"There is also a marked division between the people of Cornwall and Devon that almost exactly matches the county border"

The genes of the UK. In addition to noting that the Cornish and Devonians are a little different, the study reveals (spoiler alert) that there are "two genetic groupings in Northern Ireland" that the Celts are not really one thing. On the other hand, we do get the interesting news that there are "subtle but distinct differences between those sampled in West Yorkshire and the rest of the country".