Ancient DNA study reveals large scale migrations into Bronze Age

• Ancient DNA reveals large scale migration from Europe into southern Britain during the Bronze Age
• Evidence strengthens the case for the appearance of Celtic languages in Britain in the Bronze Age, and shows that lactose tolerance became prevalent in Bronze Age populations in Britain
• Late Bronze Age was a period of intense and sustained contacts between many diverse communities, both in Britain and other parts of continental Europe

A major new study of ancient DNA has traced the movement of people into southern Britain during the Bronze Age. In the largest such analysis published to date, scientists including those from the Natural History Museum examined the DNA of nearly 800 ancient individuals.

The new study, led by the University of York, Harvard Medical School, and the University of Vienna, shows that people moving into southern Britain around 1300‒800 BC were responsible for around half the genetic ancestry of subsequent populations.

The combined DNA and archaeological evidence suggests that, rather than a violent invasion or a single migratory event, the genetic structure of the population changed through sustained contacts between mainland Britain and Europe over several centuries, such as the movement of traders, intermarriage, and small scale movements of family groups.

The study finds evidence that the new migrants became thoroughly mixed into the Southern British population in the period 1000‒875 BC. While the researchers say the origin of these migrants cannot yet be established with certainty, they are most likely to have come from communities in and around present-day France.

The Middle to Late Bronze Age was a time when settled farming communities expanded across the landscapes of southern Britain, and extensive trade routes developed to allow the movement of metal ores for the production of bronze. These new networks linked wide-ranging regions across Europe, as seen from the spread of bronze objects and raw materials.

‘When archaeologists examine ancient human remains, they have an idea of who they are based on the associated culture, such as through the manner in which they were buried, the artefacts that they're buried with and - after radiocarbon dating - the timing of their death,’ said Dr Selina Brace, co-author of the study and Principal Researcher in Earth Sciences at the Natural History Museum. ‘By looking at the DNA from these individuals we can analyse their genetic signature. This can tell us many things about the individual but also about their genetic background, so where their ancestors came from, and hence about the movements of groups of people.’

Acquiring a set of samples dispersed around Britain was crucial for getting an all-round understanding of migration and variation in genetic ancestry of groups who lived in Britain through the Bronze and Iron Ages. Scientists from the Natural History Museum, London, including Dr Selina Brace, Dr Tom Booth, and Professor Ian Barnes, travelled across Britain to sample relevant ancient human remains held in collections at museums and commercial archaeological units. They then drilled a few milligrams of bone powder from some of these bone samples, before extracting DNA and preparing it for sequencing in the Museum’s purpose-built ancient DNA clean room.

‘When a change in material culture is observed, we can analyse the DNA from individuals before and after to see if this is associated with a change in genetic signature’ said Dr Brace. ‘Through genetic analysis, we can tell that the Early Bronze Age is accompanied by shifts in genetic ancestry indicating a migration of people into Britain at this time and then a further migration of peoples occurs through the Middle to Late Bronze Age.'

Some of the earliest genetic outliers have been found in Kent, suggesting that the south-east may have been a focus for movement into Britain. This resonates with previously published isotope evidence from archaeological sites like Cliffs End Farm on the Isle of Thanet peninsula, where some individuals were shown to have spent their childhoods in continental Europe.

The new DNA evidence may also shed light on the long-standing question of when early Celtic languages arrived in Britain. Since population movement often drives linguistic change, the new DNA evidence significantly strengthens the case for the appearance of Celtic languages in Britain in the Bronze Age. Conversely, the study shows little evidence for large-scale movements of people into Britain during the subsequent Iron Age, which has previously been thought of as the period during which Celtic languages may have spread. 

Dr Tom Booth, former postdoctoral researcher at the Natural History Museum said: ‘There have been ongoing debates about the origins and development of Celtic languages in different parts of Britain, and many theories have involved migration from continental Europe as a possible influential factor. Our results by no means resolve these questions absolutely, but by finding evidence for substantial migrations in the Middle-Late Bronze Age rather than the Iron Age, our results do increase the chances that it was in this earlier period when Celtic languages were actually introduced to Britain, and that these languages originated in southern present-day France.’

A further unexpected finding of the study is a large increase in the frequency of the allele for lactase persistence (a genetic adaptation that allowed people to digest dairy products) in Iron Age populations in Britain relative to the Continent.

'It's easy to assume that lactase tolerance (the ability to drink milk) would happen at the same time as people started farming but it didn't. It's been a real wild card, but it's very strongly selected for in Britain in the Iron Age and it doesn't seem to coincide with a specific   migratory event,’ said Dr Brace. ‘We don't know exactly why the frequency of this allele increases so sharply in Britain at this moment, but it is very strongly selected for at this time’.

Although the new DNA evidence sheds most light on Britain, the data also indicate population movements between different parts of continental Europe, confirming what archaeologists have long suspected – that the Late Bronze Age was a period of intense and sustained contacts between many diverse communities.

The study Large-scale migration into Britain during the Middle to Late Bronze Age is published in Nature.

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Partnerships: The study is led by academics from the Universities of York, Vienna, and the Harvard Medical School. It forms part of the COMMIOS Project, which examines the structure and social dynamics of Bronze and Iron Age societies in Britain and Continental Europe.

The project received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme.

It also received funding from the National Institute of Health; the John Templeton Foundation, the Howard Hughes Medical Institute, the Allen Discovery Center program, a Paul G. Allen Frontiers Group advised program of the Paul G. Allen Family Foundation, and a range of other organisations.