Researchers have sequenced ancient Irish human genomes for the first time. The study was published in independent.ie.
They discovered that mass migrations to Ireland thousands of years ago caused huge changes to the ancient Irish genetic genome.
A team of geneticists from Trinity College Dublin and archaeologists from Queen's University Belfast made the findings, which show a massive modification in our genetic mix over just 1,000 years.
They believe the genetic influxes brought cultural change such as moving to settled farmsteads, bronze metalworking - and may have even been the origin of western Celtic language.
Researchers studied the genome of a woman farmer who lived 5,200 years ago near what is now Belfast. They also carried out DNA analysis of three men on Rathlin Island from 4,000 years ago in the Bronze Age after metalworking began.
The female farmer had had black hair and brown eyes, like current south Europeans. She lived in the Middle East, where agriculture was invented.
The Bronze Age genomes of the men were dissimilar, with about a third of their ancestry coming from ancient sources by the Black Sea in modern-day Ukraine.
The three men's genomes showed significant difference, with one-third of their ancestry from the Pontic Steppe.
There were also signs that they were lactose tolerant, and suffered from haemochromatosis - excessive iron retention - a disease commonly called the 'Celtic curse'.
Professor in Trinity College Dublin Dan Bradley, who led the study, said a genome was the sum of all our genetic material.
"Every genome comes from two parents, four grandparents, eight great-grandparents and so on -it's a sample, not only of a person but of a community. You can use that to figure out how the community they come from related to other communities. You're building up a picture of how they relate to us today," he said
The landmark results are published today in international journal 'Proceedings of the National Academy of Sciences, USA'.