Saturday, October 1, 2022

DNA reveals massive Anglo-Saxon and French migrations to England

One of the largest studies of historic DNA to date gives “overwhelming” support to the view that mass migration from continental Europe was central to the creation of Anglo-Saxon England, scientists say.

Until recent decades it was widely believed that Britain was transformed by a massive invasion of Angles, Saxons and Jutes after the end of Roman rule around 410AD. This was traditionally believed to have occurred after the British ruler Vortigern hired Saxon mercenaries, “like [bringing] wolves into the sheep-fold”, to fend off Scots and Picts. More recently, some scholars have argued that a cultural shift, including the adoption of the English language, occurred without significant levels of migration, perhaps with the arrival of a small continental elite.

The new genetic study, led by researchers at the Max Planck Institute for Evolutionary Anthropology and the University of Central Lancashire, is the largest yet to have addressed the question. It supports previous genetic research indicating that there was large-scale post-Roman migration to what is now England from today’s Germany, Netherlands and Denmark. In addition, it reveals that there was also large-scale migration from what is now France to England during the medieval period.

Archaeologists excavate grave 112 at Oakington Cambridgeshire, containing an adult male buried with a knife. He had 99.99 percent continental northern European ancestry © Duncan Sayer, University of Central Lancashire

Nevertheless, the authors said the findings do not support notions of an Anglo-Saxon “invasion”. Dr Stephan Schiffels, research group leader for population genetics at the Max Planck Institute, and one of the lead authors, said: “After the Roman Empire, we see this large-scale arrival of people from the continental North Sea zone into England, which is bigger than I would have expected. Even in the early Anglo-Saxon graveyards, we see this staggeringly high proportion of continental ancestry. But it’s clearly not an invasion because we see from very early times mixing with people of local ancestry and we do not see any signs of male or female bias.”

The team analysed the genomes of 460 medieval northwest Europeans, including 278 from England and 182 from neighbouring regions of continental Europe and from Ireland. Alongside these newly reported genomes, they studied previously published genetic data from 4,336 historic individuals’ remains and genetic data of 10,176 present-day Europeans.

They found continental northern European ancestry, similar to that of northern Germans and Danes today, to have been present at very low levels in Britain and Ireland before the early Middle Ages — accounting for no more than 1 per cent of people’s genomes in the Bronze Age and Iron Age. The proportion of this ancestry increased in Roman Britain to 15 per cent, although based on a small sample of seven individuals. In contrast, most early medieval people from England in the dataset derived all or a large part of their ancestry from continental northern Europe, averaging 76 per cent. This ancestry was almost identical to that of medieval individuals from Lower Saxony in northwestern Germany.

The researchers stress that there were regional differences within England, noting that continental northern European ancestry was predominant in eastern and central England but less prevalent in the south and southwest.

Despite the very high levels of continental northern European ancestry in the early medieval English samples, they found that this ancestry accounted for only about 40 per cent of the DNA of English people today. About 20-40 per cent of their remaining ancestry derives from the Romano-British population and a further 20-40 per cent from people genetically close to the Iron Age population of France.

The study indicates that this French-like ancestry came to Britain after the Roman period and is most likely to be the result of various waves of migration, including Frankish immigration to Kent in the Anglo-Saxon period and migration from France and surrounding regions following the Norman Conquest.

The team said the higher levels of Romano-British ancestry in modern English people, compared with among the early medieval English samples, may be partly due to genomes of post-Roman Britons being underrepresented in the existing genetic datasets. Given this, Schiffels said they would be keen to expand their sampling, particularly in western England, in future research.

Burial goods from grave 3532 at Issendorf cemetery in Lower Saxony, a region from which some of the immigrants sailed ©Landesmuseum Hannover

They nevertheless found abundant evidence of mixing between the continental incomers and locals of Romano-British stock. This included remains of a family at Buckland cemetery, Dover, where three generations were of wholly continental ancestry before a male family member had children with a woman of Romano-British ancestry. Another Briton married into the family in the next generation. Overall, there was no evidence of sex bias in this mixing of populations, with men and women appearing to have arrived from the continent in similar numbers and intermarried with Britons at similar rates.

Archaeological findings integrated into the study show that women with immigrant ancestry were more likely than women with local ancestry to be buried with grave goods such as brooches and beads. However, men of Romano-British origin were as likely as their continental counterparts to be buried with weapons.

“It’s clearly not an invasion because we see from very early times mixing”

Dr Stephan Schiffels

In their paper, published in the journal Nature, the authors write: “Our results overwhelmingly support the view that the formation of early medieval society in England was not simply the result of a small elite migration but that mass migration from afar must also have had a substantial role. We identified numerous individuals with only continental ancestry, suggesting that many of them were migrants themselves or were their unadmixed descendants.”

The authors have not speculated on the number of people involved in the migration from the continental North Sea regions. Schiffels said there were too many unknown factors, including the extent to which Romano-British people may have migrated to western regions and whether disease may have reduced the Romano-British population. He added: “That’s something that I think could be done in the future with careful modelling involving more fine grained archaeological data.”

The study’s findings will contribute to the debate but still leave open many questions about changes and continuity in post-Roman Britain.

Among other findings, the team noted that most present-day Scottish, Welsh and Irish genomes showed ancestry from the Bronze Age and Iron Age populations of the British Isles, with little or no later continental contribution. They said the genetic contribution of the Vikings to modern English populations was much smaller than that from the earlier Anglo-Saxon period migration.

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