King's College London

Researchers have revealed how a new method of analysing ancient DNA has enabled them to build a clearer picture of how people moved across the world.

The method called Twigstats, revealed today in Nature, offers a more precise way of measuring the differences between genetically similar groups, something that was previously difficult to do.

The study, which was led by the Francis Crick Institute, applied the new method to over 1500 European genomes (a person’s complete set of DNA) from people who lived primarily during the first millennium AD. Covering year 1 to 1000, this encompassed the Iron Age, the fall of the Roman Empire, the early medieval ‘Migration Period’ and the Viking Age.

The Romans, whose empire was flourishing at the start of the first millennium, wrote about conflict with Germanic groups outside of the Empire’s frontiers.

Using the new method, the scientists revealed waves of these groups migrating south from Northern Germany or Scandinavia early in the first millennium, adding genetic evidence to the historical record.

Co-author of the paper, Professor Peter Heather, Professor of Medieval History at King’s, said Twigstats opens up the exciting possibility of finally resolving some crucial questions.

The study found evidence that groups migrated south from Northern Germany or Scandinavia as their ancestry was found in people from southern Germany, Italy, Poland, Slovakia, and southern Britain, with one person in southern Europe carrying 100% Scandinavian-like ancestry. The team showed that many of these groups eventually mixed with pre-existing populations.

The two main zones of migration and interaction mirror the three main branches of Germanic languages, one of which stayed in Scandinavia, one of which became extinct, and another which formed the basis of modern-day German and English.

Analysis of the ancestry of an individual in 2nd-4th century York, who could have been a Roman soldier or slave gladiator, found that 25% of their DNA came from early Iron Age Scandinavia. This highlights that there were people with Scandinavian ancestry in Britain earlier than the Anglo-Saxon and Viking periods which started in the 5th century AD.

The team also used the method to uncover a later additional northward wave of migration into Scandinavia at the end of the Iron Age (300-800 AD) and just before the Viking Age. They showed that many Viking Age individuals across southern Scandinavia carried ancestry from Central Europe.

Leo Speidel, first author, former postdoctoral researcher at the Crick and UCL and now group leader at RIKEN, Japan, said robust analyses of finer-scale population changes, such as the migrations revealed in this paper had largely been obscured until now.

Pontus Skoglund, Group Leader of the Ancient Genomics Laboratory at the Crick, and senior author, said: “Questions that wouldn't have been possible to answer before are now within reach to us, so we now need to grow the record of ancient whole-genome sequences.”