10 April 2015

When and how the Europeans turned white

A new genetic study has found,
that the most important evolutionary change is whiteness
– it appeared among Europeans 8000 years ago

Marina Astvatsaturyan, Echo of Moscow

In a comparative study of the genomes of ancient populations and modern humans, presented at the recent, 84th conference of the American Association of Physical Anthropologists (American Association of Physical Anthropologist), several genes related to changes in diet and skin pigmentation and subjected to strict natural selection were identified.

According to Science NOW (How Europeans evolved white skin – VM), first of all, population geneticists from Harvard University David Reich and Ian Mathieson confirmed previous data that European hunter-gatherers 8000 years ago were unable to digest milk sugar, lactose. The first cattle farmers did not digest milk either. There was no gene responsible for the assimilation of lactose – it is called LCT – neither in farmers who came from the Middle East 7800 years ago, nor in cattle breeders of the Yamnaya culture who came from the Eastern European steppes 4800 years ago. Lactose tolerance began to spread across Europe only 4,300 years ago, not earlier. As for the genes that determine skin color, their evolutionary history is more complicated.

According to new data, about 8,500 years ago, hunter-gatherers in Spain, Luxembourg and Hungary, like their ancestors who came out of Africa 40 thousand years ago, had a dark skin color. They did not have two mutations in the SLC gene (SLC24A and SLC45A2), which are responsible for depigmentation – the white skin of modern Europeans. But further north, for example, in Sweden, both "light-skinned" gene variants were found in the genomes of seven hunter-gatherers who lived 7700 years ago. The carriers of both of these genes turned out to be Middle Eastern farmers who came to Europe at about the same time. It was one of their "light-skinned" variants that appeared in the Central and Eastern European populations as soon as they began to interbreed with the indigenous hunter-gatherer population.

The second "Middle Eastern" variant began to spread with high frequency only 5800 years ago. In the article (Mathieson et al., Eight thousand years of natural selection in Europe; you can also download the full text in pdf – VM there), which the authors of the study posted on the bioRxiv biology preprints website, nothing is said about the reasons for strict natural selection by skin color genes, but there is an assumption that in the northern at latitudes, the owners of fair skin with the lactose tolerance gene had a clear advantage. Light skin accumulates the solar ultraviolet, which is scarce in northern latitudes, but necessary for the formation of vitamin D, is more effective than dark, and milk is a source of vitamin D, and therefore its assimilation in Europe was vital.

Portal "Eternal youth" http://vechnayamolodost.ru10.04.2015

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