One of the peculiarities of the synthesis of 19th and early 20th historical linguistics and biological anthropology was the perception by many British thinkers that the English, as the scions of the Anglo-Saxons, were fundamentally a different race from the Celtic nations to their west, the Welsh and Irish, and the Scots to the north (yes, I know the Scottish nation emerged is a mix of Celtic and Anglo-Saxon elements which were preponderant at different times and periods). In other words English nationalists would characterize their own race as a branch of the German peoples. English was a Germanic language, and the linguistic chasm emphasized more starkly a distinction from the Celts who inhabited Britain prior to the arrival of the Germans, and gave the island its name before they were marginalized and pushed to the "Celtic fringe." The historical context of this does not need to be elaborated in detail. The Emerald Isle's integration into the United Kingdom of England, Wales, Scotland and Ireland was always a difficult affair. This was due in large part to religion (the lack of an effective Irish Reformation may have had other structural causes); the Irish were a Roman Catholic populace at a time when Roman Catholicism and loyalty to the monarchy were presumed to be contradictory. In 1800, before the potato famine and the English demographic explosion, Ireland accounted for one third of the population of the United Kingdom (I do not put much stock in the linguistic difference, as the Welsh speaking regions were firmly Protestant and so not perceived to be sources of equivalent dissension despite their cultural marginality). With the rise of taxonomic science what was a crisp social chasm was reconceptualized as a biological and evolutionary gap along the Great Chain of Being. In the twentieth century the tide turned, today most scholars would assert that the shift from Celtic to Anglo-Saxon speech and culture in what became England was a matter of emulation, not genetic replacement. Personally I suspect that the pendulum has swung too far, but it does show how strongly influenced by fashion these sorts of preconceptions are. Modern genetics can clear up the confusion to some extent. A new paper in The European Journal of Human Genetics surveys samples from Dublin, the south & southeast of England (the heart of Saxon Britain), Aberdeen, Portugal, Bulgaria and Sweden. Population structure and genome-wide patterns of variation in Ireland and Britain. I'll just focus on the figures of interest in relation to the questions I aired above. I've added some labels to figure 1, but it's pretty obvious what it's depicting. Each point is an individual. CEU = Mormons from Utah. This is mostly a British origin sample, but I assume its overlap with Swedes is indicative of the European immigration to Utah by early Mormon converts, some from Scandinavia.
And here is what economists would term a more stylized figure from the supplements:
These figures are showing what we know from other studies on European genetics; the largest component of variation seems north-south (at least until you start pushing into Russia where a simple European wide pattern starts to break down), and the second component is west-east. This is more evident in the frappe plots, where you see the individuals within the populations broken down by K ancestral groups. Again, from the supplements:
The above figures require a little art in their interpretation. Remember that the PC charts are just representing the biggest components of independent variation within the data set. As for the frappe results, they don't always represent real ancestral populations in a straightforward manner. Or at least we have no independent checks on what was going on ten thousand years ago in Europe. So below are the pairwise Fst values. Remember, these compare the proportion of between group genetic variation across the pairs. The print is small, so let me just tell you that the Fst value for England-Sweden is twice a large as England-Ireland. In other words the English of the south and east of England are closer to the Irish of Dublin than they are to the Swedes.
Ideally the Swedes would not be the reference population for the Germans of yore. Rather you'd want Frisians, Danes and Saxon Germans. From what I've seen in the other results on European genetics Swedes have been somewhat influenced by the Finns, who are genetically peculiar, so that might understate the German affinity of the English as some of the distance might be due to the Fennic component in the Swedish gene pool. But I've seen other studies which lead me to infer that the peoples of the Isles share more than not, and the English share more ancestors with the Irish and Scottish than they do with the Saxons over the sea.H/T:DienekesCitation:Population structure and genome-wide patterns of variation in Ireland and Britain, doi: 10.1038/ejhg.2010.87