The first draft Neanderthal genome was published in 2010. Since then, researchers at the Max Planck Institute for Evolutionary Anthropology have sequenced another 18 genomes from 14 different archaeological sites across Eurasia.
Although these genomes have provided information on the broad strokes of Neanderthal history, we still know little about individual Neanderthal communities.
To explore the social structure of Neanderthals, the researchers turned their attention to southern Siberia, a region that has previously been highly successful for ancient DNA research – including the discovery of Denisovan hominid remains in the famous cave of Denisova. From work done at this site, we know that Neanderthals and Denisovans were present in this region for hundreds of thousands of years, and that Neanderthals and Denisovans interacted with each other – as the discovery of a child with a Denisovan father and a Neanderthal mother. showed.
First Neanderthal community
In their new study, the researchers focused on Neanderthal remains in the Chagyrskaya and Okladnikov caves, which are less than 100 kilometers from the Denisova cave. Neanderthals briefly occupied these sites around 54,000 years ago, and several potentially contemporary Neanderthal remains had been recovered from their deposits. The researchers managed to recover DNA from 17 Neanderthal remains – the largest number of Neanderthal remains ever sequenced in a single study.
Chagyrskaya Cave has been excavated for the past 14 years by researchers from the Institute of Archeology and Ethnography of the Russian Academy of Sciences. Along with several hundred thousand stone tools and animal bones, they also recovered over 80 Neanderthal bone and tooth fragments, one of the largest assemblages of these fossil humans not only in the region but also in the world.
The Chagyrskaya and Okladnikov Neanderthals hunted ibex, horses, bison and other animals that migrated through the river valleys overlooked by the caves. They collected raw materials for their stone tools from tens of kilometers away, and the presence of the same raw material in the caves of Chagyrskaya and Okladnikov also confirms genetic data that the groups inhabiting these localities were closely linked.
Previous studies of a fossil toe from Denisova Cave have shown that Neanderthals also inhabited the Altai Mountains much earlier, around 120,000 years ago. Genetic data, however, shows that Neanderthals from the Chagyrskaya and Okladnikov caves are not descendants of these earlier groups, but are closer to European Neanderthals. This is also supported by archaeological material: the stone tools from Chagyrskaya Cave are most similar to the so-called Micoquian culture known from Germany and Eastern Europe.
The 17 remains came from 13 Neanderthal individuals – 7 males and 6 females, including 8 adults and 5 children and young adolescents. In their mitochondrial DNA, the researchers found several so-called heteroplasms that were shared between individuals. Heteroplasms are a special type of genetic variant that only persists for a small number of generations.
The most eastern Neanderthals
Among these remains were those of a Neanderthal father and his teenage daughter. The researchers also found a pair of second-degree relatives: a young boy and an adult woman, possibly a cousin, aunt or grandmother. The combination of heteroplasms and related individuals strongly suggests that Neanderthals at Chagyrskaya Cave must have lived – and died – around the same time.
“The fact that they were living at the same time is very exciting. This means that they are probably from the same social community. Thus, for the first time, we can use genetics to study the social organization of a Neanderthal community,” explains Laurits Skov, who is the first author of this study.
Another striking finding is the extremely low genetic diversity within this Neanderthal community, consistent with a group size of 10-20 individuals. This is much lower than those recorded for any ancient or current human community, and is more similar to the size of groups of endangered species on the brink of extinction.
However, Neanderthals did not live in completely isolated communities. By comparing the genetic diversity on the Y chromosome, which is inherited from father to son, with the diversity of mitochondrial DNA, which is inherited from mothers, researchers were able to answer the question: Was it males or females? who moved between communities? They found that mitochondrial genetic diversity was much higher than Y-chromosome diversity, suggesting that these Neanderthal communities were primarily linked through female migration. Despite the proximity of Denisova Cave, these migrations do not appear to have involved Denisovans – researchers have found no evidence of gene flow from Denisova to the Chagyrskaya Neandertals in the last 20,000 years before these individuals lived.
“Our study gives a concrete image of what a Neanderthal community might have looked like,” explains Benjamin Peter, the study’s final author. “It makes Neanderthals a lot more human to me.”
Max Planck Institute for Evolutionary Anthropology
Header Image – Denisova Cave – Image Credit: Shutterstock (Copyright)