New research led by the Francis Crick Institute has revealed waves of human migration across Europe during the first millennium AD. Using a refined method of analyzing ancient DNA ancestry, they analyzed genetic data to map people’s movements, but this is particularly challenging when historical populations are genetically similar.
The study introduces a new analytical tool, Twigstats, which can more precisely measure genetic differences between closely related groups. This has led to the discovery of new information regarding European migrations at crucial periods, such as the Iron Age, the fall of the Roman Empire, the Migration Period, and the Viking Age, based on over 1,500 genomes from individuals who lived primarily during this era (1–1000 AD).
Genetic mutations refer to the small changes in the DNA that influence our closeness or distance from relatives. Since every inheritance of a genetic mutation reflects inheritance from ancestry, we could argue that genetics are the cornerstone for constructing an equivalent “family tree” but instead linking humanity at large.
Recent advances have allowed scientists to reconstruct these genetic family trees directly by examining how individuals share mutations. These trees can determine the age of mutations and who shares them.
The new technique, Twigstats, analyzes such genetic family trees but focuses only on recent mutations. This highlights relationships between individuals who are closer in time to each other, affording a more accurate perception of our genetic inheritance and relationships.
Germanic-speaking people move south in the early Iron Age.
At the beginning of the first millennium, the Romans recorded battles with Germanic tribes outside the borders of their own empire. By applying the innovative Twigstats technique, researchers have found genetic proof for the migration of these groups downwards from Northern Germany or Scandinavia, which is also reflected in history.
This genetic ancestry was identified in populations in southern Germany, Italy, Poland, Slovakia, and southern Britain. A particular individual from southern Europe displayed 100% Scandinavian-like ancestry. The researchers found that most of these migratory groups later assimilated into local populations.
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This paper identified two principal migration zones corresponding to the three main branches of Germanic languages: the one that survived in Scandinavia, the one that went extinct, and the one that branched into modern German and English.
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One of the inhabitants of 2nd-4th century York, Britain, carried 25% of their ancestry from early Iron Age Scandinavia. This is robust evidence of Scandinavian ancestry in Britain considerably earlier than previously thought possible—before the Anglo-Saxon and Viking periods, which started in the 5th century AD.
Germanic-speaking people move north into Scandinavia before the Viking Age
The team used the method to discover a later wave of migration into Scandinavia at the end of the Iron Age (300-800 AD), just preceding the Viking Age. They found that most Viking Age individuals in southern Scandinavia carried ancestry from Central Europe.
Teeth from the individuals buried on the island of Öland in Sweden allowed for biomolecular analysis, showing that the ones of Central European ancestry had grown locally. The data indicate that this wasn’t just a singular influx of people into Scandinavia but a long-lasting shift in ancestry.
Although archaeological evidence shows signs of repeated conflicts in Scandinavia during this period, the researchers suggest that such unrest could have triggered migration. Nevertheless, more archaeological, genetic, and environmental data is needed to understand the underlying reasons behind these movements.
Viking expansion out of Scandinavia
The Viking Age (c. 800-1050 AD) is commonly associated with Scandinavian peoples raiding and settling throughout Europe. Recent studies confirm this historical record, showing that many individuals outside Scandinavia at this time had a blend of local and Scandinavian ancestry.
For instance, the researchers found Viking Age people in present-day Ukraine and Russia who had ancestry from Sweden and people in Britain who had ancestry from Denmark. The bodies of men found in Viking Age mass graves in Britain who had died violently were genetically linked to Scandinavia, which indicates that they most probably were executed members of Viking raiding parties.
Leo Speidel, first author, a former postdoctoral researcher at the Crick and UCL, and now group leader at RIKEN, Japan, said: “We already have reliable statistical tools to compare the genetics between groups of people who are genetically very different, like hunter-gatherers and early farmers, but robust analyses of finer-scale population changes, like the migrations we reveal in this paper, have largely been obscured until now.
“Twigstats allows us to see what we couldn’t before, in this case, migrations across Europe originating in the north of Europe in the Iron Age and then back into Scandinavia before the Viking Age. Our new method can be applied to other populations worldwide and hopefully reveal more missing pieces of the puzzle.”
Pontus Skoglund, Group Leader of the Ancient Genomics Laboratory at the Crick and senior author, said: “The goal was a data analysis method that would provide a sharper lens for fine-scale genetic history. Questions that wouldn’t have been possible to answer before are now within reach, so we need to grow the record of ancient whole-genome sequences.”
Peter Heather, Professor of Medieval History at King’s College London and co-author of the study, said: “Historical sources indicate that migration played some role in the massive restructuring of the human landscape of western Eurasia in the second half of the first millennium AD which first created the outlines of a politically and culturally recognisable Europe, but the nature, scale and even the trajectories of the movements have always been hotly disputed. Twigstats opens up the exciting possibility of finally resolving these crucial questions.”
Journal Reference:
- Leo Speidel, Marina Silva, Thomas Booth, Ben Raffield, Kyriaki Anastasiadou, Christopher Barrington, Anders Götherström, Peter Heather, Pontus Skoglund. High-resolution genomic history of early medieval Europe. Nature, 2025; 637 (8044): 118 DOI: 10.1038/s41586-024-08275-2