Stupid Evolution

[KingMerv00]

Lately, there have been a few thread that discuss the evolution of specific features. For example, head hair and the ability to do quantum physics. Why must there always be a reason behind our features? Can't evolution just be stupid sometimes?

Say we have a population of blue frogs that divides geographically in two. One population evolves green camouflage, the other does not. The green frogs start to move into blue territory and the two species are in competition for a while but the green frogs have the advantage.

Suddenly, a meteor destroys the greens primary habitat leaving the green frogs outnumbered by blues. The greens go extinct.

Hundreds of years later, humans try to dicern why the frogs are blue. They ask what advantage did it give them. The answer is that it did NOT give them an advantage, it was just a random trait it picked up along the way. Sheer luck allowed them to survive.

Long question short, isn't evolution ALSO a product of dumb luck? Couldn't hair on the head be a random and meaningless leftover that has no reproductive advantage whatsoever?

[mummymonkey]

You started off with blue frogs. Why were they blue?

[KingMerv00]

You started off with blue frogs. Why were they blue?

Do we have to assume that blue is useful in the first place? I mean they had to be SOME color right? Why NOT blue?

I guess my point is, why assume that all features provide a benefit? Maybe they are neutral features that randomly got paired up with beneficial ones?

[SimonD]

Long question short, isn't evolution ALSO a product of dumb luck? Couldn't hair on the head be a random and meaningless leftover that has no reproductive advantage whatsoever?

Yes it is. The big 5 extinctions that have happened show that creatures who were at the "bottom" of the rung can become a major player. The most obvious example of this is the extintion of the dinosaurs and the rise of the mammals

We still have a tail bone even though we don't use it. Some people are even born with a tail. This is an example of an envolutional leftover that does not have any reproductive advantage

[KingMerv00]

Yes it is. The big 5 extinctions that have happened show that creatures who were at the "bottom" of the rung can become a major player. The most obvious example of this is the extintion of the dinosaurs and the rise of the mammals

We still have a tail bone even though we don't use it. Some people are even born with a tail. This is an example of an envolutional leftover that does not have any reproductive advantage

Then why the unspoken assumption that hair on the head is automatically useful?

(I'm not saying it isn't useful. I'm just challenging that assumption.)

[Crazycowbob]

Well, I don't know about other animals, but for humans I think intelligence might have been the trump card to evolution. Before we were smart enough to sculpt our environment to suit us, we were probably much more dependant on physical features to survive, like pretty much every other species in the world. But I think once we learned we could build fire and wear clothes to stay warm, to make tools to compensate for any physical shortcomings, we made a lot of physical evolution irrelevant. I'm sure environment still played a big role, but if we learned we could wear fur over our head, then it really didn't matter if some of our kind went bald or not, both would still survive equally well. As we learned more and more how to control our environment, evolutionary traits that would have been removed or encouraged by natural selection were instead able to continue as they were, since they had no real impact on the species.

I think this is continuing even more so today, as once fatal flaws, like diabetes, are now controllable, allowing those with them to contribute to the gene pool, and be active, productive members of the species.

[SimonD]

Then why the unspoken assumption that hair on the head is automatically useful?
(I'm not saying it isn't useful. I'm just challenging that assumption.)

Uumm...because it is useful.

You loose quite a bit of heat through your head. You need to have some protection to that area as that's where your brain is (well for most people :D ). It's not essential but it does help

[qayak]

Then why the unspoken assumption that hair on the head is automatically useful?

(I'm not saying it isn't useful. I'm just challenging that assumption.)

I agree. There are probably some traits or features that are side affects of other traits that are advantageous to survival.

I think of the experiment that was done where they bred foxes for domesticity (Is that a word?). The result in 20 or so generations was a tame fox that looked like a border collie. So the physical traits were a side affect of domesticity as they were not specifically bred for.

Couldn't the hair on our head, arm pits and pubic region just be a side effect of some more important trait that was required for survival.

It could also be that the hair in those regions were the last places to go when we became the naked ape. Our hair was lost until it no longer made a difference in natural selection and then it stopped. Does it make a large difference if women have hair to their shoulders or butts when a man is looking for a mate? I think at a point, the amount of hair left is overidden by other desirable traits. In other words, the vast majority of females fall within the range of acceptability to males as mates. In effect, they are all breedable. :D (Sorry, couldn't resist!)

[Soapy Sam]

There are two parts to adaptation-
1. The organism.
2. The environment.

If 1. does not fit well into 2. It's screwed, or soon will be.

However there are also design constraints.
1. Can't suddenly rebuild itself. "Choices" which were made to fit the ancestral 1. into the early 2. are not always reversible. We are, for instance, stuck with a range of structural proteins and other materials. Plants cannot just change the chemistry they use for photosynthesis.

One reason for parallel, or convergent evolution, is that the laws of physics and the facts of organic chemistry will only permit certain solutions to certain problems.

Is there always an adaptationist reason for a feature? This is Gould's "Spandrel" argument. Some things just happen. But they happen for reasons of physics, chemistry or architecture. There is always a reason if you look in the right place, but that place may be far away, and long ago subducted.

There was a reason your frogs were blue to start with. If they could become green, then there was a chemical bias in their metabolism that allowed this, inherent in the original blue stock. So why were they not already green? Something in their environment was keeping them blue. When part of the group moved away from that constraint,(maybe a blue-blind snake?) the green gene became dominant in that sub population.

Sure it was chance that then destroyed one population- it could have been green or blue, but if the blues survived, the potential to go green is still there. If the greens survived, there might not be an ability to revert to blue. You would have a new variety. If greens chose not to mate with blues, you would have a new species.

Why is the crack in the human ass vertical , not horizontal? This has no evolutionary significance. It results from two hemispherical buttocks requiring an interface line and from the fact that humans walk upright.

But are there good mechanical reasons?

You bet your...bottom dollar.

[KingMerv00]

Uumm...because it is useful.

You loose quite a bit of heat through your head. You need to have some protection to that area as that's where your brain is (well for most people :D ). It's not essential but it does help

I never meant to suggest that hair on the head wasn't the product of "smart evolution". I just meant that some features just are the way the are and might not play a part in reproductive success.

[SimonD]

I never meant to suggest that hair on the head wasn't the product of "smart evolution". I just meant that some features just are the way the are and might not play a part in reproductive success.

Hey Merv I hope you didn't think I meant you "...as that's where your brain is (well for most people :biggrin: )..."

I find some people have their brains up there ar5e....
Most men have theirs in their pants....
And some people don't seem to have any at all...

[AgingYoung]

Couldn't hair on the head be a random and meaningless leftover that has no reproductive advantage whatsoever?

That's what all those bald suckers would have you believe.

Gene

[Dogdoctor]

Evolution starts with random mutations which are accumulated in the breeding population of animals. At some point they may offer an advantage and then more animals with those genes survive or it could be random effects. Sometimes a gene is selected for and also the gene next to it is selected for which would be random. Or a gene may have more than one effect and selecting for the one effect randomly selects for the rest of the effects it has. Or somehow there could be dumb luck as you call it. For instance a population may have been dwindled down to low numbers due to lack of resources and by dumb luck most of the survivors had a gene that wasn't common in the general population before the resource restriction occurred.

[Foster Zygote]

Long question short, isn't evolution ALSO a product of dumb luck? Couldn't hair on the head be a random and meaningless leftover that has no reproductive advantage whatsoever?

I'm sure there are many examples of useless physical features that survive because they have a completely neutral effect on reproductive success. Of course there are many, many physical features that have a marked impact on reproductive success. Just look at the leopard: Those claws, the powerful musculature, the spine severing canine teeth. Beautiful adaptations like that seem like perfect examples of design to many people. Most here are familiar enough with evolutionary theory to understand how blind natural selection acting on random variations from generation to generation can yield amazing results. But if you're trying to rationalize a belief in teleology you're likely to focus on and try to justify an assumption of design and ignore those irritating facts regarding the workings of evolution. As I pointed out to the author of one of those other threads you mention, even the idea that our intelligence will be of long term benefit to our species' reproductive success is an assumption. That very intelligence has given us the ability to annihilate ourselves. That certainly would support your 'dumb luck' idea.:) Wait a minute, I mean :scared:

[primemover]

Couldn't the hair on our head, arm pits and pubic region just be a side effect of some more important trait that was required for survival.

It could also be that the hair in those regions were the last places to go when we became the naked ape. Our hair was lost until it no longer made a difference in natural selection and then it stopped. Does it make a large difference if women have hair to their shoulders or butts when a man is looking for a mate? I think at a point, the amount of hair left is overidden by other desirable traits. In other words, the vast majority of females fall within the range of acceptability to males as mates. In effect, they are all breedable. :D (Sorry, couldn't resist!)

While the remaining hair on our body is probably due to evolution stalling, the hair on our head, armpits and pubic region most likely have very valid reasons.

A theory I know of about the hair/fur receding from early hominids is that it was easier for a mate to judge overall health, as seeing the bare skin was important for that. Parasites in the fur, another probable additional reason for receding body hair, would leave visible damage on the skin, so seeing more of the skin was advantageous for a mate to see how parasite free one was.

Hair on our pubic region was left full to aid in scent propigation, as moisture would linger due to the hair, helping possible mates know that they are receptive. Taking this a step further hair under our arm pits is probably for a similar reason, as propigation of general scent is so important in other animals, and this could aid that.

Hair on our head is a bit trickier, but as I see it there are four major areas, hair in orifices(nose/ears), eye lashes, eye brows and head/beard.

Hair in orifices are obvious, it's to trap particles of dust and dander from getting in.

Eye lashes are most likely to either keep sunlight out of the eye, keep dust out of the eye, and/or for some cosmetic reasons.

Eyebrows, from what I have heard, was to keep sweat from getting into the eyes, but I think I can also imagine it keeping dust out also. BUT, I have a pet theory for eyebrows also, that they help us emote, as the eyebrows line the brow ridge accentuating any read coming from the brows. As we became more visual animals, favoring sight over the other senses, reading faces became more and more important, as did reading the emotional state of those you come into contact with. I do character art for video games, and getting the brows right in construction and animation, really helps characters come across to the viewer.

Hair on the head and beard is a weird one, as even though it's most likely there to protect the top of the head from the hot African sun when we went erect, that doesn't explain the fact that the hair on our head, and beard, are programmed to grow to tremendous length. This from what I know is unique in mammals(maybe somebody can correct me here), and is unique to our own bodies, as hair everywhere else is programmed to stop growing a much shorter length.

The only thing I can think for this is cosmetic reasons, as it is one of the only areas on the human body, barring clothing and ornamentation later on in our evolutionary history, that a human can show ornamentation.

This has flaws as I doubt our early hominid ancestors styled their hair, but maybe this is a sign of virility, as since we lost our coats and we still had a yearning to see some hair cover, and what better way to show your coat off by letting the wind blow through your flowing locks :D

[primemover]

While it is probably true that here and there some traits were chosen by something less than survival means, I am betting that most features of the animals we see are there for a good reason, and when I say 'most', I am talking like 99.9 percent.

You got to remember that all traits aren't selected for purely survival reasons, as sexual selection plays a big role, and also the path that evolution takes has many many sidesteps, oftentimes leaving certain traits out of the survival picture. Most of the time those traits are reappropriated for another reason, like lungs, but I am sure there are examples of some that just happen to recede to a point as to where selection pressures ignore them. This can include things like hair on our fingers, to the color of a frog.

[dann]

Hair on our pubic region was left full to aid in scent propigation, as moisture would linger due to the hair, helping possible mates know that they are receptive. Taking this a step further hair under our arm pits is probably for a similar reason, as propigation of general scent is so important in other animals, and this could aid that.I've heard that the hair in your armpits and between your legs functions like a kind of lubricant or ball bearings: to protect areas where skin rubs against skin. Same explanation for the pubic hair placed above your genitals: skin rubbing against (sombody else's) skin!
http://forums.randi.org/showthread.php?postid=2205350#post2205350

[dakotajudo]

Do we have to assume that blue is useful in the first place? I mean they had to be SOME color right? Why NOT blue?

I guess my point is, why assume that all features provide a benefit?

It might be better to stop thinking in terms of "useful" or "benefit".

Think of a dynamic system that operates more or less effectively in different conditions. Any specific trait is less important the operation of the whole.

Some genes will contribute to performance in a specific environment, some will degrade performance, others are more neutral. Don't think of this as discrete - there's a continuum from low to high performance.

Not that you can't discuss the contribution of specific traits to overall operation, just that you start with the idea of the collection, then look to specifics.

Consider C3 vs C4 metabolism in plants. In dry climates, C4 plants are more competitive, wet conditions favor C3; at some climate in between, both wll be roughly equal.


Maybe they are neutral features that randomly got paired up with beneficial ones?

Think of the mechanics of inheritance.

Several thousands of genes, distributed on a few dozen chromosomes.

Even with recombination, genes will tend to cluster together. Consider the problems with pure-bred dogs. There are features that define the breed; breeders select for these. But, too frequently, the desirable traits are linked to undesirable traits. So, purebreds frequently have, well, problems (I had dalmation with several).

Don't forget the importance of heterozygosity (or, in terms of dog breeding, hybrid vigor - mutts may, in general, be healthier than purebreds).

Being homozygous for the sickle cell gene is pretty much deadly, and being heterozygous isn't exactly healthy, either. But, heterozygous with sickle cell is healthier than normal type but infected with malaria, so the sickle cell trait persists in the population.

That raises an important point. Sometimes traits persist not because of the benefit to individuals, but the benefit to the population. Not so important that individuals survive through bad times, but that a significant percentage of the group survive to reproduce.

I work a lot with plant breeders, this affects my thinking. Their goal isn't so much to develop varieties that product high yield in the best conditions, but to produce varieties that will grow well in all conditions; wet, dry, cold, hot years, farmers may not get rich, but they'll get a harvest in every time.

[primemover]

I've heard that the hair in your armpits and between your legs functions like a kind of lubricant or ball bearings: to protect areas where skin rubs against skin. Same explanation for the pubic hair placed above your genitals: skin rubbing against (sombody else's) skin!


Never heard of that explanation and I don't really see too much merit in it, as most humans do not have much hair between their thighs and there is much rubbing there.

Also saying that we kept pubic hair due to sexual contact is very tenuous at best as that pre-supposes that our ancestors had sexual intercourse missionary style, while I believe most primates do it doggy style.

[dann]

Also saying that we kept pubic hair due to sexual contact is very tenuous at best as that pre-supposes that our ancestors had sexual intercourse missionary style, while I believe most primates do it doggy style.But the funny thing is that most of us lost most of the body hair except there when we shifted to the upright position. I'll see if I can come up with a reference ...

[Eos of the Eons]

Long question short, isn't evolution ALSO a product of dumb luck? Couldn't hair on the head be a random and meaningless leftover that has no reproductive advantage whatsoever?

We'll see a lot of that right now in the human population. Right now, just about anyone with anything will survive long enought to pass on all sorts of seemingly neutral or even potentially harmful traits (like in dakotajudo's malaria example-a trait may seem harmful for the most part, but oddly beneficial in some scenarios ).

We won't know what will help us until some sort of selection pressure is applied. Can you imagine a selection pressure that would reduce the population to a few poor saps with one kind of beneficial bunch of traits?

Imagine if we never were able to discover that it was HIV virus causing AIDS in people. Billions of people die. Some thousands are left going "WTF?". Why did we survive? We have different colors of hair, we are of different heights, different nationalities...etc.

All those with the highest level of HIV immunity share a pair of mutated genes -- one in each chromosome -- that prevent their immune cells from developing a "receptor" that lets the AIDS virus break in. If the so-called CCR5 receptor -- which scientists say is akin to a lock -- isn't there, the virus can't break into the cell and take it over.
http://www.wired.com/news/technology/0,66198-0.html
Well, they were the only ones that didn't have the receptor on their T-cells that the HIV virus needed to find in order to get into the cells and replicate. That is not something you can see, and the mutation was quite useless before the HIV virus came along to kill everyone else.

What may seem like a useless trait at one time, may suddenly be your only ticket to survival.

That is why diversity, that our genes allow for in times of plenty like this, is so essential to the survival of life on the planet. Differences are GOOD!!

[dann]

I'll see if I can come up with a reference ...

I should have known that googling ”pubic hair” and ”lubricant” might not be the best way of finding relevant links …
I have only found references to pubic hair as a dry lubricant (http://sg.answers.yahoo.com/question/index?qid=20060704025331AAH9gSi) on other discussion or question-answer boards, nothing really scientific. However, some of them claim that you can actually experience the discomfort hairlessness brings in these areas if you remove the hair.
Wikipedia does not write about the purpose of pubic hair (http://sg.answers.yahoo.com/question/index?qid=20060704025331AAH9gSi). Warning: lots of photos.
However, you should consider that in the missionary position pubic bone meets pubic bone (http://en.wikipedia.org/wiki/Pubic_bone), which is much harder than what our simian ancestors experienced.

[dakotajudo]

Well, they were the only ones that didn't have the receptor on their T-cells that the HIV virus needed to find in order to get into the cells and replicate. That is not something you can see, and the mutation was quite useless before the HIV virus came along to kill everyone else.
That's an interesting example, I'd forgotten about that one.

But, IIRC, the mutant CCR5 gene was previously selected for - in Europeans, because it conferred some resistance to the Plague.

I seem to remeber a Nova special that tracked in down to a town in England, that had something like 0 deaths during the plague years.

May help explain why the African AIDS epidemic is much more severe than other countries (although there is a cultural component).

Ooop - Googled, found a link to PNAS that suggests it may have been smallpox that drove the selection of the CCR5 variant.

"Evaluating plague and smallpox as historical selective pressures for the CCR5-32 HIV-resistance allele"

[Post count not high enough for links]
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Lotsa other good links at the bottom.


This reminds why I find arguing with anti-evolutionists tiring.

There are just so got-damned many examples - but the anti debate seems to be drawn to just a few, mostly those shown in introductory texts.

And I forget all the good ones.

[Eos of the Eons]

http://www.pnas.org/cgi/reprint/100/25/15276.pdf

lol. Yeah, I was ignoring the previous selective pressures for the receptor since I was using it for an example of trait we may not know we have, and couldn't think of a cool hypothetical one.

It does really illustrate my point though. We don't know what weird mutation will save us from an unforseen selective pressure (horrible disease or disaster).

-Should start a contest for most creative scenarios of:
a seeminly neutral mutation mixed with some wild selective pressure that nobody else can imagine.

[CapelDodger]

Lately, there have been a few thread that discuss the evolution of specific features. For example, head hair and the ability to do quantum physics. Why must there always be a reason behind our features? Can't evolution just be stupid sometimes?
It's quite possible, and I don't think contentious, that insignificant genetic variations can piggy-back on significant ones purely by chance. Significant changes tend to take hold and propagate at times of stress on a population, and they will arise in particular families which will have shared insignificant differences - the sort of things that create family features, for instance.

Each feature needs to be examined in itself for significance. To use your example of head-hair, a major difference between humans and other apes is our relative hairlessness so there must have been some selection pressure to lose our body-hair, but also selective pressure to make the hair-loss selective (if that's not too convoluted). So in that case I'm pretty sure there's a reason behind the retention of head-hair.

[Skeptic Guy]

http://www.pnas.org/cgi/reprint/100/25/15276.pdf

lol. Yeah, I was ignoring the previous selective pressures for the receptor since I was using it for an example of trait we may not know we have, and couldn't think of a cool hypothetical one.

It does really illustrate my point though. We don't know what weird mutation will save us from an unforseen selective pressure (horrible disease or disaster).

-Should start a contest for most creative scenarios of:
a seeminly neutral mutation mixed with some wild selective pressure that nobody else can imagine.

My beer gut will protect me in the event of a front-end car accident.

Ok, maybe it's not genetic but perhaps once women start selecting for it in men...a guy can dream, can't he?

[Dogdoctor]

My guess is that selection of head hair and underarm and pubic hair is a remnant of selection for the birth of a more immature infant. In order to have a larger brain the babies needed to be smaller when they are born and the way that was accomplished was to have them born less mature, requiring more aftercare but allowing them to have a large brain. The hair pattern resembles that of infant apes and why do infant apes have that hair pattern? I don't know but it may be an example of random genes being selected due to selection of another trait (small birth size). There may have been advantages of that hair pattern at some point in time (less external parasites and protection of the top of the head from sunburn and providing warmth to face in cold weather)

[primemover]

However, you should consider that in the missionary position pubic bone meets pubic bone, which is much harder than what our simian ancestors experienced.

What I am saying is the missionary position was invented much later far after our traits were finalized as they are now, I just don't think our early hominid ancestors engaged in intercourse this way, as primates usually attack from the rear, like ninjas.

Also, though I am sure our early hominid ancestors knocked the boots frequently, I doubt it would be enough for this to be an issue.

[I less than three logic]

[snip], like ninjas.
And rogues (http://www.thinkgeek.com/tshirts/gaming/72ef/). :D

[Skeptic Guy]

My guess is that selection of head hair and underarm and pubic hair is a remnant of selection for the birth of a more immature infant. In order to have a larger brain the babies needed to be smaller when they are born and the way that was accomplished was to have them born less mature, requiring more aftercare but allowing them to have a large brain. The hair pattern resembles that of infant apes and why do infant apes have that hair pattern? I don't know but it may be an example of random genes being selected due to selection of another trait (small birth size). There may have been advantages of that hair pattern at some point in time (less external parasites and protection of the top of the head from sunburn and providing warmth to face in cold weather)

DD, I think you are in the right of it. I'll have to thumb through my copy of Dawkins's Ancestor's Tale, but I believe he sketched out a theory that said that maybe we are an immature form of the ape, or vice versa. In order that we could be born with such a large head we needed to be born earlier in the gestation cycle and never quite caught up. I over-simplify but that's what I remember.

[Dancing David]

DD, I think you are in the right of it. I'll have to thumb through my copy of Dawkins's Ancestor's Tale, but I believe he sketched out a theory that said that maybe we are an immature form of the ape, or vice versa. In order that we could be born with such a large head we needed to be born earlier in the gestation cycle and never quite caught up. I over-simplify but that's what I remember.

Tis called neotany. The period in which an infant is dependant upon it's parents for suvival?

[ImaginalDisc]

We still have a tail bone even though we don't use it. Some people are even born with a tail. This is an example of an envolutional leftover that does not have any reproductive advantage
Actually, the muscles in your butt are attached to your tailbone, and if it breaks you'd barely be able to stand, let alone walk. It's not the best anatomical arraignment, but evolution works with what's on hand. It never goes back to the drawing board. Existing features are modified much more often than new ones develop.

[dann]

What I am saying is the missionary position was invented much later far after our traits were finalized as they are now, I just don't think our early hominid ancestors engaged in intercourse this way, as primates usually attack from the rear, like ninjas.You're guessing now, right?! How would you know when the missionary position was invented? Even bonobos use it, and they engage in sex all the time ...

[Skeptic Guy]

You're guessing now, right?! How would you know when the missionary position was invented? Even bonobos use it, and they engage in sex all the time ...

Oh, it's grand to be a bonobo....

And I agree, how do we know when the missionary position was invented? Was it really those wacky missionaries?

[dann]

Was it really those wacky missionaries?Who taught the two bonobos (http://www.primates.com/bonobos/bonobos-sexual.html) the missionary position? Hard to tell ...

[Skeptic Guy]

Who taught the two bonobos (http://www.primates.com/bonobos/bonobos-sexual.html) the missionary position? Hard to tell ...

Hey, those missionaries get kind of lonely out there all by themselves...

[dann]

”The species is best characterized as female-centered and egalitarian and as one that substitutes sex for aggression.” (http://www.primates.com/bonobos/bonobosexsoc.html) I'm afraid that I probably couldn’t live up to the high ideals of Bonoboism. I hate to admit it, but there are a lot of people that I would definitely prefer to beat up. Even some that I am not even angry at …

[Dogdoctor]

Who taught the two bonobos (http://www.primates.com/bonobos/bonobos-sexual.html) the missionary position? Hard to tell ...

That looks like a mother and her offspring ( the mother is on top)

[primemover]

You're guessing now, right?! How would you know when the missionary position was invented? Even bonobos use it, and they engage in sex all the time ...

Bonobos use it, but not chimpanzees or other primates, and since Bonobos/Chimpanzees and and Humans all have come from a common ancestor, and Bonobos and Chimpanzees split later from another common ancestor, that technique could be completely unique to Bonobos and more civilized humans, and not present in our pre-human ancestors. If Gorillas and Orangutans were shown to use this position, then that would be evidence to our pre-human ancestors using it, and thus it having bearing on the evolution of some body traits.

Of course this could all be true, but it's connection to us having hair left in our pubic region due to impact from pelvic to pevlic contact during missionary sex is very tenous.

[dann]

That looks like a mother and her offspring ( the mother is on top)I guess you're probably right. That the bonobos use the missionary position, however, is a fact:
The missionary position is a common human sex position also used by certain other species including bonobos and armadillos. ( http://en.wikipedia.org/wiki/Missionary_position) I don’t think armadillos have pubic hair, though, do they? :)
Bonobos are the only non-human apes to have been observed engaging in all of the following sexual activities: face-to-face genital sex (most frequently female-female, then male-female and male-male), tongue kissing, and oral sex. ( http://en.wikipedia.org/wiki/Bonobo#Sexual_social_behavior)
Bonobos copulate in a variety of positions, including the eponymous missionary face-to-face position ( http://www.positiveatheism.org/writ/pennock.htm)

This photo seems to be the real thing ( http://baconeatingatheistjew.blogspot.com/2006_01_01_baconeatingatheistjew_archive.html)
Photo ( http://dlynnwaldron.com/BonoboGallery/pictures/missionary.html)

[dann]

Bonobos use it, but not chimpanzees or other primates, and since Bonobos/Chimpanzees and and Humans all have come from a common ancestor, and Bonobos and Chimpanzees split later from another common ancestor, that technique could be completely unique to Bonobos and more civilized humans, and not present in our pre-human ancestors. If Gorillas and Orangutans were shown to use this position, then that would be evidence to our pre-human ancestors using it, and thus it having bearing on the evolution of some body traits.

Of course this could all be true, but it's connection to us having hair left in our pubic region due to impact from pelvic to pevlic contact during missionary sex is very tenous.
Possible, but you are still only guessing:
What I am saying is the missionary position was invented (!) much (!) later far (!) after our traits were finalized (!) as they are now, (My (!), dann)
Do you have any evidence or convincing arguments? Now you are talking about "our pre-human ancestors", and I don't think anybody claimed anything about how they had sex.

(By the way, a good argument against pubic hair as a dry lubricant would be the photo of the female bonobo, who appears to have shaved very recently. http://baconeatingatheistjew.blogspot.com/2006_01_01_baconeatingatheistjew_archive.html )

[primemover]

I guess you're probably right. That the bonobos use the missionary position, however, is a fact:
The missionary position is a common human sex position also used by certain other species including bonobos and armadillos. I don’t think armadillos have pubic hair, though, do they?
Bonobos are the only non-human apes to have been observed engaging in all of the following sexual activities: face-to-face genital sex (most frequently female-female, then male-female and male-male), tongue kissing, and oral sex.
Bonobos copulate in a variety of positions, including the eponymous missionary face-to-face position

This photo seems to be the real thing
Photo

Definately a fact, Bonobos are quite freaky when it comes to the making of the love, I'd love to read some theories on how they got to be so perverted compared to their closest kin the chimpanzees.

I wonder too when the missionary position enterered in our species lives, I know it became ultra popular during the Victorian sexually repressed era, but there are documents much much earlier depicting the position. I would imagine as our species became so visually impressive and as our person to person connections gre visually, that having sex while staring into eachothers eyes would follow suit.

[opqdan]

I think one of the most important aspects of body hair that has been ignored here (or maybe I missed it), it that pubic, and armpit hair both show up at puberty. This is probably not a coincidence.

I even recall reading once (though I cannot remember where), that pubic and underarm hair would be outward signs of maturity and the ability to produce offspring.

As our ancestors originally evolved in Africa, it seems that with a hot and dry veldt type of existence would pressure us to grow less body hair in order to not overheat, but would need to keep armpit/pubic hair in order to determine sexual maturity.

By the time H. erectus moved out of Africa and into Europe and Asia, they were already using Acheulean tools, and even shelters of some sort. By the time that our ancestors migrated to a colder climate, where thicker body hair would have been an advantage, they were already sufficiently advanced in clothing/shelter/fire that there was no environmental pressure to evolve.

Hair on the head does not seem to fit this idea quite right. If heat were the only factor, it seems that this hair would have been lost also. Maybe, sun protection was a significant factor (although, why not also have hair on the shoulders and back?).

This also does nothing to explain why head hair grows indefinately.

[opqdan]

Ahh, I see that there is even another thread on this (the hairy evolution) topic, which mentions my points.

http://forums.randi.org/showthread.php?t=71208

[primemover]

I think one of the most important aspects of body hair that has been ignored here (or maybe I missed it), it that pubic, and armpit hair both show up at puberty. This is probably not a coincidence.

I even recall reading once (though I cannot remember where), that pubic and underarm hair would be outward signs of maturity and the ability to produce offspring.

As our ancestors originally evolved in Africa, it seems that with a hot and dry veldt type of existence would pressure us to grow less body hair in order to not overheat, but would need to keep armpit/pubic hair in order to determine sexual maturity.

Interesting observation, and it kind of fits with the 'helping to spread scent' theory too, but it really depends on if genital scent is the same before puberty as after, or if the scent that attracts mates is due to some feature of ovulation.

If lets say scent was something they have since birth, or close to, the delay in pubic hair growth could be due to the negative effects of somebody attempting to fornicate with someone that was not sexually mature, so if pubic hair does help spread scent, then not having it would help prevent that.

As to why this would have any bearing on armpit hair, you have to think of body hair in general, as pre-pubescents don't have any hair on their body except their head, so whatever selection pressure put on pubic hair delay would affect the whole body.

[Skeptic Guy]

Hair on the head does not seem to fit this idea quite right. If heat were the only factor, it seems that this hair would have been lost also. Maybe, sun protection was a significant factor (although, why not also have hair on the shoulders and back?).

This also does nothing to explain why head hair grows indefinately.

You obviously have not seen my back.

But I think the sun protection does fit. The head contains the brain and it is much more sensitive to heat than the rest of the body/organs. Add to it that our ancestors probably had much more melanin in their skins, they probably had enough protection elsewhere.

I think perpetually growing hair is just an unintended byproduct of being a living cell.

[primemover]

Another thing to think about is the general difference in hairiness between males and females. It would seem that the males have a hand in this one due to their sexual selection, they wanted more and more hairless women. This affect in selection towards less hair would end up circulating back to men but with some lag as those traits chosen through the female work their way into the general gene pool.

[blutoski]

Lately, there have been a few thread that discuss the evolution of specific features. For example, head hair and the ability to do quantum physics. Why must there always be a reason behind our features? Can't evolution just be stupid sometimes?

Say we have a population of blue frogs that divides geographically in two. One population evolves green camouflage, the other does not. The green frogs start to move into blue territory and the two species are in competition for a while but the green frogs have the advantage.

Suddenly, a meteor destroys the greens primary habitat leaving the green frogs outnumbered by blues. The greens go extinct.

Hundreds of years later, humans try to dicern why the frogs are blue. They ask what advantage did it give them. The answer is that it did NOT give them an advantage, it was just a random trait it picked up along the way. Sheer luck allowed them to survive.

Long question short, isn't evolution ALSO a product of dumb luck? Couldn't hair on the head be a random and meaningless leftover that has no reproductive advantage whatsoever?

Absolutely. The key word is 'contingent'. Every trait is all of advantageous, disadvantageous, and neutral at the same time. It depends on the environment.

This is what many creationists overlook: evolution is an example of the second law in action. Just as a gas fills the entire volume of a container, so does life fill all ecological niches in a biosphere. It's just the net effect of a lot of random motion. In the case of the ecosystem, the random motion is mutations, and if there is any 'direction' to evolution, it is toward more variation.