can use genetics to study the social organization of a Neanderthal community.”
Another striking finding was the extremely low genetic diversity within this Neanderthal community, consistent with a group size of 10 to 20 people. This was much lower than has been recorded for any ancient or present-day human community, and more similar to the group sizes of endangered species on the brink of extinction.
But Neanderthals did not live in completely isolated communities. By comparing the genetic diversity in the Y chromosome passed down from father to son with the diversity of mitochondrial DNA from mothers, researchers can answer the question: Is it men or women who move between communities?
The researchers found that mitochondrial genetic diversity was much higher than Y-chromosome diversity, suggesting that these Neanderthal communities were primarily associated with female migration. Despite being close to Denisova Cave, these migrations do not appear to have included Denisovans – the researchers found no evidence of Denisovan gene flow in the Chagyrskaya Neanderthals in the 20,000 years before these individuals lived.
Benjamin Peter, the study’s senior author, said: “Our study provides a concrete picture of what a Neanderthal community looked like. It makes Neanderthals seem much more human to me.”
Article: Skov, L., Peyrégne, S., Popli, D. et al. (2022). Genetic insights into the social organization of Neanderthals. Nature 610, 519–525.
