For thousands of years the Eurasian steppes have been a centre of human migrations and cultural change. Here we sequence the genomes of 137 ancient humans (about 1× average coverage), covering a period of 4,000 years, to understand the population history of the Eurasian steppes after the Bronze Age migrations. We find that the genetics of the Scythian groups that dominated the Eurasian steppes throughout the Iron Age were highly structured, with diverse origins comprising Late Bronze Age herders, European farmers and southern Siberian hunter-gatherers. Later, Scythians admixed with the eastern steppe nomads who formed the Xiongnu confederations, and moved westward in about the second or third century BC, forming the Hun traditions in the fourth-fifth century AD, and carrying with them plague that was basal to the Justinian plague. These nomads were further admixed with East Asian groups during several short-term khanates in the Medieval period. These historical events transformed the Eurasian steppes from being inhabited by Indo-European speakers of largely West Eurasian ancestry to the mostly Turkic-speaking groups of the present day, who are primarily of East Asian ancestry.

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.

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

with In this Article, Angela M. Taravella and Melissa A. Wilson Sayres have been added to the author list (associated with: School of Life Sciences, Center for Evolution and Medicine, The Biodesign Institute, Arizona State University, Tempe, AZ, USA). The author list and Author Information section have been corrected online.

No abstract