Question

how is the coloration of skin color an "evolutionary balancing act."

Answer 1

Human skin color reflects an evolutionary balancing act within tens of thousands of years in the making.

the explanation for why human skin tone varies as a global gradient, with the darkest populations around the equator and the lightest ones near the poles. the dark complexion is advantageous in sunnier places, whereas fair skin fairs are better in regions with less sun.  considering the suffering that ensues when pale folks visit the beach.

But actually, humanity’s color gradient probably has little to do with sunburn or even skin cancer. Instead, the complexion has been shaped by conflicting demands from two essential vitamins: folate and vitamin D.

Folate is destroyed by the sun’s ultraviolet (UV) radiation. Whereas the skin kickstarts the production of vitamin D after being exposed to those same rays.

Here comes the balancing act!

humans need a happy medium dosage of the sun that satisfies both. While the intensity of UV rays is dictated by geography, the amount actually penetrating your skin depends on your degree of pigmentation, or skin color.

Several million years ago, our ancestors’ skin tone would not have been obvious. That’s because early hominins were almost certainly cloaked in dark fur. But beneath the body hair, they probably had pale skin based on the fact that our evolutionary cousins, chimpanzees, and gorillas, have light skin under dark fur today. Our ancestors eventually lost this fur and gained pigment in their skin. Although the exact timing and causes are unverified, many agree that when humans lost their fur, it helped us stay cool while foraging as upright-walking bipeds in the sunny, open habitats of equatorial Africa. The tradeoff, however, was bare skin that was exposed to intense, year-round UV rays.

roughly 1 to 2 million years ago darker skin was likely better to protect folate stores.