Ancient genomes provide a rare opportunity to see family groups of Neanderthals

Ancient genomes provide a rare opportunity to see family groups of Neanderthals
Ancient genomes provide a rare opportunity to see family groups of Neanderthals

More than 49,000 years ago, a Neanderthal family set up camp in a cave high in the Altai mountains, overlooking the river valley, where bison, red deer and wild horses roamed. In the main gallery of the cave, a teenage girl lost a tooth, possibly gnawing on the meat of a bison her father hunted in the vast meadows nearby.

The group of researchers was able to analyze the genomes of the father and daughter, as well as their 12 relatives, who were hiding in the same cave for less than 100 years. The resulting genomes are almost twice the number of known genomes of Neanderthals and give an idea of ​​the population of Neanderthals in the eastern part of their habitat, at a time when they were on the verge of extinction.

As noted in the Science journal article, genomes provide the first real clues to understanding the social structure of Neanderthals. According to geneticist Laurits Skova of the Max Planck Institute for Evolutionary Anthropology, in addition to identifying the first father-daughter pair, genetic evidence suggests that Neanderthals lived in family groups, like representatives of many communities of modern man. Skova presented the work in a virtual presentation at the 9th International Symposium on Biomolecular Archeology in early June.

“It's really great that they were able to get genomes from seven males from one place,” says paleogeneticist Cosimo Post of the University of Tübingen. "This incident really suggests that they lived in small groups of closely related males."

TOM BJORKLUND Ancient DNA from a Siberian cave reveals the first known Neanderthal father-daughter pair.

Over the past decade, geneticists have sequenced the genomes of 19 Neanderthals. But this DNA mostly belonged to women, who are very distantly related to each other: they lived in different parts of Europe and Asia between 400,000 and 50,000 years ago.

Computational biologist Benjamin Peter and paleogeneticist Svante Päabo of the Max Planck Institute conducted a new study with a team that included postdoc Skova. They extracted Neanderthal DNA from teeth, fragments of bones and a jawbone excavated during excavations of the Chagyrskaya and Okladnikovaya caves by archaeologists of the Siberian branch of the Russian Academy of Sciences. Optical dating of deposits around teeth and bones suggests that Neanderthals lived between 49,000 and 59,000 years ago. Both caves are located not far - from 50 to 130 kilometers - from the famous Denisova Cave, which was inhabited by both Neanderthals and their close relatives Denisovans in the interval from 270,000 to 50,000 years ago.

The researchers analyzed DNA from more than 700,000 genome regions of seven men and five women from Chagyrskaya, as well as men and women from Okladnikov Cave. Family ties were discovered: the nuclear DNA of one fragment of the Chagyr bone linked the father to a tooth that had fallen out from his teenage daughter. Some people had two types of maternally inherited mitochondrial DNA (mtDNA). These genomes have not yet differentiated from each other, which has been happening for several generations, so people must have lived in a group for one century.

DNA analysis provides a more detailed picture of Neanderthal society. Several men of the Chagyr Cave carry long fragments of identical nuclear DNA from the same recent ancestor. Their Y chromosomes were also similar and descended from a common ancestor, like the other three known male Neanderthal genomes.Nuclear DNA showed that they were more closely related to later Neanderthals in Spain than to earlier Neanderthals in neighboring Denisova, suggesting migration.

The similarity of the males suggests that they belonged to a population of only a few hundred males - roughly the same number of breeding males is found in the population of endangered mountain gorillas today. “If you evaluate this population of Neanderthals in terms of modern criteria, they would be endangered,” says Skova.

Unlike the Y chromosome and nuclear DNA, the mtDNA of both males and females was relatively diverse, which means that female ancestors contributed more to the development of this population than males. This could be due to the founder effect, when there were fewer fertile males in the original group than females. Or it could reflect the nature of Neanderthal society, says paleogeneticist Qiaomei Fu of the Chinese Academy of Sciences: "Either men contribute less to the next generation than women, or women are more likely to move from one group to another."

According to Skov, the facts speak for the latter. The simulations show that it is unlikely that the small group of migrants traveling from Europe to Siberia will be composed mostly of women, he said. Instead, he believes that these Neanderthals lived in very small groups of 30 to 110 breeding adults, and that young females left their families of origin to live with the families of their mates. Most modern human cultures are also patrilocal, highlighting another similarity between Neanderthals and modern humans.

Despite the fact that 14 genomes cannot reveal the essence of the social life of all Neanderthals, the fact of the low diversity of males is an ominous sign of impending extinction. The end was fast approaching for our closest relatives: in just 5,000-10,000 years they would disappear.

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