The findings emerge from the first work to sequence the genomes — genetic codes made up of three billion parts buried in our DNA — of ancient Irish people.
A farmer woman who lived near Belfast 5,200 years ago had dark hair and brown eyes, according to information in her genome which was sequenced by researchers at Trinity College Dublin.
However, this distinguishes her from what is known of hunter gatherers who had lived here in earlier periods.
“Instead she looked like other early farmers from Spain or Turkey, where farming had been brought from the Middle East,” said Dan Bradley, professor of population genetics at TCD.
The findings may strengthen arguments that farming was a practice brought by people arriving by sea to Ireland from Europe, or beyond, rather than the native population adopting it independently.
However, the cross-border collaboration with archaeologists at Queen’s University Belfast also found evidence from the genomes of three more recent pre-historic remains — three Bronze Age men buried on Rathlin Island around 4,000 years ago — that some of the migratory patterns into Ireland may have slowed by then.
Because their genomes are much nearer those of modern Irish people than the earlier farmer woman’s, Prof Bradley says it looks like our own genes were beginning to be established around that time.
Although they lived more than a millenium after the Belfast woman, with her dominant Middle East ancestry, one-third of the men’s ancestry is from ancient sources in the Pontic Steppe around modern Ukraine and the Black Sea.
Among the traits found in Bronze Age men was a genetic variant for the iron retention disease, haemo-chromatosis, that is more prevalent in modern Irish people than elsewhere in the world.
Prof Bradley said it is the first time a genetic variant for disease has been found in ancient genomes.
The results, published in Proceedings of the National Academy of Sciences USA, are just a taste of what may emerge in the next few years.
Dozens more genomes from around the island are being sequenced, and should show if the traits in these four ancient people were unique to the north of Ireland or to the periods in which they lived.