Celtic tongues were spoken widely across Europe before the Romans imposed Latin on their conquered masses 2,000 years ago, but nobody knows how the various Celtic languages spread so far and wide. Peter Forster, a geneticist at the University of Cambridge, has used the tools of molecular biology to find an answer and has revised the timescale of Indo-European languages along the way.
Forster recognized that phylogenetic analysis, a mathematical method used to reconstruct genetic relationships between species, could apply to languages as well. So he and linguist Alfred Toth of the University of Zürich designed a method to compare differences between common words in 14 languages the way that biologists analyze variations in DNA sequences.
The resulting linguistic family tree showed that Celtic speakers—possibly early farmers—migrated from continental Europe to Wales, Ireland, and Scotland in one wave perhaps 6,000 years ago. Once isolated on the British Isles, the ancient ...
