Spoken words do not linger in soil for archaeologists to recover, but the movement and mixing of people can survive in ancient DNA. A sweeping genomic study has now used that evidence to illuminate the emergence and spread of Germanic and Celtic languages across Europe.

Scientists at the University of Copenhagen and Leiden University analyzed DNA from more than 4,500 ancient people. Those individuals lived across Europe from the Late Neolithic and Early Bronze Age, around 5,000 years ago, through the end of the Viking Age, around 1,000 years ago.

Researchers used the genetic information to follow the movement and mixing of populations. They then combined those findings with archaeological and linguistic evidence, including runic engravings, written records, domestic architecture and burial practices.

The resulting picture revealed a surprising migration around 1,500 years ago, only a few centuries before the Viking Age. Large numbers of people moved from what is now northern Germany into Denmark and southern Sweden.

That migration coincided with the emergence of Old Norse and may help explain why the language became known as the “Danish tongue.” The findings also connect Danish and Swedish Vikings closely with populations from northern Germany.

Those northern German populations were closely related to groups that contributed to the Anglo-Saxons in Britain. The results therefore present Vikings and Anglo-Saxons as populations with deeply intertwined genetic, linguistic and cultural histories.

“This migration came as a real surprise. Archaeologists and linguists had not predicted it, but it helps explain several cultural and linguistic connections between Scandinavia and Britain that have puzzled researchers for a long time,” Hugh McColl, lead study author and Assistant Professor at the Globe Institute at the University of Copenhagen, said in a statement.

The research produced another surprise involving a previously unknown population that migrated from the Baltic Sea region into what is now Sweden around 4,000 years ago. According to the study, these people brought early Germanic languages with them.

Within around 500 years, the group’s genetics and language had spread through much of Scandinavia. Their arrival left a lasting impact on populations across Northern Europe, while the proposed timing differs sharply from the existing consensus.

The study places this movement more than 1,000 years later than the currently accepted timeframe. That revision addresses a question scholars have debated for more than a century about when Germanic languages reached Northern Europe and where they came from.

“For over a century, scholars have debated when and from where the Germanic languages arrived in Northern Europe. What is exciting is that we can now test some of these ideas directly,” McColl explained.

“We discovered a previously unknown migration that occurred at exactly the time and place where we would expect the earliest form of Germanic to be spreading,” McColl added. The genetic evidence gave researchers a way to examine longstanding linguistic theories against measurable population movements.

The origins of Celtic languages were also reconsidered. Although Celtic languages are now spoken in only a few areas of Ireland, Wales, Scotland and Brittany, they were spoken throughout much of Europe around 2,500 years ago.

Linguists have disagreed over whether Celtic first appeared in western Europe or in a more central part of the continent. Based on the population movements revealed by ancient DNA, the study argues that an origin somewhere in Central Europe is more likely.

“The question of where Celtic languages came from has been debated for more than 100 years. Ancient DNA gives us an entirely new way to evaluate competing theories and brings important new evidence into the discussion,” said Guus Kroonen, Associate Professor of comparative linguistics at Leiden University and the University of Copenhagen.

The researchers cautioned that genetics alone cannot reveal which language any individual spoke. A mother tongue is often transmitted within families and genetically related communities, but languages can also change through cultural exchange.

Even with that limitation, the researchers believe that combining genetics, archaeology and linguistics can help explain how cultures developed. The approach links population movement with material evidence and linguistic records without treating ancestry as a direct substitute for language.

Kristian Kristiansen, Professor of Archaeology at the University of Gothenburg, noted: “These studies show what becomes possible when genetics, archaeology and linguistics are brought together. Questions that have remained unresolved for generations can now be addressed with a level of evidence that was previously impossible.”

The study was published in the journal Nature. Its findings offer new evidence about the population movements associated with early Germanic languages, the ancestry shared by Vikings and Anglo-Saxons, and the possible Central European beginnings of Celtic languages.