Understanding ourselves: the miracle of sweat

Sweat is the greatest miracle it could happen to our specie. Maybe it is going to be our main mean of survival (again). Still we sank such a miracle in the dirt of our insecurities. For profit.

This is heavily inspired by an interesting book I read recently: The Joy of Sweat by Sarah Everts. Sarah Everts is a science-journalist and did an amazing job at bringing clarity about what sweat is.

Sweat always reminds me of the negative remarks of my (female) family members. "You smell! Go washing yourself" or "you really need some deodorant". In hindsight, I must say that these comments really happened only in my family. Other close people would not remark about that, even when I curiously asked about it. That stayed a mystery until the other day.

We are going to get Darwinian pretty fast here, so get ready. There is a reason why you cannot (by law) marry a close family member. The children of a couple of close family members will (have greater chances to) be at disadvantage against diverse couples. For example, they may develop blue skin. This may seem far from our sweat issues, but survival does not wait for human laws, right? Our body needed a way to avoid procreating with somebody too similar to us. The eyes don't work here because it is easy to trick our main sensors! But smell...

Claus Wedekind in 1995 showed that women can pick partners that carry a compatible immune system via smell. Yin Yang kind of compatible. His experiment required some smelly t-shirts, but women found partners with an immune system complementing theirs. If you find that surprising, there is more: did you realize that greetings between people (pre-COVID) are always in "nose-proximity"? It seems we do use this sense a lot (subconsciously)!

To return to my family, my conjecture is that I got told off by my female family members for a (very good) reason! They perceived me very smelly because their body was screaming that I was the worst possible partner for them.

Now let's get into deodorants a moment. We live in a capitalist system. The best way to sell something is to make another person feel they need it. So we just said that smell makes you find the best (immune system) partner available. But there is nothing to sell like this! Time to make you feel insecure: "men/women will not like you if you smell so badly: rather buy this product to attract them". It worked. A bit too well. To the point that sweat makes some people feel guilty. Sure, if you don't like somebody else's smell, it may be unbearable. Still, we must not shame others because they are who they are. (Also, try to get a whiff of your partner real smell if you are looking for the best immune system for your children -- that sounds so 'eugenetics' :).

Anyway, let's move onto why (most) people have hair on their heads. It's still about sweat. I think you are reading this on a digital device. Maybe you know that if your device overheats a lot, it will stop working (if not exploding). If you observed dogs in summer, you may have seen they overheat too. Typically they throw their tongue out and start shallow breathing. Also a computer does something similar: you typically hear the fan when that happens. The dog is more efficient at it. We win though.

The computer is not good. The fan moves just air. The dog is so so: the breath moves air but also water! The saliva on the tongue but also the water from their lungs. And us?!? We are pros thanks to: sweat!

Evaporation. I guess there is a reason why we dedicated so many gods to water. Water exploding into vapour (its gas form) disperse heat! Somebody even made a product from that. Bet what we expel from our bodies? Well, it is blood not water. Sweat is really blood filtered of (most) useful minerals. We really don't manage to retain all the minerals (too much effort) and that is why our sweat is salty. That is also why sweating is not releasing impurities (the kidneys are). Sauna is not a detox, sorry. On the other hand, Sauna is a great training for the heart to avoid strokes!

Since we are speaking of saunas, let's see the miracle: in this video, a person enters in a sauna filmed with a thermal camera. The miracle appears when he exits the sauna: his body is in a darker color than the sauna. That means it is colder. When you put a potato in a warm oven, the potato will reach the oven temperature. A human will not until he is dead. Its sweat will shield a person from the heat by dissipating it. We defeat physics! Well.. we make the best out of physics!

But why? What is the reason for this amazing feature (we became so ashamed of)?

We know that devices don't like saunas. So think again about the dog. A dog dissipates heat from its mouth. That is not going to work in a sauna because the heat is too great. Its hair is also insulating the dog! So the internal heat cannot escape quick enough.

Next, dogs were once wolfs. And what is comparable to a sauna for internal heat? Prolonged physical exercise. If wolves were to run for a very long time, they would overheat. So they need to stop eventually. What about us? We would just blood out. Our sweat guarantees we don't overheat. (Still, two things can go wrong: not enough water in our body or too high intensity movement. This causes heart failure.) This documentary is a proof of how we used our unique resilience skills to make a living. And by the way, you know when you get nervous and your hands sweat? That may make you feel sticky and stress you out, but hear this: say that instead of your boss starting to tell you off there was a wolf in front of you, what do you think are you doing in a second from now? Right run at full speed. What happens when you run at full speed? You (and the wolf) heat up. What do you do to cool down? You sweat, the wolf shallow breathes. But you start sweating before: wet hands remember? Your body cools down early! It prepares you for the sprint. This is just too cool! In modern days our stress does not mean we will sprint. We end up even more stressed out because we are wetting the desk, and others may notice. For serious situations though, what a great feature!

And a final question for you dear reader: in the previous video, where was the (midday/hottest) Sun hitting the running man? On the head! Indeed, that is the only place that is most exposed to the Sun's heat when we stand. That is why it is still worth insulating with hair. I guess, that way we save sweat (like when the people dress in the desert).

That is just a portion of the beautiful things I read in that book! How unappreciated is our body! How preposterous our insecurities. Next time you smell somebody, think (also) how clever is that mechanism!

And when climate change hits, sweat may gives us a chance at survival (again).

Happy sweating!