Why are we naked?

[bombus]

Hair provides so much needed protection from the elements. It only became redundant after humans started wearing clothing.

 

 

 

Considering you're contradicting Richard Dawkins here' date=' I'm going to go ahead and assume you're wrong.

 

Mokele? Care to chime in on that?[/quote']

 

Richard Dawkins was wrong and I am right. Just had to clear that one up.

[bombus]

I believe sexual selection was at least partially the reason Homo Sapiens lost their hair.

 

A male who had less hair might have appeared more masculine' date=' therefore being chosen by the opposite sex. As for females, the loss of hair would have made their breasts more exposed, leading once again to sexual selection. Now it is unlikely that individuals would lose hair on one place of the body (e.g.: breasts) but a certain mutation would make the individual overall less hairy.

 

There could have been a mutation in the either sex that favored hairless partners. The gene would be successful because the offspring would be more equipped to deal with bipedalism (Sweat theory as mentioned before in the post) and therefore pass the gene for "preferring hairlessness" down the generations.

 

One of the theories is that the reason we became bipedal in the first place is because our penises were more exposed to the opposite sex once we are standing up.[/quote']

 

I think sexual selection is the answer, and it is neotenic features that were (and still are) being selected. It's not just hairlessness, its also small jaws, big brains, head articulation etc. Hairlessness is just another example of a general trend. The question is why were/are humans the only apes that select for neotenic features? We generally favour young mates whereas other apes generally favour more mature mates Ipresumably as they tend to make better mothers).

[FreeThinker]

Because we became bipedal and the apes did not. Hence, being 'less hary' had a bigger effect on our bodies ( since they were more exposed).

[bombus]

Because we became bipedal and the apes did not. Hence, being 'less hary' had a bigger effect on our bodies ( since they were more exposed).

 

Mmm... I would ask 'Why did we start to walk upright?'. The thing is, the only other savannah-living primate we know is the Baboon, and rather than becoming more human-like, it has become more dog-like. The only other truly 'upright' animal on earth (apart from man) is a penguin, and guess what, it's a semi aquatic bird! It's adaption for swimming in water has changed its body shape making it upright. Unfortunately for the penguin, it has gone for the short legs approach to swimming (like otters, seals, and ultimately cetaceans) rather than the long leg approach (like frogs) so although it walks upright, it can't exactly peg it when it needs to move fast - unlike the aquatic (nay semi-aquatic) ape!

[Daecon]

That almost sounds like you're implying People started to walk upright so they could become better swimmers?

 

That's an... abstract viewpoint.

[starbug1]

Because we became bipedal and the apes did not. Hence, being 'less hary' had a bigger effect on our bodies ( since they were more exposed).

 

 

Would becoming bipedal and losing hair have anything to do with our genitals becoming exposed? Now, to me, this would be a big push towards loinclothes and ultimately more and more clothing.

[bascule]

I'd say our loss of hair comes from a number of factors, sexual selection and the uselessness of body hair after the advent of clothes being two of the biggest. Hair on the head serves two purposes, first as a sort of peripheral warning system for if we're about to hit our head on something, and secondly hair, especially long hair, is useful in tool/basket/craftmaking.

[Specusci]

One of the best explanations that I read to date said that when humans were almost extinct we resorted to being fishermen, and as aquatic apes it was more beneficial to lose the hair in favor of sweat glands. Another good explanation was sexual selection.. less hair meant more skin contact which heightened sexual pleasure, and as emerging intelligent thinkers and sex machines, it was sexually selected into us. Would love to know what others think.

 

I didn't bother reading the entire of the posts (bad habit, I know, I sincerely apologize to those offended ) But this seems a somewhat obvious question. The idea that we became fisherman is, to me at least, a very ridiculous notion that needs to stay in the 19th century, regardless of when it was theorized. I highly doubt humans came even close to becoming even semi-aquatic, simply because they could fish for food (tribes that exist today practice primitive fishing methods that would have existed in primitive Africa, but I don't see them with webbed feet or gills ). Anyways, I think the current and most acceptable theory on this would be that, in the African plains, a hairless body constituted as a better coolant and heater then a hairy one. Indeed, Lions and Gazelles both have very thin coatings of hair compared to more northern relatives.

 

As a sexual development, chances are that was a side effect or a co-evolutionary development. More contact with the skin is, undoubtably, more sensual then having to deal with a thick coating of hair. Indeed, the complexity of human emotions compared to more simplistic creatures demanded added qualities to previously methodical and mechanical tasks, tasks such as sexual reproduction. With greater skin contact, hairless bodies where most likely genetically preferable at the time. Or maybe the heightened sexual pleasure was a failsafe for the emergence of hairless apes (if hairy bodies had been more kinky, chances are we'd all be running around with ape fur). In any case, sexual sensuality could very well have been a major contributor.

 

Anyways, discard the fisherman theory, it is complete rubbish.

 

secondly hair, especially long hair, is useful in tool/basket/craftmaking.

 

I think the major theory is social habits. A major relationship solidifier amongst primitive humans (before language) would have been grooming, and hairless bodies aren't as easy to groom. This is evident with children (especially girls) having a tendency to play with one anothers hair.

 

Would becoming bipedal and losing hair have anything to do with our genitals becoming exposed? Now, to me, this would be a big push towards loinclothes and ultimately more and more clothing.

 

The taboo of exposed genitals is a purely religious thing. Loincloths probably first arose when humans wandered into the frigid Europe and needed to protect thier naked genitals from the elements.

We generally favour young mates whereas other apes generally favour more mature mates Ipresumably as they tend to make better mothers

 

Mainly because we are intelligent enough that age doesn't really discriminate against (useful) knowledge. IE, a first time mother could perform like a many time mother now because we can share information at a MUCH more efficient rate.

[bombus]

Mainly because we are intelligent enough that age doesn't really discriminate against (useful) knowledge. IE, a first time mother could perform like a many time mother now because we can share information at a MUCH more efficient rate.

 

I don't think intelligence has much to do with it - we feel it in our loins man! We are programmed that way, but other apes aren't. But even if u are correct, it's only 'cos we got bigger brains in the first place, which is (probably) a result of evolutionary neoteny. The thing that set us on that path in the first place may have been adaptation to a semi aquatic lifestyle which favoured neotenic features (i'm not listing them now!).

[MM]

As a first try I would see if loss of hair consists with conservation and gaining of energy of the whole system.

 

I don't know if this is true or not but a friend of mine told me yesterday about a documentary he saw where bushman as he called them hunted for pray using only primitive tools like spears. Now the interesting part was the way the hunted down the animal. I first thought they sneaked up on the animal but he said they chased the creature for hours in terrible heat so at the end the animal would just stand still. Here I assume it was because of heat exhaustion. This hunting method clearly needs rapid cooling so less hair is preferable.

[gcol]

I like that. Does that mean that if we were extremely hirsute and worked up a good old sweat, we would all loll about with 12" tongues waving about, salivating and drooling? I can just imagine that. Very sexy!

[Norman Albers]

Are we the only species that fashions clothing? Why not identify ourselves as Homo Ropus (is my Latin close?) Every twenty-two degree morning I walk outside and greet the birds, saying "It's a good day to have feathers. Wish I had some."

[bombus]

As a first try I would see if loss of hair consists with conservation and gaining of energy of the whole system.

 

I don't know if this is true or not but a friend of mine told me yesterday about a documentary he saw where bushman as he called them hunted for pray using only primitive tools like spears. Now the interesting part was the way the hunted down the animal. I first thought they sneaked up on the animal but he said they chased the creature for hours in terrible heat so at the end the animal would just stand still. Here I assume it was because of heat exhaustion. This hunting method clearly needs rapid cooling so less hair is preferable.

 

Yeh, I saw that. It was a real eye opener. In fact the 'bushmen' didn't need to use any tools or weapons at all. They did chuck a spear into the animal (an elan I think) at the very end, but it was more of a token gesture, it was exhaustion that killed it.

 

The thing is, they were able to do it because they were able to carry water with them, else they would have died from dehydration before the elan. This seems to suggest that hair loss to aid sweating is a great adaptation - but only if you have evolved a brain big enough to carry water around with you.

 

I would suggest that perhaps a semi-naked, semi-aquatic ape, with a nice big brain (due to selection of neotenic features to aid a semi-aquatic lifestyle) was pre-adapted for life on the savannah. Once on the savannah its flipper-like feet were great for walking, its elongated body was great for an upright stance, and its big brain allowed tool use (e.g water carrying). Then it can lose almost all its hair as it's not really needed an in fact becomes an advantage..!

[MM]

Yeh' date=' I saw that. It was a real eye opener. In fact the 'bushmen' didn't need to use any tools or weapons at all. They did chuck a spear into the animal (an elan I think) at the very end, but it was more of a token gesture, it was exhaustion that killed it.

 

The thing is, they were able to do it because they were able to carry water with them, else they would have died from dehydration before the elan. This seems to suggest that hair loss to aid sweating is a great adaptation - but only if you have evolved a brain big enough to carry water around with you.

 

I would suggest that perhaps a semi-naked, semi-aquatic ape, with a nice big brain (due to selection of neotenic features to aid a semi-aquatic lifestyle) was pre-adapted for life on the savannah. Once on the savannah its flipper-like feet were great for walking, its elongated body was great for an upright stance, and its big brain allowed tool use (e.g water carrying). Then it can lose almost all its hair as it's not really needed an in fact becomes an advantage..![/quote']

 

 

Yes water is essential to us. However I don't think we evolved from an semi-aquatic animal so _late_ in our evolutionary history if you mean an animal specially adapted to water like having big flipper-like feet.

 

The reason I don't belive this is our well developed brain. Since we are great at solving problems our environment would have to be diverse and challenging and one driving force is that of finding water. Since this would directly influence the ability to pass on one's genes and become dominant. I belive this was in the documentary also, that the people were able to find water in many unlikely places.

[bombus]

Yes water is essential to us. However I don't think we evolved from an semi-aquatic animal so _late_ in our evolutionary history if you mean an animal specially adapted to water like having big flipper-like feet.

 

The reason I don't belive this is our well developed brain. Since we are great at solving problems our environment would have to be diverse and challenging and one driving force is that of finding water. Since this would directly influence the ability to pass on one's genes and become dominant. I belive this was in the documentary also' date=' that the people were able to find water in many unlikely places.[/quote']

 

When I say big flipper-like feet I mean the feet we (humans) actually have. My feet are certainly big and flipper like and I bet yours are too compared to chimps! And to further back up the aquatic ape theory (semi-aquatic I should say), did you see those swimming/diving monkeys on Planet Earth last week? Give them half a million years and betcha they lose their hair, grow big flipper-like feet (not flippers though!), develop subcutaneous fat, a dive response, an upright stance etc etc etc...!

[MM]

When I say big flipper-like feet I mean the feet we (humans) actually have. My feet are certainly big and flipper like and I bet yours are too compared to chimps!

 

Ok, I misunderstood you about the feet comparison. Although I see them adapted mostly for walking and I belive walking upright is an energy conservation issue.

 

Here's some recent news on upright stance.

 

ape-like people

http://www.world-science.net/exclusives/060221_unertanfrm.htm

 

And to further back up the aquatic ape theory (semi-aquatic I should say), did you see those swimming/diving monkeys on Planet Earth last week? Give them half a million years and betcha they lose their hair, grow big flipper-like feet (not flippers though!), develop subcutaneous fat, a dive response, an upright stance etc etcetc...!

 

I don't have that channel so I will have to wait.

 

What I think is certain is that as we evolved we were able to live further and further away from water and by the way I think we evolved through a diversity of surroundings I will grant you it's not farfetched to think that some of our traits came from a water environment. It is however hard to pinpoint the exact traits because the reasons for some of the traits would come from multiple factors all working together.

 

All and all I belive we evolved from a predominant land creature.

[bascule]

I completely dismissed the aquatic ape theory until I read about how a diet rich in fish provided us with DHA and the fats we needed to support rapid brain growth. I certainly think our common ancestors went through a period where they were quite the fishermen, but as to whether or not this entailed actually going in the water to fish versus developing tools like spears to let them fish from shore is another question entirely.

[NeonBlack]

No aquatic apes?

 

Haven't you guys ever heard of sea monkeys?

Jesus.

[Norman Albers]

I would assume to fish you were messing around in the water with your hands, spears, or nets. We were not fly-casting from the shore. I'd want my spear back, too.

[iglak]

firstly, snakes do (in a way) have hair. feathers, down feathers, hair, and fur are all simple mutations of scales.

 

sweating: seems right.

why do we still have a little hair? well, notice that when you sweat, the sweat clings to the hair. this helps the sweat evaporate by giving it more surface area, and more area of contact with moving air.

 

why do we have hair on our heads? our brains prefer a certain temperature to function correctly. people who are bald or shave their heads often mention how much colder it is without hair, and usually have to wear a hat when it's a little bit cold to feel comfortable. beards, too, keep us warm.

 

could we have evolved semi-aquatic? sort of.

i have heavy doubts about AAH. but i have my own conjecture. the African savahna has quite a few rivers. strong rivers with predators. migrating animals all have their own apporach to crossing the rivers. Zebra have slick hair, and use the shotgun apporach, guaranteeing that a fairly random portion get across. buffalo are larger and stronger, and aren't affected as much by hair, and use the shotgun apporach. elephants are very large, and not affectetd much by the water at all, but at their slow pace, having lots of hair would slow them down even more. cats and dogs swim quite well, and have slick air, and their body shapes are good for passing through water.

 

humans, being upright, would have a problem if they had ape hair. slick hair would probably be okay, but then we get into the sweating problem. less dense hair, like the apes in the picture recently shown, would dramatically reduce our ability to cross the rivers. at the same time, apes aren't exactly great at crossing rivers, and could easily be swept out of control. it became extremely beneficial to be able to swim well, and control your body in water, so our feet and hands are slightly more webbed than necessary. with only tool-using and running defining our feet and hands, it would make more sense to have less webbed hands (to move fingers in a wider range, and with more control), and slightly longer and stronger toes (to provide more spring in each step, as well as more balance).

 

 

i don't know if i believe the hypothesis that we out-enduranced our prey. we have brains with complex communication abilities, and a complex understanding of strategy and tactics. presumably, this was to catch prey.

although on second thought, it could have been to survive war, and predators.

but still, it's not good for humans to run as much as most people do. it puts excessive strain on the whole body, including important internal organs, especially when running for extended periods of time. it seems much more likely that we didn't run after our prey, but instead scared it into sprinting away, and walked the short distance to where it stopped running away to scare it again (only really running when scaring it). the animal would have likely tried to join the herd again, so it was a matter of predicting where it would come from, and walking with the herd in wait for it to come. we could have also confused it by coming from multiple directions, to try to get it to run around in circles, or to a predicted, predetermined spot.

[MM]

i don't know if i believe the hypothesis that we out-enduranced our prey. we have brains with complex communication abilities' date=' and a complex understanding of strategy and tactics. presumably, this was to catch prey.

although on second thought, it could have been to survive war, and predators.

but still, it's not good for humans to run as much as most people do. it puts excessive strain on the whole body, including important internal organs, especially when running for extended periods of time. it seems much more likely that we didn't run after our prey, but instead scared it into sprinting away, and walked the short distance to where it stopped running away to scare it again (only really running when scaring it). the animal would have likely tried to join the herd again, so it was a matter of predicting where it would come from, and walking with the herd in wait for it to come. we could have also confused it by coming from multiple directions, to try to get it to run around in circles, or to a predicted, predetermined spot.[/quote']

 

The hunting method ( "chasing hunt" ) is portrayed in the film "The Great Dance, a hunter's story".

 

http://www.senseafrica.com/greatdance/movie/run.html

 

As for running I don't think we exercise enough being a regulatory system and it seems from the article above and below that running is a key part in our evolution.

 

http://news.bbc.co.uk/2/hi/health/4021811.stm

[SubJunk]

elephants dont have much hair

 

but they walk on four legs and have broad backs exposed to sun

 

Mokele gave the theory that when apes stood up and walked on two legs they didnt need protection from sun' date=' that hair gives, like for example on a broad level back area.

 

my guess is still the HEAT THEORY which is that you lose hair when you have a problem dumping or getting rid of surplus heat

 

the reason the elephant has a problem is because she is big

so there is this reduced AREA/VOLUME ratio

big things hold in heat better because they have less surface area

 

the elephant makes waste heat depending on her volume, because all her cells have to metabolize, so she makes a lot of waste heat but does not have good ways to get rid of it. Big ears do probably help as a place to cool the blood by radiation and convection. But also HAIRLESSNESS or having very little wimpy hairs instead of fur, that would help.

 

So I am conjecturing that people lost their hair (by adaptive neoteny suggested by Mokele) under similar evolutionary pressure[/quote']

Elephants have extremely thick skin which negates the need for hair.

[pink_trike]

Anyone have any ideas on why human head hair grows as long as it does, at what point in our development this might have developed, and what factors might have triggered it ?

 

I imagine that ankle length hair would present problems when we lived in trees and before sophisticated tool use. The inconvenience and associated dangers seem to work against the idea of sexual selection. Are there any other species that have steady head hair growth?

[bombus]

Elephants have extremely thick skin which negates the need for hair.

 

Elephants had a semi-aquatic ancestor, which is perhaps why they have little hair today. Rhinos also have a semi-aquatic ancestor, and Hippos are still semi-aquatic.

 

In fact, the case of elephants and these other pachyderms is very interesting and may have parallels with humans. They were land dwelling, then spent a period of time closely associated with water (semi-aquatic) and then came back on to the land 9for the most part). They still retain many of the watery traits though, and the elephants trunk may be one of them. They also still love spending time in water!

 

Maybe humans went through a similar process !

[bombus]

Ok' date=' I misunderstood you about the feet comparison. Although I see them adapted mostly for walking and I belive walking upright is an energy conservation issue.

 

Here's some recent news on upright stance.

 

ape-like people

http://www.world-science.net/exclusives/060221_unertanfrm.htm

 

 

 

I don't have that channel so I will have to wait.

 

What I think is certain is that as we evolved we were able to live further and further away from water and by the way I think we evolved through a diversity of surroundings I will grant you it's not farfetched to think that some of our traits came from a water environment. It is however hard to pinpoint the exact traits because the reasons for some of the traits would come from multiple factors all working together.

 

All and all I belive we evolved from a predominant land creature.[/quote']

 

Planet Earth is David Attenborough's new programme on the BBC. I'd agree that we evolved from a predominantly land-based creature. The semi-aquatic period could explain why we went on a different path to chimps. We've only been separate species for around 5 million years (so they say!).