http://www.bbc.co.uk/news/science-environment-42311403
great to see the genetic 'cluster' map for Ireland and Britain
QuoteThe detection of Norwegian-like ancestry in Irish samples probably reflects migrations during the Viking era. While this component is relatively small (a maximum of 20%) compared to the native Irish background, the researchers were surprised to find it at higher levels in the Irish than in the Welsh and English (though at lower levels than those found in the Orkneys, with their traditional ties to Scandinavia).
However, Dr Cavalleri said it was possible the high levels of Norwegian ancestry in the Irish might be confounded if substantial amounts of Irish DNA had found its way to Norway over time: "Perhaps people the Vikings brought back," he speculated.
Now is that not a quintessentially Irish solution to the Norwegian ancestry question? ;)