The Aquatic Ape Hypothesis

[Auburn]

So I know The Introvert made a thread about this back in 2012, which didn't seem to go very far, and which is now stored away in archives... so I wanted to refresh the topic with a new thread, if that's ok with the mods...

The TED talk with Elaine Morgan, which is necessarily brief, does not cover nearly as many details as this documentary by Mark Kessell who takes no position for or against the hypothesis, but merely elaborates on its explanatory power above the existing theories for our transition from apes to hominin:

https://www.youtube.com/watch?v=QokbVnZsN9I

https://www.youtube.com/watch?v=G8WI4XtPIFM

https://www.youtube.com/watch?v=f270tQYk-n0

For this thread, I may take the side of the advocate. I see this hypothesis as having an enormous amount of not just explanatory power, but actual evidence.

I think a big problem with the way this hypothesis is being taken is that people ask for the evidence as though they are hoping to find some fossil somewhere that has it. But fossils could not prove the assertions of this hypothesis (because skin and blubber, and so forth, don't survive into fossilization) more firmly than our own genetics and physiology can. The evidence is not in the fossil record, but in us - the living fossils that are our vestigial traits. If the aquatic phase did indeed happen, then as evidence we should have the results of that phase in our bodies; which we can see and measure.

I'm terrifically interested in what you guys have to say. What do you think? How can we explain our differences from apes if we consider that evolution happens through selective pressures; what pressures necessarily pushed us into our current features?

 

[The Introvert]

Here's the link to my thread too, a couple years a ago.

http://intpforum.com/showthread.php?t=14943&highlight=aquatic+ape

Sorry for not seeing that disclaimer the first time round.

Typical 1,000th post...

I'll have to look over everything again, and reply when I have thought about it... this post was going to point everyone to my thread before I saw the disclaimer. Much love.

 

[Teffnology]

Congrats on 1000!

I had noticed the thread before in the archives but didn't want to be the one kook who brought it out into the light again. It didn't seem to generate a ton of discussion. I have yet to watch the TED talk but I believe she is one of the scientists on the documentary The Cove.

I believe I saw The Cove on one of the free documentary sites mentioned on the forum. I had seen it previously via a torrented copy and it originally aired on Animal Planet. They claim to have had in their possession at one time a possible aquatic ape skeleton. The doc relies upon some sketchy footage to prove its point that the US Navy has been covering up the sightings of supposed aquatic ape corpses.

It does lean towards conspiracy themed but it was entertaining and left with me with just enough suspicion to keep it up in the air. I look forward to the clips posted. And hopefully some more discussion this time.

 

[PhoenixRising]

@Auburn - I think this is a great topic to bring to the table again, since so little discussion was had on it before. I know there was another thread posted about it, but I think it may be advantageous to start with a fresh analysis of the resource you have posted here rather than referencing material from prior discussion.

I think Kessell does an excellent job of explaining the Aquatic Ape theory in a cohesive way. What I really like about his explanation is that it provides support for the theory without his invested opinion. He presents intelligently conceived correlations and explains things as logical consequences, rather than actively trying to prove or disprove any point. He also avoids stating general concepts or appealing to shaky evidence such as inconclusive fossil finds. His honesty and straight-forwardness on the topic allow for a clear view of the evidence.

Personally, I'm a proponent of Aquatic Ape theory. Since, as Kessell states, there isn't any empirical evidence to prove any theory of human evolution, I think it's most intelligent to side with the theory that makes the most logical sense. There are several convincing points that make this theory more favorable than the Savanna theory. The one that stands out to me most is the existence of our subcutaneous fat layer. That would be inefficient indeed in a hot environment such as the Savanna. The Savanna theory also provides no explanation for why we have conscious control over our breath (and therefore are capable of swimming and speech), while the Aquatic Ape theory provides a very strong explanation for why we would have that capability.

 

[Teffnology]

Having just watched the Kessell videos I greatly appreciated his presentation. It is a much more objective approach than the source I reccomended previously.

The fact that human infants respond instinctively in water has always fascinated me and he touches on this a bit. The video does lay out a pretty plausible theory for human evolution and its association with water.

 

[redbaron]

Seems awfully difficult to actually find a freely available scientific study on the topic. Only information on the topic is between 30-40 years old. Find it hard to come to any sort of understanding when all I've got is YouTube video science from a doctor-turned-artist and a TED talk.

Are there other sources of information you're parsing these ideas from?

 

[Auburn]

@Phoenix & Teffnology - Aye. The Aquatic Ape hypothesis accounts, all at once, for the majority of all differences between hominin and apes.

This is in stark contrast to the way that we've looked at the ape-human transition before; as conglomerate of a bunch of separate reasons to account for the many peculiarities between us and them. Furthermore, so far as I've seen, these independent reasons don't exert enough selective pressure to truly rule-out those without the adaptation, according to Darwinian principles.

Spoiler

Nakedness:

When trying to explain a phenomenon it's important to see examples where the same phenomenon occurs in the rest of the animal kingdom. We know that we lost our fur, so we must ask ourselves what natural pressure causes animals to lose their fur.

If humans lost their fur in order to stay cool in the savanna, because they were so hot with the fur, then why don't we see other animals such as the Cheetahs of Africa or the Kangaroos of Australia, who frequent in temperatures of over 110 degrees, lose theirs. If heat itself was the selective pressure, we would see examples of the transition to naked skin being far more widespread in mammals. Instead, we see that the only known cases (aside from the naked mole rat) where mammals lose their fur is in the transition to aquatic environments, and we see this frequently. However, we also see that upon returning to the land, mammals don't necessarily regrow their fur, which precisely coincides with the human appearance.

Ability to Hold Breath:

Humans have the ability to consciously control their breathing, which is something that is anatomically impossible for other apes or land-based mammals.

When the argument is posed that we have conscious breath control in order to be able to talk, I ask myself how long it would have taken to develop our larynx the way it is and it simply doesn't make sense to me. Natural selection is very immediately-focused, and we didn't develop the ability to hold our breath for some far-future time when we can speak in words and languages.

But a very plausible, natural and immediate pressure/necessity that would have made us develop this ability is if we needed to survive immersion in water. Like diving birds, we had to develop this ability to be able to hunt for fish in deeper waters. From then, I think we took that hard-earned evolutionary trait and did more creative things with it later -- such as develop dialects.

Down-facing Nose:

The downward position of our nose, and our nasal bone, is another feature that differentiates us from other apes. Likewise, our down-facing nose may have evolved to prevent water from going into our noses while we were immersed.

Bipedalism: Kessell did a great job explaining why bipedalism is not a trivial problem, or something that is even advantageous to a land-based animal. But a bipedal stance would have given apes the ability to wade deeper into the water and to collect the necessary food. For the same reason, longer legs would have been more advantageous as well - which is another element we see that differs between us and chimpanzees. Apes typically have longer arms than legs, but in a setting where you were trying to keep your head out of the water, longer legs would be more beneficial.

The gravity lifting effects of the water would have eased the stress on the back of apes as they made the transition in the pelvis. We see another species that has made this transition in their pelvis in the elephant seal. See here for example:

Spoiler

​

The sea lion has its pelvis facing forward, while the elephant seal has made the transition to a pelvis that's facing backward. This position of the pelvis also makes it easier for elephant seals to swim, as they can put their legs directly behind them to act like fin-proxies. So to add to what Kessell said, an additional benefit of the pelvis' transition to a vertical stance would have been the ability to swim in a far more streamlined, fish-like form.

Tethered Skin Layer:

Human skin is thicker than that of chimpanzees and is cris-crossed with strands that tether onto the subcutaneous fat layer in the same way that whales, seals and other aquatic mammals have their skin.

10% Thicker Fatty Layer:

The average percent of body fat for a healthy adult male is about 18% and about 25% for an adult female. We can compare this to the average of 9% body fat in Chimpanzees. Extra body fat adds more insulation and thus preserves heat. We know that the environment in which humanity transitioned from quadrupedal to bipedal was a tropical one. Acquiring more insulation would have been disadvantageous for us in the majority of circumstances. The two exceptions that come to mind are ice-age temperatures or aquatic conditions.

For example, we know that snow leopards keep fatty reserves in their tail, and wrap their tail around themselves to stay warm during the night. And we know that walrus, whales, seals, dolphins, etc, use fat to stay warm. But if we consider all the above, and the conditions in which humans first came into being, we see the origins of our body far resemble that of aquatic mammals far more.

Excessive Water & Electrolyte Loss:

Compared to other mammals, humans are very inefficient at conserving water, and we require a lot more of it to stay hydrated compared to our cousins the Chimpanzees. It is unlikely that we became less capable of efficiently handling water, as we diverged from them, as an evolutionary advantage. Instead, this disadvantage points to a side-effect of an alternative evolutionary path in which water was not a scarce resource, and where we consumed and secreted water on a constant basis.

Larger Brain Size:

This is more of my own notion, but it's even conceivable that the transition to a fish-diet, which is rich in omega fatty acids (which contain the calories and lipids needed for brain development) contributed to our ability to evolve larger brains.

Partial webbing between toes and feet:

Humans, unlike other apes, have vestigial webbing between their fingers and toes. Different humans have different levels of it. ( http://i.imgur.com/iNyCqTH.jpg )

Water-Based Births & Floating Babies:

We are the only apes to give birth in water rather seamlessly, and to have babies born with 15% body fat from the start, compared to the 3% body fat of Chimpanzee babies. ( http://carta.anthropogeny.org/moca/topics/fatness-birth )

And so on...
These are just the ones that I remember from the top of my head - and recaps from the video to make discussion easier.

~~~
​

If we come across a single circumstance (such as aquatic adaptation) that so elegantly accounts for such a broad range of unexplained phenomena, then it's nonsensical to not at least deeply consider it, and to weight it against existing models and see which has the most explanatory power.

 

[Auburn]

https://www.dropbox.com/s/gzpsvv7oxv2ilbe/The_Aquatic_Ape.pdf?dl=0
https://www.dropbox.com/s/ku2wgu4rb98pfs3/The_Naked_Darwinist.pdf?dl=0

@redbaron - Here are a few that may help. The issue right now is that people are just unwilling to even properly debate the topic. Hence why I wanted to bring this up. It's not something that's been 'verified' by the scientific community, in fact it's gotten a lot of pushback but nothing that really refutes it to me.

The idea is in the process of moving from "radical/absurd" to "plausible" in modern opinion. It's... not uncommon for worthwhile ideas to start off this way. Which is why I am hoping the members here can discuss the topic on its own merits, without weighing it based on its official/unofficial status in academia.

Relevant Criticism: http://en.wikipedia.org/wiki/Aquatic_ape_hypothesis#Theoretical_considerations

 

[redbaron]

I was really hoping you'd link a study as opposed to two books written by the same person who gave the TED talk. Anyway I've managed to find some actual studies that I'll upload when I have PC access again.

 

[Teffnology]

Looking forward to those studies. Thank you for finding them, hard to find objective material on the matter.

 

[Vrecknidj]

Sarah Hrdy does a reasonably good job dismissing the hypothesis in her book Mother Nature: Maternal Instincts and How They Shape the Human Species: Sarah Hrdy: 9780345408938: Amazon.com: Books@@AMEPARAM@@http://ecx.images-amazon.com/images/I/51fzd0aTcnL.@@AMEPARAM@@51fzd0aTcnL.

 

[Auburn]

Ah, curious. I couldn't find the book anywhere online (I might order it though, it seems quite interesting). Maybe you could give us a rundown of her arguments against the hypothesis?

Heh, it kinda seems like we're spinning our wheels with "this source here might have something to say" and "that source there might have something to say" ...without really getting into discussing anything. 0:

 

[Teffnology]

Mermaids are REAL!!!!! There maybe that will spark some discussion haha.


I don't totally believe that but I don't totally discredit it either. There is enough to be suspicious at least.

 

[marc verhaegen]

Thanks a lot. There's no doubt any more that human ancestors were semi-aquatic. Unfortunately, Elaine Morgan was wrong in thinking that our waterside evolution happened some 6 mill.yrs ago. More likely, archaic Homo's littoral dispersal was early-Pleistocene, i.e. less than 2.6 Ma.
The open-plain ideas of human evolution are based on the traditional assumption (but logical error) that ape-->human = quadruped-->biped = forest-->savanna.
All objective data (paleo-environmental, fossil, physiological, nutritional...) show that Pleistocene Homo did not run over the African plains (sweating water + salt = scarce in savannas), but followed the African & Eurasian coasts & rivers, beach-combing, diving & wading bipedally for littoral, shallow aquatic & waterside foods (rich in brain-specific nutrients, e.g. DHA).
Some recent publications:
-J.Joordens... S.Munro... 2014 Homo erectus at Trinil on Java used shells for tool production and engraving, Nature doi 10.1038/nature13962
-S.Munro 2010 Molluscs as ecological indicators in palaeoanthropological contexts, PhD thesis Univ.Canberra
-J.Joordens... 2009 Relevance of aquatic environments for hominins: a case study from Trinil (Java, Indonesia), J.hum.Evol.57:656-671
-S.Cunnane 2005 Survival of the fattest: the key to human brain evolution, World Scient.Publ.Comp.
-M.Vaneechoutte... eds 2011 Was Man more aquatic in the past? eBook Bentham Sci.Publ.
-M.Verhaegen 2013 The aquatic ape evolves: common misconceptions and unproven assumptions about the so-called Aquatic Ape Hypothesis, Hum.Evol.28:237-266
google researchGate marc verhaegen, or independent academia edu/marcverhaegen

 

[Vion]

http://media.treehugger.com/assets/images/2013/10/seal-of-approval-meme.jpg

Makes sense what with manatees, seals, otters, beavers, platypus, and just about everything else mammalian still crawling about in the primordial ooze.

 

[Auburn]

Thanks for dropping by Marc!
Reading your paper right now, so far very fascinating.

For those who also want the link it's:
https://www.academia.edu/6835100/Co...en_assumptions_about_the_so-called_AAH_-_2013

You'll need to approve facebook or google+ linkage, but otherwise access is free.

 

[Auburn]

Found some more interesting insights:

https://www.youtube.com/watch?v=Aa1FRQ2o-wI

In brief, (most) all the main ways humans differ from other apes are conducive to, or hypothetically emergent from, semi-aquatic conditions, such as:

(among others)

I'd add the wrinkling of our fingers to that list, as it improves our ability to grasp objects in water (something we would have needed if we were wading in water and needed to not slip)

What do you guys think? Do you think we came from a semi-aquatic past?

Spoiler

I'm still quite disheartened that the hypothesis isn't being taken seriously. The biggest criticism I've seen toward it is a lame argument that "we can't prove that because soft tissue doesn't fossilize" - and we probably never will be able to prove it.

The other is that the hypothesis is an attempt to stitch together observations into an umbrella theory using comparative anatomy. Apparently "comparative anatomy" doesn't count as a source of insight between other species?

Don't we do this all the time, by comparing the anatomy of existing species? If we analyze humans strictly anatomically, you'd see that we are far more well suited toward aquatic conditions than any other primate. I don't think it's sensible to believe that this happened by sheer accident totally unrelated to a semi-aquatic past, especially when these characteristics are also seen in all other mammals that have taken to semi-aquatic life.

It seems like anthropologists rarely get into the soft tissue anatomy of species, because it's hard to prove things about it. They contest that only fossil evidence is uncontestable. But I think this is a flaw in their way of doing research.

Much of the reality about a creature's habits, origins, and lifestyle are embedded into their soft tissue anatomy. It tells you the function and nature of their lifestyle. Zoologists can tell you how important this is, but anthropologists over-emphasize bones and discard the rest.

A cross-disciplinary examination, and way of thinking, should be applied to the subject. A collaboration between anthropologists and biologists, zoologists, etc.

I think it's a type of narrow-minded ignorance. Just because the answer exists in a domain that's difficult to prove the way you're used to proving it, doesn't mean it's not real. Ugh. Makes me so mad.

 

[Black Rose]

Unless a feature has some benefit or if it has a negative selection pressure then that feature naturally goes away. Humans did not appear until one hundred thousand years ago. If the aquatic ape hypothesis holds then those features which appeared 5 million years ago must have been spread to all bipeds that were not humans. Yet only humans survived and retained those features that they did not require for five million years.

The body fat being 12 percent must have existed 5 million years ago. Yet why did being in the hot savannah not select against this feature? Why would having 12 percent body fat in the water benefit a biped in the hot sun for 5 million years? There must be another reason body fat benefits a biped other than living in the water. The body loss of 10 percent of water vs other mammals loss of 20 percent water before dehydration death must also be explained for being a feature that remain 5 million years after leaving the aquatic life style.

Bipedalism happened because of an increase in intelligence. Being a biped is dangerous so only those bipeds that were smart enough to survive being in that position were able to live on. Sexual selection happens by mate selection. The best walkers were the ones that got together to mate. The same thing happens now. People of the same intelligence or of other "like" features get together and have kids where those features are amplified. Bipedalism could have been completely a sexual selection of those apes that could walk only mating with the best walkers. The negative selection pressure for walking would need to not exist. And as walking became beneficial the positive selection pressures enhanced walking features.

How would walking in water be a positive selection pressure for walking? Walking on land as long as the negative selection was eliminated can all be explained by sexual selection. Apes that walk good like to have sex with other apes that walk good. This does not require water and it requires no other pressures from the environment. The water hypothesis would need to show why water was a positive selection pressure and why gave us the foot and why it gave us the pelvis. Walking on land explains the foot and pelvis. Walking in water would not result in a foot the shape it is we have right now. All features we gained from living in the water would need to be explained for why they still exist 5 million years later.

 

[Reluctantly]

I wish I could find the procedure. But I remember seeing a doctor keep a baby alive by making it breath oxygen through water. Apparently the lungs go through some kind of transitional phase where it can be made to breath water right after being born. I'll have to find it again.

 

[Reluctantly]

It was something like this. https://www.sciencedaily.com/releases/2006/04/060414015051.htm

Oh so i guess its not water but "Fluorocarbon". Well still interesting that the lungs can breath liquid.

 

[Auburn]

Good points!

One of the key points of Morgan's argument is that the traditional Savanna theory is questionable. She mentions that fossil evidence has been found that, during that time period the area shows lush, almost tropical plant life. Implying that we were already bipedal by the time our environment became a savanna.

But I admittedly can't seem to find many sources of that anymore, and most online articles say the environment was savanna-like. But here is one that points back 7 million years: Sahelanthropus. There's suspicion that this ancestor could have been bipedal already, which pushes back the origin of bipedalism into the miocene era. Africa is described in some places as being forest-like and rich in vegetation at that stage of our evolution.

How would walking in water be a positive selection pressure for walking? Walking on land as long as the negative selection was eliminated can all be explained by sexual selection. Apes that walk good like to have sex with other apes that walk good.

Well, for something as risky and initially disadvantageous as bipedalism, any ancestors making the transition would have been *worse* walkers, worse in locomotion altogether, and thus less sexually selected for. We've refined the design now, but the interim would have been horrible.

The species would have been selected for based on competence, speed, strength --- a bipedal-ish homonin would have been clumsy, stumbly, slow. Bipedalism causes problems in balance, more tendency to fall (and get hurt) and doesn't give the trade-offs of long marathonic endurance until way later.

So overall, it's a poor and ineffective strategy. And so, true, a females would have selected "apes that walk good" but that wouldn't be the quasi-bipedals. The most attractive mates would have been those that walked properly with four limbs.

Bipedalism happened because of an increase in intelligence. Being a biped is dangerous so only those bipeds that were smart enough to survive being in that position were able to live on.

This is a bit circular to me.
I think intelligence doesn't justify the bipedalism itself, as a sort of piggyback trait.

The advantages of bipedalism would have had to have their own "reason" for being advantageous to the intelligent apes. And the intelligent apes would have leveraged this advantage the most, and thus procreate, but what did bipedalism do that made them more at an advantage?

Was it peeking over the grass? Was it wading further into the water for brain-rich sea food (i.e. growing brain = intelligence) without drowning?

The body fat being 12 percent must have existed 5 million years ago. Yet why did being in the hot savannah not select against this feature? Why would having 12 percent body fat in the water benefit a biped in the hot sun for 5 million years?

This is a challenging one. I haven't found much support for why we've kept some of these traits for 5 million years. Sweating the way we do, losing so much water/salt, yet needing so much water daily, is terrible for survival.

But the savanna theory makes no more sense of this... so I think this is something I haven't seen either side present a good argument for. ):

 

[scorpiomover]

Wouldn't there be transitional fossils?

Also, how come humans didn't evolve gills or the ability to hold one's breath for 30 minutes, like other aquatic species? Would be really useful for aquatic apes.

 

[Auburn]

Wouldn't there be transitional fossils?

I think soft tissue doesn't fossilize very well, so it's hard to tell by fossils if we were already hairless/etc at the time we became bipedal.

But if we found evidence of early bipedal-transitioning hominin fossils surrounded by water life fossils, that would be solid evidence. So it can be confirmed.

Also, how come humans didn't evolve gills or the ability to hold one's breath for 30 minutes, like other aquatic species? Would be really useful for aquatic apes.

Well it doesn't seem mammals ever develop gills. Dolphins and whales didn't evolve gills in their transition to fully-aquatic, so it's likely not something we would've done either if we had stayed completely aquatic too.

But the hypothesis only suggests semi-aquatic adaptation, at a level slightly below seals or hippos. That's enough to produce a subcutaneous fat layer, hairlessness, and minor morphological changes like bipedalism and some webbing of hands/feet.

Also, I googled and our world record holders can hold their breath for 20+ minutes at a time! Wow o_o