I'm still wondering if those living nearer the poles are selecting back for more body hair. Cause they sure needed it, even with clothes. I also had some objections to Ice's very reasonable suggestion.
Why are we near hairless?
- Thread starter wise acre
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Less hair=less fleas, perhaps? Maybe it was easier for prehumans to destroy their resident vermin if they didn't need to scratch through a thick layer of hair. For that matter, why do we have any hair, seeing as we've got rid of most of it from the rest of our bodies, why do we still have it on the head/underarms/crotch? What's the biological or evolutionary advantage of those thatches? For that matter, why didn't prehumans develop camoflage colouration like other animals (which is all we were between about 8-2 mya?) A dappled coat in forest-shadow, or vertical stripes, say, in the African grasslands, might have given us an extra survival advantage in the presence of faster, larger and more agile predators--so why aren't we zebra-striped or leopard-spotted?
The Native Americans who live in Alaska and northern Canada, at least the ones I've met don't appear to be very hairy, unless they all shave constantly, but I do know that people of middle eastern descent who live what have to be some of the hottest countries on earth are very hairy. My friend in 8th grade was from Iran and she had to shave every single day. I knew a whole lot of people of middle eastern descent in high school, all from different countries and none of them mixed with any other race, all of them were hairy people.
Actually, they tend to have LESS body hair and have shorter limbs. Thick beards and such hold ice.
hahaTheir social groups never get that large, though. Never over a couple dozen individuals. Better counter-examples would have been bats or swallows.
How social are bats and swallows, exactly, in terms of physical contact?
Is that comparable to 'early humans'?
Bats are just as close if not closer than humans are.
At this point the preference is embedded in sexual selection. And they don't really need it - the skills the traditional cultures had saw them surviving quite well without it, even in such an inhospitable climate.
I did.
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But it would have to help.
And why'd we keep our head hair and pubic hair?
The latter is a wonderful grazing area for parasites. The former home to lice.
OK. Bats are hairy. And still. Groups of hairless lions or wolves who could hunt when others were resting would still have an advantage. Hell, they could even have seasonal sheddings. Hair that comes when it is cold - not think so much of african species here, but mammals in areas with wider seasonal variance.
So I'm still skeptical of the hair temperature theories.
The question is whether it would be an advantage for many of them, incrementally.wise said:
It's not just a matter of occasional gain, but survival the rest of the time. It gets cold at night, it rains, there are flies and enemy claws - hair is near universal for good reasons. It is difficult to point to an incremental advantage of a little less hair for a leopard, for example. Mammals that do need to dump heat most of the time, and can grow thick hides with little proportional penalty - the very large ones, like elephants - do have much less hair.
The proposal is that the freehand bipedal stance and tool using or long distance planning intelligence of humans maximized the gain from this kind of scavenging and foraging and travel, and the vulnerability to predation and inability to compete otherwise maximized the loss avoidance - that early hominids, having been set up on their hind feet somehow and provided with the brainpower to plan treks, build shelters and fire, rig clothing, and see the point of all this initially unrewarding effort,
and having evolved these features in the right place at the right time (the great drying out of game-rich northern Africa),
were uniquely set up to take advantage of various heat adaptations and other distance running/traveling features.
Now of course given such incremental advantages, other factors come into play - sexual selection dominant among them, in monkeys like us. When chance variation in visual preference in a visual animal is reinforced by a real advantage, evolution can be rapid.
I doubt that the loss of hair produced advantages over disadvantages.
I think that we humans have chosen flawless skin as an indicator of health
Many creatures have ungainly and extravagant features which would not enhance their breeding potential were it not for them being a signal of genetic health.
The attraction of bare skin is unique to humans, I think.
(It certainly draws my attention.)
I have not heard of any other animal which focuses on patches of bare skin.
I think that we humans have chosen flawless skin as an indicator of health
Many creatures have ungainly and extravagant features which would not enhance their breeding potential were it not for them being a signal of genetic health.
The attraction of bare skin is unique to humans, I think.
(It certainly draws my attention.)
I have not heard of any other animal which focuses on patches of bare skin.
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I think they're probably wrong. We sweat, so a lot of hair would hinder the heating/cooling process. Look at pigs: They have hair kind of like we do. They also have sweat glands, although theirs are less efficient.
There's a chicken and egg problem with positing that as the initial evolutionary driver, though. Unusually thin and patchy hair is not a sign of good health in any known animal (nor even humans, now), and hairlessness would a severe handicap in almost all land mammal niches - so how to get from Apelike to Bare?kremman said:
Like the bipedal stance with its dramatic skeletal demands, the small and weak fighting teeth, the unique childbirth sequence, the bizarre larynx morphology, and so forth, unless you are willing to posit a hopeful monster of inexplicable sexual attractiveness or extraordinary survival advantage surviving a double length childhood and mate competition within a pack of chimpanzees, you have the task of providing a step by step incremental advantage to the initial stages of your now completed innovation; starting with an ape probably similar to a modern chimp, or possibly baboon.
Horses sweat, and the hair doesn't interfere much. Wild pigs are actually pretty hairy:takeandjive said:
Why would the hair that we do have be concentrated on our heads?
My bet is that the Aquatic ape theory is correct. My bet is that the reason we won't find the missing link is because the missing link lived on the beach's and ate clams. I think early man was a wading animal. Most of those beaches are now under water and the waves destroyed bones just as the waves destroy coke bottles.
I expect out of the trees and into the water-aquatic ape theory to defeat out of the trees and into the savannas theory in what is left of my lifetime.
My alternate theory is that man does not has much hair because man had clothes. But did Africans on the Savannas need clothes?
Regarding the clues from the animals, why don't elephants and rhinos have hair? Is it because they don't need hair to make it harder for predators to eat them? Is it because their roundness and body mass requires them to be hairless for better cooling?
Most of the other hairless animals are water animals. I believe the missing link between elephants and manatees was a wading animal and this may explain why elephants don't have hair.