Genetic analyses of several Swedish archaeological sites have found unexpected gene flow in Scandinavia at the time of Viking raids against Medieval Britain and Europe.
The study published in Cell found while Vikings were launching their famous attacks on neighbouring regions, their victims were themselves migrating northward into Scandinavia.
Researchers pieced together two millennia of human migration into the region using gene samples from human remains at the site of the fifth century Sandby borg massacre, early medieval cemeteries and burial chambers, and bodies in the 1676 shipwreck of the warship Kronan.
Their results show an influx of British-Irish and Baltic ancestries into the Scandinavian gene pool up to the peak of the late Viking period.
But they were surprised to find these genes were substantially ‘diluted’ in samples extracted from the Kronan ruins, as well as in present-day Scandinavians.
This might indicate migrants failed to procreate successfully, while some migrant groups – like slaves or missionaries – may have been precluded from reproductive opportunities.
“Although still evident in modern Scandinavians, levels of non-local ancestry in some regions are lower than those observed in ancient individuals from the Viking to Medieval periods,” says the study’s lead author Ricardo Rodríguez-Varela.
“This suggests that ancient individuals with non-Scandinavian ancestry contributed proportionately less to the current gene pool in Scandinavia than expected based on the patterns observed in the archaeological record.”
As well as excavations suggesting a diverse range of people having migrated to the region, the analyses also suggest a higher proportion of females moving to Scandinavia among western and Baltic migrants.
Building further understanding of why the medieval period resulted in these ancestries disappearing from the gene pool by the 17th century is next on the list for the research team.
But that might be a challenge, given the scarcity of suitable individuals from that period, as well as ones in the preceding thousand years.
“Individuals from 1000 BCE to 0 are very scarce,” explains Rodríguez-Varela.
“Retrieving DNA from Scandinavian individuals with these chronologies will be important to understand the transition from the Bronze Age to the Iron Age in this part of the world.
“More individuals from the Medieval period until the present will help us to understand when and why we observe a reduction in the levels of non-local ancestry in some current regions of Scandinavia.”
Matthew Agius is a science writer for Cosmos Magazine.
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