Study: Early humans created ‘mating networks’ to prevent inbreeding

CAMBRIDGE, England — When early humans lived in small groups during prehistoric times, the danger of inbreeding was very real.

In fact, some scientists say inbreeding may have left closely related species, such as Neanderthal, at a disadvantage compared to modern man. The speculation comes following a new study determining that anatomically modern humans figured out mating structures to avoid inbreeding at least 34,000 years ago.

Illustrations of the Sunghir burials.
Illustrations of the Sunghir burials. (Image Credit: Libor Balák, Anthropark.)

“This social structure may have affected the development of cooperation and information transfer that underlie the evolution of culture in humans, and may be crucial to understanding our species unique evolutionary resilience and trajectory,” say researchers from University of Cambridge and the University of Copenhagen in a paper published this month in the journal Science.

The discovery was made while the researchers studied genetic material from a famous Upper Paleolithic burial site in Sunghir, Russia. The Upper Paleolithic marked a time when modern humans first began to habit western Eurasia, and burial sites of the period, such as Sunghir, are incredibly rare. Unlike most human remains that have been discovered from the Upper Paleolithic, the people at Sunghir appear to have been buried together, on purpose.

But the surprise that made this site really stand out came during the genetic analysis: None of the people buried there were closely related, including two children buried head-to-head together.

“This goes against what many would have predicted,” says senior author of the study Professor Eske Willerslev in a press release. “I think many researchers had assumed that the people of Sunghir were very closely related, especially the two youngsters from the same grave.”

In the paper, the researchers describe the fantastic details of the surprising scene.

“All remains were covered in ochre, and accompanied by rich grave goods including ivory beads and spears, armbands and carvings, as well as arctic fox canines,” the researchers write. “Adjacent to (the children) was the femoral diaphysis of an adult that had been polished, hollowed-out and filled with red ochre.”

Detail of one of the burials from Sunghir, in Russia.
Detail of one of the burials from Sunghir, in Russia. The new study sequenced the genomes of individuals from the site and discovered that they were, at most, second cousins, indicating that they had developed sexual partnerships beyond their immediate social and family group. (Credit: University of Copenhagen)

After studying such symbology alongside the genetic evidence, the researchers suggest that together they provide evidence of ceremony and ritual that may have accompanied the exchange of mates between groups.

“What this means is that even people in the Upper Paleolithic, who were living in tiny groups, understood the importance of avoiding inbreeding,” says “The data that we have suggest that it was being purposely avoided. This means that they must have developed a system for this purpose. If small hunter–gatherer bands were mixing at random, we would see much greater evidence of inbreeding than we have here.”

This stands in contrast to genetic evidence from other hominids such as the Neanderthal whose remains found in the Altai Mountains reveal they did not avoid inbreeding. However, the researchers caution that before conclusions are made about mating differences between humans and Neanderthal more research must be done.

Nevertheless, the study authors call the ornamentation at the site “incredible,” noting there is no evidence of anything like it in Neanderthal or other archaic human sites. And while it is still just educated conjecture that this represents new levels of societal structure aimed at promoting genetic diversity, there is no argument that the Sunghir site offers special insight into the beginnings of modern man.

“When you put the evidence together, it seems to be speaking to us about the really big questions; what made these people who they were as a species, and who we are as a result,” Willerslev says.

Alongside new genetic details of human mating with Neanderthal, ghost species, and other ancient hominids, the DNA analysis of the Sunghir site adds much to expand the view into our own deep past.

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Calum Mckinney

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  1. Could these persons have been a group of refugees from different tribes or migrants who had to pool their resources?

  2. BS!!!!
    They had no idea of the effects of inbreeding. It was avoided by promiscuity not by any conscious act to avoid something they had no clue about. That same promiscuity which helped the human race is now the leading cause of divorce as it is still part of the human condition.

  3. My ex mother in law was Cherokee. They have a rule that you cannot marry within your clan. She was from the Locust clan, and could only marry into another group. I guess this is where that idea comes from.

  4. Taking female captives during conflicts with competing tribes was no doubt a factor contributing to genetic diversity. Ditto for arranged marriages to cement tribal alliances.

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