Stone Age burial ground reveals deep family trees
If you could share your grave with anyone, who would it be? Researchers investigating the genetic relationships between people buried at the Swedish Stone Age site of Ajvide have revealed that those buried together were not always immediate relatives.
“Quite surprisingly, the analysis showed that many of those who were buried together were second- or third-degree relatives, rather than first-degree relatives – in other words, parents and children or siblings – as is often assumed,” Helena Malmström, an archaeogeneticist at Uppsala University, said in a statement. “This suggests that these people had a good knowledge of their family lineages and that relationships beyond the immediate family played an important role.”
Malmström and colleagues describe their findings in a study recently published in the journal Proceedings of the Royal Society B Biological Sciences. They studied the relationships between individuals in four tombs from a hunter-gatherer culture that existed in the Ajvide archaeological complex on the Swedish island of Gotland around 5,500 years ago. While agriculture was widespread in Europe, hunter-gatherer cultures remained further north.
DNA analysis of the deceased in these four graves revealed a set of unexpected relationships. One grave contained a 20-year-old woman with a four-year-old child on one side and a toddler on the other. The two children are full siblings and the woman is likely their aunt or half-sister. Another grave contained a young girl next to her adult father’s remains, which were probably originally located elsewhere.
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The third grave contained two children with a third-degree relationship – probably cousins ​​– and the fourth grave contained a young woman and a girl, also third-degree related. It is likely that one of them was the cousin or great-aunt of his deceased friend. The four graves represent only half of the eight common graves identified at a funerary site of 85 burials known to researchers.
“The analyzes provide insight into social organization in the Stone Age,” said Paul Wallin, an expert on Ajvide cemeteries.
The team used DNA taken from their bones and teeth to determine the sex and blood relationships of the hunter-gatherers. Although the children’s skeletons did not indicate their gender, the researchers were able to determine whether they had one X and one Y chromosome or two X chromosomes, which would mean male or female, respectively.
As for their relationships with other people in the cemetery, this was revealed by the amount of shared DNA. For example, half of the DNA of first-degree relationships is the same. For second-degree relationships (half-siblings or grandparents-grandchildren), it is a quarter. And for the third degree (great-grandparents/great-grandchildren or cousins), it’s an eighth.
“As it is unusual for this type of hunter-gatherer graves to be preserved, studies of kinship in archaeological hunter-gatherer cultures are rare and generally limited in scale,” said Tiina Mattila, a population geneticist at Uppsala University and co-author of the study.
In the future, the team hopes that interdisciplinary studies of the remains of more than 70 people from the same site will shed light on more aspects of the life history, burial practices and social organization of ancient hunter-gatherer cultures.
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