Did Sweating Evolve To Keep Us Cool Or Expell Excess Salt?

[common_sense_seeker]

The standard explanation is that sweating evolved to keep us cool. But it doesn't make a lot of intuitive sense. Animals which survive in hot environments don't use sweat to maintain a managable body temperature. You would need a lot of water to drink for starters. It seems more likely to me that it was used to get rid of excess salt, similar to a marine iguana. If our ancestors started to pick fruit and seeds that had fallen into a marine estuary or delta from overhanging trees, then a pattern begins to emerge. The more seafood which is collected would slowly alter the physiology of the mammal group. Is this the secret of man's success?

 

[Asguard]

i doubt it for 3 reasons

1) the kidneys are responcable for ridding the body of excess ions in combination with the desire to drink (why did you think you felt thirsty after eatting salty food)

2) if you sit down to really salty chips (or anything else salty) you dont start sweating

3) sweat is hypotonic not hypertonic or at least isotonic which is why salt levels initially go up after you start sweating compared to extracelluar fluid. that doesnt mean that your salt levels arnt depleated by sweating, they are but only over a longer time period and only in apsolute terms rather than relitive to extra cellular fluid especially when its water alone which is used to rehydrate.

 

[Asguard]

oh and in regard to your point in other animals not sweating, that could have more to do with us developing in a warm DRY enviroment (evaporation is inefficent in humid conditions) were a surplie of fresh water is readerly available.

rember the reason the body craves sodium is that our diet had very little of it compared to potasium which was readly available

 

[common_sense_seeker]

oh and in regard to your point in other animals not sweating, that could have more to do with us developing in a warm DRY enviroment (evaporation is inefficent in humid conditions) were a surplie of fresh water is readerly available.

rember the reason the body craves sodium is that our diet had very little of it compared to potasium which was readly available

I'm not convinced by your arguments. Just to say we developed in a DRY enviroment seems way too simplistic. It would have been changing all the time over millions of year. I saw a TV documentary where our very early ancestors are closely associated with river deltas and the coastal transition between fresh and salt water. My simple idea still has potential. Is there a scientific link to this way of thinking, one way or the other?

 

[Asguard]

your ides maybe simple but makes no metabolic sence. the simple fact that there is no evidence that people with mild hypernatrimia sweat more than people with mild hyponatrimia suggests your theory is wrong.

cooling by evaporatiin is very effective especially concidering our lack of hair, there for the simple answer is that the conventional theory is the most logical

 

[common_sense_seeker]

your ides maybe simple but makes no metabolic sence. the simple fact that there is no evidence that people with mild hypernatrimia sweat more than people with mild hyponatrimia suggests your theory is wrong.

cooling by evaporatiin is very effective especially concidering our lack of hair, there for the simple answer is that the conventional theory is the most logical

We are only hairless because we began to walk upright. So sweating would only be effective after this evolution. But I've heard theories that our ability for bipedalism arose out of wading through water. Maybe it was the expelling of salt to start with, (the salt would wash out from the fur) and later used for cooling? Note that horses similarly sweat heavily to stay cool and that they are also associated with water and salt licks (or is this a stretch of the imagination too far?).

 

[Asguard]

again, there is no evidence for that. what benifit would there be in expelling a hypotonic solution through the skin when compared to the kidneys ability to select its concentration based on solvent and solute levels

 

[Orleander]

how about sweating for sexual attraction. Pheromones

 

[iceaura]

Animals which survive in hot environments don't use sweat to maintain a managable body temperature.

Lots of animals sweat to cool off from exertion in warm temperatures - horses, for example.

It is not known whether humans evolved in a dry environment, in which conserving water would have been a priority. There is good reason to suspect otherwise. Humans do not do well for long in high temperatures far from water, without taking serious precautions involving tools, techniques, and foresighted planning capabilities that appear to be recently acquired in evolutionary terms.

 

[common_sense_seeker]

again, there is no evidence for that. what benifit would there be in expelling a hypotonic solution through the skin when compared to the kidneys ability to select its concentration based on solvent and solute levels

I thought salt is expelled through the skin. If the seafood diet was so intense that the kidneys were already working to full capacity, wouldn't the excess be expelled through the skin?

how about sweating for sexual attraction. Pheromones

I saw a TV doc where it wa shown that pubic hair evolved for this purpose after walking upright and being hairless.

Lots of animals sweat to cool off from exertion in warm temperatures - horses, for example. There aren't many more examples though are there? The horse could have evolved from a seaweed eating predessor, you never know!

It is not known whether humans evolved in a dry environment, in which conserving water would have been a priority. There is good reason to suspect otherwise. Humans do not do well for long in high temperatures far from water, without taking serious precautions involving tools, techniques, and foresighted planning capabilities that appear to be recently acquired in evolutionary terms.

I agree totally. It doesn't really make sense to me to be that amazing an ability. A camel's ability to stay in high temperatures is much more impressive. I still think that I may have a case.

 

[common_sense_seeker]

And another thing; horses have a grazing technique which is especially suited to seaweed, due to the yanking action. I've worked with horses and remember being surprised when they suddenly take a mouthful of leaves and twigs from overhanging trees along the road. Is this a characteristic of picking seaweed from boulders and rock egdes in the distant past? The more I think about it, the feasible a river delta existence seems to be. Also sweating is a poor cooling mechanism in not only humid conditions (which it is in the Congo basin) but also in cold conditions! Just on TV last night I saw how farmers shave the backs of the dairy cows so that they don't suffer from pnuemonia due to the sweat!

Seaweed eating ponies

"What do the wild horses eat and drink?" Almost 80 percent of their diet is coarse saltmarsh cordgrass and American beachgrass, supplemented by thorny greenbrier stems, bayberry twigs, rose hips, seaweeds, and even delectable poison ivy! Because they eat so much salty food, the horses drink twice as much fresh water (from natural ponds) as do domestic horses and may also drink some salt water; this gives them a "fat" appearance. Although this seems like a meager subsistence, the horses of Assateague have adapted well to an island diet and do not need "help" from people. In fact, such help in the form of "good" food can be detrimental to their digestive system and overall health.

 

[phlogistician]

I'm not convinced by your arguments. ?

Go read a book.

 

[common_sense_seeker]

I've come up with a good idea. The evidence speaks for itself.

 

[Asguard]

yes it does. it says your compleatly wrong

 

[fedr808]

I dont think that sweat is real salt water.

think about it. How would your body be able to measure exactly how much salt goes into the water droplet.

And if sodium was so precious back then, then why waste it on sweat?

Taste your skin on lets say your hand (dont do it if you have washed your hands with soap recently or been in a pile of mud) it tastes kinda salty.

Probably between bacteria, dirt, and dead skin cells make the taste salty. Sweat droplets probably just pick up these things and thus taste very salty.

 

[CharonZ]

Sweat does contain a significant amount of electrolytes including sodium, potassium, magnesium, etc. These are most definitely not excess ions as continued perspiration can reduce your electrolyte concentrations to dangerously low levels, especially if exercise is coupled with drinking of electrolyte-poor water. However, one could also apply common sense. When do you sweat? Is it temperature dependent or rather dependent on electrolyte intake?

 

[fedr808]

Sweat does contain a significant amount of electrolytes including sodium, potassium, magnesium, etc. These are most definitely not excess ions as continued perspiration can reduce your electrolyte concentrations to dangerously low levels, especially if exercise is coupled with drinking of electrolyte-poor water.

So why are they found in sweat? Not to argue the point you made.

But are those things used specifically for sweat? Or are they found in the skin or something?

 

[D H]

So why are they found in sweat? Not to argue the point you made.

They're found in sweat because your body doesn't have a handy pool of distilled water to use for cooling. Instead it has to draw from that which it does have a lot of -- the fluids between cells. When you are sweating lightly your sweat glands can extract some of the electrolytes before excreting the fluid to the surface. When you are sweating heavily your sweat glands don't have time to do that. Heavy perspiration is essentially pure plasma.

 

[fedr808]

They're found in sweat because your body doesn't have a handy pool of distilled water to use for cooling. Instead it has to draw from that which it does have a lot of -- the fluids between cells. When you are sweating lightly your sweat glands can extract some of the electrolytes before excreting the fluid to the surface. When you are sweating heavily your sweat glands don't have time to do that. Heavy perspiration is essentially pure plasma.

So, thje reason why gatorade has electrolytes, is because if you lose all your electrolytes your body will use plasma, which i would believe is very bad right?

 

[common_sense_seeker]

Sweat does contain a significant amount of electrolytes including sodium, potassium, magnesium, etc. These are most definitely not excess ions as continued perspiration can reduce your electrolyte concentrations to dangerously low levels, especially if exercise is coupled with drinking of electrolyte-poor water. However, one could also apply common sense. When do you sweat? Is it temperature dependent or rather dependent on electrolyte intake?

The original reason for heavy sweating could have been due to expelling excess salt, due to a consistant diet of seaweed and seafood. This would have been millions of years ago, before man learnt to walk upright and headed for the plains. Only afterwards did evolution respond with heavy sweating in response to high temperature. Or perhaps it was always a combination of both.