I become more of an atheist every day
Many of humanity's distinctive features - walking upright, hairlessness, the ability to sweat copiously - arose due to the fact that the place where we evolved has been scorchingly hot for millions of years, according to noted boffins. The cradle of humanity, according to most research, was the Turkana Basin in Kenya's Great …
Where I live the temps hit 30c in early April, spend weeks on end at 35c+, and by late August there are peaks that pass 37.77777 (100F) more often than I can count; 30c is a cool wave. And we love it for boating, hiking, swimming and such. This is news only to people who haven't experiemced the finer climates.
Want cooler? We travel.
I've been in Arizona in summer (well above 40C at times) and it's quite OK once you get used to it, provided (big proviso) you have enough water at all times. Your sweat evaporates immediately and keeps you cool. You drink gallons and need to eat more salty snacks than usual to avoid cramps. Run out of water and you are in serious trouble.
People can work in steel-mills where I'm told it's even hotter than this.
I've also been in Philadelphia in a heatwave. Nowhere near Arizona hot, but very humid. Your clothes get soaked with sweat, stick to your skin, start dripping. There's so much water already in the air, that sweating doesn't solve the heat problem. Really, really horrid weather if you want to do anything outdoors. Go into an air-conditioned interior and you shiver until the sweat in your clothing has evaporated into the over-cool dehumidified air. Why do USAians set the indoor thermostat at 68F in Summer, rather than 75F?
So yes, I can believe that we are evolved for hot low-humidity surroundings. Only one question - where did prehistoric man in the Turkana find enough fresh water to survive and thrive?
in the southeastern U.S., temps between 30c and 40c are not only common, but are also accompanied by 90%+ relative humidity levels. Yes, it's rather warm. The humidity makes it extremely uncomfortable because the evaporative cooling effect of sweating just doesn't work. The only thing one gets is smelly damp clothing.
Now in the much drier climes of the southWESTERN U.S., temps reach well over 40c in the summer, but the low relative humidity allows evaporative cooling to work as intended. So long as one remains appropriately hydrated, it's not that uncomfortable at all.
Why aren't other mammals in hot(ter?) environments not (relatively) bald too? Only other bald mammals I can think of are either aquatic, burrowing or really big...
And, if we evolved certain physical characteristics to cope with an extremely hot and dry environment, getting rid of lots of water in the form of sweat doesn't seem like a particularly good survival trait....it makes us ming too.
Man has one outstanding ability amongst the animal kingdom; we can endurance run like pretty much no other. We can be outdistanced by almost all animals in a sprint; gazelles, wildebeest and other plains dwellers can outrun us for a bit but then their muscles get tired and we catch up, and keep on coming in for the kill on a prey that is too exhausted to get away or even fight much.
A long distance runner has to shed heat efficiently to maintain the pace, so a reduction in hair/fur would be beneficial, as would the sweating for cooling. Once you have flushed out the prey you don't need to be too subtle about running it down, being a bit whiffy makes little difference once the prey knows you are there. Even water should not be too much of a problem. Humans are social animals and hunt in groups. Get thirsty and break off for a drink while the rest of the hunters carry on pushing the prey past it's limit, rejoin when you can and give someone else the chance for go for a drink.
Good point about the Cape Hunting Dogs. Canines evolved a completely different cooling strategy - they cool themselves by panting rather than sweating, which can be sufficient for a CHD size long distance hunter, but problematic if the animal is larger due to the limited area of mouth and tongue for evaporation. This would less of an issue for a sprinting dog, which would tire quickly anyway. I think this cooling strategy may be the primary size inhibitor for canines. Given this size limitation some form of camouflage and defense from wiry undergrowth and cornered prey would enhance the benefits of a fur coat to protect the skin.
I can't comment on peccaries - I know little about them.
I was going to mention dogs/ wolves but another poster already has, and your answer sounds reasonable.
Human ancestors were bipedal long before they ate meat at all, never mind hunted, so I don't see being able to run down prey as a valid reason for the evolution of bipedalism, although it could certainly be a reason for humans being mostly hairless (one of my ex girlfriends being an alarming exception).
TBH I don't think there's any one reason why we are the way we are (although the aquatic ape theory tries to explain a whole bunch of human features) . I don't know if bipedal locomotion is any more/less efficient for walking than walking on all fours the way a dog/cat/horse etc does, and in any case that's a false comparison, the point is probably that it's more efficient than knuckle-walking on the ground the way other apes do, and has other benefits which would/ could have been an advantage and led to the increased fitness of bipedal proto-humans (leaves hands free, etc etc etc).
Fresh sweat doesn't stink. Old sweat does because of bacteria. And people didn't used to be fussed about a bit of smelliness, anyway, it's only relatively recently that someone invented soap and had to stoke up a lot of paranoia about BO to make people buy it.
Y'know, more or less.
People most certainly did care about smelliness. Why do you think the Bourgeoisie carried pomanders and other scented adornments during the Middle Ages? A handkerchief soaked in scented oils, maybe?
Besides, soap is the lazy man's cleaning product. In ancient Greece it was preferred to apply hot wax or oil to the body and strip it off, like many a lady is prone to doing nowadays (only for different reasons). It was much more effective at removing dead skin and other particulates than soap is, leading some to believe the ancient Greeks were more cleanly than we are today.
I'd also wager that old sweat didn't hang around long in the arid heat of the Turkana Basin. The whole BO thing probably got started about the same time we got clothes to hold on to the sweat and the church figured we shouldn't be naked when it's hot. Before I figured the church out, I always wondered how Adam and Eve were bothered by being naked when so many indigenous people in tropical climes don't seem to care so much.
"People most certainly did care about smelliness. Why do you think the Bourgeoisie carried pomanders and other scented adornments during the Middle Ages? A handkerchief soaked in scented oils, maybe?"
People did not care about bad smells, from the smelliness angle anyway, however some clever chap managed to associate people dying of plague with them being in particularly smelly areas. Thus they started thinking bad smells caused the plague, that was the reason for the oils and handkerchiefs.
Ironically, cleaning up what caused the bad smells, also got rid of the rats, causing less people to get sick!
...because we were the only species in this scorching heat with the good sense to evolve this way.
The chimps and gazelles that came from the same place were stupid enough to keep their fur!?
That heat theory suggests that no other mammal evolved under those same hot conditions, because otherwise they would very likely have evolved in the same way. Dismissed.
Ummm, natural selection doesn't work that way. Things don't evolve to suit their environs. They mutate entirely randomly - if the mutation harms them they die off and are less likely to have offspring that survive to carry on the mutation; if the mutation helps them they are more likely to have offpsring that survive to carry on the mutation and so the population is more likely to end up with the new/improved feature.
If gazelles, chimps etc never had the random mutations that reduces hair/increases sweat etc then they won't have those features. If they did have those mutations but the one creature that had it got eaten/disease/wasn't strong enough to get mates etc then it won;t show in the population.
In other words, we got lucky.
I completely agree. 30-35 C is only 85-95 F. Where I live in the American Midwest, 30-35 C is what we call summer! In fact, temperatures generally get up to 40 C (105 F) every August. I've never been there but I've heard the Southwest goes to 45 C (113 F) frequently in the summer. So humans being "evolved" enough to "cope" with 30-35 C heat isn't news.
We can "cope" with it, we just damn well don't like it!
I studied this exact same idea when I was at Uni.
To the Moderatrix...
I hate to correct you but Soap (rather than soap-like materials) has been around since at least Celtic times. And there's plenty of evidence that grooming was very important to most early civilisations.
Excessive washing is actually a very modern idea. Though there's been lots of beneficial side effects (human fleas are very rare these days) some others might not. My old microbiology lecturer suggested that one of the reasons we're smellier is because the stuff we obsessively put on our bodies kills off the bacteria that lives on our sweat. Which means we smell more... and so chuck more antibacterials on.
Actually this might explain why so many people... like to be lounge lizards soaking up the sun's rays.
Dark skin is more natural than white; who lack a pigment probably caused by evolution in colder climates.
Living up in trees is more comfortable because the air will be slightly cooler due to shade... and so live the spiders for whom some have instinctive fear.
Endurance running is definitely fun... although we have also savaged our bodies with malnurishment, poor nurishment, beef burger chemicals etc... and have not trained... that we become obese; sweat more and die early of heart attacks. Go barefoot; eat healthily (meat and vegetables) without E numbers and artificial rubbish... and get rid of this '3 meals a day' crap. Browse healthily on fruits and air dried meat and spot how much weight you put on. Probably a lot because the meat is stuffed full of hormones and crap fed to our animals...
But if all this is really true then we should send all obese people to the great rift valley and get them endurance running. If they survive then our bodies are well adapted...
"But if all this is really true then we should send all obese people to the great rift valley and get them endurance running. If they survive then our bodies are well adapted.."
Yeah, but don't send 'em there all at once - else it would no longer be a valley - they would fill it to the brim and turn it into a saturated fat marsh.
I for me don't for a moment believe that it's subtleties in language that caused the creationists to invent their fantasy-in-religion-sauce and start to foist it unto others. That they get away with stupid tricks like ``evolution is JUST a theory'' (emphasis added) means there are a lot of people Out There who can be easily conned with some cheap shots, but that alone won't have caused the movement.
Rather, failure to discern between religion and science, failure at basic logic and critical thinking, caused by culture just as much as very low education standards, I'd blame for a much larger part in its popularity. Like how even British ``professors'' advocate ceasing to mark down students for bad spelling because it's too much work. The sheer gall to propose that, and by extension to refuse to pinpoint the real problem, is another sign on the wall.
Then again, there is an element of science hoisting itself on its own petard. For one, though quite a lot has been said about scientific rigour and so on, actually teaching it mostly consisted of letting people ``get it'' by themselves. That in itself isn't so bad --certain monks use that all the time-- but without a barrier to weed out the clueless it is a problem. Increasingly so with the deluge of information and difficulty of reviewing it all. Hence the opportunity of some (certain Chinese publicist ``scientists'' come to mind) to game the review system. See also: _Cargo cult science_ by Feynmann.
Then there is the newfangled communication methods that now also allow cranks, nutjobs, weirdos, kinks, and the most voluminous of all: the stupid and clueless, to easily find like minded (FSVO) people. They too flock and join up for a bit of mindless babble and prattle, and have their ideas and memes breed.
To get out of the bind we need to improve the educational system so that the people with the capacity and talent to weed out cluefree information are taught how to do it, and to make it a habit to do it, too. Otherwise we'll keep on being stuck with ``concerned citizens'' managing to game school boards and push their pet religious and/or political agendas into millions of children's schoolbooks.
Where I live 30*C is just a nice warm spring / autumn day..... 45*C is fucking stinking hot... 50*C is awful.
And there are dessert type places that get to 50 - 60*C as a matter of course, and people live there as well.
So where do these stupid professor types come out with this shit that 30*C is scorchingly deadly hot?
Biting the hand that feeds IT © 1998–2019