By mapping the DNA of people buried in the megalithic graves at Falbygden, archaeologists from the University of Gothenburg - working in partnership with geneticists from the University of Copenhagen - have been able to answer questions about how the plague spread at Falbygden and how the individuals in the graves are related to each other. The study has been published in the prestigious scientific journal Nature.
Archaeologists from the University of Gothenburg may have worked out why Scandinavia's population shrank around 5,000 years ago. Repeated outbreaks of plague are thought to be the reason why this happened. The researchers have analysed DNA from more than 100 individuals from different graves, mostly from megalithic graves in Sweden's Falbygden area. The study was carried out together with geneticists from the University of Copenhagen.
"We can follow the development of the plague in detail," says Karl-Göran Sjögren, a reader in archaeology who is one of the researchers behind the study. "It's not the same plague - it evolves with each generation. We've identified three different variants of the plague."
Between 5,300 and 4,900 years ago, the population of Scandinavia shrank. Researchers refer to this as the Neolithic decline. Various theories have been proposed over the years, with plague being one of them. However, it is not known whether early outbreaks could have caused widespread epidemics or just smaller, isolated outbreaks.
To investigate outbreaks of plague in Scandinavia before and during the Neolithic decline, DNA was sequenced from 108 individuals buried in passage graves in Falbygden and the surrounding area.
"We found traces of the plague-carrying bacterium Yersinia pestis," adds Frederik Seersholm, a geneticist at the University of Copenhagen. "It turned out that 18 of these 108 individuals, or 17%, had been infected with plague when they died."
This shows that at least three waves of the plague spread through society over the course of around 120 years. The first two waves were small and limited, but the third was more widespread within the population.
The study also provides an insight into how Falbygden's Stone Age society was organised. The researchers have used DNA analysis to show that four men had multiple children with different women, but have not found any evidence of women having had children with more than one man. Kinship within the graves follows the male line, with women being included from other groups. This is exemplified by a woman who was buried in a different grave to her two brothers.
"We can also show that the kinship group in the passage grave at Frälsegården was divided up into two subgroups, which were buried in separate parts of the burial chamber," concludes Karl-Göran.
The study Repeated Plague Infections Across Six Generations of Neolithic Farmerhas been published in the scientific journal Nature.www.nature.com/articles//s41586-024-07651-2
