Very few mammals sweat all over, but is there a benefit/reason why sweat is not used and instead other cooling functions (panting, flapping ears, wallowing) is used instead?
In: 3
Most mammals don’t have lots of exposed skin that’s only covered in short hairs. If a dog sweat through its fur, it wouldn’t be that effective at cooling, and now you just have a wet dog. So they sweat and lose heat where they can, namely their tongues, ears, and foot pads.
Humans can wear clothes, which allows exposed skin to vary as needed: wear less clothes when it’s hot to allow sweat evaporation, and wear more clothes when it’s cold to compensate for a lack of fur.
Humans can make portable containers to carry water in, making dehydration significantly less of a threat and allowing more liberal use of precious water without having to travel back to a water source as often.
These advantages allowed early humans to act as endurance hunters to catch prey: just keep chasing even if the animal is faster than you, and eventually it will overheat and become exhausted, while you sip from your waterskin and sweat the heat away.
Animals without clothes or portable water have limited ability to cool, since they need to maintain a moderate amount of fur to protect from cold, and have more limited access to water. So sweating wouldn’t work as well even if they could do it.
Sweat from apocrine glands evolved first in early mammals with the apparition of hairs. Their main utility is to feed the bacteria that produces the pheromones to attract mates.
Milk glands and ear wax glands evolved from them.
Eccrine glands evolved from them too in the palm and sole to increase friction and enhance grip.
Afterwards, primate evolved to use the eccrine glands to cool and got eccrine glands all over their body.
Some other animals, like horses, evolved to use apocrine sweat for cooling too.
This could be useful for other animals too, but evolution is random and there’s no guarantee for any animal to get any feature even if it’s useful. They just never got the mutations that allow primates and some other animals like horses to use sweat to effectively cool down.
Sweat’s function is to cool the body without stopping running. Most animals don’t have sufficient excess food and water to “invest” into distance running. Only a super-predator like humans can afford such input cost.
https://en.wikipedia.org/wiki/Persistence_hunting
“Humans are the only surviving primate species that practises persistence hunting. In addition to a capacity for endurance running, human hunters have comparatively little hair, which makes sweating an effective means of cooling the body.”
Latest Answers