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Thread: How did early Amerindians survive living so far north?

  1. #1
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    1 members found this post helpful.

    How did early Amerindians survive living so far north?



    Getting enough Vitamin D is, as we now know, essential for good health. The best natural source (when they didn't have fortified milk, etc., where it is added) is sunlight, although organ meats of certain animals also support it.

    New research indicates that a genetic mutation affected the milk ducts of Amerindian women gave them the ability to provide more nourishment to nursing children.

    See:
    https://www.sciencemag.org/news/2018...medium=Twitter

    They're talking about EDAR.

    "When the ancestors of Native Americans ventured across the Bering land bridge from today’s Siberia to Alaska about 20,000 years ago, they struggled to get enough sunlight during the long, dark winters. Living so far north with scant sunshine should have led to rickets and other health problems, yet somehow the population survived and even thrived enough to live there for thousands of years. Their lucky break, according to a new study, was that they carried a genetic mutation—revealed in ancient teeth—that boosted the development of milk ducts in women’s breasts, which may have helped nursing mothers pass more nutrients to their infants."

    "
    The gene in question is known as EDAR. Native Americans and Asians carry a version of the gene that is linked to thicker hair shafts, more sweat glands, and shovel-shaped incisors. A variant of this gene—V370A—arose about 30,000 years ago or so in China when the climate was hotter and more humid, which prompted researchers to speculate initially that it was advantageous to have more sweat glands in that environment. But the gene variant swept through the ancestors of Asians and Native Americans about 20,000 years ago, when the climate where they lived in Asia and Beringia (the now-submerged land between Asia and Alaska) was colder and dryer. So the actual cause of the gene’s spread has been unknown."

    "
    The new study reveals that the variant was so beneficial it spread to everyone in the Americas. When researchers led by biological anthropologist Leslea Hlusko of the University of California, Berkeley, examined data on the teeth of more than 5000 people from 54 archaeological sites in Europe, Asia, and North and South America, they found shoveled teeth—and hence, the gene variant that causes themin about 40% of the individuals in Asia and all of the 3183 fossils of Native Americans they examined (who all lived before European colonization).This suggests that some members of the first group to arrive in Beringia probably carried the gene, which arose in Asia. Then it quickly swept through the rest of the small isolated population of people who settled there between 28,000 and 18,000 years ago.
    Living at such a high latitude puts nursing infants at risk of not getting enough sunlight in winter to synthesize vitamin D in their skin. Unlike adults, nursing infants can’t eat marine foods and organ meat rich in vitamin D to compensate. Vitamin D deficiency can trigger serious problems with bone development, such as rickets. It also interferes with the many ways fat insulates and fuels our bodies, as well as how the immune system wards off disease.
    The EDAR variant led to the development of more elaborate branching of milk ducts in studies of mice. Hlusko and her colleagues hypothesize that those extra branches cause mothers to produce more milk or deliver more nutrients in their milk. If so, children of mothers with the EDAR variant would have been more likely to survive, thus spreading the variant throughout the population, the team proposes today in the Proceedings of the National Academy of Sciences."

    Well, I suppose once the children had teeth and could eat meat and fish you could stop, although nursing reduces fertility, so European women often, before the invention of birth control methods, nursed until the child was eighteen months old or so. That's too much for me. Nine months to a year is sufficient. Once all the teeth are in it's time to stop. :)

    I don't understand, though, if EDAR variants are so beneficial, why didn't it spread from the Swedish Hunter Gatherers, some of whom did have them if I remember correctly?

    Also, why didn't they get a lot paler, as Northern Europeans did? Was it all that organ meat and fish?


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    1 members found this post helpful.
    There's a free test for EDAR at https://www.yourdnaportal.com/

    It’s the same test that they use to detect Native American ancestry.


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    there are a lot of 'could' and 'would' in the wording
    you'd think things would be more clear and obvious, but they are not

    with DNA testing so cheap now, data available should multiply and things should become clearer in future

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