Andy Coghlan summarizes current genetic data on the ancient peoples of Great Britain.

Mar 18, 2015
Andy Coghlan

Andy Coghlan, "Ancient invaders transformed Britain, but not its DNA," New Scientist, March 18, 2015, accessed March 15, 2023

New Scientist
Andy Coghlan
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THEY came, they saw, they conquered. But while the Romans, Vikings and Normans ruled Britain for many years, none left their genetic calling cards behind in the DNA of today’s mainland Caucasian population. That’s the message from the most comprehensive analysis yet of the genetic make-up of the white British population.

The only invaders that left a lasting legacy are the Anglo-Saxons. As well as giving us the English language, the Anglo-Saxons, whose influx began around AD 450, account for 10 to 40 per cent of the DNA in half of modern-day Britons.

The analysis also springs some surprises. There was no single Celtic population outside the Anglo-Saxon dominated areas, but instead a large number of genetically distinct populations (see map below). The DNA signatures of people in the neighbouring counties of Devon and Cornwall are more different than between northern England and Scotland. And there are also unexpectedly stark differences between inhabitants in the north and south of the Welsh county of Pembrokeshire.

The only appreciable genetic input from the Vikings is in the Orkney Islands, which were part of Norway for 600 years. Viking DNA accounts for 25 per cent of today’s Orcadian DNA.

The insights come from a study of DNA samples donated by 2039 Caucasian people from around the UK. Each was selected because all four of their grandparents were born within 80 kilometres of each other, allowing the researchers to infer their grandparents’ DNA and later link it to a location. Because the grandparents were born on average in 1885, the analysis enabled a genetic snapshot of Caucasian Britain prior to immigrations since then. “Any one person’s genome is a random sample of DNA from all four of their grandparents, so it’s a way to look back in time,” says Peter Donnelly of the Wellcome Trust Centre for Human Genetics in Oxford, UK.

To identify differences between people who have similar genetic make-ups, Donnelly’s team searched not just for single genetic alterations, but how common combinations of those alterations were inherited in large chunks of chromosomes. “That’s much richer than looking at each genetic difference individually,” says Donnelly.

The team found that the genetic profiles of the participants formed 17 distinct clusters. When they mapped this information based on where the participants lived they were surprised to see the clusters mapped almost exactly to geographical location.

The largest cluster accounted for half the participants and occupies almost the whole of eastern and southern England and most of the Midlands. This turned out to be the genetic legacy of the Anglo-Saxon invasions. Even so, at least 60 per cent of the DNA in the cluster had survived from earlier migrants (Nature, DOI: 10.1038/nature14230).

In fact, all 17 clusters are dominated by DNA from settlers that arrived prior to the Anglo-Saxons. By comparing the clusters with genomes from modern-day continental Europe, the team was able to piece together the general migration pattern that took place.

The first wave of arrivals crossed by land bridges, when sea levels were so low that Britain was attached to what is now northern Germany. This wave was dominated by people with genomes most similar to modern-day inhabitants of northern Germany and Belgium. In parallel, migrants from the west coast of France were arriving by boat. Traces of the combined DNA from all these three pioneer settlers forms the basis for the genetic-make up of all white Britons.

Given the cultural significance of the Roman, Viking and Norman invasions, it’s surprising they didn’t leave greater genetic legacy. For the Romans and Normans, that may be because they were ruling elites who didn’t intermarry with the natives.

The overall message is that despite their large cultural impact, Britain’s main invaders left no genetic stamp of note. “When you study the past through history, linguistics or archaeology, you learn about successful people,” says Donnelly. “History is written by the winners, so much of current historical information is from a relatively small subset of people. Genetics, by contrast, is the history of the masses.”

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