If you put a human and a chimpanzee next to each other, perhaps the most striking difference is that the human lacks the chimpanzee's shiny black hair.

From orangutans to dogs, cats, cows and sheep, most mammals we come into contact with have thick coats of hair.

Perhaps it's because we don't and they do that humans feel so good about these furry creatures.

Of course, not all animals have a proud coat of human fur. Besides ourselves, whales, elephants, rhinos, hippos and other animals have very little or no hair.

Why are both animals hairy and bald?

1, why are some animals bald, but others have strong hair?

For a variety of less hairy animals, there's a reason for shedding hair. In nature, this self-selecting alopecia offers significant advantages.

Elephants, for example, are better able to cope with hot temperatures because they shed their thick fur, without wet fur to stop them.

Sea mammals, such as manatees and dugongs, are also better able to swim in water.

This adaptive evolution allows animals to live better and more comfortably in their own environment.

The less common naked mole rat also spends his days burrowing through the ground with his flesh-pink skin, the few hairs left on his surface looking pathetic and obscene. And the reason they're bald is pretty simple -- they don't need to be.

They spend their lives underground, where their narrow, oxygen-deprived environment makes them their most comfortable home.

Because of their stable underground environment, naked hidnas don't have to deal with the fluctuating temperatures that come and go from the wind to the sun. For naked hidnas, the most important insulation function of hair is useless. By not growing hair, they save energy.

Of course, the underground environment is not always friendly.

At least there are plenty of bugs underground, and social naked moles are prone to passing on parasites to each other.

So being bald also makes them better able to deal with parasites on their body surfaces, preventing the entire population.

After all, their eyesight is really not very good, if also need to find a little bit of worms in the thick hair, it is really difficult to kill "mouse" me!

2. Why are we so bald?

The reason for baldness in humans is similar to that in rats -- we don't need thick hair to keep us warm, but we also want our skin to be lighter and cleaner.

But the reason we don't need hair to keep us warm is because we learned not only how to warm ourselves with fire, but also how to make clothes.

Clothing that can change is not so convenient as hair that stays the same all year round.

Of course, baldness doesn't just improve survival, it also improves competitiveness in the dating market.

In South America, for example, males of balding monkeys are attracted to females by their faces, which are bald and red like lanterns.

For bald monkeys, both baldness and red indicate that the male is in good physical condition, which makes him ideal for fathering young monkeys together.

But alopecia monkeys are bald and red all year round, and some other monkeys are bald intermittently.

For example, when the drill is in heat, its red and swollen skin creates a strange pattern on its chest. From a distance, it looks like a huge red arrow suggesting: "I am in good health. Of course, it is me!"

The strange structure is actually called sex swelling (swelling), which is caused by local congestion, and is quite common in many apes and monkeys, but the position is not as strange as in the head or chest.

Mandrills, for example, are known as "bald" mandrills. Every breeding season, female mandrills climb trees with a red apple on their butt, posing a unique attraction to the opposite sex.

Red like monkey butt, is probably observed this phenomenon and summed up it!

Of course, this kind of bald to show their physique, not only the Monkey King exclusive. Birds are equally expressive in the matter of baldness.

The elegantly beautiful-looking red-crowned crane is a serious bald crane, whose "red top" is actually the bright red color of their exposed skin.

This skin is not only red, but also full of fleshy warts, if you look at it carefully, it is not beautiful at all.

For red-crowned cranes, the larger the bald area, the redder and brighter the body, so they can naturally cross the field and attract the desired female birds to dance.

Here, again, is a cue to humans, whose bare skin does the same thing.

Although human skin does not redness, naked skin is a better display of health, without parasites or wounds.

In primitive people's time, this is quite important marriage capital ah!

As a result, over time, the balder genes were passed down to the mainstream.