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"AAT" The other "Theory of Evolution"

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posted on May, 7 2005 @ 11:52 PM
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The Other Theory of Evolution, or, Could an 'aquatic ape' be the missing link?

Many are probably familiar with the " Darwinian evolutionary chart" found here Vision Learning.com

But most 'lay' people, probably, are not aware of another "theory of evolution", known as the "Aquatic Ape Theory". First presented by Elaine Morgan at the 1968 Dual Congress on Paleontology and Human Biology. This theory simply stated postulates that during a period of a million or two years after hominids broke away from chimpanzees, human ancestors spent a considerable time living and evolving in estuaries, marshy jungles and along coastal shorelines.

Some Interesting Similarities:

The fascinating thing is that most of our apomorphic characteristics are shared with marine mammals. There are physiological traits that humans and dolphins share that chimps, monkeys and gorillas do not. In fact, these characteristics are completely lacking in most land mammals.



If we look at the characteristics that we share with dolphins and do not share with chimpanzees, we find conscious breath control, greatly reduced body hair, subcutaneous body fat, and greater brain size and complexity.Dolphins, however, became fully aquatic, whereas humans evolved to be semi aquatic.



Human babies are born fat, whereas all other primate babies are born lean. Human babies can swim from the moment of birth. Other primate babies cannot. Human babies not only float but also, after being born submerged, can swim under their own power, holding their breath until reaching the surface. In the water, the human baby is not helpless. From the moment of birth on, the human baby can swim alongside its mother.
Fat is a characteristic of marine mammals. It encourages buoyancy. It is an excellent insulator in the water. No other primates have it all over their bodies. The fat on aquatic mammals adheres to the skin, whereas on terrestrial animals it is attached to the muscle. In humans it is attached to the skin.


I had to add this quote 'cause it made me laugh:

The development of the human female breast can also be explained by this theory. A female breast is primarily fat, and fat floats, thus the child in the water would have access to the nipple at the surface.
Sea Shepard.org
Its important to also mention that no other (known) terrestrial animal has ever exchanged fur or thick hair for body fat as a form of thermoregulation.

Some involved with "AAT" theory argue that the "characteristics" of man are more likely to have come from a marine environment rather than from the savannah environment that the current "evolutionary theory" supports.

Why do they say this:

It suggests that when our ancestors moved onto the savannah they were already different from the apes; that nakedness, bipedalism, and other modifications had begun to evolve much earlier, when the ape and human lines first diverged.



The "enigmatic" features of human physiology, though rare or even unique among land mammals, are common in aquatic ones. If we postulate that our earliest ancestors had found themselves living for a prolonged period in a flooded, semi-aquatic habitat, most of the unsolved problems become much easier to unravel.There is powerful geological evidence to support this hypothesis, and nothing in the fossil record that is inconsistent with it.



Humans are classed anatomically among the primates, the order of which includes apes, monkeys and lemurs. Among the hundreds of living primate species, only humans are naked.



One general conclusion seems undeniable from an overall survey of mammalian species: that while a coat of fur provides the best insulation for land mammals the best insulation in water is not fur, but a layer of fat.



Humans are by far the fattest primates; we have ten times as many fat cells in our bodies as would be expected in an animal of our size. There are two kinds of animals which tend to acquire large deposits of fat - hibernating ones and aquatic ones


"AAT" proponents also argue that bi-pedalism is not advantageous to a savannah based animal, but more likely an adaption of a four-legged animal to a marine environment:

It is not surprising bipedalism is so rare. Compared with running or walking on four legs it has many disadvantages. It is slower; it is relatively unstable; it is a skill that takes many years to learn, and it exposes vulnerable organs to attack.



One hypothesis used to be that they first developed big brains and began to make tools, and finally walked on their hind legs to free their hands for carrying weapons. But we now know that it was bipedalism that came first, before the big brain and tool-making.



Today, two primates when on the ground stand and walk erect somewhat more readily than most other species. One, the proboscis monkey, lives in the mangrove swamps of Borneo. The other is the bonobo or pygmy chimpanzee; its habitat includes a large tract of seasonally flooded forest, which would have covered an even more extensive area before the African climate became drier.
Both of these species enjoy the water. It is interesting that the bonobos often mate face-to-face as humans do; in our case it is explained as a consequence of bipedalism. This mode of mating is another characteristic very rare among land animals, which we share with a wide range of aquatic mammals such as dolphins, beavers and sea otters. What we have in common with them is a mode of locomotion in which the spine and the hind limbs are in a straight line, and that affects the position of the sex organs


Repiratory system:

The human respiratory system is unlike any other land mammal's in two respects. The first is that we have conscious control of our breathing. In most mammals these actions are involuntary, like the heart beat or the processes of digestion.



The other human peculiarity is called "the descended larynx". A land mammal is normally obliged to breathe through its nose most of the time, because its windpipe passes up through the back of the throat and the top end of it (the larynx) is situated in the back of its nasal passages.



This arrangement means that we can breathe through our mouths as easily as through our noses. It is probable that this is an aquatic adaptation, because a swimmer needing to gulp air quickly can inhale more of it through the mouth than through the nostrils. And we do know that the only birds which are obligatory mouth breathers are diving birds like penguins, pelicans and gannets. As for mammals, the only ones with a descended larynx, apart from ourselves, are aquatic ones - the sea lion and the dugong.


How/Why we sweat:

we have a different way of sweating from other mammals, using different skin glands. It is very wasteful of the body's essential resources of water and salt. It is therefore unlikely that we acquired it on the savannah, where water and salt are both in short supply.



We have millions of sebaceous glands which exude oil over head, face and torso, and in young adults often causes acne. The chimpanzee's sebaceous glands are described as "vestigial" whereas ours are described as "enormous". Their purpose is obscure. In other animals the only known function of sebum is that of waterproofing the skin or the fur.


Development of our "Bigger Brain"

One factor may have been nutritional. The building of brain tissue, unlike other body tissues, is dependent on an adequate supply of Omega-3 fatty acids, which are abundant in the marine food chain but relatively scarce in the land food chain.
Drom the "AAT" Leaflet

Timing is everything:

It is now generally agreed that the man/ape split occurred in Africa between 7 and 5 million years ago, during a period known as the fossil gap. Before it there was an animal which was the common ancestor of human and African apes. After it, there emerged a creature smaller than ourselves, but bearing the unmistakable hallmark of the first shift towards human status: it walked on two legs. This poses two questions: "Where were the earliest fossils found?" and "Do we know of anything happening in that place at that time that might have caused apes and humans to evolve along separate lines?"The oldest pre-human fossils (including the best known one, "Lucy") are called australopithecus afarensis because their bones were discovered in the afar triangle, and area of low lying land near the Red Sea. About 7 million years ago that area was flooded by the sea and became the Sea of Afar.



AAT suggests that some of them survived, and began to adapt to their watery environment. Much later, when the Sea of Afar became landlocked and finally evaporated, their descendants returned to the mainland of Africa and began to migrate southwards, following the waterways of the Rift Valley upstream. There is nothing in the fossil record to invalidate this scenario, and much to sustain it. Lucy's bones were found at Afar lying among crocodile and turtle eggs and crab claws at the edge of a flood plain near what would then have been the coast of Africa. Other fossils of Australopithecus, dated later, were found further south, almost invariably in the immediate vicinity of ancient lakes and rivers. We now know that the change from the ape into Australopithecus took place in a short space of time, by evolutionary standards. Such rapid speciation is almost invariably a sign that one population of a species has become isolated by a geographical barrier such as a stretch of water.


There are many, many more 'evidences' to support the "Aquatic Ape Theory", and it also helps to explain the "missing links" not found in the geological record. Mostly because we have been looking in the wrong place.

But if worse comes to worse we might just be able to ask the dolphins:

If dolphins are intelligent, self-aware, and can understand a language similar to ours, do they have a language of their own? If the answer turns out to be yes, then many more questions automatically follow. Will we one day be able to communicate with dolphins in the way that John Lilly thought we might? Are the dolphins, as they swim through the sea, composing dolphin sagas for each other? Do they have their own history of interactions with humans, to be passed from generation to generation in some whistle-language story or sound-picture film that we cannot decipher?
From PBS.org

I think we can all agree that the "Encyclopedia Dolphinica" would be a great read, talk about your interesting perspectives.

I would appreciate any thoughts, comments, or rebuttals anybody might have.....Rren

For those interested in more information pertaining to "Aquatic Ape Theory":
'The Scars of Evolution' by Elaine Morgan (hardback, Souvenir Press, 1990, paperback, Penguin, 1991.)
There is a short ATS thread here , that mostly refutes "Aquatic Ape Theory"

Another ATS thread here where an "ATSer" asked if his webbed-feet could be evidence of "Aquatic Ape Theory"

Academics wishing to read detailed arguments on both sides will find the views of 22 contributors presented in: 'The Aquatic Ape: Fact or Fiction?', Souvenir Press, 1991.



apc

posted on May, 8 2005 @ 12:55 AM
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Wow.. thank you. I never knew a thing about this theory and it definitely fills a lot of gaps my head had kept expanding.
I bet if we ever were able to linguistically communicate with dolphins, we'd find a way to start a war.

Now I wanna go swimming.



posted on May, 8 2005 @ 02:12 AM
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this looks to me as if science is not above "creative workarounds" to patch up their theories. many religions use this form of defense when questioned by reasonable thought as well. might i add my bit of propaganda and make a pointing gesture to evangelicals?

where one might see "evidence" of an alternate evolutionary path, i see scientists scrambling to make excuses for reality not supporting their hypotheses.

evolution, although not 100% ruled out in my mind, hangs by a thread as an even reasonably sane idea. a thread that is losing strands over time. then again, as a reformed christian, i must acknowledge the catch 22 of the requirements of the scientific process and God not being examinable or testable.

when science and religion meet, we will find realistic answers (no, i am not talking about theistic evolution. something much more "harmonious" and realistic). but as long as religion ignores science and science abhors religion, we will simply be left with more and more questions.

daved


apc

posted on May, 8 2005 @ 02:17 AM
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i see scientists scrambling to make excuses for reality not supporting their hypotheses.

Uhm this is the basis of a theory. When new data conflicts with an existing theory, the theory must either be modified or discarded. There is nothing defensive about it, it is how we gain understanding about our reality.
It is when one attempts to modify the evidence to fit the theory, that scientific rigor has been abandoned.



posted on May, 8 2005 @ 11:29 AM
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Originally posted by Rren
Many are probably familiar with the " Darwinian evolutionary chart" found here Vision Learning.com
[img]


Arrgh.....

Okay... stop the bubble machine.

That isn't the Darwinian evolutionary chart for homo sapiens. That's the way that the ancient Greeks (circa 200 BC) thought of the place of humans in the universe.

It's called the Aristotolean model and does not involve evolution but rather their idea of "technical sophistication.

Here's two pages about human ancestors... the first with pictures, the second with descriptions (1 paragraph for each)

www.wilderdom.com...
www.pbs.org...





The Other Theory of Evolution, or, Could an 'aquatic ape' be the missing link?

Actually, it's not proposed as a "missing link." Or shouldn't be.


But most 'lay' people, probably, are not aware of another "theory of evolution", known as the "Aquatic Ape Theory". First presented by Elaine Morgan at the 1968 Dual Congress on Paleontology and Human Biology. This theory simply stated postulates that during a period of a million or two years after hominids broke away from chimpanzees, human ancestors spent a considerable time living and evolving in estuaries, marshy jungles and along coastal shorelines.


There begins part of the problem... the paper was done in 1968, based on material found before that time. To add to the problem, Internet enthusiasts (often with no knowledge of Paleobiology or ancient humans) have tossed in their own theories into the mix of the Aquatic Ape Theory (Known as "AAT") and turned what was a reasonable hypothesis into a pack of outright nonsense.

AAT was of interest to the scientific community and WAS debated in acadeic circles because it did hold some promise about explaining bipedalism. It was dismissed on later evidence.
www.talkorigins.org...

The human fossil discoveries since the 1970's have put the nail in the coffin of AAT in the scientific world. Here's The Straight Dope column on it (in nice, readable English without the scuzzy science details):
www.straightdope.com...



Some Interesting Similarities:

The fascinating thing is that most of our apomorphic characteristics are shared with marine mammals. There are physiological traits that humans and dolphins share that chimps, monkeys and gorillas do not. In fact, these characteristics are completely lacking in most land mammals.


Well, no. They're really stretching the point there. As I pointed out in another thread, you can pick a set of characteristics and make humans and rabbits equivalent. Selecting out a group of characteristics and saying "See! Because they share THESE traits, you can tell that this group once had THESE traits!"

Let me give you an example :
* swallows (birds) occasionally fly into houses. Cats wander into houses.
* swallows have large eyes in comparison to their bodies. Cats, ditto.
* swallows have claws on their feet. Cats, ditto.
* swallows have quick reactions. Cats, ditto.
* swallows are brown and gray and grayish brown. Ditto many cats.
* swallows eat bugs. Cats will eat bugs.
THEREFORE cats once had wings and flew around and ate bugs and chased swallows. You can even find cats with loose skin and hair knots that look like wings and this therefore proves that cats originally had some sort of flight capability.

Hopefully you see how ridiculous this is... and yet, most people accept this same sort of tenuous evidence for the "aquatic ape theory."

Anyway, check out The Straight Dope for a point-by-point refutation of the whole thing. As I said, it was once a notable and discussed theory among paleobiologists but was abandoned (as theories are) when later evidence contradicted it:
www.straightdope.com...

Some interesting side reading (there's a ton of stuff on Internet. I just picked interesting and easily readable material):

Here's an excellent paper on what we mean by evolution (with some pretty neat pictures). Warning, it's in PDF
fire.biol.wwu.edu...

Here's Wikipedia about our earliest ancestors:
en.wikibooks.org...

More...
www.wilderdom.com...


[edit on 8-5-2005 by Byrd]



posted on May, 8 2005 @ 11:46 AM
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The best and most accepted theory of evolution is Stephen Jay Gould's punctuated equilibrium. I would suggest to go read his books, because he changed the general idea.


apc

posted on May, 8 2005 @ 06:42 PM
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Lol yeah I was wondering, if I'm adapted for part-time aquatics, why do my fingers get all pruney?

Oh well it was fun while it lasted.



posted on May, 9 2005 @ 07:25 PM
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I can't get over those orangutans. They look funny even as skeletons.

I wonder if all the hairy people didn't quite acclimate to fire



posted on May, 9 2005 @ 07:41 PM
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Human babies can swim from the moment of birth. Other primate babies cannot. Human babies not only float but also, after being born submerged, can swim under their own power, holding their breath until reaching the surface. In the water, the human baby is not helpless. From the moment of birth on, the human baby can swim alongside its mother.


Can Human babies really swim from their moment of birth. Even after so many years, I have not yet learnt to swim.
*runs off to check if he is an alien*


Correct me if I am wrong, but I believe Humans learn to swim, just as they learn to walk....Or do they forget swimming over time?


[edit on 9-5-2005 by Quake]



posted on May, 9 2005 @ 07:55 PM
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The suggestion of an aqautic ape, I don't know about you but, to me seems quite absurd. This to me would seem as though that this theory's foundation rest upon the idea that apes evolved in the water? At least that's what I get from "Aquatic Ape". The anatomy of primates heavily favors the idea that apes evolved and began to live and breathe on land.


apc

posted on May, 9 2005 @ 08:29 PM
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From what I gather the theory claims ground in the location of Lucy's discovery, an area once flooded by the Red Sea and subsequently landlocked, causing rapid evolution of her species. Noone has suggested that apes or man evolved with the fishies. It is suggested that man's ancestors evolved in a swamp-like environment, where travel through water was common.
Atleast that's my take on it.
However it seems most possibilities have been ruled out.
It is true however that human babies can propel themselves through water, but they cannot raise their heads to breathe. If you take an infant and drop them in a pool, they will open their mouths and allow water to enter and will not attempt to take a breath. Most likely a result of development in the womb, this is one curiosity I noticed rather 'left out' of the rebuttals to the AAH claims. Also, there are many strange benifits attributed to water-birth, a very old method of delivery still practiced today.
Curiosities indeed, but not necessarily explained through this route.



posted on May, 9 2005 @ 08:34 PM
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So where does the monolith fit in to all of this, hmm?



posted on May, 9 2005 @ 09:58 PM
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Between 4 million and 2 million years ago, the hominid lineage diversified, creating a community of several hominid species that ranged through eastern and southern Africa. Among the members of this community, two distinct patterns of adaptation emerged:

One group of creatures (Australopithecus, Ardipithecus, Paranthropus) evolved large molars that enhanced their ability to process coarse plant foods;
The second group, constituted of members of our own genus Homo (as well as Australopithecus garhi) evolved larger brains, manufactured and used stone tools, and relied more on meat than the Australopithecines did.From: en.wikibooks.org...
Byrd's Link from above

Does this mean that humans are between 2 and 4 years old?

If not what is the oldest human(IOW not "human like") and is there fossil evidence or tools discovered?

Why is there so much distaste for "AAT" in the scientific community. I did read your(Byrd) links, but I thought the "missing link" still had not been found, and that there were some big gaps as yet unexplained by the fossil record.

I thought these "transitional species" were mostly theory, has there ever been a complete/mostly complete skeletal fossil found of the "missing link"?

I just learned about this about a week or so ago, and thought it was probably something most people, never heard of. Was surprised, in my reading, how vehemently the scientific community is in there objection to the theory.

Seems to be some legitimate points/observations that help fill in some of the gaps/holes in evolutionary theory, is there no doubt that the "savannah apes" evolved without having to adapt to a marine environment?

Has there ever been any archeological investigation done at possible "aquatic ape" sites? They(aat proponents) say that geologic evidence supports the theory and that the fossil record does not contradict it.



[edit on 9-5-2005 by Rren]

[edit on 9-5-2005 by Rren]



posted on May, 9 2005 @ 10:26 PM
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Here is a good FAQ on fossil hominids.
From it, and its updated rather frequently, it looks like the oldest Homo genera appears around 2 million years ago, Homo habilis, the 'handy man', named such because of its use of tools.
However, Homo erectus, as far as I recall, is thought to be the first man to make use of fire, since erectus is the first to leave africa and disperse throughout the globe. It tends to depend on what one means by 'man like', but stuff in the same genus (here, Homo) tends to be pretty similar, so these guys are similar to Homo sapiens in that sense.


The 'missing link' isn't a theory, there've been found lots of different intermediates between man and ape, with 'progressive' (tho I hate to use the term as its not technically correct and is rather misleading) traits that come to resemble man.

The intersting thing is that all these different genera and species seem to be telling us that man didn't evolve 'simply' in a progression from primitive apes to chimps to man, with a 'link' in between. But rather we see lots of different co-existing ape-men running around, and can't be certain which, if any, for a 'straight line' to man. Any idea about the connections between animals, their relationships, are called 'phylogenetic hypotheses'. Like all hypotheses/theories, they are dependant upon data, and are subject to change. Things like Austalpithecus (of which "Lucy" is one) used to be thought of as the ancestors of man, the descendants of chimps, but now, as far as I understand it, the picture isa little more muddy, ironically, because we have more data.

This is what science is all about in a sense. Think of the missing link idea. There is a gap between man and chimp. So we say 'there is a missing link between the two'. We find the Australpithecines, we say, 'aha, there is the missing link'. But wait, now we have two more gaps, one between australpithecine and man, and another between chimp and australpitehcine. Then we find specimins to fill both those gaps, and get more gaps all the while. The more we know, the more we know we know little!

On the aquatic ape, I can't speak for how it was received orignally, but I think part of the problem now with it is that its associated with a lot of non-scientific ideas, and becase of that lots of scientists tend to strongly reject it now. I mean, keep in mind, its a (moderately) old theory, one that most scientists considered and rejected a while ago, yet it sticks around.

It is a neat little idea tho.

AAT might not be contradicted by any evidence, but another aspect of science thats important, especially when trying to decide between two scientific theories, is too look at which is more explanatory and which is simpler or more 'parsimonious'. I don't know if AAT is rejected generally because of this, but if it explains the fossil record 'just as well' as the alternative, the it'd be best to not postulate an extra, aquatic stage for those reasons. So merely because something isn't contradicted by the evidence doesn't mean it can't be rejected. Thats where science gets interesting, the contradictory stuff can be 'done away with' rather easily, its the 'relatively equal' stuff that gets nutty.



posted on May, 10 2005 @ 01:31 AM
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nygdan:
The 'missing link' isn't a theory, there've been found lots of different intermediates between man and ape, with 'progressive' (tho I hate to use the term as its not technically correct and is rather misleading) traits that come to resemble man.


you say '....lots of different intermediates between man and ape.....', but then I found this:


If you are of the impression that there are many intermediate ancestors to man, take notice of the following statement by an expert in the field: "The fossils that decorate our family tree are so scarce that there are still more scientists than specimens. The remarkable fact is that all the physical evidence we have for human evolution can still be placed with room to spare inside a single coffin."

Link

Is that quote true? Do we really have such limited fossil evidence, if so how is one speculation theory better than another?

I read through your link Nygdan, I have trouble with the names and understanding what is man and what is man-like. For instance I saw earliest humans as early as 18,000 years old to over 100,000 years old(again not sure if man or man-like). Do we know when humans(no different than you or I) show up in the fossil record, IOW do we know or have a theory as to how old modern-man is?

Finally do we have any fossils that can be unequivocally called human? Not trying to bait you here I really dont know and every search I try shows finds of "possible" human ancestors or human-like(subjective term at best IMHO), and often have no more in common with modern man than modern apes do now.



posted on May, 10 2005 @ 08:31 AM
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Quote: "The fossils that decorate our family tree are so scarce that there are still more scientists than specimens."

Q: In what way shape or form is this relevant to an arguement against or for evolution?

A: This is a tactic used by either an ignorant irrate group of creationist who don't seem to understand that these fossils date back millions of years and aren't simply laying around in mass quantities to be dug up or these are tactics of radical evolutionist who don't understand that the world was not as populated by primates as it is today (due mainly to technological and medical advances).


Look at it this way: Scientist, vastly underfunded for what they are doing (as most scientist are), have only been searching for a supposed missing link the last 100 or so years. Within this time only a fraction of intended dig sits have been surveyed, and a tinier fraction have actually been excavated.


[edit on 10-5-2005 by Frosty]



posted on May, 10 2005 @ 11:08 AM
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I've studied the evidence offered for the aquatic ape theory for over a decade, and the evidence for it mentioned above is just incorrect. I know it's not your fault it's incorrect; you've been given information that is wrong is all.

My site is Aquatic Ape Theory: Sink or Swim? and has been used by The Straight Dope, for an article in last October's Fortean Times, and by several college courses -- plus of course just plain folks interested in facts. Here's a couple direct links as well: you may have seen the "AAT Leaflet" around the web which lists supposed aquatic characteristics (it's mentioned above); I have an annotated version which corrects the errors in it AAT Leaflet -- annotated. My latest addition is a critique of the recent BBC Radio 4 show by David Attenborough.

My site covers many of the extremely numerous mistakes Elaine Morgan and other AAT proponents have made in constructing their theory. These include errors of fact, misunderstanding of basic evolutionary principles, and techinques sadly common in pseudoscience and fringe science (and creationism) like ignoring contrary evidence, even when it's in the same book, or on the same page, as evidence they use; altering quotes to make them seem to prop up their theory; and saying that experts said one thing when they actually said the opposite. Being one of the people that Elaine Morgan got information from online, and having personally corrected her many times, with references to back it up, I can say she's not too keen on correcting her work -- she's still saying many of the same things that've been discredited long ago. But then many of the "facts" that the AAT used when it was first proposed (by respected marine biologist Alister Hardy, an expert on plankton) were known to be false for decades before he used them. Pretty poor scholarship all around.



posted on May, 10 2005 @ 11:16 AM
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Originally posted by Rren
If you are of the impression that there are many intermediate ancestors to man, take notice of the following statement by an expert in the field: "The fossils that decorate our family tree are so scarce that there are still more scientists than specimens.

Sure, thats true.


The remarkable fact is that all the physical evidence we have for human evolution can still be placed with room to spare inside a single coffin."

I seriously doubt that. That also makes it sound like there's enough to make one complete specimin.



if so how is one speculation theory better than another?

In terms of the AAT, it postulates this unecessary aquatic stage. Why postulate it at all? Simply to explain 'webbing' between man's fingers or subcutaneous fat and hairless bodies??


Do we know when humans(no different than you or I) show up in the fossil record,

Anthropologists have refer to what you are thinking of 'Anatomically Modern Humans'. Prior to them, you can find members of Homo sapiens (which is what modern man is classified as) that are sometimes called 'archaic' types. I think whats sometimes refered to as Cro Magnon Man is an anatomically modern human. The FAQ reports


Archaic forms of Homo sapiens first appear about 500,000 years ago. The term covers a diverse group of skulls which have features of both Homo erectus and modern humans. The brain size is larger than erectus and smaller than most modern humans, averaging about 1200 cc, and the skull is more rounded than in erectus. The skeleton and teeth are usually less robust than erectus, but more robust than modern humans. Many still have large brow ridges and receding foreheads and chins. There is no clear dividing line between late erectus and archaic sapiens, and many fossils between 500,000 and 200,000 years ago are difficult to classify as one or the other.
[...]
Modern forms of Homo sapiens first appear about 195,000 years ago. Modern humans have an average brain size of about 1350 cc. The forehead rises sharply, eyebrow ridges are very small or more usually absent, the chin is prominent, and the skeleton is very gracile. About 40,000 years ago, with the appearance of the Cro-Magnon culture, tool kits started becoming markedly more sophisticated, using a wider variety of raw materials such as bone and antler, and containing new implements for making clothing, engraving and sculpting. Fine artwork, in the form of decorated tools, beads, ivory carvings of humans and animals, clay figurines, musical instruments, and spectacular cave paintings appeared over the next 20,000 years. (Leakey 1994)

Even within the last 100,000 years, the long-term trends towards smaller molars and decreased robustness can be discerned. The face, jaw and teeth of Mesolithic humans (about 10,000 years ago) are about 10% more robust than ours. Upper Paleolithic humans (about 30,000 years ago) are about 20 to 30% more robust than the modern condition in Europe and Asia. These are considered modern humans, although they are sometimes termed "primitive". Interestingly, some modern humans (aboriginal Australians) have tooth sizes more typical of archaic sapiens. The smallest tooth sizes are found in those areas where food-processing techniques have been used for the longest time. This is a probable example of natural selection which has occurred within the last 10,000 years (Brace 1983).


This timeline graphic can be helpful to keep in mind

But, of course, this is a field in which opinions can vary.

There might be confusion about the order now because, in february, this article in the journal Nature was published.

In 1967 the Kibish Formation in southern Ethiopia yielded hominid cranial remains identified as early anatomically modern humans, assigned to Homo sapiens. However, the provenance and age of the fossils have been much debated. Here we confirm that the Omo I and Omo II hominid fossils are from similar stratigraphic levels in Member I of the Kibish Formation,[...]Thus the 40Ar/39Ar age measurements, together with the sapropel correlations, indicate that the hominid fossils have an age close to the older limit. Our preferred estimate of the age of the Kibish hominids is 195 +\- 5 kyr, making them the earliest well-dated anatomically modern humans yet described.




Finally do we have any fossils that can be unequivocally called human?

Certainly. This page notes that the first discovery of Cro Magnon man was of five individuals. I don't know how many 'anatomically modern human fossils' there are tho, I'd imagine that the number is quite large, I don't think anyone would include them in the 'coffin count' mentioned above either. In my opinion, anything from Homo habilis on is 'more man-like than ape-like', but obviously retaining characteristics of both. I mean, modern man is very similar to the apes. The differences are, in a sense, differences of degree (a less thick pelt, smaller canines, larger brains, more erect stance, etc etc) than kind.

Here is a skull of Homo habilis. I'd say that its pretty well human. An anatomist might disagree, and of course its a smaller braincase, but its a rather humanish skull.

Whereas below is Sahelanthropus tchadensis

and Australopithecus boisei

are more apelike. But notice, the differences are slight to begin with. Either way, by the time Homo sapiens is walking around, you have fairly modern, extremely humanlike creatures, which go thru some 'final refinements' and become indistinguishable from 'modern man'. Of course, thats all rather subjective anyway. The old story was, if i give a neanderthal a good shave and a business suit, you wouldn't want to sit next to him on a subway, but you wouldn't think he's a different species.


antrosciguy
My site covers many of the extremely numerous mistakes Elaine Morgan and other AAT proponents have made in constructing their theory. These include errors of fact, misunderstanding of basic evolutionary principles

Oh wow, welcome to ATS, thanks for the info, should be interesting!



posted on May, 10 2005 @ 12:07 PM
link   

from frosty:
Quote: "The fossils that decorate our family tree are so scarce that there are still more scientists than specimens."

Q: In what way shape or form is this relevant to an arguement against or for evolution?


I wasn't trying to argue against evolution, when I said "why is one speculative theory better than another" I was speaking of "aat" versus savannah ape evolution, I was honestly asking the question not trying to be sarcastic, or to imply evolution was bunk.


from anthrosciguy
My site is Aquatic Ape Theory: Sink or Swim? and has been used by The Straight Dope


Thanks for the link, very informative, I read the straight dope point by point refuttal posted by Byrd above.

Thanks for all the help guys, as I said earlier I had just heard of "AAT" and as a layman it seemed credible, I now know that largely it is not, and the 'straight dope' link does a good job of countering all the "AAT" claims. Thanks again for all the help.


[edit on 10-5-2005 by Rren]

[edit on 10-5-2005 by Rren]



posted on May, 10 2005 @ 12:11 PM
link   
How dare you ask and honest and open question!!!!!




[/sarcasm off]




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