20 October 2022

Neanderthal family life

Siberian Neanderthals preferred brides-travelers

Alisa Gadzhieva, Naked Science

Like all humans, Neanderthals lived their lives in communities. They ate, slept, loved and died in the company of their relatives. These communities were connected with others, thus forming the Neanderthal population of a particular region. But how were these communities organized? What relationships formed the basis of the group? Who left home to join another clan, and who stayed put?

A paper has been published in the journal Nature, the authors of which conducted the largest study of Neanderthal DNA to date (Skov et al., Genetic insights into the social organization of Neanderthals). These bones once belonged to 13 representatives of Homo neanderthalensis — men, women and children. If it seems to you that 13 sets of DNA are not enough, then we note: before this work, since 2010, genomic data was obtained only for 18 Neanderthals.

What makes the new study particularly noteworthy is that the studied individuals are not scattered throughout the vast zone of existence of Neanderthals, but are concentrated in specific space and time. Eleven samples of ancient DNA were obtained from bones found in the Chagyr cave in the south of the Altai Territory. There, in the northwestern foothills of Altai, somewhere between 51 and 59 thousand years ago, Neanderthals hunted migrating bison.

The largest collection of Neanderthal remains in North Asia and approximately 90 thousand stone artifacts were found in this cave. Most likely, the dwelling was seasonal, since the cave is not too big. Archaeological materials from the Chagyr cave have only one analogue in Altai — finds made in the nearby Okladnikov Cave. From the bones found there, geneticists obtained two more samples of ancient DNA.

All these individuals, as it turned out, belonged to the same broad population — descendants of the late expansion of Eastern European Neanderthals into Siberia, different from the earlier (but also Neanderthal) inhabitants of Denisova Cave, located just 100 kilometers to the east.

Archaeological evidence suggests that the Chagyr cave was used by Neanderthals for several millennia. This is too long a time interval to study social organization. But the authors of the work managed to drastically reduce it. Through DNA analysis, they found out that at least some of these ancient people were contemporaries and even relatives.

Scientists have identified members of the same family: a man and his teenage daughter, as well as a man-woman couple related by the second degree of kinship (they are connected by about 25 percent of DNA). One of the relatives of the father mentioned above was identified due to a genetic phenomenon called heteroplasmia.

With heteroplasmia, a person has two different versions of mitochondrial (inherited through the maternal line) DNA. These different versions coexist for only a few generations, so the researchers concluded that individuals with a common heteroplasm are relatively close female relatives. The authors of the work suggest that these men had a common grandmother.

Samples of genetic material from the Chagyr cave, as well as the genome of an earlier Neanderthal from Denisova, contain signs of inbreeding — closely related crossing. It is well known that Neanderthals lived in small communities (perhaps 10-30 individuals per group) with a very low population density in a particular region. That is, there was simply no influx of fresh genes sometimes.

But if such an influx did happen, it was thanks to women. Genetic analysis showed that it was they who moved between groups — that is, at least the Altai Neanderthals practiced patrilocality (women lived in a partner's family).

The authors draw parallels with examples of patrilocality and matrilocality in the history of our own species. As far as can be judged from the ancient hunter-gatherer communities, those in which women went to the husband's community were connected to each other by closer ties than those where a man came to the wife's family. True, such connections are normally formed only if the population density is high enough — which the Neanderthals did not seem to have.

Therefore, the question of how patrilocality influenced the organization of the life of the closest relative and rival of Homo sapiens remains to be clarified. The Chagyr Cave, like many other places throughout Eurasia, still holds many secrets.

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