The first genetic map of the Irish reveals geographic clusters that reflect the impact of immigration, invasion, and plantation. Seven of those clusters show Gaelic ancestry, aligned with the borders of ancient kingdoms, while three show a shared ancestry with the British.

Researchers led by the Royal College of Surgeons in Ireland (RCSI) and the Genealogical Society of Ireland (GSI) have published ‘The Irish DNA Atlas: Revealing Fine-Scale Population Structure and History within Ireland’ in the journal, Scientific Reports.

The landmark study is the first fine-scale genetic map of Ireland, revealing patterns of genetic similarity in 10 clusters, roughly corresponding with the ancient provinces, as well as with major historical events, including Viking invasions and the Ulster Plantations.

These findings can contribute to the diagnosis of diseases in which genes play a strong role, particularly for populations of Irish ancestry.

Findings from this study will be of help to the new FutureNeuro Science Foundation Ireland Research Centre, which is seeking to improve the diagnosis of rare neurological disorders and to personalise treatment.

Edmund Gilbert of the RCSI, first author on the paper, said: “We have demonstrated that the structure emerging from genetic similarity within Ireland mirrors historical kingdoms of Ireland, and that Ireland acts as a sink of Celtic ancestry.

“Additionally, we find evidence of a west-Norwegian-like ancestry that we believe is a signature of the Norse Vikings.

“We also observe the impact of historical events, such as the Ulster Plantations, on the DNA of the people of Ireland.”

Co-author Michael Merrigan, of the GSI, said the study challenges the accepted narratives on the origins of the people of Ireland.

“We now get a clearer, scientifically-based map of the distribution and settlement of our ancestral groups across the island of Ireland,” he said. “Historians and students of medieval Ireland have now a wonderful resource on the movements and inter-relationships of our ancestor groups through their DNA.”

He said the study will open up new research opportunities for many disciplines, especially those researching Irish medieval genealogies and the history of Irish clans.

It also reveals relatively high levels of Northwest French (probably Celtic) and Norwegian-like (probably Viking) ancestry in Ireland.

“Having a genetic map of the Irish population will be invaluable in studies of the genetic component of some common diseases in the Irish population, especially those diseases which show a difference in prevalence rates across the island of Ireland,” said Sean Ennis, a co-author of the paper.