The Irish were there in numbers when the settlement of Iceland got underway some time around 800AD. Genetic analysis has shown that a quarter of the men and up to half of the women among the founding population would have been of "Gaelic" origin.

What is not clear is the status of these settlers. They could have arrived as immigrant families or might have been dragged there to work as slaves.

Mr Agnar Helgason, an Icelander studying at Oxford University, is the main author of a research report analysing the genetic origins of his country. The report was recently published in the American Journal of Human Genetics, and included the participation of researchers from Trinity College Dublin, deCODE Genetics Inc of Reykjavik (where Mr Helgason also works) and the blood-bank in Oslo, Norway.

The work got underway when Dr Dan Bradley, a lecturer in genetics at Trinity and an expert in genetic anthropology, met Mr Helgason at a conference in Oxford. "We agreed it might be great if we could add an Irish dimension to the story of Gaelic origins in Iceland," Dr Bradley said. "There is a whole body of lore in Iceland which involves their Irish ancestry." The new study was an attempt to assess the origins of the male founders by looking for genetic markers in the Y chromosomes of men living in Iceland today. "The Y chromosome is very good for distinguishing populations," Dr Bradley explained.

It is passed on from father to son like a person's surname, he said. Its DNA includes "neutral markers" which are unique to individual populations of men. These "fingerprints" could be compared between populations to establish the relatedness of the various groups.

The study included 181 Icelanders, 233 Scandinavians and 283 "Gaels" from Ireland and Scotland. "Gaelic" was the preferred term in the study, given the fact that the Vikings in 800AD populated both eastern Ireland and also the Western Isles of Scotland, explained Mr Helgason. They would have interacted with this broader Gaelic population.

The study showed that between 20 and 25 per cent of Icelandic founding males had Gaelic ancestry, with the remainder having Norse ancestry, Mr Helgason said. These findings match up with earlier work done by Mr Helgason which looked at mitocondrial DNA in women. This DNA is only passed from mother to daughter and so gives a picture of female lineages, he said. The mitocondrial work showed that about half of Iceland's founding females were of Gaelic ancestry.

"This supports the model, put forward by some historians, that the majority of females in the Icelandic founding population had Gaelic ancestry, whereas the majority of males had Scandinavian ancestry," he stated in his paper.

"The genetic evidence really doesn't tell us who they were," he said - but there was room to speculate. "In some cases, they were established family groups, but most of the Vikings who were raiding and forming ad hoc armies in Ireland and Britain were young men."

Many tried to settle in Ireland and Scotland, "but apparently just around the time that Iceland was being settled, there was a bit of trouble. The Irish kings ganged together to drive out the Vikings," he said.

"It is not inconceivable that the men who had come over from Scandinavia and lived for a time in the British Isles would have taken wives and then travelled to Iceland," he added.

Some Gaelic men could have travelled with them, he said, people who lived in or near early Norse settlements such as Dublin or Wexford. Or they might have been taken away against their will. "It is known there was a significant number of slaves they took there," he said.

What is not in doubt, however, is that a large proportion of the earliest Icelandic settlers reached Iceland from these islands. This accounts for the surprise felt by many Irish who visit Iceland when they see people walking down the streets of Reykjavik who look so Irish they could have been plucked from the streets of Dublin. Perhaps their ancestors were.