The medieval Icelandic text, The Book of Settlements, hints that many of the island's first female settlers came from the British Isles, rather than migrating from Scandinavia with the men. Now a genetic study backs up folklore. A study of mitochondrial DNA (mtDNA) in North Atlantic islands suggests that as much as 60% of Iceland's original female population was British, even though the majority of male settlers came from Scandinavia.
During the 8th to 11th centuries, Vikings conquered and settled large swathes of Northern Europe, including northwestern Britain. From there they colonized the islands of the North Atlantic, some of which already had small indigenous Gaelic populations (the Celtic people of Scotland and Ireland). A number of studies have used genetic markers to determine the proportion of Viking and Gaelic ancestors among the settlers on Iceland. But estimates for the Scandinavians ranged from 2% to 86%.
The new study focused instead on mtDNA. Because mtDNA is only inherited through eggs, and not through sperm, researchers can reconstruct maternal lineages. Geneticists led by Agnar Helgason of deCODE Genetics in Reykjavik and the University of Oxford analyzed mtDNA from 1664 volunteers in the U.K., Scandinavia, and the North Atlantic islands, as well as other parts of Europe. They then estimated the most likely proportion of various mtDNA lineages in original settlers that explained the observed distributions of mtDNA lineages today. The study indicated that 60% of Iceland's original female settlers were Gaelic. Unexpectedly, it turned out that Viking women were the ancestors of some modern British Islanders, such as those of Orkney (35% Scandinavian mtDNA), the Western Isles (12%), and the Isle of Skye (12%), the researchers report in the March edition of the American Journal of Human Genetics.
The same team reported last year, based on Y chromosome analysis, that 80% of Iceland's early male settlers came from Scandinavia. The two studies suggest that men and women don't always migrate together, says Helgason. The group speculates that Viking men took brides from Gaelic settlements before migrating to Iceland and other North Atlantic islands.
"Studies of this kind have not been done in Iceland before, and are so interesting, as it is the most recent landmass in Europe to be colonized," says Mark Tomas, a genetic anthropologist at University College London. The study is part of a wider initiative, the ambitious Oxford Genetic Atlas Project, which is intended to characterize the genetic diversity which exists within the people of the British Isles.