Genetics: Mass migration into Britain during the Bronze Age

A previously unrecognized, large-scale migration from continental Europe into Great Britain during the Middle to Late Bronze Age may have facilitated the spread of early Celtic languages. This finding, reported in Nature, helps to explain the genetic makeup of people living in Britain today. The study also highlights differences in the frequency of an allele associated with lactose tolerance, suggesting that there could have been differences in the Bronze Age usage of dairy products between Britain and Central Europe.

Studies of ancient DNA have revealed that Britain has experienced at least two large-scale population turnovers in the past 10,000 years. The first Neolithic farmers, who lived around 3950–2450 BC, are thought to have been descended from early European farmers and hunter-gatherers (accounting for around 80% and 20% ancestry, respectively). The second migration, around 2450 BC, was associated with the arrival of continental Europeans, who brought Steppe ancestry derived from pastoralists living on the Pontic-Caspian steppe (a region spanning Europe and Asia between the Black Sea and Caspian Sea). This wave resulted in an approximately 90% replacement of the population’s ancestry, after which the proportions of Steppe ancestry in England and Scotland were indistinguishable. However, the present-day proportion of Steppe ancestry is significantly lower in England. Subsequent events must have happened to account for this change, but they have remained a mystery until now.

David Reich and colleagues generated genome-wide data for 793 ancient individuals from this time period, the largest ancient DNA study reported to date. They reveal a third, previously unknown migration into Britain that peaked between 1000 and 875 BC. The migrants, who are thought to have come from France, went on to contribute about half the ancestry of Iron Age people in England and Wales. Language typically spreads through the movement of people, so the results also support the idea that Celtic languages came to Britain from France in the Late Bronze age. The large pool of genome data also highlighted changes in the frequency of a gene variant associated with lactase persistence into adulthood. The study of this allele indicates that the ability to digest cow’s milk increased about a millennium earlier in Britain than in Central Europe. This finding raises the possibility that dairy products played a different cultural role in Britain during this period, compared with Central Europe.