Welsh are closest relatives to early settlers of Britain, DNA study shows

The Welsh are genetically the most closely matched to the early settlers of Britain who started arriving about 10,000 to 11,000 years ago just after the last Ice Age, a study carried out by an international team of geneticists revealed.

In the first comprehensive DNA analysis of the UK population, scientists found that Britons share approximately 30% of their DNA with modern Germans, through the Anglo-Saxons who started coming to the islands about 1,500 years ago.

They were surprised to find there is very little genetic trace in the British population of Romans, Vikings or Normans. It appears the bulk of modern Briton’s genes consists of post Ice Age pre-Roman early settlers.

The Norman Conquest left little genetic trace in modern Britons’ DNA. (Image: English Heritage)

The study revealed subtle variations in the makeup of modern Brits as a result of the colonization of people’s from continental Europe after the last Ice Age.

The study was co-directed by Simon Myers and Peter Donnelly, both from the Wellcome Trust Centre for Human Genetics (WTCHG), Garrett Hellenthal from University College London, and Stephen Leslie of Murdoch Childrens Research Institute in Australia.

 

The co-directors wrote:

“It has long been known that human populations differ genetically, but never before have we been able to observe such exquisite and fascinating detail.”

Invaders interbred with locals

The invaders of the British Isles did not, as many had suggested, wipe out existing populations, but rather they interbred with them.

The genetic analysis showed considerable traces across the UK of DNA which came from the pre-Roman post Ice Age settlers. With the Welsh having by far the highest genetic traces of these people, followed by people in eastern and central regions of England, where the Anglo-Saxons settled after the fall of the Roman Empire.

Despite the Anglo-Saxon spread, they left a smaller (but still significant) mark on modern Brits’ DNA (up to 40%) compared to the earliest settlers.

In other words, most of modern Britons’ genetic inheritance comes from the earliest pre-Roman settlers, followed by the Anglo-Saxons, with the Vikings, Normans and Romans having hardly any impact at all.

The idea for the project came from Sir Walter Bogmer, from the Department of Oncology at WTCHG. He had wanted to find out whether there might be meaningful levels of genetic differentiation between populations within the UK as a background to studies of genetic diseases.

The researchers collected DNA samples from 2,039 Britons in rural areas. They only selected individuals whose four grandparents had been born within a 50 mile (80 kilometre) radius of each other, thus making it possible to sample the grandparents’ DNA, all of whom had been born before the 20th century’s major population shifts began.

After the genetic analysis, the UK was divided into 17 regional cluster. (Image: WTCHG)

Genetic clusters coincided with geographical areas

After completing their analysis, they found 17 different genetic clusters, which coincided strongly with geographical areas.

For example, the DNA of samples taken from those in Cornwall were quite different from their neighbours in Devon, while the people in Orkney were very different from all the other groups.

They then compared each of the 17 clusters with samples from 6,209 people in ten countries in Europe with a history of migration to the British Isles.

The comparisons showed that Orkney’s unique signature was due to a strong dose of Norse Viking DNA. They were surprised to find virtually no Viking genetic trace in eastern and northern England, despite Danish dominance in the two areas from the 9th to 11th centuries.

The study used high-performance computing and sophisticated statistical techniques that had been developed by Simon Myers, Garret Hellenthal and two other colleagues, to reveal these subtle effects.

Myers said:

“In future, increasingly large datasets will allow us to learn even more about the genetic history of the UK, and the similarly rich histories of other world regions, by applying similar techniques.”

Despite their dominance in eastern and northern England for about two centuries, the Vikings left little genetic trace.

No single ‘Celtic’ genetic group

The scientists had expected to find strong genetic similarities among the Celtic parts of the UK – Scotland, Northern Ireland, Wales and Cornwall.

They were surprised to find these groups were the most different from each other.

The Cornish samples, for example, were genetically more similar to other groups in England than to the Welsh or Scots.

How much did the Anglo-Saxons contribute?

While contributing to a chunk of modern Briton’s genetic makeup, it was considerably less than what was inherited from the pre-Roman settlers.

The study does, however, settle one historical debate – the Anglo-Saxons interbred with existing populations rather than killing them off and replacing them.

The Landsker line

The Landsker line is the language boundary between the Welsh-speaking and English-speaking areas in southwest Wales. The English-speaking area is often referred to as “Little England beyond Wales.”

The DNA study points to the effect of the Landsker line.

Genetic contribution of pre-Roman settlers

The study suggests a significant migration to Britain after the original post-Ice Age settlers, but before the Romans started to come.

These migrants’ DNA spread across the whole of Britain.

Even though “nothing is known about them,” these migrations, which occurred over thousands of years, are the largest single contributor to the DNA of modern Britons, the authors wrote.

According to WTCHG:

“Many of the genetic clusters show similar locations to the tribal groupings and kingdoms around end of the 6th century, after the settlement of the Anglo-Saxons, suggesting these tribes and kingdoms may have maintained a regional identity for many centuries.”

Stephen Leslie said:

“Rich genetic information such as this tells us a great deal about our history and augments what we know already from archaeology, linguistic and historical records.”

“Much of what we’ve learned about our history comes from the successful people of society, as they leave the strongest marks on history and archaeology. By using genetics and sophisticated statistical methods, we have been able to tell the story of the masses.”

According to Graham Coop, a population geneticists at the University of California, Davis, it should be possible to map the British ancestry of people in the United States as well as those from more diverse genetic backgrounds.

Ewen Callaway, writing in Nature, quotes Mr. Coop, who said:

“(However) it gets trickier the further back that ancestry is in your family tree, as less and less of your genome is from any one ancestor.”

Reference: “The fine-scale genetic structure of the British population,” Stephen Leslie, Bruce Winney, Garrett Hellenthal, Dan Davison, Abdelhamid Boumertit, Tammy Day, Katarzyna Hutnik, Ellen C. Royrvik, Barry Cunliffe, Wellcome Trust Case Control Consortium 2, International Multiple Sclerosis Genetics Consortium, Daniel J. Lawson, Daniel Falush, Colin Freeman, Matti Pirinen, Simon Myers, Mark Robinson, Peter Donnelly & Walter Bodmer. Nature. Published March 19, 2015. DOI: 10.1038/nature14230.