The "aquatic ape" and the fate of eccentric hypotheses in science

Holly Dunsworth is a fine and responsible scholar and a highly knowledgeable paleoanthropologist. That's why we are delighted to have her occasional participation as a guest blogger on The Mermaid's Tale. In a recent post, she took issue with the 'aquatic ape' hypothesis, and staunch defenders of that hypothesis took issue back. The many blog hits that generated was nice, and strong debate, kept reasonable, is an essential part of science.

When someone suggests an hypothesis that is eccentric--off-center--to the mainline views of a science at any given time, it is received as a heresy, in just the way a new religious ideology is. Science has to defend its current beliefs if it is to be a coherent way to address questions in nature. In fact, from the point of view of responsible science, the vast majority of fringe hypotheses deservedly stay in the junkyard of wrong ideas. That's why they should be greeted skeptically.

The credibility, whackiness, or seriousness of new hypotheses has to be worked out over time. History is little guide. Wrong ideas, fervidly or even universally held, have had long shelf-lives in science: the four humors, trephanation, miasma. Some have come from the fringe to become mainline at least for a while, only to wither from lack of cogency: alchemy, phrenology, Freudian psychiatry. Others have started on the fringe and deservedly stayed there: astrology, hormesis, homeopathy, even while retaining at least some followers.

Hypotheses can eventually show that they have at least some truth. Acupuncture is an example. And of course a few have been resisted until expressed properly, or until enough really strong evidence develops, at which time they transform a field: evolution and plate tectonics (continental drift) are great examples of this.

Now, while one can never tell which idea will have legitimate staying power, one characteristic of those that come from left field and make it to home plate is that they are eventually supported by sufficiently strong, serious evidence that even skeptical peer reviewers have to begin recognizing. Typically, predictions based on the new theory are born out (as in evolution and plate tectonics).

The aquatic ape hypothesis must currently be viewed as a wild-guess Just-So story that got some attention in the popular press. It was apparently first promulgated in 1940, then pushed hard by Elaine Morgan for decades. The question of whether she is a qualified person to be taken seriously for such views may be part of the skeptical lack of credence given to her ideas by the mainline science club. As with other fringe ideas, the blogosphere is alive with advocates and critics, but in these media-saturated days the amount of attention given to such ideas is not a reflection of their credibility (to wit: creationism, Intelligent Design).

Scientists may be clubby, but we're (mostly) not idiots. Indeed, we all hunger to seize on a captivating idea. After this much time, if an idea deserves to be accepted as science rather than popularized speculation, it legitimately can be expected to have developed strong, consensus-building evidence to support it. Put another way, scientists cannot be faulted for their resistance in the absence of such evidence.

If that evidence ever is produced, it will have to be compellingly consistent with the wealth of evidence on hominid evolution that has accumulated since the hypothesis was first aired, which evidence should clearly and preferentially have supported the hypothesis's predictions. If such evidence does some day arrive, a lot of us will have to eat crow. It won't be the first or last time this has happened to the often self-satisfied mainline science.

On the other hand, when an assertive hypothesis is long maintained in the absence of clear-cut evidence, it can fairly be judged to be show business until it does better. If Morgan and her followers argued too strongly, and hence can't bring themselves to back down, too bad. They will have deserved to stay in the corner they zealously painted themselves into. That's what happened to much more qualified and distinguished scientists such as Linus Pauling (vitamin C miracles), Francis Crick (life here was seeded from outer space) and Peter Duesberg (HIV doesn't cause AIDS).

The burden of proof remains on them in the meanwhile.

The three of us who write this blog want it not to be a rant, but to be thought-provoking. That's why, despite having our own opinions, we generally try to stay out of the fervid creationism or scientific atheism blogogalaxies. We want to be open to new ideas and we certainly think the status quo or stupid antiscientific ideas should be challenged when they stray from what the best evidence shows. But we try to do that responsibly, and to stay within the evidence. In this case, you may or may not accept Holly's take on the aquatic ape hypothesis, but that's what she was doing, too, and she is an expert in her field.

Ken and Anne

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: http://www.aquaticape.org/

A website dedicated to supporting the Aquatic Ape (where you can find Hardy’s original paper): http://www.riverapes.com/