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The Aquatic Ape Theories of Evolution


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Poll: Which Theory of Human Evolution do you Accept (14 member(s) have cast votes)

Which Theory Makes the Most Sense to You?

  1. The Aquatic Ape theory (3 votes [21.43%])

    Percentage of vote: 21.43%

  2. The Neoteny Theory (0 votes [0.00%])

    Percentage of vote: 0.00%

  3. Savannah Theory (9 votes [64.29%])

    Percentage of vote: 64.29%

  4. Other Theory (Please elaborate) (0 votes [0.00%])

    Percentage of vote: 0.00%

  5. None of the above (2 votes [14.29%])

    Percentage of vote: 14.29%

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#16    Mattshark

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Posted 29 November 2008 - 01:25 PM

HKCavalier on Nov 27 2008, 10:31 PM, said:

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, 29 November 2008 - 01:26 PM.

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#17    HKCavalier

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Posted 29 November 2008 - 04:24 PM

Mattshark on Nov 29 2008, 05:25 AM, said:

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?


#18    OilFight

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Posted 29 November 2008 - 09:49 PM

Mattshark on Nov 29 2008, 05:24 AM, said:

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  disgust.gif


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.gif


#19    HKCavalier

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Posted 29 November 2008 - 10:18 PM

OilFight on Nov 29 2008, 01:49 PM, said:

Take a look at Savannah creatures and you'll see that none of them are bald  hmm.gif

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.


#20    Copasetic

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Posted 30 November 2008 - 03:17 PM

OilFight on Nov 29 2008, 04:49 PM, said:

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  disgust.gif


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.gif



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).

HKCavalier on Nov 29 2008, 05:18 PM, said:

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.

HKCavalier on Nov 27 2008, 05:31 PM, said:

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).

HKCavalier on Nov 27 2008, 05:31 PM, said:

deemphasis of hair on the body,


Covered this above.

HKCavalier on Nov 27 2008, 05:31 PM, said:

subcutanious fat,


You may find this interesting;

QUOTE
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.


QUOTE (HKCavalier @ Nov 27 2008, 05:31 PM) <{POST_SNAPBACK}>
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.


QUOTE (HKCavalier @ Nov 27 2008, 05:31 PM) <{POST_SNAPBACK}>
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.

QUOTE (HKCavalier @ Nov 27 2008, 05:31 PM) <{POST_SNAPBACK}>
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, 30 November 2008 - 03:44 PM.


#21    Mattshark

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Posted 30 November 2008 - 03:55 PM

HKCavalier on Nov 29 2008, 04:24 PM, said:

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.

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#22    HKCavalier

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Posted 30 November 2008 - 06:58 PM

Copasetic on Nov 30 2008, 07:17 AM, said:

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?

Quote

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.

Quote

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.  original.gif

Quote

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?

Quote

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.  thumbsup.gif




#23    Mattshark

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Posted 30 November 2008 - 07:26 PM

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

Quote

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.

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#24    OilFight

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Posted 30 November 2008 - 08:39 PM

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  thumbsup.gif . I'm learning a lot.


#25    Copasetic

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Posted 01 December 2008 - 04:37 AM

HKCavalier on Nov 30 2008, 01:58 PM, said:

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

HKCavalier on Nov 30 2008, 01:58 PM, said:

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'.

HKCavalier on Nov 30 2008, 01:58 PM, said:

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.


HKCavalier on Nov 30 2008, 01:58 PM, said:

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.  

HKCavalier on Nov 30 2008, 01:58 PM, said:

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.  

QUOTE (HKCavalier @ Nov 30 2008, 01:58 PM) <{POST_SNAPBACK}>
Yes, on dry land.  original.gif


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".

QUOTE (HKCavalier @ Nov 30 2008, 01:58 PM) <{POST_SNAPBACK}>
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.

QUOTE (HKCavalier @ Nov 30 2008, 01:58 PM) <{POST_SNAPBACK}>
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

QUOTE (HKCavalier @ Nov 30 2008, 01:58 PM) <{POST_SNAPBACK}>
I'll check it out.  Thanks again for not being a snarky lout about this.  You've given me some things to think about.  thumbsup.gif



Thinking is always a good thing  wink2.gif





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