Family Tree DNA: Genetic Testing Service
DNA testing will show your connections with other families and ethnic groups. The database includes many peoples from throughout Europe and the rest of the world including Cornish, Welsh, English, Irish, Scots, and members of many other ethnic groups. If you have bonafide Cornish ancestry you can apply to join Family Tree DNA's "Cornwall" project administered by Joe Flood which tracks the uniparental markers of participants. Also of interest is Kym Edwards's "CORNWALL-mtDNA" project at Family Tree DNA.
Cornish people have long lived in southwestern Britain's Cornwall (Kernow) region and have their own variety of Celtic language, which is endangered but making a comeback. They are currently part of the political unit "England and Wales" but some people advocate devolution or independence for Cornwall. In 2014 the Cornish people were officially recognized as an ethnic minority by the government of the United Kingdom.
According to Joe Flood's carefully vetted "Cornwall" project, a little more than 80% of Cornish people who participate carry the Y-DNA haplogroup R1b. Some specific varieties they carry include R1b1c and R1b1c6. Flood stated that around two-thirds of Cornish R1b lines are southwestern European (R-P312) while roughly a third are northwestern European (R-U106) but those are not the exact proportions nor the only versions of R1b they have: the Celtic R-L21 and Anglo-Norman R-U198 varieties are also present among them. Perhaps a better way to state it would be that R-P312 is roughly twice as prevalent as R-U106. Cornish people in the "Cornwall" project less frequently belong to the Y-DNA haplogroups I1a, I1b, G, G2, J1, J2, R1a, and E-L542 and T-M70 are rare.
H, H5a1, H6a1b4, J, J1c2, J1c3g, K2a, K2b1, U4, U5, U5a2c3a, and X2e2a are some of the mtDNA haplogroups found among people who specifically state their most distant maternal-line ancestor lived in Cornwall, per the "CORNWALL-mtDNA" project.
About 35 percent of Cornish people have blue eyes.
Stephen Leslie, Bruce Winney, Garrett Hellenthal, Dan Davison, Abdelhamid Boumertit, Tammy Day, Katarzyna Hutnik, Ellen C. Royrvik, Barry Cunliffe, Wellcome Trust Case Control Consortium, International Multiple Sclerosis Genetics Consortium, Daniel J. Lawson, Daniel Falush, Colin Freeman, Matti Pirinen, Simon Myers, Mark Robinson, Peter Donnelly, and Walter Bodmer. "The fine-scale genetic structure of the British population." Nature 519 (March 19, 2015): pages 309-314. First published online on March 18, 2015. Cornish form part of this intensive evaluation of autosomal DNA. Excerpts from the Abstract:
"[...] We use haplotype-based statistical methods to analyse genome-wide single nucleotide polymorphism (SNP) data from a carefully chosen geographically diverse sample of 2,039 individuals from the United Kingdom. [...] The regional genetic differentiation and differing patterns of shared ancestry with 6,209 individuals from across Europe carry clear signals of historical demographic events. [...] in non-Saxon parts of the United Kingdom, there exist genetically differentiated subgroups rather than a general 'Celtic' population."
"Scientists discover genetic 'border' between Devon and Cornwall." Western Morning News (March 18, 2015). This journalistic account of the study published in March 2015 by Stephen Leslie and his colleagues explains that Cornish people are distinct from the people living in the nearby English county of Devon. Additionally, there is diversity within Cornwall itself, with "a separate group at the very tip of Cornwall" in the area called Land's End. One of the researchers involved in the study, Professor Simon Myers of Oxford University, is interviewed for this piece and says "We identified 17 groups in total in the UK and two corresponded very closely to Devon and Cornwall. [...] One of the distinguishing factors between them was the levels of Anglo-Saxon DNA. In the East of England Anglo Saxon contributions are between 10-40%, but in Cornwall it is around half that level." The Celts weren't a homogeneous bunch despite the common roots of their languages; the Cornish are more genetically distant from the Welsh and the Scots than they are to certain English people.
Jonathan Leake. "DNA shows Welsh and Cornish to be 'purest' Britons." The Sunday Times (June 17, 2012). Another article on the research of Stephen Leslie and his colleagues. The accompanying graphic states "Cornish are genetically distinct from Devonians".
Harriet Cooke. "Welsh and Cornish are the 'purest Britons', scientists claim." Telegraph.co.uk (June 17, 2012). British people who contributed samples to the study by Stephen Leslie, Peter Donnelly, and their colleagues were required to be living in rural areas and to have "had to have four grandparents born in the same area". Donnelly was interviewed here and says that the Cornish "are different from the rest of southern and central England." The preliminary results of the team were presented in July 2012 at the Royal Society's summer science exhibition in London.