Wednesday, August 10, 2005

Vikings: family guys

A nice article in the journal Heredity reviews genetic evidence of the last decade to re-assess the Viking image. In contrast to their reputation as "smash and grab" raiders, Vikings colonized islands in the North Atlantic islands (for example, the Shetlands) with both men and women, and it can be seen in the DNA of their descendants.

The evidence comes from the separate inheritance patterns of the Y-chromosome (passed from father to son) and mitochondrial DNA (inherited only from the mother). If Vikings were exclusively marauders, you would expect a male-dominated inheritance, so that the descendants would show Nordic origins on the Y-chromosome but not mtDNA. Admixture analysis shows a large Scandinavian input into the Shetland (about 44%), Orkney (about 30%) and the northwest coast of Scotland. But these contributions are both maternal and paternal, suggesting that whole families made the trip.

In contrast, Iceland seems to show an excess of Y-chromosome Scandinavian input. The review suggests that more distant areas might have been settled by unattached males. I guess the real "smash and grab" areas might be expected to have minimal lasting Scandinavian input.

I'd be curious to see what the deal was for Ireland, and also Russia. There is a tie-in to a human mutation, CCR5-delta32, which has gotten attention recently because it confers resistance to HIV. This mutation may have been spread by Vikings in their travels down the Volga. The map from that work suggests a very widespread Viking genetic impact.

In the end, the genetic data are already jiving pretty well with archaeological evidence. For example, the review mentions a Norse graveyard in the Isle of Man which had only male skeletons.

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