An investigation of differentiation between Cornwall and Devon based on history, surnames, and Y-chromosomes

Understanding genetic diversity among human populations can help uncover their histories. In 2015 the ‘People of the British Isles’ (PoBI) study of autosome-wide diversity revealed subtle but significantly different genetic clusters, including a clear distinction between the neighbouring counties of Cornwall and Devon; it proposed that Bodmin Moor and the River Tamar had formed a barrier between the two. This thesis uses a combination of historical, onomastic, and genetic approaches to investigate differentiation in this region in more detail.

A survey of the historical literature examines whether Cornwall has been isolated from the rest of England and the Continent. Evidence from archaeology, historical documents, and place-names shows that both Roman and Anglo-Saxon influence on Cornwall was less than that on Devon, supporting the idea of Cornish distinctiveness at least over the last two millennia. However, the historical record also shows abundant evidence for Cornwall’s connectedness with the nearby nations of Ireland, Wales, and Brittany.

Based on census and parish records, research was undertaken to analyse the specificity and persistence over time of surnames of the people of the Bodmin Moor region between 1702 and 1881. This showed a lack of regionally-specific names, and clear evidence of input from Devon and the rest of England.

Analysis of the male-specific Y chromosome examined whether the autosomal Cornwall-Devon distinction seen in the PoBI study was also reflected in paternal lineages. Surname-ascertained samples were recruited from Bodmin Moor and supplemented with PoBI samples. DNAs were analysed with short tandem repeats and single nucleotide polymorphisms. Population genetic analysis supported Cornish distinctiveness, with Bodmin Moor more closely related to Devon. Differences are compatible with lower Anglo-Saxon influence on west Cornwall. Co-analysis with other datasets clusters Cornwall most closely with Wales and Ireland and supports affiliation with Brittany, while Bodmin Moor and Devon more closely resemble other English populations.