Genetic evidence for a family-based Scandinavian settlement of Shetland and Orkney during the Viking periods.

The Viking age witnessed the expansion of Scandinavian invaders across much of northwestern Europe. While Scandinavian settlements had an enduring cultural impact on North Atlantic populations, the nature and extent of their genetic legacy in places such as Shetland and Orkney is not clear. In order to explore this question further, we have made an extensive survey of both Y-chromosomal and mitochondrial DNA (mtDNA) variation in the North Atlantic region. Our findings indicate an overall Scandinavian ancestry of approximately 44% for Shetland and approximately 30% for Orkney, with approximately equal contributions from Scandinavian male and female subjects in both cases. This contrasts with the situation for the Western Isles, where the overall Scandinavian ancestry is less ( approximately 15%) and where there is a disproportionately high contribution from Scandinavian males. In line with previous studies, we find that Iceland exhibits both the greatest overall amount of Scandinavian ancestry (55%) and the greatest discrepancy between Scandinavian male and female components. Our results suggest that while areas close to Scandinavia, such as Orkney and Shetland, may have been settled primarily by Scandinavian family groups, lone Scandinavian males, who later established families with female subjects from the British Isles, may have been prominent in areas more distant from their homeland.