Welsh people could lay claim to be the most ancient Britons, according to scientists who have drawn up a genetic map of the British Isles.
Research suggests the Welsh are genetically distinct from the rest of mainland Britain.
Professor Peter Donnelly, of Oxford University, said the Welsh carry DNA which could be traced back to the last Ice Age, 10,000 years ago.
The project surveyed 2,000 people in rural areas across Britain.
Participants, as well as their parents and grandparents, had to be born in those areas to be included in the study.
Prof Donnelly, a professor of statistical science at Oxford University and director of the Wellcome Trust centre for human genetics, said DNA samples were analysed at about 500,000 different points.
After comparing statistics, a map was compiled which showed Wales and Cornwall stood out.
Prof Donnelly said: "People from Wales are genetically relatively distinct, they look different genetically from much of the rest of mainland Britain, and actually people in north Wales look relatively distinct from people in south Wales."
While there were traces of migrant groups across the UK, there were fewer in Wales and Cornwall.
He said people from south and north Wales genetically have "fairly large similarities with the ancestry of people from Ireland on the one hand and France on the other, which we think is most likely to be a combination of remnants of very ancient populations who moved across into Britain after the last Ice Age.
"And potentially also, people travelling up the Atlantic coast of France and Spain and settling in Wales many thousands of years ago".
He said it was possible that people came over from Ireland to north Wales because it was the closest point, and the same for people coming to south Wales from the continent, as it was nearer.
However he added: "We don't really have the historical evidence about what those genetic inputs were."
The geography of Wales made it more likely that ancient DNA would be retained.
Because of its westerly position and mountainous nature, Anglo-Saxons who moved into central and eastern England after the Romans left did not come that far west, and neither did the Vikings who arrived in around 900AD.
The professor said modern people from central and southern England had many genetic similarities to modern people in Denmark and Germany.
The mountains were also the reason why DNA may have remained relatively unchanged, as people would have found it harder to get from north to south Wales or into England compared with people trying to move across the flatter southern English counties, making them more likely to marry locally and conserve more ancient DNA.
"In north Wales, there has been relative isolation because people moved less because of geographical barriers," Prof Donnelly said.
He added that some of these factors also held true for the extreme edges of Scotland, while the Orkney islands showed DNA connections to Norway.
The next stage of the research will looking at physical similarities between different groups, in which the team will use photographs of people and make 3D models to measure quantitative similarities between related groups.