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Abstract:
The authors pointed out, what was already assumed, that geneticists can‘t really predict the skin colour of very ancient people. Which means, that the very dark (dark brown till black) skin tone concluded for the Cheddar man, is rather speculative. In addition to that neither the Cheddar man, La Brana nor Lola possessed the loci TMEM138, OCA2 and HERC2 associated with the "black" skin pigmentation identified in Sub- Saharan African populations which is a modern, more recent mutation, too.
source:
https://www.pnas.org/content/118/1/e2009227118
Skin pigmentation is a classic example of a polygenic trait that has experienced directional selection in humans. Genome-wide association studies have identified well over a hundred pigmentation-associated loci, and genomic scans in present-day and ancient populations have identified selective sweeps for a small number of light pigmentation-associated alleles in Europeans. It is unclear whether selection has operated on all of the genetic variation associated with skin pigmentation as opposed to just a small number of large-effect variants. Here, we address this question using ancient DNA from 1,158 individuals from West Eurasia covering a period of 40,000 y combined with genome-wide association summary statistics from the UK Biobank. We find a robust signal of directional selection in ancient West Eurasians on 170 skin pigmentation-associated variants ascertained in the UK Biobank. However, we also show that this signal is driven by a limited number of large-effect variants. Consistent with this observation, we find that a polygenic selection test in present-day populations fails to detect selection with the full set of variants. Our data allow us to disentangle the effects of admixture and selection. Most notably, a large-effect variant at SLC24A5 was introduced to Western Europe by migrations of Neolithic farming populations but continued to be under selection post-admixture. This study shows that the response to selection for light skin pigmentation in West Eurasia was driven by a relatively small proportion of the variants that are associated with present-day phenotypic variation.
The authors pointed out, what was already assumed, that geneticists can‘t really predict the skin colour of very ancient people. Which means, that the very dark (dark brown till black) skin tone concluded for the Cheddar man, is rather speculative. In addition to that neither the Cheddar man, La Brana nor Lola possessed the loci TMEM138, OCA2 and HERC2 associated with the "black" skin pigmentation identified in Sub- Saharan African populations which is a modern, more recent mutation, too.
Relatively dark skin pigmentation in Early Upper Paleolithic Europe would be consistent with those populations being relatively poorly adapted to high-latitude conditions as a result of having recently migrated from lower latitudes. On the other hand, although we have shown that these populations carried few of the light pigmentation alleles that are segregating in present-day Europe, they may have carried different alleles that we cannot now detect. As an extreme example,Neanderthals and the Altai Denisovan individual show genetic scores that are in a similar range to Early Upper Paleolithic individuals (SIAppendix,Table S1), but it is highly plausible that these populations, who lived at high latitudes for hundreds of thousands of years, would have adapted independently to low UV levels. For this reason, we cannot confidently make statements about the skin pigmentation of ancient populations.
source:
https://www.pnas.org/content/118/1/e2009227118