If you had to choose between the power to heal fast or to cool fast, would you not choose the cooling power? It's what evolution chose for us, but not for all those other animals. Why?
Mayo 1, 2025
"They found that human wounds took more than twice as long to heal as wounds of any of the other mammals."
"Our slow healing may be a result of an evolutionary trade-off we made long ago, when we shed fur in favor of naked, sweaty skin that keeps us cool.... Each hair grows from a hair follicle, which also houses stem cells.... 'When the epidermis is wounded, as in most kinds of scratches and scrapes, it’s really the hair-follicle stem cells that do the repair,' Dr. Fuchs said.
Furry animals are covered in follicles, which help quickly close up wounds in mice or monkeys. By comparison, 'human skin has very puny hair follicles,' Dr. Fuchs said. And our ancestors lost many of those follicles, packing their skin with sweat glands instead.... Most furry mammals have them only in certain places, mainly the soles of their paws. But human ancestors went all-in on sweat — modern humans have millions of sweat glands all over our bodies, and they’re about 10 times denser than those of chimpanzees...."
Mga Post
66 (na) komento:
Sweat glands make women a rich, alluring aroma. It goes on from there.
Women need to keep cool to be able to outrun the Jeffrey Epstein, Harvey Weinstein and the Sean John "Love" Combs of the wild kingdom.
It's what evolution chose for us, but not for all those other animals. Why?
God said we have to work hard and toil "by the sweat of our brow" when we were ejected from The Garden. God knew we'd need to cool off fast after all that sweating.
It's funny to think that body hair has healing power.
Song lyric: "She asked him why/Why I'm a hairy guy/I'm hairy noon and nighty-night night...."
Now we know why.
"If you had to choose between the power to heal fast or to cool fast, would you not choose the cooling power? It's what evolution chose for us, but not for all those other animals. Why?"
Humans evolved to hunt on the hot savannas of Africa. Not being very fast, they had to rely on endurance, which required efficient cooling. As a result, a man can outrun a horse over a marathon distance.
Does it work intra-species? I'm a light-haired Irishman, but I haven't noticed any shortcoming in my wound healing versus more hirsute Mediterraneans.
Good question--what is it about humans that made cooling more valuable than healing? Why would we over-heat more than animals that run faster than we do?
Jack, it would have been better for me if you posted 1 minute later.
"It's what evolution chose for us, but not for all those other animals. Why?"
I would guess intelligence, which allows us to avoid injury and treat wounds.
YouTube: Then again, I shudder to think how many more creepy crawlers would we have crawling around all that hair.
The slower healing (as the article says) might have been more survivable for humans because we developed the ability to tend to the injured and to protect each other during longer period of being unable to be productive.
That capacity developed concurrently with the complex skills we developed to hunt and longer efforts in the heat paid off for us. (Again, this is in the article.) The other animals were keeping it simple and the trade-off from healing to cooling wasn't valuable.
Another issue is that cooling is nice, but the hair is useful for keeping animals warm in cold weather. Meanwhile, we invented clothing. Again, that's in the article.
"They found that human wounds took more than twice as long to heal as wounds of any of the other mammals."
Now, more than ever, we need to ban assault knives.
tim maguire said...
“Does it work intra-species? I'm a light-haired Irishman, but I haven't noticed any shortcoming in my wound healing versus more hirsute Mediterraneans.”
My wife is half Irish, and the other half is mostly a mixture of Scottish, Welsh, and English. One trait common in her family is the ability to recovery from injuries and sickness faster than other people.
I remember when everyone was reading "The Naked Ape." What did that book say about why we became "naked":
Grok says, and I paraphrase, that nakedness was better for keeping cool as we moved out of the shade and into the glaring savannas.
When we became bipedal, hairlessness made us better at running — less drag.
And then there was the nonverbal communication through the skin — notably blushing!
And being able to see the skin was part of mate selection. I guess you could determine the health of another person by looking at the skin.
My palms sometimes sweat, but even so, they never grew hair.
OTOH most human cultures clothe or cover the parts that are hairiest on most of us.
"They found that human wounds took more than twice as long to heal as wounds of any of the other mammals.”
If I told my cat that “Trump is great!”, she would ignore me and have forgotten it by 20 minutes later. If I told my very liberal sister-in-law the same, she wouldn’t speak to me for well more than 40 minutes.
I guess you could determine the health of another person by looking at the skin.
Seeing the skin in its entirety is indeed an invaluable component of my mate selection criteria. But not the first step of course.
at Long distances, humans are faster than ANY other animal
(even Pronghorn Antelopes, which is saying something!)
Our long legs and big hearts are reasons, but our ability to keep cool is the MAIN reason
The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter
(available through amazon portals)
As for me, I’ll take what’s behind the fur curtains!
"The slower healing (as the article says) might have been more survivable for humans because we developed the ability to tend to the injured..."
That's what I thought. We can tend to injuries, animals just lick them. (Related to hair = healing?)
Anyway, HUMANS RULE.
Chesterson's fence comes to mind. I have no theories myself.
Parasites might be part of it too, as noted above. But whatever the answer, I am sure it is the weighted summation of all of the reasons, pro and con, to losing our fur. Maybe the fur simply fell away because it's kind of an iron law of evolution that useless traits that have any cost at all, and hair requires protein, fall away over time, and it turned out that the fur no longer served any purpose that outweighed the cost of the protein to grow it.
"Why?"
Firstly, evolution doesn't choose. That's an unfortunate misapprehension spurred by another misleading term, natural selection. There's no agency involved.
If we look for a cause to associate our sweaty hairlessness with, look no further than our appetite for fresh meat. This probably started before our genus evolved with the Australopithecines scavenging carasses. Our pre-human ancestors used their ability to accurately hurl stones and other projectiles at jackals and hyenas, thus driving competitors away from large prey animals killed by lions and other predators. This involved consider upper body strength in our hominin ancestors, but not extreme endurance. What evidence we have regarding Australopithecines integument supports the assumption that they were as hairy and non-sweaty as modern chimpanzees. (One piece of that evidence is the nearly identical genetic match between the human pubic louse and the lice that infest gorillas.)
Though they were undoubtedly obligate bipeds, the gate of Australopithecines was not the same as ours. There is reason to believe they were not efficient runners compared to members of the Homo clade. From the waist down there is hardly any biomechanical difference between a male Homo erectus and a modern human male. Both can be highly efficient long-distance runners. Though not fast by comparison to virtually any hooved mammal, both modern and prehistoric humans can exhibit extreme endurance, which has allowed us to thrive as pursuit hunters who wear down and exhaust the prey before the final kill. Being hairless and sweaty contributes to this endurance, consequently, those who were less hairy and more sweaty had greater success at reproduction. Being able to run a little further they lived and copulated a little longer than the hairier guys. Their sons and daughters inherited those genetic tendencies, and so generation by generation we unconsciously traded quick healing for greater capacity for endurance running.
What about the H. erectus women? The less hairy female may have been more sexually attractive to the less hairy males, and there's reason to believe that male sweat contains pheromones that sexually excite females. However, none of that really matters since whatever genetic advantage that appears in given population, whether first appearing in the males or the females gets evenly spread throughout that population over time.
"It's what evolution chose for us, but not for all those other animals. Why?"
You ever seen monkey naked?
Also, this is junk science. The fur theory, espoused by a "scientist" who made it clear upfront that she wasn't a part of this and she didn't cut no monkeys, only applies to wounds to the epidermis. This is not new knowledge but now the internet is convinced that animals heal quicker because they have fur. The weasel words are ignored.
This doesn't read like the whole story is there - it reads like they started with a premise and then extrapolated. All furred animals don't heal at the same rate, for one thing, nor do al injury types within the same animal.
I want my fur back.
The "schnitzel sack" would be one of those in-between areas that evolution left behind?
Brains produce a lot of heat.
So does endurance running.
Does fur reduce an animal's ability to run/move for long periods of time?
You say evolution chose and “we” didn’t, but if our ancient ancestors figured out that cooling faster gave them an advantage in the environment, might they have chosen to exploit that advantage which allowed us to thrive?
I chose cooling faster today, because worrying about global warming is nuts.
I chose chose when I should choose.
"Does fur reduce an animal's ability to run/move for long periods of time?"
The lack of sweat glands, and thus cooling, keeps animals from being able to run for long periods of time. Humans are really, really, really good moving at a steady pace for long periods. To the point that on a savannah a few humans can pick out an antelope and pursue it using a steady jog/walk. The antelope is going to be able to out run them, at first. But if the humans keep after it a point will eventually be reached where the antelope won't be able to run away any longer.
I'm curious if marine mammals heal at the same rate as humans or faster.
https://whalescientists.com/dolphins-have-super-healing-powers/
Humans are also the only animals that can throw stuff overhanded with precision and strength.
https://www.youtube.com/watch?v=I_bYlY6AHew
@Gilbar
at Long distances, humans are faster than ANY other animal
(even Pronghorn Antelopes, which is saying something!)
Our long legs and big hearts are reasons, but our ability to keep cool is the MAIN reason
Not camels.
Slow healing requires care, which meant we had to develop social structures of cooperation to provide that care, and that cooperation enabled us to rise from a few thousand to billions and billions of individuals.
Observation, speculation, and faith. All we know for certain in a universal frame is that human evolution requires a dual, complementary tango to sustain viability.
Now do elephants.
Ok, it seems to me it goes something like this: very flexible front paws with a digit that becomes an opposable thumb develop among primates. These are wildly useful. One group of primates, for some reason, uses them more than others, and becomes exclusively bipedal (the genetic causation arrow might go the other way from what I imply here, or be absent altogether). Bipedalism slows them down. Like many primates, this group already hunts in teams; now it turns out that the teams with members who have somewhat more sweat glands and somewhat less fur do better in these endurance hunts. Note that the sweat glands might have begun to proliferate before the exclusive bipedalism - I'm not trying to be all Lamarckian.
Meanwhile, back at the ranch, fire! For some reason, maybe because their brains are already a bit larger than other primates' (or more fold-y - I don't know if it's true that early hominids had greater brain mass than their primate neighbors), this group didn't just take advantage of cooked meat resulting from wildfire as other predators do, but thought, "What if I can trap a little of this hot thing?"
I've read one hypothesis that because cooking food liberates more nutrients more easily in our digestive systems, it was cooking that allowed the explosion in our brain size, since the human brain uses so disproportionate an amount of energy. So this group now has bigger brains, causing babies to be born in a terribly vulnerable state, they're exclusively bipedal, they cook food, they're slow but unstoppable because they sweat all over their bodies, they team-hunt because they're so slow, and they have to develop interpersonal bonds that go beyond what other primates do because of those very helpless young. It's all a big net of evolutionary traits, resulting in what we are now - or, more accurately, what we were back before agriculture, I suppose, since we've been interfering with our own animal destiny for quite some time now. My natural eyesight alone would've killed me in childhood, more than likely, in hunter-gatherer days.
Now me, I think we are the way we are because we are Intended To Be what we are, if you know what I mean.
I dunno Lions and Tigers seem to do pretty well in the heat, and they have fur to help with wounds. What's their deal?
And then you have elephants. No fur, but doing pretty well in dealing with heat.
If you had to choose between the power to heal fast or to cool fast, would you not choose the cooling power? It's what evolution chose for us, but not for all those other animals.
Not exactly how evolution works. Evolution works by random mutations that result in a higher likelihood of reproduction (which includes the classic "survival of the fittest" but also requires the survivor to pass down the trait to future generations). So it is possible that humans, for whatever reason, were the sole species to actually get the random mutation(s) that led to hair loss and increased sweat glands, or that other species got the same mutation but it was not reproductively advantageous. It seems reasonably likely that the whole walking upright and slowly chasing down prey aspect described above is the primary reason this trait would be of benefit to humans but not other species (I can't think of any other predators that don't rely on greater speed or ambush skills to hunt down food), but it is not evolution "choosing" anything - had the random mutation not have occurred, humans would have a full coat of fur, regardless of the potential advantages otherwise (unless you are attributing evolutionary to intelligent design).
What kind of clothes do elephants wear?
Anything in their trunk
Humans are daytime endurance hunters. A bunch of ancient guys learned to throw rocks and spears. They then, eventually with helper dogs, tracked, attacked, wounded, and wore down four-legged grass-eating animals.
Humans with two legs are WAY more efficient in covering distance than animals with four legs. There's much less energy use in leaning slightly forward and moving one foot a couple inches up than in lifting one's body up and down every step like a cow, horse, etc. So, heat control (sweat; no body hair, head hair) became a huge advantage for even greater endurance.
The first few thousands of generations of humans were dark skinned and lived in warm East Africa. Two legs let them migrate out several times over, both in late ape form and in early or dead-end human form (e.g., Neanderthals, Denisovans). Once humans hit Eurasia they either stayed in the tropics by the coast (e.g., Australia, Melanesia), or they went inland and had to deal with snow and winter. Then, heat rather than cooling, became a factor. Pale skin = limited need for sun blocking melanin per the weak sun and better vitamin D production.
Heat Exhustion can result in cool moist skin. Figure that one out.
"Other mammals" didn't invent bandages, sutures, antibiotics, laparoscopic appendectomies or contraceptives.
Having dog mushed to and from Manley Hot Springs and Tanana, Alaska, where the dog teams kept a constant pace of above 10mph for most of the night, I would dispute that any human could do that much distance in that much time.
The record for the Iditarod race is 7 days, 14 hours to cover 957 miles.
@John: Probably get eaten due to too many links, but it isn't a radical idea that humans are supreme endurance runners.
https://www.newscientist.com/article/mg23231031-300-humans-are-better-endurance-runners-than-any-other-animal/
https://bigthink.com/life/humans-best-endurance-runners/
I dunno Lions and Tigers seem to do pretty well in the heat, and they have fur to help with wounds. What's their deal?
Lions sleep between 16 and 20 hours per day, and sleep a lot during the hot parts of the day because of the heat.
Having dog mushed to and from Manley Hot Springs and Tanana, Alaska, where the dog teams kept a constant pace of above 10mph for most of the night, I would dispute that any human could do that much distance in that much time.
That is an area of the world, and a climate, that is wildly different from the climate in which humans and dogs evolved, and provides natural cooling due to the temperatures whereby the ability to retain heat through fur likely provides an advantage. Also, dogs have been so heavily selectively bred that I would not try to extrapolate anything about natural selection from modern dog traits.
I came here to say what @Enigma said. Human beings are "endurance" or "persistence hunters" (we run things down over very, very long distances and periods of time). Quite a few notable differences between human beings and other primates are a reflection of this adaptive difference.
Hmmmm ... If humans' ability to recover from injuries lessened over time, doesn't that disprove the theory of evolution?
No, of course not. There is no conceivable observation that would disprove the theory of evolution. The theory of evolution is not falsifiable.
Quaestor brings up a good point, though obliquely. Maybe we are hairless for the same reason that a vulture's head has no feathers, so that the UV of the sun disinfected our skin as we fed on carrion. One theory is that we used rocks to break open the bones of large prey once all of the meat that was easily accessible by tearing teeth of animals like jackals, or the animals who first did the kill. Supposedly you could break open with a rock the leg bone of a large animal killed by pride of lions that had abandoned the kill since it was now just the bones, and get 1500 calories worth of protien and fat.
Not all that charming of an origin story, but it is one theory that hangs together.
I bet that there are a dozen primary reasons that we are largely hairless.
@Jupiter: "If humans' ability to recover from injuries lessened over time, doesn't that disprove the theory of evolution?"
Evolution merely means change and adaptation. Some changes/mutations help in one context but cause issues in another. See sickle cell disease vs. malaria resistance.
Evolutionary explanations indeed rely on a lot of circular logic, but there's no other way to explain the combination of (1) geographic distribution of species, (2) temporal changes in fossils, (3) convergent evolution of similar forms and functions in fossils and living animals (e.g., some insects vs. humming birds), (4) predator-prey relationships such as camouflage and poison/venom, and (5) explaining how adaptations allow species to inhabit new environments (e.g., hippos became whales; penguins lost the ability to fly but became fantastic swimmers).
There's no other way to account for the fuzzy intermediate shapes, forms, and functions of plants and animals.
“If you had to choose between the power to heal fast or to cool fast, would you not choose the cooling power?”
In these times of Global Warming, the cooling power is very important.
Enigma said...
“Evolution merely means change and adaptation.”
For another example, google “hairless chimp”. They look like freakishly buff gym rats. All of our ape cousins are buffer and stronger than we are. Even the Neanderthals were far stronger and more muscular than we are.
But maintaining all those muscles takes a lot of energy. Early Homo sapiens were able to adapt and thrive in a lot of environments where a lot of food wasn’t easily available once we lost the gene to make us naturally more buff.
@Enigma I read as much as I could from the first link (until they wanted money) and the full second link. Thanks for them.
I think the question is ill-defined. You point out that I cite dogs bred specifically for racing, and you are correct. But find me a human that under ideal conditions could carry its own food for 957 miles and do that distance in 7 days and 14 hours. The article I could read was about some Africans who can do 200 miles over a couple of days. What are they carrying? Are they subsisting on the land that way? Are they typical of humans or humans selected (I won't say bred!) for what they do?
Having recently read Foote's 3 volume The Civil War, got me to thinking about military aspects of speed. Stuart's calvary, absent at Gettysburg, was Lee's eyes, and he was blind because Stuart was still out on his run around Meade. Why did they use horses rather than men on foot? I would say it is because men on foot cannot carry their own food and move as quickly (though Jackson's "foot cavalry" did some impressive marching when they defeated Banks).
In Africa, the predator that has the highest success rate is wild dogs (85% is the number I've seen). How do they do it? They run the animal they are hunting until it collapses. Humans in North America before horses had to use lots of people to direct herds of buffalo off of cliffs. They gladly adopted horses when they became available.
While I can walk 20 miles a day with a heavy backpack with all I need to survive, I can only do it for 4 or 5 days. If I use dogs and a sled, or horses and pack horses, I can do that for maybe 10 days.
Again, I think it is an ill-defined question.
I read an account of a starving family in Russia. The son chased a deer for several days, wearing it down, until he killed it with his hands.
in terms of the amount of hair, humans are actually on par with other primates.
Humans have about five million hair follicles across our entire body, or about 60 hairs per square centimetre of skin. This is not much less than other apes.
If you had to choose between the power to heal fast or to cool fast, would you not choose the cooling power? It's what evolution chose for us, but not for all those other animals. Why?
When we diverged from out common ancestors with chimpanzees we became persistence hunters.
A human in good shape can run down almost any animal over time.
Because we have lots of sweat glands.
“Humans evolved to hunt on the hot savannas of Africa. Not being very fast, they had to rely on endurance, which required efficient cooling. As a result, a man can outrun a horse over a marathon distance.”
Maybe. But Ann brought up “The Naked Ape” (which really dates her - we read it in the fall of 1968, as we started as freshman in college). We apparently separated from our closest genetic relatives, the chimps and bonobos, roughly 7.5 million years ago. And partway through that we greatly diverged from the rest of the apes. And according to that book, a number of those changes suggest that we had a semi aquatic existence:
- our relatively hairlessness
- hair pattern that suggests optimization for moving through water
- relatively flexible backbone, that allows for swimming
- subcutaneous fat layer, that is common in aquatic mammals, but not in those that are not.
- digestion that digests fish better than other animal flesh (followed by poultry, then white meat, and finally red meat).
- a reflex in the very young that closes the throat when immersed in water. You apparently lose that when you are 1-2 years old.
So, an alternate theory is that we (as a species) spent a period of time living by a lot of water, and spending a lot of time in it. That’s when we lost our hair, gained the flexible backbone, our legs straightened out, and we became optimized for eating fish. Then, possibly, we moved to running the savannas of Eastern Africa, and developed sweat glands (which would have been useless in the water). Our noses grew too, better for breathing while running.
I do believe in natural selection and evolution. We saw it in action in 2021 and into 2022. The idea behind the mRNA vaccines was to inset mRNA into cells, and have them produce the two most visible proteins on the outside of the SARS-CoV-2 virus - the S1 and S2 spike proteins. Our immune systems would recognize them as antigens, and then, in the future, whenever encountered, the corresponding antibodies would be quickly produced. So, significant evolutionary pressure was placed on those spike proteins, and they quickly (initially, with Delta, in 3 months, and later, to a greater extent, Omicron is a bit over 6 months) mutated around the vaccines. Respiratory viruses, like SARS-2, mutate easily and quickly because they are RNA (and not self correcting DNA) viruses with a simple, but robust, infection path.
I see evolution as temporary optimization of usually several competing traits. Thus human head size is limited by female pelvis size, and that affects their ability to walk and run. But in the other direction, head size affects intelligence, which for humans is a survival trait. That can be addressed by a significantly longer brain maturation time, but that in turn requires other mutations, such as hidden estrus and fairly constant sexual receptivity, in order to push pair bonding, in order to significantly add resources to the females during this extended brain maturation required for developing large brains despite relatively narrow birthing canals. Women with too narrow hips (or that don’t open up when preparing to deliver) don’t have as many children. Those whose hips are too wide, cannot escape lions, etc. And those with too little intelligence don’t acquire as much food. There is tension between all these competing pressures, and we find ourselves in temporary minimums. And when something changes, diversity in the gene pool allows us to reach a new temporary minimum.
One of the big benefits of sexual reproduction is that genes are always being recombined. This is probably necessary for larger animals with corresponding longer maturation. Without it, we couldn’t evolve quickly enough to address changes in our environment (and species that don’t evolve quickly enough go extinct).
So, where does genetic diversity come from? Mutations. Gene replication isn’t always perfect. Mutations can be negative, neutral, or positive, in relation to the present environment. Negative mutations are most common, but quickly die out. And positive ones end up sweeping through the population, as their carriers outcompete those without, in terms of surviving descendants.
One example is tricolor vision. Most mammals don’t have it. We do, as well as most Old World monkeys and their descendants. Turns out that it started with the duplication of the (I believe) genes that create green sensing cones in our eyes. Initially, it was a neutral mutation, but then one copy was “tuned” to respond to red light. And at that point, it became advantageous (possibly for recognizing more nutritious red vegetation), and swept through the population, pushing towards more recognition of red light. Interestingly, it appears that some small percentage of humans appear to have tetracolor vision - which means a 4th type of cones in their eyes. My partner is likely one of them. It appears to be sex linked, as is color blindness (typically 2 color vision) which means that the genes for it are probably on the X chromosome.
Final digression.
One way to distinguish mutations is whether a new feature is created, or an old one deactivated or reactivated. We have the genes for a lot of things from our evolutionary past. Thus, for example, humans don’t have tails - generally. Except that some do. And are typically eliminated at birth. It really doesn’t provide us with an evolutionary advantage, and, indeed, is probably mildly disadvantageous, so somewhere along the way (somewhere around when the apes separated from other primates), the feature was turned off. And it most often stays turned off, because it’s mildly disadvantageous. But should a tail ever be evolutionarily advantageous, the gene for turning it back on would sweep through the population.
When Johnson and Johnson invented the band-aid in 100,000 BC, humans evolved to move away from follicle healing and became mostly hairless. The primary evolutionary advantage was major savings on hair care products. Imagine what we'd all be spending if we were covered with long hair all over instead of just a few strategic areas.
I am amazed at how quickly I heal when I use one of the tube type antibiotic ointments like neo…. An overnight cure for cuts. So tech beats evolution.
Mag-post ng isang Komento
Please use the comments forum to respond to the post. Don't fight with each other. Be substantive... or interesting... or funny. Comments should go up immediately... unless you're commenting on a post older than 2 days. Then you have to wait for us to moderate you through. It's also possible to get shunted into spam by the machine. We try to keep an eye on that and release the miscaught good stuff. We do delete some comments, but not for viewpoint... for bad faith.