The Viking maritime expansion from Scandinavia (Denmark, Norway, and Sweden) marks one of the swiftest and most far-flung cultural transformations in global history. During this time (c. 750 to 1050 CE), Viking sailors reached Greenland, North America, and large parts of western Eurasia, and left a legacy that persists today. To understand the genetic structure and influence of the Viking expansion, we sequenced the genomes of 442 ancient humans from across Europe and Greenland ranging from the Bronze Age (c. 2400 BCE) 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.

We have identified a variant in adenylate cyclase 3 (ADCY3) associated with markedly increased risk of obesity and type 2 diabetes in the Greenlandic population. The variant disrupts a splice-acceptor site and carriers display decreased ADCY3 RNA expression. Additionally, we observe an enrichment of rare ADCY3 loss-of-function variants among type 2 diabetes patients in trans-ethnic cohorts. These findings provide novel information on disease etiology relevant for future treatment strategies.

87 The Viking maritime expansion from Scandinavia (Denmark, Norway, and Sweden) marks one 88 of the swiftest and most far-flung cultural transformations in global history. During this time 89 (c. 750 to 1050 CE), the Vikings reached most of western Eurasia, Greenland, and North 90 America, and left a cultural legacy that persists till today. To understand the genetic structure 91 and influence of the Viking expansion, we sequenced the genomes of 442 ancient humans from 92 across Europe and Greenland ranging from the Bronze Age (c. 2400 BC) to the early Modern 93 period (c. 1600 CE), with particular emphasis on the Viking Age. We find that the period 94 preceding the Viking Age was accompanied by foreign gene flow into Scandinavia from the 95 south and east: spreading from Denmark and eastern Sweden to the rest of Scandinavia. 96Despite the close linguistic similarities of modern Scandinavian languages, we observe genetic 97 structure within Scandinavia, suggesting that regional population differences were already 98 present 1,000 years ago. We find evidence for a majority of Danish Viking presence in England, 99 Swedish Viking presence in the Baltic, and Norwegian Viking presence in Ireland, Iceland, and 100Greenland. Additionally, we see substantial foreign European ancestry entering Scandinavia 101 during the Viking Age. We also find that several of the members of the only archaeologically 102 well-attested Viking expedition were close family members. By comparing Viking Scandinavian 103 genomes with present-day Scandinavian genomes, we find that pigmentation-associated loci 104 have undergone strong population differentiation during the last millennia. Finally, we are able 105 to trace the allele frequency dynamics of positively selected loci with unprecedented detail, 106 including the lactase persistence allele and various alleles associated with the immune response. 107We conclude that the Viking diaspora was characterized by substantial foreign engagement: 108 distinct Viking populations influenced the genomic makeup of different regions of Europe, 109 while Scandinavia also experienced increased contact with the rest of the continent. 110 111

No abstract