Angela
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Nick Patterson and some other people at Harvard have previewed a new paper where they compare modern UK autosomal data with the ancient samples which have become available, and reach some interesting conclusions.
See:
http://biorxiv.org/content/biorxiv/early/2016/05/27/055855.full.pdf
Population structure of UK Biobank and ancient Eurasians reveals adaptation at genes influencing blood pressure
"Analyzing genetic differences between closely related populations can be a powerful way to detect recent adaptation. The very large sample size of the UK Biobank is ideal for detecting selection using population differentiation, and enables an analysis of UK population structure at fine resolution. In analyses of 113,851 UK Biobank samples, population structure in the UK is dominated by 5 principal components (PCs) spanning 6 clusters: Northern Ireland, Scotland, northern England, southern England, and two Welsh clusters. Analyses with ancient Eurasians show that populations in the northern UK have higher levels of Steppe ancestry, and that UK population structure cannot be explained as a simple mixture of Celts and Saxons. A scan for unusual population differentiation along top PCs identified a genome-wide significant signal of selection at the coding variant rs601338 in FUT2 (𝑝 = 9.16 × 10−9). In addition, by combining evidence of unusual differentiation within the UK with evidence from ancient Eurasians, we identified new genome-wide significant (𝑝 < 5 × 10−8) signals of recent selection at two additional loci: CYP1A2/CSK and F12. We detected strong associations to diastolic blood pressure in the UK Biobank for the variants with new selection signals at CYP1A2/CSK (𝑝 = 1.10 × 10−19) and for variants with ancient Eurasian selection signals in the ATXN2/SH2B3 locus (𝑝 = 8.00 × 10−33), implicating recent adaptation related to blood pressure."
One interesting thing they did is "To identify the populations underlying the 6 clusters, we projected the PoBI dataset20, comprising 2,039 samples from 30 regions of the UK, onto the UK Biobank PCs (Figure 2, Supplementary Figure 3). The individuals in the PoBI study were from rural areas of the UK and had all four grandparents born within 80 km of each other, allowing a glimpse into the genetics of the UK before the increase in mobility of the 20th century."
Also, "Modern European populations are known to have descended from three ancestral populations: Steppe, Mesolithic Europeans and Neolithic farmers21,22. We projected ancient samples from these three populations as well as ancient Saxon samples24 onto the UK Biobank PCs (Figure 3, Supplementary Figure 4, see Online Methods). These populations were primarily differentiated along PC1 and PC3, indicating higher levels of Steppe ancestry in northern UK populations."
From the body of the paper:
"We consistently obtained significantly positive 𝑓4 statistics, implying that both the modern Celtic samples and the ancient Saxon samples have more Steppe ancestry than the modern Anglo-Saxon samples from southern and eastern England. This indicates that southern and eastern England is not exclusively a genetic mix of Celts and Saxons. There are a variety of possible explanations, but one is that the present genetic structure of Britain, while subtle, is quite old, and that southern England in Roman times already had less Steppe ancestry than Wales and Scotland."
Southern and Eastern England is the largest genetic cluster in the U.K. and has the least steppe ancestry, and they seem to think it's likely that this was already the case in Roman times. That's contrary to the position of the Hellenthal group, which is fine with me, because some of their work makes no sense to me in light of what we know from history.
So, the obvious question is why? Could the Belgae have been a more "southern" leaning group? Could it be the Romans? If it increased later, then the Normans are a possibility, an idea which Dienekes seems to favor.
http://dienekes.blogspot.com/2016/05/british-celts-have-more-steppe-ancestry.html
Btw, they make an interesting point about the Welsh:
"Additionally, the lack of any ancient sample correlation with PC2 suggests that Welsh populations are not differentially admixed with any ancient population in our data set, and likely underwent Welsh-specific genetic drift."
What do you guys think about that? That would mean that the Anglo-Saxon admixture went right through the mountains to the west coast. I don't know that I buy that given the differences in yDna.
See:
http://biorxiv.org/content/biorxiv/early/2016/05/27/055855.full.pdf
Population structure of UK Biobank and ancient Eurasians reveals adaptation at genes influencing blood pressure
"Analyzing genetic differences between closely related populations can be a powerful way to detect recent adaptation. The very large sample size of the UK Biobank is ideal for detecting selection using population differentiation, and enables an analysis of UK population structure at fine resolution. In analyses of 113,851 UK Biobank samples, population structure in the UK is dominated by 5 principal components (PCs) spanning 6 clusters: Northern Ireland, Scotland, northern England, southern England, and two Welsh clusters. Analyses with ancient Eurasians show that populations in the northern UK have higher levels of Steppe ancestry, and that UK population structure cannot be explained as a simple mixture of Celts and Saxons. A scan for unusual population differentiation along top PCs identified a genome-wide significant signal of selection at the coding variant rs601338 in FUT2 (𝑝 = 9.16 × 10−9). In addition, by combining evidence of unusual differentiation within the UK with evidence from ancient Eurasians, we identified new genome-wide significant (𝑝 < 5 × 10−8) signals of recent selection at two additional loci: CYP1A2/CSK and F12. We detected strong associations to diastolic blood pressure in the UK Biobank for the variants with new selection signals at CYP1A2/CSK (𝑝 = 1.10 × 10−19) and for variants with ancient Eurasian selection signals in the ATXN2/SH2B3 locus (𝑝 = 8.00 × 10−33), implicating recent adaptation related to blood pressure."
One interesting thing they did is "To identify the populations underlying the 6 clusters, we projected the PoBI dataset20, comprising 2,039 samples from 30 regions of the UK, onto the UK Biobank PCs (Figure 2, Supplementary Figure 3). The individuals in the PoBI study were from rural areas of the UK and had all four grandparents born within 80 km of each other, allowing a glimpse into the genetics of the UK before the increase in mobility of the 20th century."
Also, "Modern European populations are known to have descended from three ancestral populations: Steppe, Mesolithic Europeans and Neolithic farmers21,22. We projected ancient samples from these three populations as well as ancient Saxon samples24 onto the UK Biobank PCs (Figure 3, Supplementary Figure 4, see Online Methods). These populations were primarily differentiated along PC1 and PC3, indicating higher levels of Steppe ancestry in northern UK populations."
From the body of the paper:
"We consistently obtained significantly positive 𝑓4 statistics, implying that both the modern Celtic samples and the ancient Saxon samples have more Steppe ancestry than the modern Anglo-Saxon samples from southern and eastern England. This indicates that southern and eastern England is not exclusively a genetic mix of Celts and Saxons. There are a variety of possible explanations, but one is that the present genetic structure of Britain, while subtle, is quite old, and that southern England in Roman times already had less Steppe ancestry than Wales and Scotland."
Southern and Eastern England is the largest genetic cluster in the U.K. and has the least steppe ancestry, and they seem to think it's likely that this was already the case in Roman times. That's contrary to the position of the Hellenthal group, which is fine with me, because some of their work makes no sense to me in light of what we know from history.
So, the obvious question is why? Could the Belgae have been a more "southern" leaning group? Could it be the Romans? If it increased later, then the Normans are a possibility, an idea which Dienekes seems to favor.
http://dienekes.blogspot.com/2016/05/british-celts-have-more-steppe-ancestry.html
Btw, they make an interesting point about the Welsh:
"Additionally, the lack of any ancient sample correlation with PC2 suggests that Welsh populations are not differentially admixed with any ancient population in our data set, and likely underwent Welsh-specific genetic drift."
What do you guys think about that? That would mean that the Anglo-Saxon admixture went right through the mountains to the west coast. I don't know that I buy that given the differences in yDna.