Anonymous
Anonymous asked in Social ScienceAnthropology · 3 months ago

How long did it take for migrants from Africa to evolve colored eyes?

I wonder why for example Kazakhs who get very little amount of sun haven't evolved their eyes to colored eyes. How long did it take for those migrants from Africa to evolve thousands (or millions of years ago)?

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  • Anonymous
    2 months ago

    Kazakhs are not native to the region. The original inhabitants of Kazakhstan were European and did have blue and green eyes: (See here):

    https://en.wikipedia.org/wiki/Andronovo_culture

    (Click on further portals to read more, if you're interested)

    Europeans were displaced in the region starting around 200 BC - 100AD.

    It took a couple thousand years for Europeans to develop different eye colors.

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  • 3 months ago

    9400 yrs ago; it happened

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  • 3 months ago

    Research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye color of all blue-eyed humans alive on the planet today.

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  • Anonymous
    3 months ago

    It's a recessive mutation that becomes dominant through inbreeding. It's not about the sun or years, it's about population size and isolation. There are group of dark skinned Melanesians with blue eyes and blond Afros (they are isolated on an island).

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  • Zirp
    Lv 7
    3 months ago

    Wrong question, Lamarck

    Mutations happen RANDOMLY, and then are passed on to (part of the) offspring of those who had them first.

    Millions of generations can go by without anything "evolving"

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  • 3 months ago

    About 60,000 but with the help of some Neanderthal genes

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  • Anonymous
    3 months ago

    Most people around the world have lots of eumelanin in their eyes. Eumelanin is a dark brown to black pigment that also give hair and skin their dark color. Humans evolved in Africa, and we evolved to be almost hairless with lots of sweat glands to stay cool. When we sweat or skin gets wet and it cools when the sweat evaporates from our skin. A hairless body us vulnerable to the sun's cancer causing UV light, so we needed the dark pigment eumelanin to absorb the UV light to prevent skin cancer. The eumelanin in our eyes protect us from eye cancer.

    People who have :colored eyes (such as blue, green and hazel) do not have eumelanin in their eyes. The molecules inside the eye scatter blue light, the same way that air molecules in the sky scatter blue light to make the sky blue. There is no blue pigment in the sky or in the eyes. Green eyes is the result of a small amount of phaeomelanin (a yellow to red pigment) in the eye, mixing with the scattered blue light to make the eye look green Hazel eyes is the result of lots of phaeomelanin in the eye. Wen eumelanin is present in the eye it absorbs all the scatted blue light and reflected yellow to red light to make it look dark brown or black.

    Central Asians evolved from Africans who migrated out of Africa and settled in Central Asia 60,000 years ago. Central Asia has cooler climate than Africa, and Central Asians evolved some of the adaptations to cold climates seen in other people such as Europeans and north Asians. These adaptations include a taller and narrower nose bridge and straight hair. The taller narrower nose keeps warm air coming out of the lungs in the nose longer, where the warmth is extracted by the respiratory turbinates and returned to the lungs when cool air from the outside gets warmed before being sent to the lungs. Straight hair lies flat on the scalp and it prevents chilly wind from blowing past the scalp to chill the head. Nevertheless, Central Asia is a grassy habitat, with little shade, so the people there still need eumelanin in their skin to protect themselves from skin cancer.

    Eueopeans from Central Asians who migrated to Eueope 40,000 years ago, during the middle of the last ice age. To cope with the cold climate, the first Europeans needed to stay warm by wearing clothes or animals skins. The skin however blocks their skin from the sun, and prevents the absorption of the harmless UV light needed to manufacture vitamin D. Vitamin D helps the body absorb calcium from our food, so a dark skinned person wearing clothes would easily suffer vitamin D shortage and the result is rickets, which can cause deformed or broken bones and even death.

    Rickets, or its prevention, is the reason north Asians, Europeans and Mongolians evolved light skin tones By reducing the amount of eumelanin in the skin, it can absorb enough sunlight to make vitamin D. Since the clothes also block out the cancer causing UV light, people who are light skinned can be safe from skin cancer. The way eumelanin is reduced is by evolving a defective version of the gene that encodes the enzyme to produce eumelanin. If the cells in the eyes have the same deflect, then eumelanin is absent and the eyes will look blue, green or hazel.

    Scientists who studied blue eyes claim that it evolved about 10,000 years ago in the Black Sea Area. This area is where a lot of modern Europeans originated from. 24,000 years ago, many Europeans (after evolving light skin and other cold adaptations) migrated out of Europe because the ice age was at its peak at that time. Many of them settled in the Caucasus region and the Balkans area of eastern Europe. When the ice age ended 13,000 years ago, Europe's glaciers melted, and Europe became habitable again. So, many people who had lived in the Caucasus region migrated back to Europe. Some of these people had evolved blue eyes while living in the area and so they brought their blue eyes with them to Europe. Central Asians, OTOH, never evolved blue eyes because such a mutation did not happen, and besides, there is no benefit in having blue eyes, since people with blue eyes have a higher incidence of contractnig eye cancer.

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