Family Ties

Artist’s recreation of the Upper Paleolithic burial site in Sunghir, Russia.

Libor Balák, Antropark

Early humans likely lived in small, geographically isolated family units, which would have made them susceptible to inbreeding. At some point, modern humans developed social systems to limit within-family relatedness, but, largely due to a dearth of archeological evidence, exactly when this increased socialization occurred has been difficult to determine. New genetic analyses of 34,000-year-old human remains from an Upper Paleolithic archeological site in Sunghir, Russia suggests that prehistoric humans were taking steps to avoid inbreeding by the late Stone Age.

Led by Martin Sikora, Associate Professor at the Natural History Museum of Denmark, University of Copenhagen, an international team of scientists sequenced the complete genomes of four individuals thought to have lived in the area around the same time: an adult male, two male children, and the ceremonially-altered bones of a second adult male. They also sequenced genetic material from an adult femur buried with the children. 

The genetic analysis showed that the individuals were related but exhibited no signs of inbreeding. Their degree of relatedness was less than what would be expected if the early humans had randomly mixed and mated. Instead, the results suggest that small groups of up to 25 Upper Paleolithic humans developed social systems and mating behavior to avoid inbreeding and its negative consequences. These individuals may have been part of a larger network in which small groups were connected to a larger community with rules that governed mating behavior. “It’s one of the ways modern-day hunter-gatherers maintain high genetic diversity,” says Sikora.

The research team intends to replicate these results with other remains as much as the availability of genetic material allows, says Sikora. But, he notes, “I’m quite confident that what you see here is a more general feature of populations from that time.” (Science