2,000-year-old Viking genomes revealed the genetics of modern-day Scandinavians

British and Irish ancestry were pervasive in Scandinavia.
Nergis Firtina
Viking ship
Viking ship

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A new study from Stockholm University and deCODE genetics (Reykjavik) scrutinized genetic history across Scandinavia over the past 2,000 years. 

Published in Cell today, the study is based on the examination of 48 newly discovered and 249 previously published ancient human genomes that represent numerous famous archaeological sites, as well as genetic information from more than 16,500 current-day residents of Scandinavia.

As stated in the release, the research also sheds light on Viking-era migratory trends and gene flow (750–1050 CE). It also demonstrates that ancestries that were brought to the region during the Viking era ultimately declined for reasons unknown.

“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,” said Ricardo Rodríguez-Varela of Stockholm University.

“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,” he explained.

2,000-year-old Viking genomes revealed the genetics of modern-day Scandinavians
A bone sample.

They focused on different sites

The goal of the study was not to reconstruct Scandinavian history over time and space. Instead, they were engaged in three distinct research studies that were each centered on a different archaeological site.

“When we were analyzing the genetic affinities of the individuals from different archaeological sites such as the Vendel period boat burials, Viking period chamber burials, and well-known archaeological sites like the Migration period Sandby borg ringfort, known for the massacre that occurred there [in] 500 CE, and individuals from the 17th-century royal Swedish warship Kronan, we start to see differences in the levels and origin of non-local ancestry across the different regions and periods of Scandinavia,” Rodríguez-Varela explained.

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“Initially, we were working with three different studies,”  Anders Götherström from Stockholm University said. “One on Sandby borg, one on the boat burials, and one on the man-of-war Kronan. At some point, it made more sense to unite them to one study on the Scandinavian demography during the latest 2,000 years.”

Gene flow from 3 sources

To better understand the current genetic makeup of the Scandinavian people, it was intended to track the effects of previous migrations on the gene pool over time and space. The researchers discovered regional variation in the time and volume of gene flow from three sources: the eastern Baltic, the British Irish Isles, and southern Europe, as revealed in the new study.

In contrast to eastern Baltic heritage, which is largely restricted to Gotland and central Sweden, British Irish ancestry was pervasive in Scandinavia from the Viking Era. The ancestry of genomes from the Viking and Medieval times and the current levels of external ancestry in some locations show that ancient immigrants contributed proportionately less to the existing Scandinavian gene pool.

Last but not least, the findings demonstrate that a north-south genetic cline that distinguishes contemporary Scandinavians is primarily caused by varying proportions of Uralic ancestry. It demonstrates that this cline was there during the Viking Age and possibly earlier.

“Gene flow from the British-Irish Isles during this period seems to have had a lasting impact on the gene pool in most parts of Scandinavia,” researchers said.

“This is perhaps not surprising given the extent of Norse activities in the British-Irish Isles, starting in the 8th century with recurrent raids and culminating in the 11th century North Sea Empire, the personal union that united the kingdoms of Denmark, Norway, and England. The circumstances and fate of people of British-Irish ancestry who arrived in Scandinavia at this time are likely to have been variable, ranging from the forced migration of slaves to the voluntary immigration of more high-ranking individuals such as Christian missionaries and monks.”