Over the last 2000 years the British Isles, original home of the Celts, were repeatedly ravaged by invading hordes from the continent including the Romans, Vikings, Angles, Saxons, and Normans. Now the most extensive molecular study yet attempted shows that these invasions have had a significant effect on the genetic heritage of the British people.
The findings, detailed today in Current Biology, reveal remarkable levels of regional variation of Y chromosome markers in small towns across the U.K. and confirm archaeological evidence that men from Scandinavia and Germany replaced or contributed to indigenous populations. Y chromosomes are only present in men and are thought to be passed on 95% unchanged from father to son. In this way, they provide a unique record of male ancestry.
The survey was completed by population geneticists led by David Goldstein and Cristian Capelli at University College London and the British Broadcasting Corp. (BBC). The BBC first approached Goldstein in 2001 to collaborate on a genetic survey for the television documentary series Blood of the Vikings. Using the BBC's resources to market the project, the team enlisted more than 1700 male volunteers from 24 small towns across the nation. These men, who had to be able to trace their ancestry back several generations in the same town to qualify for the study, donated blood samples via mobile units of the National Blood Service or by submitting cheek-cell swabs through the mail.
The scientists compared these data with 400 DNA samples collected in Denmark, Germany, and Norway. The analysis revealed that 60% of men in northern Scottish islands have Norwegian Viking ancestry. It also revealed that the majority of men in some parts of east and central England show some Danish Viking or Anglo-Saxon ancestry. Y chromosomes from Wales and Ireland suggest that little continental DNA made it that far west. Surprisingly, the analysis revealed that men in southern England have almost as much Celtic ancestry as the more typically Celtic Scots.
"I waited with anticipation for this … impressive data set," comments Agnar Helgason, a biological anthropologist with deCODE Genetics in Reykjavik, Iceland. The lack of Norwegian ancestry in mainland Scotland is interesting, says Helgason, because it complements his own research suggesting that most male Norwegian settlers eventually moved on to Iceland with Scottish women in tow (ScienceNOW, 16 March 2001).