The science of skin color Angela Koine Flynn
When ultraviolet sunlight hits our skin, it affects each of us a little differently. Depending on skin color, it will takeonly minutes of exposure to turn one person beetrootpink, while another requires hours to experiencethe slightest change. So what's to account for that difference and how did our skin come to take onso many different hues to begin withé Whatever the color,
our skin tells an epic tale of human intrepidness and adaptability, revealing its variance to be a function of biology. It all centers around melanin, the pigment that gives skin and hair its color. This ingredient comes from skin cellscalled melanocytes and takes two basic forms. There's eumelanin, which gives riseto a range of brown skin tones, as well as black, brown, and blond hair,
and pheomelanin, which causes thereddish browns of freckles and red hair. But humans weren't always like this. Our varying skin tones were formedby an evolutionary process driven by the Sun. In began some 50,000 years ago when ourancestors migrated north from Africa and into Europe and Asia. These ancient humans lived betweenthe Equator and the Tropic of Capricorn, a region saturated by the Sun's UVcarrying rays.
When skin is exposed to UV for longperiods of time, the UV light damages the DNA within our cells, and skin starts to burn. If that damage is severe enough, the cells mutations can lead to melanoma, a deadly cancer that forms in the skin's melanocytes. Sunscreen as we know it todaydidn't exist 50,000 years ago. So how did our ancestors cope with this onslaught of UVé
The key to survival lay in their own personal sunscreen manufactured beneath the skin: melanin. The type and amount of melanin in your skin determines whether you'll be more or lessprotected from the sun. This comes down to the skin's responseas sunlight strikes it. When it's exposed to UV light, that triggers special lightsensitive receptors called rhodopsin, which stimulate the production of melaninto shield cells from damage.
For lightskin people, that extra melanindarkens their skin and produces a tan. Over the course of generations, humans living at the Sunsaturated latitudes in Africa adapted to have a higher melanin production threshold and more eumelanin, giving skin a darker tone. This builtin sun shield helped protectthem from melanoma, likely making them evolutionarily fitter