Join the Unexplained Mysteries community today! It's free and setting up an account only takes a moment.
- Sign In or Create Account -
Sign in to follow this  
Followers 0
thewrathofvoight

The Aquatic Ape Theories of Evolution

Which Theory of Human Evolution do you Accept   14 members have voted

  1. 1. Which Theory Makes the Most Sense to You?

    • The Aquatic Ape theory
      3
    • The Neoteny Theory
      0
    • Savannah Theory
      9
    • Other Theory (Please elaborate)
      0
    • None of the above
      2

Please sign in or register to vote in this poll.

25 posts in this topic

Thank you for particpating in my survey. I am writing a paper for school and noticed that most people tend not to really comprehend the different theories regarding human evolution. So if you all wouldn't mind assisting. I know there are several well read scientists on here and would very much appreciate the feedback.

As for me I was suprised to find that Stephen J Gould was a promoter of Neoteny which is something I had never heard of. I was under the impression that there was one uniform view but obviously not. The book dissects some of the other theories in trying to promote its own theory that at some point during evolution man went into the water. Its a fascinating read.

Another theory is the savannah theory which explores the idea that humans evolved the way we did by having to survive on the savannah.

Some information about the book

http://www.primitivism.com/aquatic-ape.htm

I also want to say that the addendum to the book read very unscientifically to me. I know this book is older however if this is an acceptable way to discuss theory I am shocked. However the woman who wrote the book didn't seem like a scientist to me so maybe that explains it.

This is posted in the Science forum and so I'd appreciate no religious or superstition theories being discussed here. Also no Alien seeding theories. Thanks again, my deadline is looming.

Edited by thewrathofvoight

Share this post


Link to post
Share on other sites

I am just going to be honest and say that the only one I recognize by name is the Aquatic Ape Theory, and I believe that all evidence of us having decended from apes (of any kind) is a lie, and I think the data saying otherwise is falsified and has been tampered with.

I believe people feel it is much simpler to believe ape decendant stories.

Picked none of the above, because I hold to a creationist-esque type of beginning....I don't think we are remotely close to a true answer.

Share this post


Link to post
Share on other sites

That's funny. The only comment in the thread in the science section after a few days is by a creationist! Tragic! LOL Thanks for the honest answer ravergirl. I realise it should say Aquatic Ape Hypothesis. I think Ape is slang, because no one is saying we decended from Apes but that we share a common ancestor.

I'm still waitng for all these really active science people to come in here and to discuss which theory they support and why. Its sort of backing my claim up that no one knows what most of these theories are about. Curious.

Share this post


Link to post
Share on other sites

Well, the evidence does suggest that hominids originated in Africa and proceeded to spread out from there. There is some disagreement as to how much contribution other populations made to our gene pool.

As for theories of human origins, the area hominids can be traced back to certainly has a lot of savahnas. However, it is certainly true that we exhibit a good deal of neoteny compared to the other great apes :our skulls are shaped remarkably like baby chimp skulls, our relative hairlessness, and facial shape, as well as the way our females do not show outwardly when they are fertile come to mind. Neoteny could play into any specific reason for human speciation, as it is a common method of adaptation.

The aquatic ape hypothesis is very fascinating and I have looked into it in the past. It would explain several features of our species - however thus far there is little direct evidence for it. As such I do not think it holds much weight.

I believe that all evidence of us having decended from apes (of any kind) is a lie, and I think the data saying otherwise is falsified and has been tampered with.

I'm sorry to hear that. I honestly can't think of why you would say that. There have been fraudulent claims in the past but they have been caught, usually immediately or at least as soon as the scientists in question had their data or specimens scrutinized by others. I am a bit wary of how quickly people are clamoring to call the tiny people of the island of Flores a new species - we just dont know enough there to know how they fit in. What makes you think data is "tampered with"???

Share this post


Link to post
Share on other sites

The thing that made it seem possible for the aquatic ape to me the most, is the bipedal explanation. That walking into the water made it necessary for the animal to rise up on their hind legs. I think that makes logical sense.

Some pictures for fun.

Some skulls for comparison

linked-image

linked-image

Baby chimpanzee skull cast

linked-image

Interesting blog, not sciencey!

http://beccasbabyblog.blogspot.com/2008/03...screwed-us.html

Edited by thewrathofvoight

Share this post


Link to post
Share on other sites
I am just going to be honest and say that the only one I recognize by name is the Aquatic Ape Theory, and I believe that all evidence of us having decended from apes (of any kind) is a lie, and I think the data saying otherwise is falsified and has been tampered with.

I believe people feel it is much simpler to believe ape decendant stories.

Picked none of the above, because I hold to a creationist-esque type of beginning....I don't think we are remotely close to a true answer.

Sorry but that is just outright ignorant and ill-thought out. WE ARE apes, we form a separate monophyletic clade with the chimpanzees to the exclusion of the other apes. Calling it a lie when you know feck all about it is ignorant and very insulting to the people have spent so much time on it.

Believing we evolved from a common ancestor to other apes that has overwhelming evidence is still more complex than believing we were just created which is baseless.

Edited by Mattshark

Share this post


Link to post
Share on other sites
Sorry but that is just outright ignorant and ill-thought out. WE ARE apes, we form a separate monophyletic clade with the chimpanzees to the exclusion of the other apes. Calling it a lie when you know feck all about it is ignorant and very insulting to the people have spent so much time on it.

Believing we evolved from a common ancestor to other apes that has overwhelming evidence is still more complex than believing we were just created which is baseless.

**stomp** **stomp** **stomp** RAWR.

Have some coffee, dear.

i know we are apes in the 'hominoidea' usage of ape.

And by whose standards does evidence become 'overwhelming' anyway?

The whole reasoning behind apes being in the water in the first place is just as good evidence for 'aquatic apes' evolving into mermaids not land dwelling humans, IMO. imagine my surprise when curiosity and cheekyness grabbed me at the same time and I goggled(<---heehee) "aquatic ape and merpeople" and it yielded a bunch of theories on how merpeople evolved into aquatic apes evolved into humans. Which yields probably similar amounts of fossilized evidence .

I do not recend my before statement, but I do not want to upset you. i do believe there are lies and manipulation in the scientific community. I believe that money and power are quite influential in certain (although I doubt all) fields of science. Money and power are corrupt my line of work all of the time.

I'm not accusing, i am just saying that the motives of scientists aren't JUST in search of the truth. Pure science doesn't lie, I know that and respect that....but people do lie, and cheat, and steal, and manipulate, and corrupt, and can be forced into things, and threatened into things.

I think the origins of man is a big issue, HUGE, and I think scientists (who ARE people) are not above those things to get ahead in their business.

I am not saying that I believe that of scientists on this site.

Edited by ravergirl

Share this post


Link to post
Share on other sites
**stomp** **stomp** **stomp** RAWR.

Have some coffee, dear.

i know we are apes in the 'hominoidea' usage of ape.

And by whose standards does evidence become 'overwhelming' anyway?

The whole reasoning behind apes being in the water in the first place is just as good evidence for 'aquatic apes' evolving into mermaids not land dwelling humans, IMO. imagine my surprise when curiosity and cheekyness grabbed me at the same time and I goggled(<---heehee) "aquatic ape and merpeople" and it yielded a bunch of theories on how merpeople evolved into aquatic apes evolved into humans. Which yields probably similar amounts of fossilized evidence .

I do not recend my before statement, but I do not want to upset you. i do believe there are lies and manipulation in the scientific community. I believe that money and power are quite influential in certain (although I doubt all) fields of science. Money and power are corrupt my line of work all of the time.

I'm not accusing, i am just saying that the motives of scientists aren't JUST in search of the truth. Pure science doesn't lie, I know that and respect that....but people do lie, and cheat, and steal, and manipulate, and corrupt, and can be forced into things, and threatened into things.

I think the origins of man is a big issue, HUGE, and I think scientists (who ARE people) are not above those things to get ahead in their business.

I am not saying that I believe that of scientists on this site.

I never said a thing about Aquatic ape theory, it is interesting, but it holds no ground in terms of evidence

Yeah, those two things, pretty much none existent in zoological science.

There is excellent physical, genetic, behavioural and fossil evidence. The evidence is overwhelming. You not believing is your choice but saying it is lies is just out right ignorance.

Share this post


Link to post
Share on other sites
I never said a thing about Aquatic ape theory, it is interesting, but it holds no ground in terms of evidence

Yeah, those two things, pretty much none existent in zoological science.

There is excellent physical, genetic, behavioural and fossil evidence. The evidence is overwhelming. You not believing is your choice but saying it is lies is just out right ignorance.

I'm shocked!. You mean there's no money or power in zoology? Aren't zoologists the puppetmasters, pulling society's strings?

Share this post


Link to post
Share on other sites

yes the aquatic ape hypothesis is an interesting one but there is no hard evidence to support it. It would explain a lot - IF it were true, and as of right now there is no evidence to say that it is. Contrast THAT with the mountains of hard evidence, paleontological and genetic, tying humans and the other great apes to a common ancestor a few million years ago (and all life to a common ancestor billions of years ago).

Share this post


Link to post
Share on other sites
I'm not accusing, i am just saying that the motives of scientists aren't JUST in search of the truth. Pure science doesn't lie, I know that and respect that....but people do lie, and cheat, and steal, and manipulate, and corrupt, and can be forced into things, and threatened into things.

I think the origins of man is a big issue, HUGE, and I think scientists (who ARE people) are not above those things to get ahead in their business.

I am not saying that I believe that of scientists on this site.

Just out of curiosity, what other motives are you talking about?

What possible financial benefit can there be for a scientist pushing one theory of human origins, over another? increased book sales?

If that was the case then the most rewarding theories would certainly be the ones splashed across the tabloid covers, not the ones written in text books IMO.

Share this post


Link to post
Share on other sites
It would explain several features of our species - however thus far there is little direct evidence for it. As such I do not think it holds much weight.

What kind of direcet evidence are you talking about? The tidal margin, where the aquatic ape theory would place us, is the worst place to find fossil evidence of much of anything. The evidence for the theory relies mainly on morphology: bipedalism, deemphasis of hair on the body, subcutanious fat, placement of the uterus, length of the birth canal, the fleshy platform of the mamary glands, the fleshy bulb of the nose, our peculiar hominid squint. Also, the ability and instinct to hold our breath under water from birth and our tears, our ability to vocalize at will. None of these characteristics can be accounted for by the savannah theory. Human development represents a radical departure from that of other apes, but merely wandering out onto the savannah isn't really all that radical to account for all the radical changes, is it?

Share this post


Link to post
Share on other sites
What kind of direcet evidence are you talking about? The tidal margin, where the aquatic ape theory would place us, is the worst place to find fossil evidence of much of anything. The evidence for the theory relies mainly on morphology: bipedalism, deemphasis of hair on the body, subcutanious fat, placement of the uterus, length of the birth canal, the fleshy platform of the mamary glands, the fleshy bulb of the nose, our peculiar hominid squint. Also, the ability and instinct to hold our breath under water from birth and our tears, our ability to vocalize at will. None of these characteristics can be accounted for by the savannah theory. Human development represents a radical departure from that of other apes, but merely wandering out onto the savannah isn't really all that radical to account for all the radical changes, is it?

:tu: Agreed, which is why I voted for Aquatic Ape. It also explains our brain power (fish = brain food).

Share this post


Link to post
Share on other sites
:tu: Agreed, which is why I voted for Aquatic Ape. It also explains our brain power (fish = brain food).

Oh, and my favorite: vestigial webbing between our fingers! :alien:

Share this post


Link to post
Share on other sites
:tu: Agreed, which is why I voted for Aquatic Ape. It also explains our brain power (fish = brain food).

No it doesn't eating all meat is important in the development of the brain.

Also, even in tropical water, we die quickly of hypothermia how is that supportive of AAH?

Share this post


Link to post
Share on other sites
What kind of direcet evidence are you talking about? The tidal margin, where the aquatic ape theory would place us, is the worst place to find fossil evidence of much of anything. The evidence for the theory relies mainly on morphology: bipedalism, deemphasis of hair on the body, subcutanious fat, placement of the uterus, length of the birth canal, the fleshy platform of the mamary glands, the fleshy bulb of the nose, our peculiar hominid squint. Also, the ability and instinct to hold our breath under water from birth and our tears, our ability to vocalize at will. None of these characteristics can be accounted for by the savannah theory. Human development represents a radical departure from that of other apes, but merely wandering out onto the savannah isn't really all that radical to account for all the radical changes, is it?

Yeah because they are amazingly unique features to us aren't they.

Also we do find fossil evidence for us, IN SAVANNAHS.

Edited by Mattshark

Share this post


Link to post
Share on other sites
Yeah because they are amazingly unique features to us aren't they.

Also we do find fossil evidence for us, IN SAVANNAHS.

Why all the snark, Shark? Among primates, our ability to hold our breath, our salty tears and our ability to vocalize at will instead of involuntarily as an expression of emotion ARE unique. However, among aquatic mammals, these characteristics are the norm. So, out of 11 characteristics I mentioned (there are plenty more), you make a lame attempt to discredit 2 and call it good?

Share this post


Link to post
Share on other sites
No it doesn't eating all meat is important in the development of the brain.

Also, even in tropical water, we die quickly of hypothermia how is that supportive of AAH?

Uh huh, and even in arctic areas, we quickly freeze to death... oh wait, there were hominids living in arctic areas 10's of thousands of years ago <_<

Tell me: if our only habitat was the Savannah, then why do we have very little hair on our bodies? Take a look at Savannah creatures and you'll see that none of them are bald :hmm:

Share this post


Link to post
Share on other sites
Take a look at Savannah creatures and you'll see that none of them are bald :hmm:

Except for elephants! And elephants also weep and they communicate willfully using sound. The theory on all that is that elephants also went through a semi-aquatic period in their evolution. Their trunks would have evolved as a kind of snorkle for walking across river bottoms. The extra skin on their bodies could indicate that they once had a fatty layer of tissue beneath the skin like humans and seals and such, but have since lost it in re-adapting to dry land.

Share this post


Link to post
Share on other sites
Uh huh, and even in arctic areas, we quickly freeze to death... oh wait, there were hominids living in arctic areas 10's of thousands of years ago <_<

Tell me: if our only habitat was the Savannah, then why do we have very little hair on our bodies? Take a look at Savannah creatures and you'll see that none of them are bald :hmm:

Being in water and air is two different things, convection causes much greater loss of heat in water than it does in air.

Humans and chimps actually have about the same number of hairs on our bodies. Our hair is very thin though, and we have lost the genes to produce thick hair in our coats. The advantage to this is it allows us to cool ourselves by sweating. Living in a hot, Savannah like environment and being able to actively forage and scavenge food all day is obviously advantageous. Most animals, during peak heats, need to retire to shade. Loss of hair, and cooling by sweat glands means our ancestors would not have had as much competition with other apemen that inhabited the Earth and large apex predators.

Another selection factor in bipedalism seems likely to be cooling. While on two legs, only our head and shoulders are exposed to direct light, other animals such as lions, Savannah herbivores and even chimps (while knuckle walking) expose their whole back to the sun as well. Notice humans, retained hair on their head. Anyone who has ever had a sunburn on their heard will tell you its not very fun, and that hair that remains there does serve a purpose (if you don't believe me shave your head and head to the beach).

Except for elephants! And elephants also weep and they communicate willfully using sound. The theory on all that is that elephants also went through a semi-aquatic period in their evolution. Their trunks would have evolved as a kind of snorkle for walking across river bottoms. The extra skin on their bodies could indicate that they once had a fatty layer of tissue beneath the skin like humans and seals and such, but have since lost it in re-adapting to dry land.

Elephants, like humans, have an alternative method for cooling. Their ears, are like giant heat exchangers, which very effectively cool the animals. Coupled with their sunburn resistant skin elephants have no need for hair. Their ears allow them to walk in the Savannah all day even during peak heat hours. This is important for them, because they must cover large distances in search of water and food.

Elephants 'extra skin' really isn't extra. It is thick. Elephants have thick skin to counter act the pressure of their insides. Think about it like this. If you fill up a regular balloon with water, it will eventually pop because the pressure inside becomes too great. If you increase the thickness of the balloon, you provide resistance to popping. If elephants had skin as thick as humans, they would pop from the pressure of their insides.

The aquatic ape and aquatic elephant hypothesis really has no supporting evidence, and what little evidence you could consider supportive is much better explained by our current understandings of human/hominid evolution.

What kind of direcet evidence are you talking about? The tidal margin, where the aquatic ape theory would place us, is the worst place to find fossil evidence of much of anything. The evidence for the theory relies mainly on morphology: bipedalism,

Being bipedal likely had many selection factors. Evolution, is not often as simple as "the birds eat the white moths". And while a single gene may have enormous positive selection for it, it could be near a gene which is experiencing unfavorable selection and is thus lost. Similarly, rarely in the natural world do you find something undergoing a single selective pressure.

Bipedalism for instance, was likely a result of having larger brained-premature children (which frees up an arm from knuckle walking for foraging), The energetics of walking around with a large head, heat reduction, predator defense and probably other reasons we're are unaware of (may never be). Having multiple selection factors such as this, allows for the advent of new feature quickly (geologically speaking).

deemphasis of hair on the body,

Covered this above.

subcutanious fat,

You may find this interesting;

Pond has also pointed out that human fat distribution indicates that it was not part of an aquatic adaptation. Such an adaptation is seen in whales and seals, but not in humans. Morgan has said that fat was an adaptation for insulation in an aquatic environment. Pond points out that fat is not adapted as insulation, although she also points out that this idea is fairly well entrenched, even in many physiology texts. For one thing, the distribution of fat, even in arctic species, doesn't indicate insulation; the fat layer is quite thin in some areas of the body of all species, even ones, such as seals, which are around 50% fat. She also notes that the subcutaneous (just beneath the skin) fat is the first fat to be used up, even in winter, and even in arctic animals, which is the opposite of what would be expected if insulation were a major purpose for fat. It plays, she suggests, no more than a minor role. The major role of fat, she feels, is as a food supply; this fits with how it's used up. The reasons for the differences seen in fat distribution in different species seem to be for shaping. Humans have the shapes they have due to fat distribution due to sexual selection; this of course makes sense in any species where fat distribution differs between the sexes; females are also much fatter than males. These sex differences make no sense if both sexes are "using" that fat (quantity and distribution) in the same way, as we would have to be for it to be an aquatic adaptation shaped by natural selection via the principle of convergent evolution. In fat aquatic species like the whales and seals Hardy and Morgan incorrectly say we resemble, both sexes are shaped basically the same, and their fat distribution seems to be primarily for streamlining while swimming. Humans and these aquatic species are radically different in their fat distribution.

placement of the uterus, length of the birth canal,

As I said above, humans give birth prematurely. To accommodate our large brains, which if left to develop as much in other animals would never fit out the birth canal. The solution evolution provided to this problem (large brains), is have babies earlier, with less developed brains. Even still, our large brains are a problem. Birth without the aid of modern medicine can still be dangerous and in underdeveloped countries, many pregnancies still end in the death of the baby and mother because the head becomes stuck in the birth canal.

The changes to the human uterus, pelvis, birth canal and vagina are the result of this selection process and having large brains.

the fleshy platform of the mamary glands, the fleshy bulb of the nose, our peculiar hominid squint. Also, the ability and instinct to hold our breath under water from birth and our tears, our ability to vocalize at will. None of these characteristics can be accounted for by the savannah theory.

Actually they can, AAH is founded on misunderstandings of what we do know and baseless assumptions. A very through and very good dissection of the AAH can be found here at www.aquaticape.org, you and anyone thinking this is a working scientific hypothesis should spend 15 minutes here browsing the AAH's claims in light of biology.

Human development represents a radical departure from that of other apes, but merely wandering out onto the savannah isn't really all that radical to account for all the radical changes, is it?

No, but who thinks the Savannah is the only reason for our divergence? It certainly played a major role (being the habitat we developed in) but many factors, such as food competition, sexual selection, neoteny etc etc all played a role in our development.

There is a lot of information out there, unfortunately (as is the case with the AAH) it is sometimes hard to differentiate between sound science and junk.

Edited by Copasetic

Share this post


Link to post
Share on other sites
Why all the snark, Shark? Among primates, our ability to hold our breath, our salty tears and our ability to vocalize at will instead of involuntarily as an expression of emotion ARE unique. However, among aquatic mammals, these characteristics are the norm. So, out of 11 characteristics I mentioned (there are plenty more), you make a lame attempt to discredit 2 and call it good?

Prove that why don't you.

Macaques in the Sundaban's are known to swim underwater, don't ya think they might hold their breath for that?

ALL PRIMATES HAVE SALTY TEARS.

Share this post


Link to post
Share on other sites
Humans and chimps actually have about the same number of hairs on our bodies. Our hair is very thin though, and we have lost the genes to produce thick hair in our coats. The advantage to this is it allows us to cool ourselves by sweating. Living in a hot, Savannah like environment and being able to actively forage and scavenge food all day is obviously advantageous. Most animals, during peak heats, need to retire to shade. Loss of hair, and cooling by sweat glands means our ancestors would not have had as much competition with other apemen that inhabited the Earth and large apex predators.

Hey Copasetic,

I really appreciate you approaching this discussion in a civil manner, rather than attacking like a wannabe Internet gladiator (I've been getting a lot of that crap lately and it's begun to put me off Internet fora completely). I like this idea that the lack of thick hair allows humans to exploit the hours when the sun is highest in the sky. Aren't there hairy mammals that regulate body heat by sweating though?

Another selection factor in bipedalism seems likely to be cooling. While on two legs, only our head and shoulders are exposed to direct light, other animals such as lions, Savannah herbivores and even chimps (while knuckle walking) expose their whole back to the sun as well. Notice humans, retained hair on their head. Anyone who has ever had a sunburn on their heard will tell you its not very fun, and that hair that remains there does serve a purpose (if you don't believe me shave your head and head to the beach).

Um, this is a little less compelling. Growing up in California I used to get the nastiest sun burns all over my body, but mostly on my back and I was never the kind of child to lay out in the sun. I got those burns every summer from running around on the beach upright.

An interesting part of the AAT that I recall is its explanation for human sexual dimorphism. The idea centers on the needs of the female during her 8 months of debilitating gestation. The idea is that the female would be spending a good deal more time in the water, staying in the water, than the male. Hence more fat on the female, less hairy, etc. (I recognize that you've stated that fat distribution has nothing to do with it). Interestingly, if you're a semi-aquatic hominid living in the tidal margin, your head and shoulders ARE the part of your body most exposed to the sun. Also, the theory goes that women have thicker and longer hair than men generally to give the clinging infant something to grab onto in the absence of thick hair on the mother's body. A woman's hair furthermore gets considerably thicker and stronger during and after pregnancy. I'd be interested to know how dangerous giving birth in water is compared to giving birth on dry land; if birthing a large headed underdeveloped baby is safer in the water or if the buoyancy of the water is a more comfortable medium than dry earth and air.

As I said above, humans give birth prematurely. To accommodate our large brains, which if left to develop as much in other animals would never fit out the birth canal. The solution evolution provided to this problem (large brains), is have babies earlier, with less developed brains. Even still, our large brains are a problem. Birth without the aid of modern medicine can still be dangerous and in underdeveloped countries, many pregnancies still end in the death of the baby and mother because the head becomes stuck in the birth canal.

Yes, on dry land. :)

The changes to the human uterus, pelvis, birth canal and vagina are the result of this selection process and having large brains.

The change I'm talking about, is the placement of the uterus at the insulated center of the woman's abdomen, instead of closer to the external genitals. This is to keep the fetus well insulated from the water and is seen in dolphins and whales. The birth canal in other primates and other land mammals in general is a good deal shorter than in sea going mammals like whales and dolphins, the penises correspondingly longer in aquatic mammals. If birthing the massive head of a human infant were at issue as you say, then wouldn't nature select for the briefest possible birthing process? How does a longer birth canal, and therefore a longer more painful birthing process benefit us?

Actually they can, AAH is founded on misunderstandings of what we do know and baseless assumptions. A very through and very good dissection of the AAH can be found here at www.aquaticape.org, you and anyone thinking this is a working scientific hypothesis should spend 15 minutes here browsing the AAH's claims in light of biology.

I'll check it out. Thanks again for not being a snarky lout about this. You've given me some things to think about. :tu:

Share this post


Link to post
Share on other sites

I wouldn't get snarky if you didn't post bad information and pass it off as fact.

ability to vocalize at will instead of involuntarily as an expression of emotion ARE unique.

Is very much wrong.

You have written it in terms as if it is a fact with out any knowledge on the subject to make such a statement. If you don't want anyone complaining at you think of what you are writing before you post otherwise, get over it.

Share this post


Link to post
Share on other sites

Copasetic, HK, you both make very compelling arguments. I just wanted to say I'm happy this hasn't degraded into another Evolution vs. Creationism thread :tu: . I'm learning a lot.

Share this post


Link to post
Share on other sites
Hey Copasetic,

I really appreciate you approaching this discussion in a civil manner, rather than attacking like a wannabe Internet gladiator (I've been getting a lot of that crap lately and it's begun to put me off Internet fora completely). I like this idea that the lack of thick hair allows humans to exploit the hours when the sun is highest in the sky. Aren't there hairy mammals that regulate body heat by sweating though?

Sweating is something unique to mammals. But, not all mammals sweat the same, furthermore it appears that the two types of sweat glands in mammals may have independent evolutionary origins. Humans have a really advanced sweating reflex, which allows us to greatly cool ourselves.

Like I was saying earlier, about the loosing hair because we can sweat, our sweat glands actually allow us to maintain homeostasis while running long distances in the hot sun. Most animals are built for short speeds and are literally exhausted when finished. Humans on the other hand (well not most of the western world's population) can run great distances, during peak heat hours and not fry their brain. There is further evidence that running played a role in bipedal development by how we breath. When you run, you breath through your mouth. Which serves two purposes, first it helps you get more oxygen. Second, it increases cooling particularly of the head -Which is obviously important to keeping your brain cool.

Animals can also pant to cool themselves, you've probably seen a dog do this. Animals cannot pant while running like humans can however.

Back to your original question though. Most other mammals that sweat, and have hair, do so in a very limited manner. Your dog and cat for instance, do have sweat glands, but only around the pads of their feet. Sweating into hair, is a sure way to nurture microbial growth.

Not sure if you have access to scientific literature, but you may find this paper helpful;

The evolution of sweat glands

Um, this is a little less compelling. Growing up in California I used to get the nastiest sun burns all over my body, but mostly on my back and I was never the kind of child to lay out in the sun. I got those burns every summer from running around on the beach upright.

Well couple of things to point out here. Firstly, its important to remember that no one selection factor was likely the cause of bipedalism. A major change to an organism's bauplan like that doesn't happen just to cool down a little. Or just to free up one hand. Many things would have likely contributed.

Second thing I would like to point out is (correct me if I am wrong), you are likely Caucasian and unlike our ancestors, are much more prone to your skin being burnt. Remember, bipedalism developed before we had Caucasian people walking around Southern Cal getting burnt.

The third is more a question; You said the sun burn was on your back, where on your back? Was the sunburn limited to your upper back? Or were you peeling all the way down to your waist? Most sun burns are limited too the face, back of neck and tops of shoulder/upper back. Being bipedal certainly doesn't prevent you from exposure to the sun, but it helps present less of a direct target to the suns rays. This is pretty evident if you have ever fallen asleep in the sun and received a full body burn, as opposed to to a typical 'walk around the amusement part in the hot sun burn'.

An interesting part of the AAT that I recall is its explanation for human sexual dimorphism. The idea centers on the needs of the female during her 8 months of debilitating gestation. The idea is that the female would be spending a good deal more time in the water, staying in the water, than the male. Hence more fat on the female, less hairy, etc. (I recognize that you've stated that fat distribution has nothing to do with it).

The marked degree of sexual dimorphism in humans is the result of our evolution for different roles in our social groups. Very distinct sexual dimorphism is often present in social animals. Human females and males likely 'looked' much similar, early on in our evolution. As time progresses and our roles become markedly different, so do the dimorphic traits we observe today. Fat deposits in women have much more to do with child bearing. Men, not bearing children, have a different distribute and much less. Men pre-agricultural revolution, were primarily hunters, at least age permitting. Which required leaner, more muscular frames (the same kind of dimorphic muscle to fat distribution can be seen in other primates who hunt, like chimps).

Sexual selection toward younger looking characteristics also likely played a role in the dimorphic traits of men and women.

Interestingly, if you're a semi-aquatic hominid living in the tidal margin, your head and shoulders ARE the part of your body most exposed to the sun. Also, the theory goes that women have thicker and longer hair than men generally to give the clinging infant something to grab onto in the absence of thick hair on the mother's body. A woman's hair furthermore gets considerably thicker and stronger during and after pregnancy.

I would interested to see any references you have for women's hair being thicker than mens'. Women with long hair, is a fashion look and has nothing to do with our evolution. Men's and women's hair grow at the same rate (about an inch every 2 months, I believe). Sleep and diet can contribute to the growth of your hair, as well as the condition (thickness, shininess etc).

Also, only small amount of human infants are capable of holding their own body weight by cling reflex, humans have nothing for babies to cling too however.

That part about the hair and pregnancy is a wives-tail.

During pregnancy, women take prenatal vitamins, have a super hormone surge and have increased circulation -Which leads to healthier hair for the duration of the pregnancy. After child birth, tissue vascularization is reduced, hormone levels tapper off and people typically tend to eat less healthy. This leads to hairs, which would have normally been shed in the absence of pregnancy, getting shed all at once. After our first son, my wife thought she was going bald because she kept loosing so much hair at once. I explained too her this is all hair, which would have fallen out anyway -It just comes out at the same time, which didn't seem to help. Once she realized she wasn't bald, she was ok.

I'd be interested to know how dangerous giving birth in water is compared to giving birth on dry land; if birthing a large headed underdeveloped baby is safer in the water or if the buoyancy of the water is a more comfortable medium than dry earth and air.

The "Oh natu-ral" crowd is big on water births. Ask the ones who have lost children to asphyxiation, water logged lungs, gross pulmonary edema and hyponatraemia.

Yes, on dry land. :)

In or out of water makes no difference. If the head doesn't fit, it doesn't fit. Women have been pulled out of the tub for C-sections, just as have women been shuffled off too surgery from "dry births".

The change I'm talking about, is the placement of the uterus at the insulated center of the woman's abdomen, instead of closer to the external genitals. This is to keep the fetus well insulated from the water and is seen in dolphins and whales.

Positioning of the human uterus is not similar to whales and dolphins. Our uterus is placed where it is because we are bipedal. Having the baby more internal, closer to the center of gravity, allows the mother the ability to walk upright still. Try it sometime, strap about 30-40lbs of something to your lower stomach and see how much fun it is walking around and how quickly you get sore.

The birth canal in other primates and other land mammals in general is a good deal shorter than in sea going mammals like whales and dolphins, the penises correspondingly longer in aquatic mammals. If birthing the massive head of a human infant were at issue as you say, then wouldn't nature select for the briefest possible birthing process? How does a longer birth canal, and therefore a longer more painful birthing process benefit us?

Humans have a greater leg-arm ratio than other primates, because we are obligate bipedal animals. We also have greater torso-leg ratios than other primates, again being bipedal full-time. Hence we have to have a longer birth canal, then other primates. It also means, that human males have longer penises to further deposit sperm. Birthing the massive head of our big brained babies is so hard not because the soft tissue of the birth canal, but rather the rigid bone of the pelvis. This is actually a great example of dimorphic traits as well.

linked-image

The top right is the human male, the top left is a human female and the bottom is a chimp.

From a 'down the canal view'

linked-image

I'll check it out. Thanks again for not being a snarky lout about this. You've given me some things to think about. :tu:

Thinking is always a good thing ;)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0

  • Recently Browsing   0 members

    No registered users viewing this page.