Mammals pant, birds fluff feathers, reptiles find shade and humans sweat.
Not many people may realise this, but perspiring to control our body temperature is a distinctly human thing. Much more than just a unique special talent, sweating has even been discussed by evolutionary scientists as a contributing factor to our ascension of the animal kingdom.
You could call it our own little super-power… well, we do anyway.
We go a little deeper into the details of sweat in this post, Let’s talk about sweat, baby, but effectively what’s happening when we perspire is ‘evaporative cooling’.
Beads of sweat that form on your arms and forehead are primarily made up of water and, when released, begin to evaporate. As each droplet of perspiration packs its bags, ready to head off into the world as vapour, it makes sure to pack some of your body heat too. The quicker your sweat evaporates, the quicker you cool down.
Ever wondered why you seem to sweat more when you immediately stop running or cycling?
As sweat evaporates, the air around you absorbs moisture and wet (humid) air results in slower evaporation. Wind helps to refresh the air around you, and when you run, you’re literally running away from moist air. Without perspiration, our bodies would overheat and we wouldn’t be able to run for as long, or as far, as we currently can.
“About 2 million years ago… humans started to develop adaptations that made them good endurance runners; so we could do persistent running, and persistent hunting and gathering.”
That’s Dr. Yana Kamberov, Assistant Professor of Genetics at the University of Pennsylvania, outlining one reason humans evolved the ability to thermoregulate through perspiration.
When a mammal is running at its top speed it isn’t able to pant; the main mechanism for cooling off is not available. Dr Kamberov says that “humans can run around at our full speed and still manage to cool off. There is a hypothesis that this allowed us to exploit persistence hunting.”
Not only could we hunt for longer, but we could also explore further.
By walking on two legs instead of four, we exposed less of our body to the sun, resulting in a lower body temperature. And through perspiration, we were able to venture out in the middle of the day when it was simply too hot for other predators. Pretty cool stuff.
Sure, but it’s not quite the same.
A horse, for instance, will perspire to cool down, however this is just one of several mechanisms it has at its disposal. The method of choice is to dilate the capillaries in its skin... we're getting slightly off-track.
Horse sweat is also heavily concentrated in fats, salts and proteins, which acts as soap (of sorts), helping to bolster the animal’s immune system. In other instances, the sweat can behave as a signal, emitting an odour in moments of danger or arousal.
If you’re thinking that this multi-purpose, odorous perspiration is très chic, we’ve got good news for you – yep, humans do it too. Studies have even demonstrated that emotions such as fear and disgust can be transmitted through a person’s natural body aroma – more on that to come.
We (clearly) find sweat fascinating, and while it’s not quite a super-power in the realms of Wonder Woman, we like to think that it’s pretty close – it has helped us rule the world after all.
So next time you’re out for a run and you notice a bead of sweat on your arm, say a little thank-you to it for keeping you cool… just try not to say it too loud.
