Seriously, a bad sunburn could limit our ability to survive in the wild. I’ve had a few so bad I could barely move and I had a super high fever. Desn’t that happen to animals? How do they manage?
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We don’t
Darker skinned humans dont have that weakness.
The pale ones however are different.
Thats why africans and indians for example are darker than Europeans. Colder climates meant no need for darker pigmentation to respond to the heat.
Simple answer, we don’t. Yes, skin cancer kills a lot of people. But on an evolutionary skill, it didn’t impact people’s reproductive success enough to favor the emergence a stronger form of biological sun protection than melanin. In theory the same goes for sunburn.
Humans in the wild would rarely if ever get sunburnt.
I am effectively albino. But being that my ancestors are from Denmark and Scotland it wouldn’t have been an issue. I would have been outside every day and could slowly tan to be able to withstand the intense Scottish summer sun.
The most simple explanation:
Humans dont need it either.
Ofc. this isnt exactly true, as the top comment says, even animals can get sunburnt, but animals either have the skintype to protect against sunlight or they also hide from the sun.
Ask any wildlife photographer when they shoot animals, all of them will say either morning or evening and thats not because of the nice lighting only.
At full sunlight most animals search shelter from the sun.
Same with humans, we got shelter 24/7 if we want, thats why our skin became so sensitive.
If you would gradually expose your skin to sun, you would get more brown because your body produces melanin, a pigment that protects your skin cells from being penetrated by UV-light.
this aswell has limits, but you can go way longer without the uv causing damage that causes cancer etc.
Every answer so far is missing the key biological difference:
Every living cell contains mechanisms to error-check its DNA and correct many, but not all, errors that might occur.
DNA is held together with a type of chemical bond called a hydrogen bond, which is fairly weak. UV photons have enough energy to break these bonds, which is how UV damages DNA. Any time this happens where two thymine molecules are adjacent to one another, they can form a new chemical bond to each other, only a much stronger covalent bond.
In many animals, like reptiles, elephants and rhinoceroses, their DNA repair mechanism is able to fix this thymine-thymine covalent bond, saving UV-damaged skin cells.
However, in humans, our DNA repair mechanism has lost this ability, so when it encounters a thymine-thymine covalent bond, there’s no way to fix it. Instead, the cell receives a chemical signal that triggers apoptosis—the cell would rather die and be replaced by a healthy cell than risk becoming cancer. It’s this process of apoptosis and growing replacement skin cells that *is* a sunburn.
People are leaving out ricketts.
Humans evolved to spend some time in the Sun, because we need that to make Vitamin D. So if we had a mechanism that completely blocked sunlight, our bones would bend and we’d have a hard time in life.
Humans in very sunny parts of Africa had skin dark enough to block most of the damaging ultraviolet radiation from the Sun but still let a little through so they would have vitamin D.
When humans moved to parts of the planet that got less direct sunlight, they started suffering from inadequate vitamin D (known as “ricketts” in children). Evolution selected for people with lighter skin, but still as dark as possible to reduce sunburns and skin cancer.
The less direct sunlight we got, the lighter our skin had to get to let us make vitamin D. But it means people who have light skin are now incredibly vulnerable to sunburns and skin cancer if they spend a lot of time in brighter sunlight than they evolved for.
So humans *are* adapted to reduce sunburns, that’s what melanin is for. But by now many of us are descended from migrants who had to weaken those defenses to survive in less brightly lit climates.
If your dog is white or mostly white you should really be putting sunscreen on its belly and hairless areas. I had a mostly white pit bull who got melanomas (skin cancer) on her belly because she used to lay out in the AZ sun all day.
Many animals without fur or feathers can get sunburned too. Thats pretty much why hippos are nocturnal and spend so much time in the water.
They adapted their behavior to prevent that. Other animals like rhinos or elephants have very thick and tough skin thats a darker color. Animals will often use mud or dust to coat their skin too.
We adapted to produce more melanin closer to the equator. The reason people in the more extreme latitudes ended up white was because their diets were lacking in vitamin D and the lighter skin color helped us get it from sunlight.
This implies people with dark skin aren’t humans, or that all humans need sunscreen. Not all of us do. Humans have lived for many thousands of years in a very hot climate without any sunscreen.
Because most of the year humans are indoors working their 9-5 job and when they finally get their 2 weeks of freedom they recklessly go out into the hottest sun and wonder why they got sunburnt. If you slowly expose yourself to increasing sunlight throughout the year, you will be perfectly fine without the cancerogenic sunscreen
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