Ancient DNA (aDNA) analysis, which has been developing as an archaeological technique for around a decade, has the capacity to revolutionise our understanding of prehistoric populations and cultural practices. As well as paying a visit to the aDNA lab at the National History Museum in London (see CA 349), previous ‘Science Notes’ (CA 333, 340, 342, 377, and 380) have explored the technique in the context of decoding genetic information and detecting ancient pathogens.
In CA 338, our cover feature reported on ground-breaking work relating to the Bell Beaker complex (the cultural phenomenon that spread across much of western and central Europe and into Britain in the middle of the 3rd millennium BC). Based on large-scale aDNA analysis of human remains excavated at 136 sites across Britain and continental Europe, this research revealed that although the Bell Beaker complex had spread throughout Iberia and central Europe primarily by way of social interaction and cultural exchange, it expanded into Britain from 2450 BC as a result of a large-scale migration of people from central Europe. Four years later, a new investigation has now seen an international team of more than 200 geneticists and archaeological scientists discover aDNA evidence for a second significant and hitherto unknown Bronze Age migration into Britain c.1,500 years later.
As the study, reported in the journal Nature (N Patterson et al.; https://doi.org/10.1038/s41586-021-04287-4), explains, previous research indicates that the earliest Neolithic farmers in Britain derived around 80% of their ancestry from early European farmers (EEF) originating from Anatolia (modern Turkey) and around 20% of their ancestry from Mesolithic hunter-gatherers from Western Europe (WHG). Then a migration of people into Britain, associated with the Bell Beaker complex, led to such widespread genetic shifts that, over only a few hundred years, Britain’s prehistoric population came to be dominated by people who derived at least 90% of their ancestry from the new migrants. By c.2000 BC, the gene pool in Britain had largely homogenised, and Britain’s early Neolithic farmers, it seems, had been subsumed within communities with more recent Continental heritage and Steppe ancestry.
These changes led to a dilution of EEF ancestry in Britain, but today the proportion of EEF ancestry is generally higher in England and Wales than in Scotland, and modern people from England and Wales derive more of their ancestry from early European farmers than people of the early Bronze Age did. Yet the previous study, which focused mainly on data from before 1300 BC, had not detected any significant change in the proportion of EEF ancestry in Britain after the major changes at the start of the Bronze Age. How, then, do we explain the apparent increase in EEF ancestry in southern Britain?
As the researchers behind the more recent study note, it cannot have been the result of later, medieval migrations of people to Britain, as early medieval migrants had less EEF ancestry than Bronze Age Britons, not more (as would be needed in order to produce this shift). Looking for another migration that could explain the apparent rise, then, the team generated genome-wide data from 793 prehistoric individuals from across Europe, including 416 people from Britain, thereby creating a total analysis dataset of 598 people found in Britain (including successful and illuminating ancient DNA extraction from the Amesbury Archer, who was buried on Salisbury Plain; see pp.50-53 of this issue). More specifically, the team focused on obtaining original aDNA data from the late Bronze Age and pre-Roman Iron Age, and, as a result, we now have data from 365 people alive in Britain between 1150 BC and AD 43 (previously, this number had been just 13). This was analysed alongside further British and Continental data, some already known, from the middle Bronze Age (1550-1150 BC).
Using statistical modelling techniques to interpret the aDNA data, the team found that EEF ancestry increased in southern Britain between 1000 and 875 BC, suggesting that there had been a further significant wave of migration into Britain at this time and in the centuries before. Further analysis of middle and late Bronze Age DNA indicated that the migrants in question were genetically similar to ancient people from France, including four ‘outlier’ individuals with especially high EEF ancestry. The remains of the earliest two have been radiocarbon dated to between 1391-1129 BC and 1214-1052 BC respectively, indicating that they may have been early generation migrants from France. All ‘outliers’, as well as later individuals with higher EEF ancestry than their early Bronze Age counterparts, were found in Kent, further indicating that the migration stemmed from across the Channel. These findings may help to explain the spread of early Celtic languages into Britain, the timing of which has long been debated by linguists and archaeologists. Certainly, the results correspond chronologically with archaeological evidence of intense cultural exchange between Britain and continental Europe during the middle-to-late Bronze Age.