The genomics of the Viking Age

A huge new preprint on Vikings (as well as the Bronze Age, Iron Age, and comparisons to moderns), Population genomics of the Viking world:

…we sequenced the genomes of 442 ancient humans from across Europe and Greenland ranging from the Bronze Age (c. 2400 BC) to the early modern period (c. 1600 CE), with particular emphasis on the Viking Age. We find that the period preceding the Viking Age was accompanied by foreign gene flow into Scandinavia from the south and east: spreading from Denmark and eastern Sweden to the rest of Scandinavia. Despite the close linguistic similarities of modern Scandinavian languages, we observe genetic structure within Scandinavia, suggesting that regional population differences were already present 1,000 years ago. We find evidence for a majority of Danish Viking presence in England, Swedish Viking presence in the Baltic, and Norwegian Viking presence in Ireland, Iceland, and Greenland. Additionally, we see substantial foreign European ancestry entering Scandinavia during the Viking Age. We also find that several of the members of the only archaeologically well-attested Viking expedition were close family members. By comparing Viking Scandinavian genomes with present-day Scandinavian genomes, we find that pigmentation-associated loci have undergone strong population differentiation during the last millennia. Finally, we are able to trace the allele frequency dynamics of positively selected loci with unprecedented detail, including the lactase persistence allele and various alleles associated with the immune response. We conclude that the Viking diaspora was characterized by substantial foreign engagement: distinct Viking populations influenced the genomic makeup of different regions of Europe, while Scandinavia also experienced increased contact with the rest of the continent.

A few notes:

– Though the broad patterns seem to have been established with the expansion between 3,000 and 2,500 BC from the Yamnaya steppe (at least in Northern Europe), some subtle details in genome-wide ancestry shifted in subsequent periods. This data set seems to show a decline in “Neolithic Farmer” and increase in hunter-gatherer and steppe ancestry after the Bronze Age, with some increase in the former by the Viking Age. This suggests that there is some sort of skew in sampling which misses populations enriched for hunter-gatherer ancestry (I suspect these groups live in the most marginal land and are the most mobile).

– There is structure by the Viking Age, which is not surprising. But the authors also report a few regions of southern Sweden where samples are enriched for Neolithic farmer ancestry down to the Viking age, suggesting that even ancient structure wasn’t well mixed (yet).

– Most of the selection for the phenotype which characterizes modern-day Northern European populations seem to have completed over the 2,000 years between the Bronze Age and the Viking Age.