While many might assume that the Irish have a strong Celtic legacy which shows itself in their DNA today, a new study has shown that they also have DNA left over from the many Viking invasions that occurred during the 8th century.

To conduct the survey, DNA was taken from 6,000 residents of Britain and mainland Europe and 1,000 Irish residents and was then tested and analyzed to learn more about the different genetic makeup of these individuals.

Scientists discovered 23 genetic clusters which linked Irish and British residents to strikingly similar groups, with the vast majority of these found in the west of Ireland, according to Newsweek.

The study also showed how frequent migration between the two islands, coupled with the intermingling between those from Ulster and Scotland, shaped the DNA seen today in Ireland and Britain, as the Irish Times report.

In their “fine-grained picture of Irish and British ancestry,” Trinity College Dublin professor Russell McLaughlin, one of the study’s authors, explained that the different clusters of the British and Irish are “closely tied to geography on the islands, along with differing influence from historical migrations.”

With regard to the amount of Viking DNA in the modern Irish individual today, McLaughlin has said that even if a precise amount cannot currently be determined, Viking DNA was uniformly found throughout Ireland.

“We can’t say for certain exactly how much Viking is in modern Irish people, but we can say that it was found among people from all different parts of the island, signifying a compelling connection among the population as a whole.”

Irish people may have more Viking DNA than we thought https://t.co/i8BU9PFa0Npic.twitter.com/phgSSAJYkW — Newsweek (@Newsweek) January 27, 2018

Ph.D. student Ross Byrne, the lead author of this study, has said that when previous work was conducted that tested Y-chromosome DNA, there appeared to be very little Viking DNA remaining in the modern Irish.

However, in those cases, Byrne noted that “these older studies used less than 1 percent of the available genetic information and focused only on signals that could be read through the paternal line, which may not tell the entire story,” and that the latest research shows that “there is indeed a small but noticeable legacy of Viking influence in Ireland.”

Dr. Russell McLaughlin has said that one of the main purposes of this new research is to help scientists better understand rogue genes that can cause diseases in individuals, and part of doing this means learning more about the differences found in the genetic makeup of these clusters of people.

“We are interested in understanding how genes can influence our risk of developing certain conditions, but fine-scaled differences in ancestry can obscure our data. Understanding these ancestral differences helps us to zero in on genes that cause diseases.”

If you are interested in learning more about the new study that examines the 23 genetic clusters of people in Ireland and Britain and links Irish DNA to the Vikings, you can read the study in its entirety in the journal, PLOS Genetics.