Why do humans have hair?

I believe you have already discovered that humans only have thick hair on their heads, while monkeys have it all over their bodies. Isn't it said that humans evolved from monkeys? Why is there such a big difference? Don't worry, today I will tell you why they evolved like this?

01. Common explanation for human hair loss: heat dissipation

The most common explanation for why humans lose their hair is to dissipate heat. Yes, we have to lose our hair to cope with the huge human brain.

Perhaps the most significant change in human evolution compared to other primate relatives is the huge change in brain capacity.

In just a few million years, the human brain has expanded three times, which is the main reason why humans appear today. We even call ourselves humans, while other primates are still monkeys/apes, etc.

This huge brain can be described as a furnace.

Just in a resting state, the human brain consumes more than 20% of the body's energy.

If such a stove cannot dissipate heat quickly, it will be troublesome. People are afraid of heat but not cold, this is a basic rule. If the brain temperature is slightly higher, just like when we have a fever, it can easily cause problems with the brain. If it is higher, it will cause irreversible damage.

Therefore, in order to promote the heat dissipation of the human body, reducing the amount of hair is a good choice. Therefore, those apes with less hair can maintain a smarter brain and survive, which becomes a selection advantage. And slowly, humans also shed their hair and became naked apes.

02. Then why do we still grow hair?

Of course, you may ask, if that's the case, why do we still have hair? In fact, this principle makes sense to some extent, that is, while dissipating heat, we should avoid heating.

The sun will directly heat up the human body, and the head is no exception. Having hair is equivalent to adding a layer of insulation to the scalp, thus preventing the head from being overheated.

So overall we are shedding hair while also retaining our hair.

So, what should we do when we lose the protection of hair and are cold? Actually, it is simple. Just put on some clothes.

In fact, early primates evolved basically in places with more suitable temperatures such as tropical temperate zones. And most importantly, humans can migrate, so when it gets cold, they just run to warmer places.

Not to mention the later period, humans have learned to use tools, animal skins and the like have become standard, so there is no need to worry. In particular, the use of fire has solved the problem of cold.

03. Why is hair loss becoming more and more common nowadays?

What’s interesting is that it reminds me of another question: why is hair loss becoming more and more serious nowadays? And why is there a saying that hair will grow back if it is not replaced? Doesn’t this contradict the above logic?

I think a possible explanation is that modern humans do not need to stay outdoors for a long time, so the heat insulation of hair is not that important to us, so another thing plays a more important role.

A typical example is keratin KRT37. This is a keratin regulated by androgens. KRT37 is distributed all over the body of our close relatives, chimpanzees, but strangely, it is not detected in human hair. This may be the reason why chimpanzees have hair all over their bodies, while modern humans have hair on their bodies that does not fade, but suffer from hair loss.

The above is just a simple guess. Evolution is like this. We like to use our imagination as long as we can explain it to a certain extent. As for repeated verification, it is basically impossible. In addition to heat dissipation, sexual selection is also an important factor.