Lineage matters: 3,000 years ago, Britain got half its genes from… France?

Three years ago in the journal Nature, a vast international research team led in part by Harvard geneticist David Reich shined a torchlight on one of prehistoric Britain’s murkier mysteries.

By analyzing the degraded DNA from the remains of 400 ancient Europeans, the researchers showed that 4,500 years ago nomadic pastoralists from the steppes on the eastern edge of Europe surged into Central Europe, and in some areas, their progeny replaced around 75 percent of the genetic ancestry of the existing populations.

Descendants of the nomads then moved west into Britain, where they mixed with the Neolithic inhabitants so thoroughly that within a few hundred years the newcomers accounted for more than 90 percent of the island’s gene pool. In effect, the research suggested, Britain was almost completely repopulated by immigrants.

In a paper published Wednesday in Nature, Dr. Reich again targeted the genomic history of Britain, the country from which geneticists have mined more ancient samples than any other. The study, which has 223 co-authors, documents a subsequent and previously unknown major migration into Britain from 1,300 B.C. to 800 B.C.

Analysing DNA from 793 individuals, the investigators discovered that a massive Late Bronze Age movement displaced around half the ancestry of England and Wales and, possibly solving another longstanding riddle about British history, may have brought early Celtic languages to the island from Europe.

According to the findings, from 1,000 B.C. to 875 B.C. the ancestry of early European farmers increased in southern Britain but not in northern Britain (now Scotland). 

Dr. Reich proposed that this resulted from an influx of foreigners who arrived at this time and over previous centuries, and who — no doubt to the disbelief of 21st-century British nativists — were genetically most similar to ancient inhabitants of France. 

These newcomers accounted for as much as half the genetic makeup of the populace in southern Britain during the Iron Age, which began around 750 B.C. and lasted until the coming of the Romans in A.D. 43. DNA evidence from that period led Dr. Reich to believe that migration to Britain from continental Europe was negligible.

Ian Armit, an archaeologist at the University of York who collaborated on the research, noted that archaeologists had long known about the trade and exchanges across the English Channel during the Middle to Late Bronze Age. “But while we may once have thought that long-distance mobility was restricted to a few individuals, such as traders or small bands of warriors,” he said, “the new DNA evidence shows that considerable numbers of people were moving, across the whole spectrum of society.” 

Lara Cassidy, a geneticist at Trinity College Dublin who was not involved in the research, described the study as “a triumph. It takes a step back and considers Bronze Age Britain on the macro scale, charting major movements of people over centuries that likely had profound cultural and linguistic consequences.” 

Dr. Reich said the study demonstrated how, in the last few years, archaeologists and ancient DNA researchers have made great strides in coming together to address questions of interest to archaeologists. 

“To a huge extent, this is due to the large ancient DNA sample sizes that it is now possible to generate economically,” he said. “These studies are also beginning to address questions that truly matter biologically and culturally.”