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- Irish, Scots & Welsh show higher French than the English.
- Irish & Scots have more Norwegian than the Welsh or English.
- England has more German & Danish.
A striking result of our admixture analysis is the surprising amount of Norwegian-like ancestry in our Irish clusters. We also detected high levels of Norwegian ancestry in Orcadian and Scottish clusters, and relatively low Norwegian ancestry in English and Welsh clusters. The Norwegian clusters that contribute significant ancestry to any Irish or British clusters predominantly consist of individuals from counties on the north or western coasts of Norway.
These areas are noted to be regions where Norse Viking activity originated from.
Whilst this surprising Norwegian signal in Ireland is most likely due to Norwegian admixture into Ireland, indeed this would corroborate with accounts of Irish slave trade in the Viking era.To test this hypothesis we ran an additional regression admixture analysis, this time modelling Norwegian haplotypes as a mixture of Irish, British, or European haplotypes (Supplementary Data 6). We observe significant proportions of Irish, Scottish, and Orcadian ancestry in modern Norway (6.82%, 2.29%, and 2.13%, respectively), particularly western Norway. This could provide evidence for Irish admixture back into Norway, but could also easily be explained by Norwegian haplotypes existing in Ireland, Scotland, and Orkney. Therefore, we are able to provide an upper estimate of ~20% Norwegian ancestry within Ireland, but unable to provide an empirical lower limit.
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