Update: A commenter noted that North England and Southwest Wales have different shape points. This is clear in the original PDF when I increased resolution. So ignore my comment about Brythonic Celtcs.
A few weeks ago I heard about the project to create a genetic map of Britain. Actually, I knew a bit about this because they’ve been publishing a few papers here and there over the years. But there is now an an exhibit up at The Royal Society Summer Science Exhibition 2012. My attention was drawn to this because British tabloids kept pushing headlines like “Cornish genetically different from other English!” I emailed one of the scientists associated with the project, Peter Donnelly, but he never got back to me. So I figured I would post anyway. Looks like they’re using thousands of samples at 600,000 SNPs. When they get a paper out it should be neat. On the other hand the map leaves a little to be desired. The clusters are clear, but what’s the genetic distance between the clusters in a relative sense? How were the cut-offs devised? I’m sure there are reasonable answers, but it’s all rather opaque at this point.
Nevertheless, I do want to point out two things. First, Anglo-Saxon England rather jumps out at you does it not? Second, the similarity between southwest Wales and northern England is explicable. The northern English region was associated with the Brythonic Celtic kingdom of Rheged, and later the southern portion of historical Strathclyde. These were the cousins of the Welsh, not Gaels like the Scots, but Britons. This is evident in the name Cumbria, it has the same root as Cymry, the ethnonym of the Welsh for themselves.