Ancient DNA untangles the origins of Celtic languages

Researchers from the University of Copenhagen and University of Wales Trinity Saint David shed new light on one of Europe’s oldest linguistic mysteries: where Celtic languages came from.

Irish, Scottish Gaelic, Welsh and Breton are all members of the Celtic language group, spoken on the Atlantic edge. But where did these languages come from?

According to two new studies published in Nature tracing the origins of Celtic and Germanic languages, part of the answer may lie in the DNA of thousands of ancient Europeans.

An international team led by the University of Copenhagen and Leiden University analysed DNA from more than 4,500 ancient individuals, including 712 genomes sequenced for the first time. By combining genetics, archaeology and linguistics, the researchers reconstructed major migrations that helped shape the languages spoken across Europe today.

“DNA sequences do not tell us directly which language people spoke. But by combining ancient DNA with linguistic and archaeological evidence, we can begin to trace how languages spread and changed over thousands of years,” says Eske Willerslev, senior author of the studies and Professor at Globe Institute at the University of Copenhagen.

Revisiting the origins of Celtic languages

Today, Celtic languages survive mainly in places such as Ireland, Wales, Scotland and Brittany. But 2,500 years ago, Celtic languages were spoken across much of Europe. Scholars have debated for more than a century whether they originated along Europe’s Atlantic coast or farther east in central Europe.

The ancient DNA points to a movement of people from central Europe around 3,000 years ago, that spread westwards into France, Britain, Ireland and the Iberian Peninsula. According to the researchers, this provides the simplest explanation for the spread of Celtic languages. It also challenges one of the most influential theories, which proposes that Celtic languages originated along the Atlantic coast.

“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,” says Guus Kroonen, Associate Professor of comparative linguistics at Leiden University and the University of Copenhagen.

Bringing genetics, language and history together

The researchers emphasize that DNA alone cannot reveal which language ancient people spoke. Instead, the studies combine genetic evidence with decades of linguistic and archaeological research.

By tracing when and where people moved, the team was able to test long-standing hypotheses about how languages spread across Europe and provide a more detailed picture of the continent’s past than ever before.

“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,” says Kristian Kristiansen, Professor of Archaeology at Gothenburg University.

Professor John Koch of the Centre for Advanced Welsh and Celtic Studies contributed to the main article ‘Tracing the spread of Celtic languages using ancient genomics’, and its linguistic and archaeological supplements. Professor Koch says, “This article is a momentous milestone in the search for Celtic origins and decisively limits the possibilities as to the prehistoric sources of Welsh and the other Celtic languages. There are a few key points to remember. There was almost no survival of the genes of the Neolithic farmers of Britain and Ireland, so almost no chance that their language was the source of Welsh. Between 4,500 and 4,000 years ago, Bell Beaker (BB) People coming from the wetlands around the lower Rhine and Meuse repopulated Britain and Ireland. After that, during the Bronze Age, two migrations entered southern Britain — first from the French/Iberian region then a second related to the population of the Knovíz Urnfield group in central Europe. Both groups of Bronze Age immigrants arose within Beaker territory and carried Beaker-derived ancestry. So it now looks like the story of the emergence and diversification of Celtic is closely intertwined with that of the Beaker People and their descendants.” 

McColl, H. et al. Tracing the spread of Germanic languages using ancient genomics. Nature https://doi.org/10.1038/s41586-025-09064-1  (2026).

McColl, H., Kroonen. G. et al. Tracing the spread of Celtic languages using ancient genomics. Nature https://doi.org/10.1038/s41586-026-11198-9  (2026).

(To be published in November)

Notes for Editors 

1. The Centre for Advanced Welsh and Celtic Studies (CAWCS) was established by the University of Wales in 1985 as a dedicated research centre conducting team-based projects on the languages, literatures, culture and history of Wales and the other Celtic countries. It is located in Aberystwyth, adjacent to the National Library of Wales, which is an internationally renowned copyright library with excellent research facilities. 

2. CAWCS offers unique opportunities for postgraduate students to work alongside specialists in a dynamic and supportive environment. We welcome enquiries about MPhil/PhD topics in any of our research areas. For more information about research opportunities, or for an informal chat about possible topics, contact our Head of Graduate Studies, Dr Elizabeth Edwards: e.edwards@wales.ac.uk 

3. CAWCS is the home of the Dictionary of the Welsh Language: https://www.welsh-dictionary.ac.uk/ 

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