DNA analyses carried out on samples from the present day inhabitants of Great Britain and Norway give a good indication of the extent to which the two populations mingled during the Viking era.
‘Norwegian’ DNA varies between 1% in Wales and Ireland to 29% in Orkney and Shetland, areas which the Vikings basically took over.
On the other side of the North Sea, Norwegian men have 5% of the Celtic Y/chromosome R1b/S145. The chromosome is particularly common in the western counties of Nordland, Troendelag, Møre and Romsdal and Hordaland. It is well known that the Vikings who plundered the British Isles in the 9th and 10th centuries were not only interested in gold and silver but also in slaves, mainly women and children. .
Many of the women and children were sold as slaves in southern Europe while others were brought back to Norway to the regions from where the voyages left. Thus the occurrence of the ‘Celtic’ chromosome in men from west Norway. As time went on the Viking settlements became more permanent and the Norwegians married local women. This explains the high percentage of Nordic DNA in the northern parts of Britain