Genetic snapshot of Icelandic population 1000 years ago published

21 January 2009

deCODE genetics has presented the results of the largest study of ancient DNA from a single population ever undertaken. Analyzing mitochondrial DNA, which is passed from mother to offspring, from 68 skeletal remains from approximately 1000 years ago, the study provides the most detailed look to date at how a contemporary population differs from that of its ancestors.

The results confirm previous deCODE work that used genetics to test the history of Iceland as recorded in the sagas. These studies demonstrated that the country seems indeed to have been settled by men from Scandinavia — the Vikings — but that the majority of the original female inhabitants were from the coastal regions of Scotland and Ireland, areas that regularly suffered raids by Vikings in the years around the settlement of Iceland 1100 years ago.

Perhaps the most remarkable finding of the study is that the gene pool of contemporary Icelanders appears to have evolved rapidly over the intervening thousand years. As a result, the original female settlers are genetically more closely related to the present day populations of Scotland, Ireland and Scandinavia, as well as those of northwestern Europe and even southwestern Europe, than they are to present day Icelanders.

This is an important demonstration of a phenomenon known as 'genetic drift.' In essence, in any population certain individuals will have more offspring and, by chance and in this case over the course of 35 generations, many more descendants than others. And as a result, particularly in a small population, the genetic variety of the original population can decrease and change over time.

In this study only mitochondrial DNA was studied, but the same phenomenon applies to the Y chromosome, which is passed from fathers to sons, and to any other part of the genome. The paper, Sequences from first settlers reveal rapid evolution in Icelandic mtDNA pool, is published in the open-access journal PLOS Genetics.

Kari Stefansson, CEO of deCODE said, "This study is a major contribution to the use of ancient DNA studies in tracing the history not just of single populations, but of our species and how we spread from Africa to every corner of the globe. It is the first such study to be large enough to permit meaningful statistical methods to be applied to ancient DNA. We very much hope this will aid and encourage others to follow with large studies in other parts of the world. In this field, as in the genetics of common diseases, we are pleased and proud to be able to put the knowledge we gain in Iceland to work for the benefit of people everywhere."

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