NEW YORK — A wave of migrants from continental Europe entered what is now Great Britain about 3,000 years ago, according to a new analysis of ancient genomes.
Neolithic farmers living in ancient Britain about 6,000 to 4,500 years ago derived about 80 percent of their ancestry from early European farmers who arose in Anatolia 1,000 years prior. But that portion then fell with the start of the Bronze Age. However, modern-day people from England and Wales harbor more ancestry derived from those farmers than the inhabitants of Britain from the early Bronze Age, researchers led by Harvard Medical School's David Reich noted, suggesting there was a shift in ancestry since that time.
By generating genome-wide DNA data on more than 400 additional pre-Roman inhabitants of Britain, the researchers found that the level of early European farmer ancestry increased between the Middle-to-Late Bronze Age and the Iron Age in England and Wales, but not in Scotland. The migrants causing this shift, the researchers added in their Nature paper, likely arrived from what is modern-day France and potentially brought Celtic languages with them to Britain.
"This shows the power of large-scale genetic data in concert with archaeological and other data to get rich information about our past from a time before writing," Reich said in a statement.
He and his colleagues sequenced and analyzed the genomes of 416 ancient individuals from across Britain who had not previously been analyzed, which they combined with newly generated as well as previously published data on individuals from across Europe.
By analyzing this dataset, they found that the portion of early European farmer ancestry in England and Wales increased from 31 percent in the Early Bronze Age to 34.7 percent in the Middle Bronze Age, to 36.1 percent in the Late Bronze Age before stabilizing at 37.9 percent in the Iron Age. During this time, though, there were no significant changes in ancestry in Scotland — the increase in early European farmer ancestry was largely confined to southern Britain.
A number of outliers had even higher levels of early European farmer ancestry, especially samples found in Kent. One sample from the Margetts Pit, for instance, had early European farmer ancestry reaching 47.8 percent.
The researchers traced the likely source of these migrants to southern France, which they said tracks with the increased early European farmer ancestry found in Kent, as it is close to France. They noted, though, that Western and Central France are poorly represented by genome-wide ancient DNA datasets and that additional data is needed to further test these findings.
Still, Trinity College Dublin's Daniel Bradley wrote in an accompanying commentary in Nature that the researchers' "findings demonstrate the power of fine-grained temporal sampling of ancient genomes, and reveal a previously unsuspected, major migration to Britain that was not detectable using previous, sparser data."
The Harvard team additionally proposed that this migration from France might have introduced Celtic languages to the British Isles. "By using genetic data to document times when there were large-scale movements of people into a region, we can identify plausible times for a language shift," Reich said. "Known Celtic languages are too similar in their vocabularies to plausibly descend from a common ancestor 4,500 years ago, which is the time of the earlier pulse of large-scale migration, and very little migration occurred in the Iron Age."
Instead, he suggested another scenario in which Celtic languages were introduced in the late Bronze Age