Researchers at Uppsala University have used ancient DNA to reveal that Stone Age burials in Sweden involved extended family members beyond immediate relatives. Analysis of shared graves at the Ajvide site on Gotland shows second- and third-degree kin were often buried together, suggesting strong community ties. The findings challenge assumptions about simple family structures in hunter-gatherer societies 5,500 years ago.
The Ajvide burial ground on the island of Gotland stands as one of Scandinavia's key Stone Age sites, dating back 5,500 years. Hunter-gatherers there relied on seal hunting and fishing, maintaining genetic distinction from contemporaneous farming groups in Europe. The site features 85 known graves, with eight containing multiple individuals. A recent study examined four of these shared burials, extracting DNA from teeth and bones of ten people to assess biological sex and kinship.
Biological sex was determined via chromosomes: two X chromosomes for girls, one X and one Y for boys. Relatedness was measured by shared DNA amounts—half for first-degree relatives like parents and children or full siblings, a quarter for second-degree such as half-siblings, and an eighth for third-degree like cousins.
In one grave, a 20-year-old woman lay with a four-year-old boy and a one-and-a-half-year-old girl, who were full siblings. The woman was not their mother but likely their father's sister or a half-sister. Another burial held a young girl and an adult man, identified as her father; his remains appeared relocated from elsewhere. A third grave contained a boy and a girl who shared a third-degree relation, probably as cousins. The fourth featured a girl and a young woman, also third-degree relatives, possibly great-aunt and niece.
"Surprisingly enough, the analysis showed that many of those who were buried together were second- or third-degree relatives, rather than first-degree relatives... This suggests that these people had a good knowledge of their family lineages and that relationships beyond the immediate family played an important role," said archaeogeneticist Helena Malmström, who designed the study.
Population geneticist Tiina Mattila, who led the genetic analyses, noted, "As it is unusual for these kinds of hunter-gatherer graves to be preserved, studies of kinship in archaeological hunter-gatherer cultures are scarce and typically limited in scale."
Archaeology professor Paul Wallin, an Ajvide expert, added, "The analyses provide insight into social organisation in the Stone Age."
This pilot project is the first to apply archaeogenetic methods to Scandinavian Neolithic hunter-gatherers. Researchers aim to analyze over 70 more individuals from the site to further explore social structures and burial practices.
