Evolution of hairlessness and large genitals

[orgaelin]

Hi, I'm new here but I'm really looking forward to some great debates. This is my first post...

I've been pondering our relative hairlessness and large genitalia (relative to other mammals, though it may not apply to some of you quite so much;-) and considering a potential explanation.

It seems the most obvious thing that happens when you take away the hair which covered our more primitive ancestors is that our sex becomes far easier to identify. Our breasts, buttocks and genitalia (all seen as sexual organs in one way or another (read "Prehistory of Sex, The", by Timothy Taylor)) are all enlarged relative to other primates, again making our gender much more readily identifiable.

Why?

Can anyone think of an evolutionarily significant benefit of having our gender made so obviously visible?

[Pooeypants]

hmm, I do believe that we've evolved to use sweating as the main form of heat loss. And large amounts/density of body would hinder air flow, thus reducing water vapour concentration gradient and hence less sweat evapourating. On the african plains, this would be very bad. As for the genitalia, let me think it over and I'll try to find some research perhaps.

[orgaelin]

OKay, I wasn't sure of the official line on why we lost our hair - just thinking off the top of my head. Obviously an advantage of having a larger penis is that it deposits sperm closer to the intended destination, thus increasing chance of causing a pregnancy... but then why are we are alone in making that evolutionary gain? And then again there are Chihuahua's!

[G. Adams]

I thought we lost our hair because as our diet improved to include a much greater fat content, which is more efficient for keeping us warm, we lost our hair.

As for sexual organs, well this is a guess but...

Large breasts signify a healthy female, which means more sex, which means big breast genes go on. It's probably, like hair, dependant on our diet changes too. I doubt many creatures consume the fat content we do, and in order to attract a partner, the body put's the fat on the breasts and hips.

[orgaelin]

Which leads to the question: why are (some) men attracted to larger breasts - because it means a healthier female, better able to feed babies?

Also, with the hair thing, any explanation has to account for the extra hair on men - why didn't we lose as much?

[harami]

Penis size: dogs (medium sized or bigger), sheep, goats have larger penises than men and are no larger. So, put that one, as an evolutionary advantage, to rest.

Our sex organs are only visible and relatively outstanding because we travel in an upright state. Most other animals are interested in sex when the female is in oestres (large mammaries or not), but humans are preoccupied with it incessantly.

Hairlessness (or better, furlessness) is a puzzle to me. Perhaps the evolutionary advantage is that it forces us to make clothes to keep warm. A related question is: what percent of women like running their hands through chest hair and what percent prefer a bare chest? Maybe knowing these figure we could get some perspective on the intent of evolution vis a vis hair. Not all men like big breasted women (stats unavailable) but most like some breasts, imho.

[shunyadragon]

</span><blockquote><span class="smallfont">Quote:</span><hr size="1" />Originally Posted by (orgaelin,)
Hi, I'm new here but I'm really looking forward to some great debates. This is my first post...

I've been pondering our relative hairlessness and large genitalia (relative to other mammals, though it may not apply to some of you quite so much;-) and considering a potential explanation.

It seems the most obvious thing that happens when you take away the hair which covered our more primitive ancestors is that our sex becomes far easier to identify. Our breasts, buttocks and genitalia (all seen as sexual organs in one way or another (read "Prehistory of Sex, The", by Timothy Taylor)) are all enlarged relative to other primates, again making our gender much more readily identifiable.

Why?

Can anyone think of an evolutionarily significant benefit of having our gender made so obviously visible?<hr size="1" /></blockquote><span class='postcolor'>

Hairlessness is an interesting puzzle in evolution, because there seems to be no direct benifit for hairlessness, except that it is commonly found in more intelligent mammals that have a long gestation period like elephants, pigs and sea mammals. Hairlessness may be a consequence of a prolonged fetal development to alow for the development of the human brain. Prolonged fetal development and hairlessness are also associated with the increased need for nurturing. The human development is unique because the infant is born totally helpless and physical development is slow. Where many new born mammals are up and walking and relatively mobile in minutes. The other primates represent intermediate stages of this prolonged fetal development. Humans represent the longest prolonged fetal development and nurturing period of any mammal.

In the evolutionary picture the human evolution took the route of the more intelligent larger specialized brain. In exchange they gave up hair, speed, size and became relatively weak in comparison to other mammmals. The newly acquired intelligence more than compensated for the loose. Humans developed speach, clothing, tools and weapons.

[Pooeypants]

</span><blockquote><span class="smallfont">Quote:</span><hr size="1" />Originally Posted by (G. Adams,)
I thought we lost our hair because as our diet improved to include a much greater fat content, which is more efficient for keeping us warm, we lost our hair.

<hr size="1" /></blockquote><span class='postcolor'>
Possibly, but mainly its to with the African savanaghs and our evolution towards sweating loads as opposed to sitting in the shade all day. And you definitely don't wait hair to hamper the evaporation.

[orgaelin]

I don't know about you but if ever I go outside with wet hair, it is my hair that feels coldest. (or my scalp if you want to be clever!)

[Pooeypants]

</span><blockquote><span class="smallfont">Quote:</span><hr size="1" />Originally Posted by (orgaelin,)
I don't know about you but if ever I go outside with wet hair, it is my hair that feels coldest. (or my scalp if you want to be clever!)<hr size="1" /></blockquote><span class='postcolor'>
If the water is evaporating off your hair then it'll take energy away with it and thus making feel cooler, it's not as fast as a bald head would dry ( ), but the brain is quite important for keeping warm and hence we still have quite a lot of hair up there.

[orgaelin]

OK, that makes sense - hair up top to keep the head warm so the brain works better.

I don't know that it's relevant to what you said exactly, but you made me think of another related question - what about people who lived in really cold climates? Why did they loose their hair? Or then again, I suppose it could be that they just died out before they lost it!

[Pooeypants]

</span><blockquote><span class="smallfont">Quote:</span><hr size="1" />Originally Posted by (orgaelin,)
OK, that makes sense - hair up top to keep the head warm so the brain works better.

I don't know that it's relevant to what you said exactly, but you made me think of another related question - what about people who lived in really cold climates? Why did they loose (only one "o" in lose ) their hair? Or then again, I suppose it could be that they just died out before they lost it!<hr size="1" /></blockquote><span class='postcolor'>
If you were sweating whilst doing a hunt and running...what do you think would happen if the sweat froze on your skin?

[Plaything48]

Early humans lost hair to beat bugs

Humans may have lost their body hair to reduce their vulnerability to fur-loving parasites and therefore attract the opposite sex, a new evolutionary theory proposes.

The nakedness of the human species is extremely rare among the 3000 or so living mammal species. Other naked mammals include elephants, walruses, pigs, whales and the bizarre naked mole-rat.

A widely accepted view is that humans lost their hair to help control their body temperature as they evolved into upright creatures on the warm plains of the African savannah. But this theory has problems that researchers believe the new theory can solve.

"The body cooling hypothesis is interesting, but some of the advantages in not having fur in the Sun become disadvantages at night," says Pagel, an evolutionary biologist at the University of Reading, UK. Humans would lose too much heat at night, he says.

"In animals, ectoparasites like biting flies, exert tremendous fitness costs - they really affect our health. Our view is that hairlessness is an adaptation for reducing the ectoparasite load."


Warmth and shelter


However, if humans evolved to beat parasites by losing the hair they hide in, why did our hirsute ape cousins not do the same? The reason, says Pagel, is that we also developed our own culture. We are the only ones who learned to build fires and shelter and to make clothes, he says, all of which helped us keep warm while shedding our fur.

"It's one of those nice cases of gene/culture co-evolution," says Pagel. "It's the culture which helped us acquire the means to lose our hair."

"It does sound quite plausible," agrees Christophe Soligo, a researcher in human origins at the Natural History Museum in London, UK. Soligo calls the theory "elegant" as it addresses a key problem.

"The question we always have in explaining unique human traits is: why didn't other animals evolve them as well if they are so advantageous?"


Sexual selection


The only other animal that has achieved something similar is the naked mole rat. These strange sausage-like creatures live underground in large social colonies in arid regions. In their densely populated networks they should suffer a huge parasite load, but they do not. Their nakedness is possible as the temperature of their underground tunnels is very even.

Sexual selection for desirable mates may be another pressure which fuelled hair loss in humans, suggest Pagel and his colleague Walter Bodmer at the University of Oxford, UK.

Pagel says natural selection might initially favour less hairy individuals, as they have fewer parasites. But sexual selection could accelerate the loss of fur, as more naked early humans could be fitter and therefore more attractive as mates.

The researchers say one way to test their theory would be to see whether humans who live in areas with large parasite populations are less hairy than those who do not.

[orgaelin]

OK, I think that shuts the argument up!

Assuming that was the reason for hair loss, however, I still have my original question sort of unanswered. The hair-loss is accounted for, but not the increased size of the sexual organs.

I've just noticed a post I missed about penis size. (By Harami) Will respond here...

Goats may have larger penises than Humans, but then so do elephants. The point is that the size relative to our bodies is largest. Although now you mention it, I wonder if I read 'largest amongst mammals' or just 'largest amongst primates'?

Some other primates have an incessant obsession with sex, like Bonobos monkeys. I don't know if you've ever seen footage of them but it is as freaky and bizarre as they come! They sit there masterbating or having sex for seemingly most of the day, not only with multiple partners and same sex partners, but even same family, and even with the young.

It is an interesting point that other mammals display their readiness to mate, i.e. when they are fertile, while Humans don't noticeably do so. Maybe there was an evolutionary swap so that instead of displaying readiness at a certain time and only mating at that time, we displayed readiness as constant by having our genitalia always visible, and mated any time too?

[Pooeypants]

I didn't know Goats had bigger penises than Humans...

[orgaelin]

Neither did/do I. I'm just taking it on faith from some guy on here who, somehow, seems to know!

[Sodfather]

</span><blockquote><span class="smallfont">Quote:</span><hr size="1" />Originally Posted by (orgaelin,)
Neither did/do I. I'm just taking it on faith from some guy on here who, somehow, seems to know! ;)<hr size="1" /></blockquote><span class='postcolor'>
Cough, he has a hoard of, cough, beastiality , cough, porn.

[Plaything48]

The picture above seems shocking, but in turn-of-the-century rural Cuba, goat suckling was quite common. A plethora of souvenir postcards survives, depicting scenes similar to the above. They are testimony to the amusement Americans found visiting their newly-conquered island.

Anyway, to me it doesn't look as though that goat is 'big', but it could be the angle or just a young goat.(Or the possibility that we do indeed have bigger knobs than a farmyard animal, not inc. a horse)

[PeterAngelo]

Good question.

Evolution.

I have always maintained that the fact when some men take off their britches - women laugh.

It is what makes men like Napoleon, George Bush, and Dickless Chaney so mean.

It is obvious that the guy with the package was going to get more attention from the females so ther are more of us.

Same for the boob tube.

As far as hair - I think baldness happens because bald men usually sweat a lot - they run hot - so the hair leaves the head for more efficient cooling.

Same with the rest of the body.

Evolution is consistant - the package counts - that's why bushie puts socks in his pants and sits like a tramp so we can see the "bulge".

What a quack.

I digress.

We have all been in showers and know some guys are at a real disadvantage.

Mean - they become serial killers - and presidents, dictators, and other losers.

Remember the song "Small People Got - No Business".

The reference was not lost on little guys.

Ever see a horse dick - it hits the ground.

I'm jealous - for a mammal it rocks.

Hair today - gone tomorrow.

[orgaelin]

Um, OK. I think that's ridiculous!

Someone else now who is excited about animal penises!

Also, you failed to explain why or even if women really do prefer larger members. How big is too big, after all?