About 2 million years ago, permanent dark skin colour imparted by the pigment– melanin—began to evolve in humans to regulate the body’s reaction to ultraviolet rays from the sun, says Nina Jablonski, Distinguished Professor of Anthropology.
Melanin allows enough ultraviolet radiation in to the skin to produce vitamin D while simultaneously shielding the skin from the intense ultraviolet radiation. It thus helps humans sustain a fine equilibrium between too much sunlight and not enough sunlight.
Nina recently presented her research about effect of modern urban life on this mechanism.
Air travel has made humans more mobile than their counterparts a few ages ago. A person having dark skin may travel to regions with less intense sunlight, and those with a fair skin may relocate to areas with lots of sunlight.
“We move around a lot now,” said Jablonski. “People can move across 90 degrees of latitude in a single day whereas early humans generally only went a few kilometres in the same time.”
Also, almost 60 per cent of the world population lives in cities now. Most urban dwellers work indoors, further decreasing their skin’s capacity to make enough vitamin D.
“Think about a farmer who lived in northern England and worked outside,” said Jablonski. “In the past, that farmer had the right amount of light pigmentation to make it possible for him to produce enough vitamin D in his skin in the summer to satisfy most of his yearly needs.”
“Now, a person in England is not getting very much sun at all, except maybe when he travels to Spain on vacation for a few weeks,” the researcher said.
It is commonly known that not receiving enough sunlight or a mismatch between our skin pigmentation and ultraviolet radiation leads to serious health issues like skin cancers. It can lead to a vitamin D catastrophe for many people.
This study emphasises that we may be losing some of our evolutionary advantage of melanin. Further hailing the importance of receiving enough vitamin D. Hence, for those who are worried about going out in the sun for fear of skin cancer, the researcher suggests vitamin D supplements “By far, the safest way and the cheapest way is to use vitamin D supplements, which are widely available in stores,” said Jablonski.