Nina Jablonski Skin pigmentation in modern humans is an adaptation to ultraviolet radiation. The most darkly pigmented skin is found among people living at or near the equator; the most lightly pigmented skin is found among people living above 45N latitude. The primary pigment in human skin is melanin, mostly in the form of the very dark brown eumelanin.
Over the course of his life, Darwin had great privilege. He lived in a fairly wealthy home. He was raised by very supportive and interested parents.
And when he was in his 20s he embarked upon a remarkable voyage on the ship the Beagle. And during the course of that voyage, he saw remarkable things: And the observations that he made on that epic journey were to be eventually distilled into his wonderful book, "On the Origin of Species," published years ago.
Now in his years of traveling on the Beagle, and from listening to the accounts or explorers and naturalists, he knew that skin color was one of the most important ways in which people varied.
And he was somewhat interested in the pattern of skin color.
He knew that darkly pigmented peoples were found close to the equator; lightly pigmented peoples, like himself, were found closer to the poles. So what did he make of all this?
But much later, inhe did have something to say about it. And it was quite curious. He said, "Of all the differences between the races of men, the color of the skin is the most conspicuous and one of the best marked. He had seen people of different colors living in different places.
And yet he rejected the idea that human skin pigmentation was related to the climate. If only Darwin lived today.
Now, one of the wonderful things that NASA does is it puts up a variety of satellites that detect all sort of interesting things about our environment. Now the really hot pink and red areas are those parts of the world that receive the highest amounts of UV during the year.
The incrementally cooler colors — blues, greens, yellows, and finally grays — indicate areas of much lower ultraviolet radiation. This has tremendous implications for our understanding of the evolution of human skin pigmentation.
And that skin pigmentation itself was a product of evolution. And so when we look at a map of skin color, and predicted skin color, as we know it today, what we see is a beautiful gradient from the darkest skin pigmentations toward the equator, and the lightest ones toward the poles.
The earliest members of our lineage, the genus Homo, were darkly pigmented.
And we all share this incredible heritage of having originally been darkly pigmented, two million to one and half million years ago. Now what happened in our history?
In those early days of our evolution, looking at the equator, we were bombarded by high levels of ultraviolet radiation.Melanin, the skin's brown pigment, is a natural sunscreen that protects tropical peoples from the many harmful effects of ultraviolet (UV) rays.
UV rays can, for example, strip away folic acid, a nutrient essential to the development of healthy fetuses.
Some of us with darkly pigmented skin live in low-UV areas. These have tremendous consequences for our health. We have to, if we're lightly pigmented, be careful about the problems of skin cancer, and destruction of folate in our bodies, by lots of sun.
People with dark skin require up to 10 times more exposure to sunlight than people with light skin to produce the same amount of Vitamin D. Darker skinned people who live in more northern latitudes than their ancestors, are at risk for Vitamin D deficiency. Watch video · What they haven't been so good about instructing people is the problem of darkly pigmented people living in high latitude areas, or working inside all the time.
Because the problem there is just as severe, but it is more sinister, because vitamin D deficiency, from a lack of ultraviolet B radiation, is a major problem.
All people with dark skin are at risk for both skin conditions. Among the most common types of pigment problems in dark skin is post-inflammatory hyperpigmentation. This occurs as a result of skin. SKIN I. INTRODUCTION Skin, outer body covering of an metin2sell.com term skin is commonly used to describe the body covering of any animal but technically refers only to the body covering of vertebrates (animals that have a backbone).
The skin has the same basic structure in all vertebrates, including fish, reptiles, birds, and humans and other mammals.. This article focuses primarily on human s.