Thursday, October 22, 2009

Ignoring the Aquatic Ape Hypothesis

Humbled by the previous post, here's my contribution to this week's discussion on what science is and is not...

After the umpteenth friend sent me the link to Elaine Morgan’s TED Talk about the Aquatic Ape Hypothesis (AAH), I finally watched it today and I thought I'd share a few things that have been on my mind since last April.

That’s when the annual meetings of the American Association of Physical Anthropologists were held in Chicago. As usual, I heard many fascinating talks including one where I was accused of ignoring the Aquatic Ape Hypothesis.

It wasn’t just me. The speaker admonished the entire ballroom for ignoring the “best idea in science,” which explains uniquely human traits by hypothesizing that they evolved during an aquatic phase of our past. The AAH was first described in an article in New Scientist by Alister Hardy in 1960 and has been championed ever since by Elaine Morgan in her books and most recently in her piece in New Scientist.

The speaker explained how years ago he read about the hypothesis, fell in love with the "best idea in science," and then went to graduate school to work on it - not a wise framework for a research talk. You’re not supposed to be outwardly infatuated with your hypothesis. By doing so, the speaker removed a healthy amount of objectivity from his research. The audience was now suspicious, which was a shame for the presenter's sake because this was one of the few times someone had actually attempted to test the AAH. (The study measured locomotor efficiency of people walking in water. Yes, there are theoretical problems with this, but if done from an objective point of view, and with a well-designed study, it could be useful.)

Sure, you’ve got to be dedicated to asking the questions and to finding the best possible evidence to answer those questions. Why else would you toil away? But once you admit your personal bias toward one particular outcome, no one will take your results as seriously as you would like. They may even dismiss them out of hand. They may ask, how can we be sure that this person did not throw out all the data that falsified their idea?

Science can't move forward very well if we have to repeat everything that everyone does. So system checks, like upholding objectivity and enduring peer-review, are built into the scientific process to make sure knowledge advances effectively.

After celebrating a laundry list of scientific progress (e.g. realizing the heliocentric solar system, discovering the DNA molecule, walking on the moon), the speaker expressed his frustration with the paleoanthropological community. With all the time we have spent trying to explain the evolution of bipedalism, he asked us, why haven’t we found the answer to “why”? (Elaine Morgan took the same tack about human "nakedness" in her latest New Scientist piece linked above.)

My answer to his challenge is that it's not our failure, but the constraints on historical sciences. We will probably never know why the first apes walked upright. We will only come closer to knowing as we figure out what anatomical and genetic changes occurred, and in what sequence, during the process. With increasing knowledge about the paleoenvironments in which hominins lived, we will understand better the selective pressures they experienced, but it will be difficult to link these definitively to the origin of bipedalism (especially since it's just a continuum anyway... other primates already use bipedal postures and behaviors so what separates the first bipeds from those other guys isn't a whole lot!).

Paleoanthropology is not rocket science where you can control events in the present or future. We face an entirely different challenge: reconstructing events that happened millions of years ago. Do you think that some creature who lands on the moon millions of years from now and finds the astronaut bootprints and asks "why?" will guess that the answers are "because it was neat and to collect rocks and to put up a flag and to hit a golf ball (miles and miles and miles) and to beat the Russians, etc..."?

The how of moonwalking would be tough to piece together. But the why might be downright impossible to fully understand. And so far according to the evidence we’ve got to work with, the how of bipedalism is coming together but the why is pretty slippery.

Supporters of the AAH, like the presenter at the conference and like Morgan, are fond of claiming that the scientific community’s critical reaction is actually some sort of visceral, emotional, inexplicable, unfounded tantrum.

Here is one way of testing whether the problem that scientists have with the AAH is scientific or just some collective bias. What if somebody presented another idea, not the AAH, the way that the AAH has been presented? What if I presented something like this?

It’s mind boggling that nobody has figured out what the earliest ape looks like. Some of you think Proconsul is one, but others think it’s a monkey. What’s wrong with you? Well, when I read Alan Walker’s interpretation of Proconsul being an ape, it inspired me to apply to graduate school to work with him so that I could prove that Proconsul was an ape. So I did my dissertation on the feet and hindlimbs of some new fossils from Rusinga in order to show everybody what a great idea Alan Walker had about Proconsul being the earliest ape and not a monkey. Here’s what I did. And here are my results. Clearly Proconsul is an ape. Any questions?*

Would you like it if I had made a presentation like that? If your answer is no, then, along with a majority of the audience, some of whom were quite vocal, you probably wouldn’t have liked the AAH presentation that I heard at the conference.

The AAH gets much more play in pop culture than it does in classrooms or professional meetings. The audience’s charmed reaction to Elaine Morgan’s lovable personality during her TED Talk explains much of the AAH appeal.

I don’t intend to write a thorough or even partial critique of the AAH. John Langdon has offered one and there is an enormous website dedicated to critiquing it (both linked in 'Further Reading' below). But there are some points in Morgan’s TED Talk that are worth discussing here. Morgan lists five human traits that, according to comparative anatomy and behavior, support the AAH. (Morgan's evidence is in bold; my comments are in italics.)

All hairless mammals are aquatic or have aquatic ancestors, except for burrowing animals like the naked mole rat. What about elephants and rhinos you ask? New discoveries and interpretations of the fossil records for elephants and rhinos support her claim. Morgan lists pigs that wallow as part of her rule linking nakedness and water, but hardly anyone would suppose that selection for wallowing drove fur loss in pigs. And what about hairless cats and dogs? We managed to make them from a non-aquatic ancestor. Morgan says that people can always find exceptions to the rules in arguing against the AAH and I admit that I’m guilty of that. However, making hominins to be the only aquatic primate is a pretty big exception. So which is it: do we follow general patterns or do we take exception where it fits our preferred explanation?

Nonhuman primates walk bipedally to cross bodies of water or to feed while standing in water. They also walk or stand bipedally to do many other things on land, including threatening, mating, foraging, practicing vigilance, carrying things, and throwing.

Humans have a fat layer under the skin that is unique among monkeys and apes and is like whale blubber. Some other explanations for our fat layer have to do with feast/famine survival adaptations and with supporting our large expensive brain, particularly during infancy when growth is intense.

Humans can hold their breath on purpose and the only other animals, she says, that do this are diving animals and diving birds. She links this to speaking ability in humans (not the other animals) and it’s not clear which comes first, speaking or controlled breathing/diving. I’m sure it’s explained on one of the websites.

Humans have a “streamlined” body. Morgan asks us to imagine what a gorilla might look like diving into the water. This is supposed to illustrate how silly that sounds and, thus, how made-for-water we are. No one can deny that this is charming.

Next Morgan says that paleoanthropologist Philip Tobias, science philosopher Daniel Dennett, and naturalist Sir David Attenborough have all “come over” to the AAH. Although I do not doubt her claims, nor know what their positions are, I have noticed a pattern in what I have read on the internet; if anyone acknowledges any one of the AAH arguments, then they can be considered a convert. And when the hypothesis covers the full spectrum of hypothetical ancestors from fully aquatic all the way down to occasional aquatic forager, and this ancestor could have existed, seemingly, at any point along the hominin lineage, well that's a broad enough net to catch nearly every reasonable person.

This “us” and “them” perspective seems to be what's feeding Morgan’s beef with science - its metamorphosis into what she calls a “priesthood”.

From this perspective, it’s somebody else's fault that a hypothesis is weak, instead of first assuming that the hypothesis itself is flawed. Sure, people are vectors of science, but when a hypothesis doesn’t hold weight, it doesn’t mean then that the “priesthood” is out to get the hypothesis or its creator. If you're reminded of the Intelligent Design movement here, you're not alone.

Maybe someone clever could come along and change the fate of the AAH and Morgan is right to say so. However, in the meantime, a person must participate in the scientific process before they can criticize and analyze the evaluators (who haven’t had much to evaluate with the AAH).

Science is no different from most social animal play: You have to obey the rules to participate in the game. Then, if you don’t provide a feasible test or actually test a hypothesis, well, you’re going to sit the bench for a while. Everyone feels ignored until they score, or at least until they get on base.

*In the feet, Proconsul looks like both monkeys and apes, which is what you might expect to find in something that existed so close to the evolutionary divergence between monkeys and apes.

~~Thanks to Kevin Stacey for his terrific input.~~

Further reading

Langdon, John H (1997). Umbrella hypotheses and parsimony in human evolution: a critique of the Aquatic Ape Hypothesis. Journal of Human Evolution Vol:33 Pages:479-494

A website dedicated to critiquing the Aquatic Ape:

A website dedicated to supporting the Aquatic Ape (where you can find Hardy’s original paper):


Unknown said...

Also, proboscis monkeys are swimming fools and are neither habitually bipedal nor naked, and there's no obvious indication that they're evolutionarily "moving" in that direction...

Holly Dunsworth said...
This comment has been removed by the author.
Holly Dunsworth said...

It probably explains the evolution of their big snorkely noses.

Holly Dunsworth said...

Up, see, I'm joking about it like she said.

Holly Dunsworth said...

anthrobrew said...

I'm not familiar with the aquatic pachyderm hypothesis (and too lazy to look at the moment) but is the story that elephants, rhinos, etc. went through an aquatic phase after they split from their whooly relatives that lived until a few thousand years ago? And each separately?

Holly Dunsworth said...

Furry swimmers: (great soundtrack!)

Holly Dunsworth said...


Holly Dunsworth said...

...and I'm not familiar with the rhino aquatic ancestor she mentioned.

Ken Weiss said...

I can't swim worth a damn and don't float very well. But, apparently, my ancestors were 'fit' or I wouldn't be here. Ironically, unless it's a myth, Africans are said not to be as good in the water as other 'races' because (I think this is the reason) they have higher bone density and hence don't float as high.

The next hypothesis will be the 'fallen angel' hypothesis: We are--or were--so noble that we were angelic and had wings. But then we (well, it was Eve, actually) sinned. Our wings fell off, and we tumbled east of Eden. The embryological evidence is a ruse: it seems to suggest that we are of quadruped stock. But look at the little bumps on our scapulae (shoulder blades); they are the vestigial wing connectors.

More proof of the fallen angel hypothesis is that we like feathered animals (birds, to the uninitiated). Indeed, I just had a chicken burrito for lunch!

Marcel F. Williams said...

First of all, is there any evidence of semiaquatic hominins or hominoids in the fossil record?


The aquatic plant eating swamp ape, Oreopithecus bambolii, frequented wetland environments on the late Miocene island of Tuscany-Sardinia probably for nearly two million years.

Secondly, is there any evidence of a semiaquatic marine phase in human evolution?


Humans are the only catarrhine primate (old world monkeys and apes) that have kidneys with multipyramidal medullas. Medullary pyramids are nearly universal in marine mammals but are also found in freshwater mammals who appear to have had marine ancestors and in some terrestrial mammals who also appear to have had semiaquatic marine ancestors.

But most terrestrial mammals and all other catarrhine primates have kidneys with unipyramidal medullas.

Multipyramidal kidneys are an adaptation to foods with extremely high salt content in environments where there are no isotonic or hypotonic sources of fresh water.

Algis Kuliukas said...

First a correction. The actual words I used about Hardy's idea was "most carefully thought out idea in science" based on the fact that he'd sat on it for 30 years. I accept that this is a bit of a stretch. I should have qualified it with " about human evolution since Darwin."

Now, the first ppart of this "critique" is bent on discrediting me simply because I admit to taking the idea seriously unlike the sneering community of anthropologists who seem to have decided it's bullshit pseudoscience purely through gossip in the corridors (but through almost nothing in the published literature.)

If this is the worst you can throw at me, I'll take that gladly.

If aanyone wants to hear the talk itself (albeit in very pool sound quality) they can find it on You Tube.

John Langdon's critique is itself a straw man portrayal of the AAH. Claiming the savannah theory was an invention of Elaine Morgan is simply incredible. Putting it under the same umbrella as Von Daniken betrays an apalling lack of discrimination. Listing 26 "aquatic" ideas equally and dismissing them in a sentence does not do justice to Elaine Morgans books. The wading model of bipedalism, for example, was rejected in a couple of sentences simply by arguing that a brachiationist model was better for small primates. Not one argument against wading was offered. This was typical.

Talkingg of "straw man" your critique of Elaaine's TED talk is exactly that. You pick the bits you think you can find holes in but ignore the elephant in the room - humans are by far the best swimmers/divers of all the apes and the one place you can guarrantee apes will move bipedally is in waist deep water.

Algis Kuliukas

Holly Dunsworth said...

"Pool sound quality" was quite the perfect typo.

Jason Hodgson said...

Are there any peer reviewed publications addressing the AAH at all?

Holly Dunsworth said...

Ken Weiss said...

Listen, this is all very silly. Unbeknownst to everyone (including, strangely, Elaine, this is a huge misunderstanding due to a typographical error that still hasn't been resolved.

It's either the Naked Apothecary, the Naked Alchemist, the Naked Astrologer, or (most lurid of all!), the Naked Aperture.

Now, I'm sure our anthropoid ancestors had various apertures, and this must be the truth behind what is otherwise a very suspect Just-So story.

Algis Kuliukas said...

@Holly, I thought the "aquatic ape" was "thankfully dead"? It might make you feel happy to be sneering at an idea that you clearly have never made the slightest effort to understand but I don't think it will do your reputation any good.

@Jason My web site has some links.

You might also try this...

Roede et al (1991) is still the one balanced (if polarised) account in the literature. We're publishing an update of that later this year for the 50th anniversary of Hardy's idea which is TODAY.

50 years of potentially the best idea about human evolution since Darwin and anthropologists have done NOTHING but sneer/ignore at it. Doesn't it make you proud?

@Ken... Yes, very silly. They (for there are more than one) should have been labelled "Waterside Hypotheses of Human Evolution".

Holly Dunsworth said...

@Algis, I'm sorry that what I wrote upset you. I left your name off to avoid embarrassment. Most people who read this blog had no idea that I was describing you until you posted. I stand by my critique of your presentation. I thought it made a really good blog considering what we try to do here. I'm sorry that the subsequent critique of the AAH also upset you personally. It is hard for me to understand someone getting so emotional about a hypothesis that in my eyes can never be falsified. I realize now that the way that I discuss the AAH is offensive to those that do seem to have a personal investment in it. I hope you noticed that I supported your research in my post. The beauty of science is not only that it's fun but that, "Maybe someone clever could come along and change the fate of the AAH" and maybe that someone is you! Cheers.

Holly Dunsworth said...

The "thankfully dead" that Algis quotes is from a naive comment that I made as a graduate student.

Algis Kuliukas said...

@Holly. Hey I'm not upset. Not personally, anyway. See, when you have the audacity to actually expect some science to be done before ideas get rejected, it's usually laudible. Except when the idea is the damned "aquatic ape" then, apparently, you're supposed to just accept the wise words of older anthropologists and accept it's bullshit pseudoscience. I've never done that. I've always thought "hey, what's wrong with this idea?" So I thought if none of you guys are going to do any science (scared of being laughed at when submitting the proposal, no doubt) maybe I should. After all, I have no precious reputation to worry about. So I returned to academia, got a Master's from UCL and started a PhD. Despite all this, I get sneered at all the time from you guys. But, hey, what did I expect?

I am upset only by the astonishing self-righteousness of a field of supposed scientists in dismissing a really good idea on the basis of gossip.

Tell me, Holly, is Nancy Tanner's "phallic display hypothesis" falsifiable in any way? Because you may know it's in the literature as another respected idea (out of around 40). What about Wheeler's thermoreg idea, or Lovejoy's Provisioning hypothesis or Jablonski/Chapman's "Threat display" idea. Please be honest: the wading hypothesis is no more, or less falsifiable than any such idea.

In addition, however, it has a number of overwhelming feactors in it's favour.

Place a group of chimps in waist deep water and they WILL ALL move (and not just pose monetarily) bipedally for as long as the condiitons prevail. This is the only model that would actually kill a would-be quadruped.

I have no personal investment in this idea. I just expect professional scientists to do their job and use science, not gossip, to dismiss things.

The thankfully dead comment, actually, was from your recent book review of Jablonski's "Skin".

“Although warranted, some of Jablonski’s arguments against aquatic ape theory are odd (p. 40). If per chance ancient hominins were adept swimmers, surely their “long gangly arms” would have been useful, not harmful. Just because aquatic ape theory is (thankfully) dead we should not overlook the possibility that ancient hominins dipped, waded, and wallowed to stay cool like we and many other mammals do.” Dunsworth (2007:34)

Dunsworth, H. Skin: A Natural History Nina G. Jablonski. Paleoanthropology :24-25, (2007).

It's great in that review that you aimed to correct Jablonski for her oberly harsh dismisaal of "all things aquatic". I think the problem's been in the label - "aquatic ape" and that it hasn't ever been defined very carefully.

I define them (plural) like this:

Waterside Hypotheses of human evolution: A set of related idea that propose that the lineage leading to humans has been exposed to greater selection from wading, swimming and diving than the lineage leading to our great ape cousins and that this slight shift in selection may explain the remarkable phenotypical differences between us.

No need for "mermaids" as a simple fact from population genetics shows us that even very slight selection can make profound differences in relatively short evolutionary timescales.

Algis Kuliukas

marc verhaegen said...

There are some recent publications on the Littoral Theory (commonly known as AAT) that Pleistocene Homo populations colonised different continents & islands (even Flores >19 km oversea >800 ka) along the coasts & from there inland along the rivers, where they collected aquatic & waterside foods, including shellfish, seaweeds, ungulates drowned or caught in mud or shallow water, stranded whales, cattails, cane etc., eg,
- M Vaneechoutte, A Kuliukas & M Verhaegen eds 2011 ebook Bentham Sci Publ (with contributions of prof.Tobias & Elaine Morgan etc.) “Was Man More Aquatic in the Past? Fifty Years after Alister Hardy: Waterside Hypotheses of Human Evolution”
- M Verhaegen & S Munro 2011 HOMO, J compar hum Biol 62:237-247 “Pachyosteosclerosis suggests archaic Homo frequently collected sessile littoral foods”
For more info, please google “econiche homo”, “aquarboreal”, “pachyosteosclerosis”, or send me an email.

Holly Dunsworth said...

Thanks Marc!

Holly Dunsworth said...

... and to measure the distance from Earth to moon by reflecting light off a tiny implant on the moon...

Delray said...

If you are judging her behavior - a lot of people need to loosen up. she seemed to be saying - AAH is not a new idea and it has yet to be properly investigated. In any case, that's all I heard.

The older you get the easier it is to fall into the habit of shaming people into thinking in a different way - It works in RL, with children and it does get harder and harder not to see children all over the place. I know I am guilty of that way too often - and it never fails that people of an opposing prospective or just never thought about a given idea themselves, to resent being shamed. Here's where I would normally something like "suck it up sunshine until you have some facts you are just whining" which is meant to be funny but no one ever gets the joke.