Ok, I’m not a creationist, nor an irreducible complexist (is that a word?) but I did think about this earlier today as I sweltered in the Texas heat.
How/why did we develop sweat glands?
Traditional evolutionary biology states that over a given period of time, mutations that were conducive to survival bred true and lead to species-wide adaptations that carried on from generation to generation. However, this took a loooong time.
So, we evolve from fish, to amphibians. They probably didn’t need sweat glands.
Then we get dinosaurs who were, by all accounts, near-lizards. No sweat glands.
Simultaneously (or near enough), hairy, small critters evolved. Leaving aside hair/sebaceous glands, how/why did extruding moisture from those glands end up become a response to trying to shed excess heat?
In other words - how did enough of our ancestors who piddled out of their hair folicles survive to ensure that no matter what I do, I can’t avoid nasty pit-stains in my shirts for about 6 months of the year? How did any of them survive long enough to make that a survival trait?
I understand there’s still considerable debate on that very topic. In an evolutionary perspective, proto-humans changed drastically and in a rather short period of time. Developing heavy use of sweat glands was one such change.
Why? As a means of providing for thermal cooling. How? As a mutation that, in the right circumstances gave proto-mammals an evolutionary edge. You could similarly ask why we have fur/hair…or myriad other aspects of modern biology.
They didn’t need hair or fur either…and we seem to have lost the fins and tails as well. Why? Mutation and evolutionary advantage in shifting environments, such as in the air and on dry land (they wouldn’t need or be able to use sweat glands in the water, so if they had such a mutation or even the gene for a proto-sweat gland it would have given them no advantage UNTIL they left the water).
Dinosaurs weren’t lizards or even of the lizard family…more like birds. They had other means of cooling themselves, and regardless, we aren’t descended from most ‘dinosaur’ species since mammals split off from them somewhere between 200 and 80 million years ago.
I doubt there is a firm answer to this one, but we have a lot of folks well schooled in evolution on this board so I’ll let them answer if there is a specific answer. My WAG is that it was a mutation sometime in an earlier species that became an advantage (or, initially not a huge disadvantage) that eventually gave our ancestor species an edge when the climate shifted or when a lot of ecological niches opened up during one of large extinction events (such as the Chicxulub impact).
Shedding heat in this way obviously gave our ancestor species an advantage. And later those sweat glands gave rise to those large breasts that many men love so much.
Other mammals have sweat glands, though they aren’t as effective at cooling and may not be as plentiful as in humans. But the genes for sweat glands were there before humans were, so what evolved was possibly an increase in the number of sweat glands, and of a more effective type.
The changes may be associated with our loss of thick fur. Thick wet fur may not be an effective system of cooling.
A perfect example of animals with sweat glands that most people think of as not having them are dogs. They have two different types, including apocrine glands that release sweat into hair follicles, possibly for pheromones.
They also have sweat glands around the pads on their paws and their noses. It’s not their primary cooling method but they do sweat through their foot pads.
Every serious cardio session we do as a group I can’t believe the difference between men and women on this. Men have literally pools under them and the women nothing - and there is no way the women work less hard. It’s an extraordinary differential.
Similarly with that ‘steam’ thing that, when you catch the sunlight, you can see eminating from men. Not a damn thing from the women.
I’m not evolutionary biologist, but it is interesting to note that humans, unlike almost any other land-dwelling mammal I can think of, are constructed for endurance, not speed. As the old saying goes, a cheetah will always catch a man, and a man will always catch a cheetah.
Predators like lions, wolves and bears are designed for short bursts of immense expenditure of energy, followed by eating a rest. We aren’t; our advantages lie not in speed and strength but in running animals into the ground. While a lion’s logical approach to cooling off would be finding a cool place to lie down after a few minutes of effort, a human has to have some sort of cooling system that can kick in while s/he is still hunting.
Is this confirmed somewhere, that women sweat less than men? I’ve never noticed anything like that. And a ‘steam thing emanating from men?’ Do others know about this?
The “factoid” that dogs “sweat” through their tongues has transformed into “dogs ‘sweat’ ONLY through their tongues” with time and misremembering. There’s an unspoken assumption “therefore they have no sweat glands” that’s developed along with that.
Besides, fish secrete a film on their scales and amphibians have moist skin due to mucus glands so it’s not unreasonable to suppose that the solution simply evolved within the Tetrapod superclass.
Evolution doesn’t necessarily require vast periods of time. Since 1972, the Punctuated Equilibrium model has offered an alternative to gradualism: extremely rapid change into a new species, followed by long periods of (relative) stasis in that form. This theory does a good job of explaining what we see in the fossil record: identical-looking species for long periods (even millions of years), followed abruptly by different- (sometimes very different)-looking animals.
I’m not up on the latest in paleontology, but Punctuated Equilibrium has always sounded solid to me.
Lions and bears are designed for short bursts. But wolves are endurance hunters like ourselves and one of a handful of species capable of giving us a good run for our money, as it were.
Otherwise I think you are on the right track. Our massive profusion of eccrine sweat glands relative to other mammals is surely tied into our development into an apex endurance predator.
