Whatever the color, our skin tells an epic tale of human intrepidness and adaptability, revealing its variance to be a function of biology. It al centers around melanin, the pigment that gives skin and hair its color. This ingredient comes from skin cells called melanocytes and takes two basic forms. There’s eumelanin, which gives rise to a range of brown skin tones, as wel as black, brown and blond hair, and pheomelanin which causes the reddish browns of freckles and red hair. But humans were not always like this. Our varying skin tones were formed by an evolutionary process driven by the sun. It began some 50 thousand years ago when our ancestors migrated from north from Africa and into Europe to Asia. These anicient humans lived between the Equator and the Tropic of Capricorn, a region saturated by the sun’s UV-carrying rays. When skin is exposed to UV for long periods of time, the UV light damages the DNA within our cells and skin starts to burn. If the damage is severe enough the cells mutation can lead to melanoma, a deadly cancer that forms in the skin’s melanocytes. Sunscreen as we know it today did not exist 50,000 years ago. So how did our ancestors cope with this onslaught of UV?
The key to survival lay in their own personal sunscreen manufactured beneath their skin, melanin. The type and ammount of melanin in your skin determines whether you would be more or less protective from the sun. When skin is exposed to UV light, that triggers special light-sensitive receptors called rhodopsin, which stimulate the production of melanin to shield cells from damage. For light-skin people that extra melanin darkens their skin and produces a tan. Over the course of generation, humans living in sun saturated latitudes in Africa adapted to have a higher melanin production threshold and more eumelanin, giving skin a darker tone. This built-in sun shield help protect them from melanoma making them evolutionarily fitter and capable of passing the useful trait on to new generations.
But soon some of our sun adapted ancestors migrated northward spreading far and wide across the Earth. The further north they traveled, the less direct sunshine they saw. This was a problem because although UV light can damage skin, it helps our bodies produce vitamin D, an ingredient that strengthens bones and lets us absorb vital minerals, like magnesium, phosphate and zinc. Without it, humans experience serious fatigue and weakened bones that can cause a condition known as rickets. For humans whose dark skin effectively blocked whatever sunlight there was, vitamin D deficiency would have posed a serious threat in the north. But some of them happened to produce less melanin. They were exposed to small enough amounts of light that melanoma was less likely, and their lighter skin better absorbed the UV light. Over many generations of selection , skin color in those regions gradually lightened. Today, the planet is full of people with a vast palette of skin colors, typically, darker eumelanin rich skin in the hot, sunny band around the Equator, and increasingly lighter pheomelanin rich skin shades fanning outwards as the sunshine dwindles. But skin color certainly does not reflect character.
Transcripted by Benazir Elahee Munni