A 5,500-year-old burial site in Sweden is offering rare insight into Stone Age social structures, showing that family ties shaped how some hunter-gatherer communities buried their dead. The study found that people placed in shared graves were not buried together by chance. They were close biological relatives, suggesting kinship played a clear role in burial customs.
The findings come from the Ajvide cemetery on the island of Gotland, one of the largest and best-preserved burial grounds linked to the Pitted Ware Culture, a late Stone Age hunter-gatherer society. Researchers say the site offers an unusual chance to study how these communities organized themselves at a time when such evidence is often scarce.
Lead author Tiina Maria Mattila of the Department of Organismal Biology at Uppsala University in Sweden and her colleagues analyzed DNA from 10 people from Ajvide, most of them taken from graves that held more than one person.
Stone Age social structures emerge from family-based burial patterns
The team combined those results with previously published genomes from 24 other people buried at four Pitted Ware Culture sites on Gotland. The study was published in Proceedings of the Royal Society B.
The results showed a clear pattern. Every shared burial examined at Ajvide contained people who were closely related, including first-, second-, and third-degree relatives. That means the links went beyond parents and children or brothers and sisters.
In one grave, researchers identified a father buried with his daughter. In another case, two young children were full siblings. In other shared graves, the people were more distantly related, such as third-degree kin.
The study also found that children appeared in shared burials far more often than expected by chance. Six of the seven well-documented multi-person burials at Ajvide included at least one child. Researchers said that points to age, along with family ties, as an important part of burial practice.
Children and close kin shaped burial choices at Ajvide
The genetic data also showed that the Pitted Ware people on Gotland were closely connected across different sites. Researchers found close relatives not only within Ajvide, but also between people buried at separate locations on the island. That suggests these groups mixed with one another rather than living as isolated communities.
At a broader level, the DNA showed that the Pitted Ware population on Gotland had mixed ancestry. About 80% came from earlier Mesolithic hunter-gatherers, while about 20% traced to farming groups. Even so, researchers found no sign of later ancestry linked to Battle Axe Culture groups.
The study also found no strong evidence of close inbreeding, despite signs of a relatively small population over time.
Researchers said the results help answer a long-standing question about how Stone Age hunter-gatherers organized social life. At Ajvide, burial patterns suggest biological family ties mattered deeply and that those ties extended beyond the closest relatives.
