Scientists create genetic map of Britain to chart immigration since the Ice Age

By Ben Miller | 19 March 2015

Scientists compare DNA samples from 2,000 Brits with people from across Europe to draw new conclusions from 10,000 years of immigration

A photo of a map divided into different colours showing the British Isles population
A new study by an international team has split the British Isles into genetic clusters© University of Oxford
The people of Britain can be divided into 17 genetic groups strongly based on where they live, according to extensive new evidence which debunks a number of long-held ancestral beliefs and gives scientific support to the tribal affiliations many people feel for their place of birth.

Using DNA samples from more than 2,000 people in rural regions, all of whom had four grandparents born close to each other, a cross-disciplinary team have drawn far-reaching new conclusions about the way regions changed before the major population movements of the 20th century.

Strong traces of the earliest settlers following the last Ice Age were detected throughout the UK, although Wales produced the highest proportion of this early British DNA. Once each cluster had been set out, the researchers compared the samples with evidence from more than 6,200 people across ten European countries with migration links to the British Isles.

“Our study focused on people in the UK of European ancestry,” Peter Donnelly, the Director of the Wellcome Trust Centre for Human Genetics at the University of Oxford, told the science journal Nature.

A photo of a map divided into different colours showing the British Isles population
The first settlers after the Ice Age, at the end of the Paleolithic-Early Mesolithic period between 9600 and 7500 BC© University of Oxford
“To a first approximation, these people look extremely similar genetically. What we were able to do, though, was delve under the surface and look at quite subtle but real differences.

“We looked at the clusters that came out of the genetic analysis and plotted those on a map of Britain to see what they revealed.

“We had no idea what to expect. The patterns we saw were quite extraordinary: two counties right next to each other, Devon and Cornwall, each corresponded to different genetic groups.”

Cutting-edge technological and statistical techniques helped experts, including co-authors from University College London and Australia, to confirm the influence of post-6th century tribes and kingdoms and dispel the idea of a single Celtic pool of genes: the Celtic parts of the country – Scotland, Northern Ireland, Wales and Cornwall – were among the most disparate from each other.

A photo of a map divided into different colours showing the British Isles population
Britain within and beyond the Roman Empire between 43 and 410© University of Oxford
“There are two different forces that would result in the pattern of differences that we see,” explained Donnelly.

“One of them is that there will be different inputs of DNA through migrations from Europe; the other effect – particularly in smaller groups, like the islands in Orkney – is that when populations evolve over time in a way that is relatively isolated from each other, then just by chance genetic differences will accrue between them.”

Orkney, in fact, had the most genetically distinct population, with a quarter of its DNA coming from Norway, suggesting that the Norse Viking invasion of the 9th century added to rather than replaced the characteristics of the indigenous settlers.

A similar story could be seen among Anglo-Saxons, who affected dramatic changes to the language, crops, place names and pottery styles of Britain.

A photo of a map divided into different colours showing the British Isles population
Irish, Britons and Anglo-Saxons in 600© University of Oxford
“There’s been a long-standing controversy among historians about what happened when the Anglo-Saxons arrived in the UK,” observed Donnelly.

“A typical Anglo-Saxon person of European ancestry in modern-day England has maybe a quarter-to-a half of their DNA as a result of that Saxon migration.

“Some would argue that was because the Anglo-Saxons replaced the existing population, whereas our data shows clear evidence of the Anglo-Saxon DNA, but because it’s in the minority it must have been the case that they inter-married with the existing population.

“So we’re able to resolve that historical question.”

A photo of a map divided into different colours showing the British Isles population
This diagram shows levels of Viking migration between 800 and 950© University of Oxford
There was evidence of the Landsker line boundary between the English-speaking people of south-west Wales and the Welsh speakers in the rest of the country. A noticeable genetic boundary was symbolised by the Tamar River, in Devon, and Cornwall’s Bodmin Moore.

“It makes perfect sense,” said Donnelly.

“Geographical boundaries to migration and movement of people will tend to foster relative isolation, and that can lead to genetic differences, as well as cultural differences or a particular sense of identity.

“It’s potentially helpful for studying the generic background of disease. That was one of our primary motivations.

“When we look for genetic factors which may influence people’s risk of disease we tend to compare sick people and healthy people. Having a good knowledge of the background can help in knowing what sort of things we can rule out in terms of confounding factors.”

People outside the selected groups will also help future innovations.

“Many of the people in the UK, particularly due to migrations in the last century, don’t have European ancestry.

“They bring their own rich genetic diversity, some of which is and will be extremely helpful in studying the genetics of diseases and using genetics to better understand human biology and changes to the way we do healthcare.”

What do you think? Leave a comment below.

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