Angela
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The link to this article from the Pritchard group is here:
Detection of human adaptation during the last 2000 years.
"http://biorxiv.org/content/early/2016/05/07/052084
"Detection of recent natural selection is a challenging problem in population genetics, as standard methods generally integrate over long timescales. Here we introduce the Singleton Density Score (SDS), a powerful measure to infer very recent changes in allele frequencies from contemporary genome sequences. When applied to data from the UK10K Project, SDS reflects allele frequency changes in the ancestors of modern Britons during the past 2,000 years. We see strong signals of selection at lactase and HLA, and in favor of blond hair and blue eyes. Turning to signals of polygenic adaptation we find, remarkably, that recent selection for increased height has driven allele frequency shifts across most of the genome. Moreover, we report suggestive new evidence for polygenic shifts affecting many other complex traits. Our results suggest that polygenic adaptation has played a pervasive role in shaping genotypic and phenotypic variation in modern humans."
Razib opines here:
http://www.unz.com/gnxp/the-2000-year-selection-of-the-british/
"Perhaps more interesting is that the authors detect continuous selection on height and pigmentation in their sample. Why height? I’ve been skeptical of some of the genetic arguments in Greg Clark’s A Farewell to Alms (and have told Greg so), but, recent selection for height does seem to align with his idea that the English were particularly wealth and healthy over the past ~2,000 years. And, it also seems to support the suggestion of elite over-production, as presumably tall men would be more well represented among elites for both nutritional and genetic reasons."
"The results for pigmentation are intriguing. Some of the older signals don’t show up (e.g., SLC24A5 andSLC45A2). They’re either fixed, or near fixed, so where are the old haplotypes going to be to compare to? But intriguingly the selection around KITLG and OCA-HERC2 still seems to be occurring! Though the authors associate them with hair and eye color, the extreme tissue specific expression does not mean they have no effect on skin color. In the supplements they note that “In all 14 cases the derived allele is associated with either lighter pigmentation (i.e., lighter hair, skin, or eyes) or increased freckling.” Additionally, they state in the main text that “We speculate that recent selection in favor of blond hair and blue eyes may reflect sexual selection for these phenotypes in the ancestors of the British, as opposed to the longer-term trend toward lighter skin pigmentation in non-Africans, generally thought to have been driven by the need for Vitamin D production.”"
I speculated that this might have been the case when we saw the results for the samples representing the population overturn in Britain after the Neolithic. They didn't look like a blonde and blue eyed population, not that they're all blonde even now, even in the areas that are more "Anglo-Saxon".
That leads me to the fact that I'm not so sure that migration didn't have some effect, and climate as well. I'm aware that the AS part of the English genome is around 20-30% yes? That probably isn't enough to produce the change.
However, if the Anglo-Saxons, who seem to be the last major folk movement into Britain, were more represented in the elite groups, and were more blonde and blue eyed than the prior "Celtic" inhabitants, then, as a natural process in such situations that look would be associated with a higher social status, and so people would sexually select for it. These kinds of processes are the products of culture once perhaps more ingrained preferences like selection for "healthy" traits like symmetry of feature, clear skin, shiny hair, and perhaps certain anatomical features related to female and male hormone levels are considered.
In terms of light eyes I still think that more research has to be done into whether solar radiation plays a factor. Ireland has extremely high levels of light eyes. Yet, the ancient samples don't show particularly high levels of light eyes. I don't think it can be all down to AS gene flow, because there was much less of it there than in England. They're also more dark haired than the English from what I remember.
Razib seems convinced that the authors factored out the effects of migration.
I haven't yet tackled the Supplement, so I don't know.
Anyway, they're very persuasive that selection can occur much more quickly than was previously imagined, as the LP increase has shown.
It would be nice if they did the same sort of analysis for other parts of Europe.
Detection of human adaptation during the last 2000 years.
"http://biorxiv.org/content/early/2016/05/07/052084
"Detection of recent natural selection is a challenging problem in population genetics, as standard methods generally integrate over long timescales. Here we introduce the Singleton Density Score (SDS), a powerful measure to infer very recent changes in allele frequencies from contemporary genome sequences. When applied to data from the UK10K Project, SDS reflects allele frequency changes in the ancestors of modern Britons during the past 2,000 years. We see strong signals of selection at lactase and HLA, and in favor of blond hair and blue eyes. Turning to signals of polygenic adaptation we find, remarkably, that recent selection for increased height has driven allele frequency shifts across most of the genome. Moreover, we report suggestive new evidence for polygenic shifts affecting many other complex traits. Our results suggest that polygenic adaptation has played a pervasive role in shaping genotypic and phenotypic variation in modern humans."
Razib opines here:
http://www.unz.com/gnxp/the-2000-year-selection-of-the-british/
"Perhaps more interesting is that the authors detect continuous selection on height and pigmentation in their sample. Why height? I’ve been skeptical of some of the genetic arguments in Greg Clark’s A Farewell to Alms (and have told Greg so), but, recent selection for height does seem to align with his idea that the English were particularly wealth and healthy over the past ~2,000 years. And, it also seems to support the suggestion of elite over-production, as presumably tall men would be more well represented among elites for both nutritional and genetic reasons."
"The results for pigmentation are intriguing. Some of the older signals don’t show up (e.g., SLC24A5 andSLC45A2). They’re either fixed, or near fixed, so where are the old haplotypes going to be to compare to? But intriguingly the selection around KITLG and OCA-HERC2 still seems to be occurring! Though the authors associate them with hair and eye color, the extreme tissue specific expression does not mean they have no effect on skin color. In the supplements they note that “In all 14 cases the derived allele is associated with either lighter pigmentation (i.e., lighter hair, skin, or eyes) or increased freckling.” Additionally, they state in the main text that “We speculate that recent selection in favor of blond hair and blue eyes may reflect sexual selection for these phenotypes in the ancestors of the British, as opposed to the longer-term trend toward lighter skin pigmentation in non-Africans, generally thought to have been driven by the need for Vitamin D production.”"
I speculated that this might have been the case when we saw the results for the samples representing the population overturn in Britain after the Neolithic. They didn't look like a blonde and blue eyed population, not that they're all blonde even now, even in the areas that are more "Anglo-Saxon".
That leads me to the fact that I'm not so sure that migration didn't have some effect, and climate as well. I'm aware that the AS part of the English genome is around 20-30% yes? That probably isn't enough to produce the change.
However, if the Anglo-Saxons, who seem to be the last major folk movement into Britain, were more represented in the elite groups, and were more blonde and blue eyed than the prior "Celtic" inhabitants, then, as a natural process in such situations that look would be associated with a higher social status, and so people would sexually select for it. These kinds of processes are the products of culture once perhaps more ingrained preferences like selection for "healthy" traits like symmetry of feature, clear skin, shiny hair, and perhaps certain anatomical features related to female and male hormone levels are considered.
In terms of light eyes I still think that more research has to be done into whether solar radiation plays a factor. Ireland has extremely high levels of light eyes. Yet, the ancient samples don't show particularly high levels of light eyes. I don't think it can be all down to AS gene flow, because there was much less of it there than in England. They're also more dark haired than the English from what I remember.
Razib seems convinced that the authors factored out the effects of migration.
I haven't yet tackled the Supplement, so I don't know.
Anyway, they're very persuasive that selection can occur much more quickly than was previously imagined, as the LP increase has shown.
It would be nice if they did the same sort of analysis for other parts of Europe.