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strichar

Aquaticism, possible or not?

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Posted (edited)

Just stating some theories on the subject, and some pros and cons on the ideas. Just write what you think about them. Are you for or against the possibility.

Three theories of aquaticism

There are three theories of how aquaticism could have featured in human evolution.

1. The aquatic ape

2. The semi-aquatic ape

3. The amphibious/generalist ape

Each theory in more detail

1. The aquatic ape

This is the original theory as outlined by Sir Alister Hardy and detailed by Elaine Morgan. At one time our ancestors were following the same evolutionary path as the ancestors of aquatic mammals, but this process was interrupted. The aquatic phase was followed by an evolutionary U-turn when hominids returned to the land.

2. The semi-aquatic ape

Similar to the above, but land was too important a resource to have been left behind. Land foods such as fruit were eaten in addition to sea foods. The boundary between the sea and the land, the intertidal zone, was as important as the open sea. The 'aquatic phase' was less intense, and occurred over a longer time scale; later hominids and pre-hominids may also have been semi-aquatic. This sort of idea is proposed by Marc Verhaegen and Paul Crowley.

3. The amphibious/generalist ape

Hominids are seen as generalists living in different habitats. The greatest population densities were found in regions where the largest number of different habitats were in proximity to each other, which was in and near the flood plains and deltas of East African rivers. Aquatic adaptations enhanced mobility and allowed exploitation of aquatic resources in addition to forest and grassland resources.

The advantages and disadvantages of each theory

1. The aquatic ape

Advantages

It is the simplest of the three. A clear model from other mammals can be seen.The evolutionary path of diverse larger aquatic mammals is clearly understood, and hominid evolution followed the same line, excepting that it was interrupted.

Disadvantages

Hominid characteristics which evolved later than the proposed time of the aquatic phase cannot be attributed to aquaticism. The Australopithecines seem to have been little more than bipedal chimps; large brains and other characteristics came later.

2. The semi-aquatic ape

Advantages

The aquatic or semi-aquatic phase is extended and allows later hominid evolution to be attributed to aquaticism; the idea of a U-turn is abandoned.

Disadvantages

This is one of the few theories of human evolution which opposes the idea that hominids exploited savanna. Morgan suggests that they did so after the evolutionary U-turn, and I suggest that as generalists some hominids some of the time did so; orthodox theories of human evolution also emphasize savanna.

Extending an aquatic or semi-aquatic phase back in time to beyond the time of the last common ancestor of humans, chimps and even gorillas complicates matters. If the LCA of humans and chimps were bipedal, chimps must have lost bipedalism. Knuckle-walking must have evolved twice, separately in chimps and gorillas.

The rejection of savanna exploitation and the concept of a bipedal LCA make this a more heterodox theory of human evolution. Also, no clear model from other mammals can be seen.

3. The amphibious/generalist ape

Advantages

It incorporates the principle of generalism; hominids seem unlikely to have evolved as specialists. The idea of a U-turn is abandoned.

Disadvantages

It is most complex of the three. No clear model from other mammals can be seen, except for elephants and perhaps pigs which could also be claimed by the other theories. Is it possible that aquatic adaptations could have arisen in hominids who were only part-time waders/swimmers/divers?

Why were aquatic adaptations retained when hominids started living on the land?

According to theory 1, there were two possible reasons

1. Aquatic adaptations aquired during an aquatic phase could have been retained on land if they had an advantage on land as well as in water.

2. Aquatic adaptations aquired during an aquatic phase could have led on to other adaptations which had an advantage on land, and thus the original adaptation and what it led to could have been retained. Thus a larynx which was low in the throat, as is found in many aquatic mammals, led onto speech which is assisted by a low larnyx.

According to theory 2, hominids did not start living inland until recent times.

According to theory 3, some hominids some of the time were in water. Up to the time of the invention of agriculture, the greatest population densities were near seas and rivers.

Why did hominids not become fully aquatic?

AAH uses analogy with cetaceans, sirenians and pinnipeds to explain certain human features, but this raises the question of why we didn't go all the way. John Gribbin, for example, wrote that one of the two problems he had with AAH was this question.

This is what the three theories have to say about it 1. Volcanic activity caused part of the Afar region that was sea to dry up 2. Apes needed to come out of the water to gather water-side plants and fruit 3. Hominids often lived away from water in other habitats

If number two is correct then number one becomes superfluous. In fact number one is contradicted by number two because if the australopithecines were "tied to the vicinity of waterways" then it could not be true that their habitat dried out due to volcanic activity, just that they exchanged rivers and lakes for the sea. If they continued to live next to deep water they could have continued to become more aquatic and eventually become like manatees.

When did our ancestors stop wading/ swimming/ diving to get food.

Theory two suggests that it was very recently, but the problem with this is that we have many fossil hominids from the interior of continents. My theory says that some hominids lived in the interior of continents while others continued to live on the coast, at least for part of the year. When Europeans started sailing round the world 500 years ago they found people living from the sea wherever they went.

My View.

1. As hominids evolved they became increasingly less restricted to one environment.

2. They moved between different environments to exploit the seasonal abundance of each.

3. Some groups of hominids lived near the coast at the same time as other groups lived inland, but coastal regions which included a grassland littoral and forested river valleys were the regions of greatest population density.

Coastal hominids exploited sea foods as well as forest valley and grassland foods. They had a wider variety of foods than inland hominids, and less risk of seasonal dearth. They had a higher population density because the area needed by each group to obtain food was smaller and so they were closer together. Most hominid evolution occurred in coastal regions and included aquatic adaptations.

4. The most likely situation in which the complex hominid brain evolved was just such a complex region. A wide variety of food sources was exploited, requiring a wide variety of strategies, and providing the quantity and quality of nutrients necessary for brain growth.

Edited by strichar

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More proof: Our hairlessness (like dolphins), the only land animal with bouyant breasts (dolphins breast are bouyant) and being the only ape to regularily swim.

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Posted (edited)

Very interesting!

Also a little detail thats probably not so important. Humans seem to be designed to eat seafood.

Humans who eat alot of fish rather than the meat of land animals tend to be healthy, thin/in shape, live longer, and supposedly alot of fish consumption also raises intelligence. Whereas stuff like beef and chicken is proven to lead to obesity, heart disease, cancer, and early impotency, etc.

And if you think about it, if there were no such things as weapons to assist us, which live food would we be able to hunt with our bare hands? It'd be fish. I'd like to see a human hunt down wild cattle and kill it and eat it with only their flat teeth and stubby nails that nature provided hehe. Also fish is the only meat we can safely still eat raw (ie sushi...)

So yea diet also shows alot the possibilty of humans being aquatic in the past.

Whee this also raises the possibility of mermaid type beings somewhere in our evolution process...

But yea very interesting!

Edited by MoonFox

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That is something I was thinking about too, I agree entirely.

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Check out www.aquaticape.org for a scientific critique of the Aquatic Ape Theory. This is the site written up in last October's (2003) Fortean Times and used by The Straight Dope (22-Jan-2002) for their column on the AAT.

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huh.gif Huh...you know, i've never heard this theory before? Maybe i havent read enough? Now, excuse my cynicism here...but, isn't it more widely held that we did NOT evolve from an aquatic ancestor? As far as i know, evolution also still is looking for a "missing link," possibly we can't find it because it's deep in the ocean? And third...do bones deteriorate under sea water? I'd appreciate a response...thanks for gettin my mind thinkin thumbsup.gif

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Bones deteriorate wherever there are bacteria, other animals and weathering effects, so yeah. However it was embedded in something like, tar or ice, it probably would be fine. Ice is the better one.

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huh.gif Huh...you know, i've never heard this theory before?  Maybe i havent read enough?  Now, excuse my cynicism here...but, isn't it more widely held that we did NOT evolve from an aquatic ancestor?  As far as i know, evolution also still is looking for a "missing link," possibly we can't find it because it's deep in the ocean?  And third...do bones deteriorate under sea water?  I'd appreciate a response...thanks for gettin my mind thinkin  thumbsup.gif

The aquatic ape idea in any of its various forms is very much a fringe idea at best, and it is argued for with phoney "facts" and misconceptions about evolution, as well as more than a touch of what seems to be outright dishonesty (it could be major ineptness instead, but that's small comfort). The proponents ignore contrary evidence, even when it's in the same sources they cite -- sometimes on the same page as things they cite! They also have a habit of misquoting people and altering quotes -- both are major no-nos of course.

Your question about bones is another interesting problem. Fossils tend to be best formed when bones are fairly quickly covered by sediments. Shorelines, which is where aquatic ape proponents say their purported creatures lived, are excellent places to get fossilized, which is why we have a great many fossils of animals which lived in such areas (either ocean or river or swamp). We would expect to find a great many hominid fossils if they were actually living in those places, but instead we find very few compared to shoreline dwelling animals. This is yet another (out of many) piece of evidence against the "AAT", yet AAT proponents simply ignore this problem (as they tend to ignore all contrary evidence).

I have the site I mentioned above, and I've been looking at the evidence surrounding the AAT and the methods the AAT proponents use for over a decade now. It just doesn't add up at all, and I've got a lot of info about it on my site. Check it out (The Aquatic Ape Theory: Sink or Swim?).

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