Genomic analyzes of Neanderthals have previously provided insights into their population history and relationship to modern humans, but the social organization of Neanderthal communities remains poorly understood. To explore the social structure of Neanderthals, an international team led by researchers from the Max Planck Institute for Evolutionary Anthropology sequenced several individuals from a remote Neanderthal community in Siberia.
According to the investigators, multiple related people were found among these thirteen people, including a father and his teenage daughter. The thirteen genomes allowed the researchers to learn about the social structure of a Neanderthal community. With between 10 and 20 members, they appear to have been a small family, with female migration serving as the primary means of connecting the groups.
To explore the social structure of Neanderthals, the researchers turned their attention to southern Siberia, a region that has previously been very fruitful for ancient DNA research, including the discovery of Denisovan hominid remains in the famous cave of Denisova. They focused on Neanderthal remains in the Chagyrskaya and Okladnikov caves, which are located 100 kilometers from the Denisova cave.
Neanderthals used these sites for a brief period about 54,000 years ago, and many possibly contemporary Neanderthal remains have been found in their deposits. The 17 Neanderthal remains successfully recovered by the researchers represent the most Neanderthal remains ever sequenced in a single study.
The Neanderthals of Chagyrskaya and Okladnikov hunted ibex, horses, bison and other animals that migrated through the river valleys that pass the caves. They collected raw materials for their stone tools tens of kilometers away, and the occurrence of the same raw material in both Chagyrskaya and Okladnikov caves also supports the genetic data that the groups inhabiting these localities were closely related
The 17 fossils come from 13 Neanderthal people: 7 men and six women, 8 of whom were adults and 5 of whom were children or young teenagers. Researchers discovered many so-called heteroplasmies in people’s mitochondrial DNA that people shared. Heteroplasmies are a unique genetic variation that only lasts a few generations.
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, perhaps a cousin, aunt or grandmother. The combination of heteroplasmy and related individuals strongly suggests that the Chagyrskaya Cave Neanderthals must have lived – and died – at roughly the same time.
Laurits Skov, the first author of this study, said: “The fact that they were living at the same time is very exciting. This means that 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”.
There is incredibly low genetic diversity within this Neanderthal community, which is compatible with a group size of 10 to 20 people, which is another impressive discovery. This compares most favorably with the population sizes of critically endangered species on the brink of extinction and is significantly lower than those seen in any ancient or modern human community.
However, Neanderthals did not live in completely isolated communities. By comparing the genetic diversity of the Y chromosome, which is inherited from father to son, with the mitochondrial DNA diversity inherited from mothers, the researchers were able to answer the question: did men or women move between communities? They found that mitochondrial genetic diversity was much higher than Y chromosome diversity, suggesting that these Neanderthal communities were linked primarily by female migration.
Despite the proximity to Denisova Cave, these migrations do not appear to have involved Denisovans: the researchers found no evidence of Denisovan gene flow into Chagyrskaya Neanderthals in the last 20,000 years before these individuals lived.
Benjamin Peter, the last author of the study, said: “Our study provides a concrete picture of what a Neanderthal community might have looked like. It makes Neanderthals seem much more human to me.”
Journal reference:
- Skov, L., Peyregne, S., Popli, D. et al. Genetic knowledge about the social organization of Neanderthals. Nature 610, 519–525 (2022). DOI: 10.1038/s41586-022-05283-y