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Here’s why sunburns are more common than ever — and how to properly protect your skin

humans have a contradictory relationship to the sun. People love sunshine, but then it gets hot. Sweat gets in your eyes. Then there are all the protective rituals: the sunscreen, the hats, the sunglasses. If you stay out too long or haven’t taken enough precautions, your skin will tell us with a nasty sunburn. First the heat, then the pain, then the regret.

Have people always been obsessed with what the sun would do to their bodies? As a biological anthropologist who has studied primate adaptations to the environment, I can tell you that the short answer is no, and they didn’t have to be. For eons the skin withstood the sun.

The skin our ancestors lived in

Man evolved under the sun. Sunlight was a constant in people’s lives, warming and guiding them through the days and seasons. homo sapiens spent most of our prehistory and history outside, mostly naked. The skin was the primary interface between our ancestors’ bodies and the world.

Human skin was adapted to the conditions it was in. People sought shelter when they could find it in caves and rock shelters, and became quite good at crafting portable shelters out of wood, animal skins, and other gathered materials.

At night they snuggled together, probably covering themselves with fur “blankets.” But during the active daylight hours, people were outdoors, and their mostly bare skin was what they had.

Throughout a person’s life, skin responds to routine sun exposure in a variety of ways. The skin’s surface layer—the epidermis—becomes thicker as more layers of cells are added. In most people, the skin gradually darkens as specialized cells become active to produce a protective pigment called eumelanin.

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This remarkable molecule absorbs the most visible light, making it appear very dark brown, almost black. Eumelanin also absorbs harmful UV radiation. Depending on their genetics, people produce different amounts of eumelanin. Some have a lot and can produce a lot more when their skin is exposed to the sun; others have less to begin with and produce less when their skin is exposed.

People’s skin adapted to their local UV light conditions.tunart/DigitalVision Vectors/Getty Images

My research on the evolution of human skin pigmentation has shown that prehistoric humans’ skin color was tuned to local environmental conditions, primarily local levels of ultraviolet light. People who lived under high levels of UV light – like you would find near the equator – had darkly pigmented and highly tannable skin capable of producing lots of eumelanin year after year. People who lived under weaker and more seasonal levels of UV—like those found in much of northern Europe and northern Asia—had lighter skin that had limited abilities to produce protective pigments.

Supported only by their feet, our distant ancestors did not move much during their lifetime. Their skin adapted to subtle, seasonal changes in sunlight and UV conditions by producing more eumelanin and becoming darker in the summer and then losing some pigment in the fall and winter when the sun wasn’t as strong. Even in people with slightly pigmented skin, painful sunburns would have been extremely rare, as sudden shock from exposure to intense sunlight never occurred. As the sun got stronger in the spring, the top layer of skin would have gradually thickened over weeks and months of sun exposure.

That’s not to say the skin was undamaged by today’s standards: dermatologists would be appalled at the leathery and wrinkled appearance of our ancestors’ sun-exposed skin. Skin color changed with the seasons, as did the position of the sun itself, and skin quickly showed its age. This is still the case for people living traditionally, mostly outdoors, in many parts of the world.

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There’s no preserved skin from thousands of years ago for scientists to study, but we can infer from the effects of sun exposure on modern humans that the damage was similar. Chronic sun exposure can lead to skin cancer, but rarely of the kind – melanoma – that would lead to death in reproductive age.

Indoor living has changed the skin

Up until about 10,000 years ago – a drop in the ocean in evolutionary history – humans lived by gathering food, hunting and fishing. Humanity’s relationship to the sun and sunlight has changed greatly after humans began to settle down and live in permanent settlements. Farming and food storage were associated with the development of immovable buildings. Around 6000 BC Many people around the world spent more time in walled settlements and more time indoors.

While most people still spent most of their time outside, some stayed inside when they could. Many of them started to protect themselves from the sun when they went out. Around at least 3000 B.C. A whole industry of sun protection developed to manufacture gear of all kinds—parasols, umbrellas, hats, tents, and clothing—that would protect people from the discomfort and inevitable darkening of the skin associated with prolonged exposure to the sun. While some of these were originally reserved for the nobility – like the parasols and umbrellas of ancient Egypt and China – these luxury items were increasingly being manufactured and used.

Parasols are among the items that people have invented to protect themselves from the sun’s rays.Reverse Couple Pictures/Moment/Getty Images

In some places, people even developed protective pastes made from minerals and plant residues—early versions of modern sunscreens—to protect their exposed skin. Some like that thanaka Paste used by people of Myanmar still exists today.

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An important consequence of these practices in traditional agricultural societies was that people who spent most of their time indoors considered themselves privileged, and their lighter skin heralded their status. A “rustic tan” wasn’t glamorous: suntanned skin was a punishment for hard outdoor work, not the badge of a leisurely vacation. From the UK to China, Japan and India, tanned skin has been associated with a life of hardship.

As people have moved faster, longer distances and spent more time indoors over the last few centuries, their skin has not kept pace with where they live and their lifestyles. Your eumelanin levels are probably not perfectly adapted to the solar conditions where you live and therefore cannot protect you in the same way as your ancient ancestors did.

Even if you’re naturally darkly pigmented or capable of tanning, everyone is susceptible to damage from sun exposure, especially after long breaks spent completely out of the sun. The “holiday effect” of sudden strong UV exposure is really bad, because sunburn signals skin damage that can never be completely repaired. It’s like a bad debt that presents itself many years later as prematurely aged or precancerous skin. There is no such thing as a healthy tan – a tan will not protect you from further sun damage; it is a sign of damage in itself.

Humans may love the sun, but we are not our ancestors. Humanity’s relationship with the sun has changed, and that means you need to change your behavior to save your skin.

This article was originally published on The conversation through Nina G. Jablonski at Penn State. Read the original article here.

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