Ancient DNA and the puzzle of the Celtic languages

Where the Celtic languages come from and how they spread across prehistoric Europe is a question archaeologists and linguists have been asking for generations, comparing different and often incompatible models. A study published in the journal Nature attempts to address the problem with a tool different from the two traditional ones: ancient DNA.

The study analysed genome-scale data — that is, the entire genetic material, not single markers — relating to 4,587 individuals who lived between the Bronze Age and the Iron Age in Europe. The stated aim is to verify whether existing archaeological and linguistic models on the origin and spread of Celtic find confirmation in the population movements that can be reconstructed from ancient genomes.

The limits of an operation of this kind must be stated clearly before even getting into its substance. Genetics can trace population movements and genetic admixture, not the circulation of a language: a community can adopt a language without a significant genetic contribution from those who spoke it, just as substantial population movements may leave no linguistic trace. Genomic data, in other words, is a clue as to who moved and when, to be put in dialogue — not automatically superimposed — with archaeological sources and with historical linguistic reconstruction, which is based on comparisons between attested and reconstructed languages.

The news currently comes from a single source (Nature); no independent confirmation available. The material available does not include information on the specific geographic areas sampled, on the chronological distribution of the 4,587 individuals within the Bronze-Iron Age timespan, or on the specific conclusions reached by the authors regarding the individual models compared — elements that would allow the real scope of the results to be assessed.

The methodological point remains: a base of nearly 4,600 ancient genomes is a large sample by the standards of palaeogenomics, a discipline in which the scarcity and degradation of biological material often limits analyses to a few dozen or a few hundred individuals at a time.