Aquatic Ape Theory: Another nail in the coffin

Posted by Greg Laden on January 6, 2013
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gorillaInWater

I just want to say that Huxley is pretty bad at swimming.

I quickly add, for a 3 year old human, he’s pretty darn good at it. Amanda’s family is very aquatic, as tends to happen when everyone spends several weeks per year (or longer) on the edge of a lake. They can all ski really well, they can all swim really well, etc. etc. So, very soon after Huxley was born, his grandfather started to bring him to age-appropriate swimming lessons. He is now 37 months old and has been to a swimming lesson almost every week. In addition to to that, Amanda brings him to the pool pretty close to once a week, often more. In addition to that, during the summer, he has spent several days at the lake and gone in once or twice almost every day the conditions allowed. In short, he should be about as good a swimmer as any 3 year old.

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And he is. In fact, better. He is far beyond his age to the extent that he’s skipped grades, and the people at the swimming school have to keep making adjustments in order to ensure he is always getting the next level of training rather than being held back by the other kids who are not as good as he is.

But still, this means he can drag himself underwater for several bananas (the unit of time used by swimming instructors, apparently), and he can thrash around moving his body across the surface several inches in a predetermined direction. He can get himself to the bottom of a pool as deep as he is tall and easily pick up a ring or some other object, and he can float around in various positions comfortably.

So he swims better than a new born through 1 month old hippo (they can’t swim at all, really) but he’s nowhere near as good as dolphin. But the thing is, this is after three years. Had Amanda and I been aquatic apes, Huxley would not have survived to this ripe old age. The diving reflex, proffered as evidence for an aquatic stage, during which we spent considerable time in (not near, in) water, happens in mammals generally and alone is not enough to count as a retained adaptation suggesting an earlier evolutionary stage. If human ancestors subsequent to the split with chimpanzees went through a significant aquatic phase (not just living near water, which is one of the backpedaled versions of the AAT) then our children would probably … not necessarily but probably … be much better at swimming than they are.

This does not disprove the Aquatic Ape Theory. Nor does a single nail secure a coffin. But it certainly does not inspire confidence in the idea.

Huxley tells me that he plans, someday, to teach me to swim.

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  1. #1 Randy Owens
    January 6, 2013

    “He can get himself to the bottom of a pool as deep as he is tall and easily pick up a ring or some other object….”

    Always a useful job skill for any aspiring troglodytes.

    Also, is ATT a typo for AAT, i.e. Aquatic Ape Theory, or is it something else, which I don’t recognize?

  2. #2 Greg Laden
    January 6, 2013

    Aquatic troglodyte theory?

  3. #3 Keith M Ellis
    Kansas City, MO
    January 6, 2013

    My understanding — correct me if I’m mistaken — is that pretty much in every way in which the aquatic ape theory has been seriously examined, it’s fared badly.

    That said, I’d quite like heavily-researched, essentially “proved” evolutionary explanations for two fascinating questions: our relative extreme lack of fur and our relatively (among primates) unusual facility submerged in water.

    Are there good, strong explanations for the former that I’m not aware of? And in the latter case, is the consensus that it’s not unusual enough to be a puzzle with a likely clear solution?

  4. #4 Steven DuBois
    January 6, 2013

    Kenneth Ellis,

    I’m no researcher, and I haven’t studied evolutionary biology extensively, so I’m quite likely wrong, but for what it’s worth:

    I’ve heard and read that one explanation for human hairlessness is due to thermoregulation required for running, which other apes don’t do.
    It makes intuitive sense to me, but I have no idea whether it’s true.

  5. #5 Greg Laden
    January 6, 2013

    Hairlessness could be simply due to the fact that a vertically oriented mammal in the tropics can’t cool efficiently. The idea of running being a factor was suggested in the 80s by carrier and more recently re-suggested by Lieberman. It could all be true to some level.

    I don’t know that humans have special underwater abilities. Some humans can hold their breath for longish periods of time, but when you look at humans in relation to all aquatic mammals we’ve got nothing. Comparing us to apes would only be fair if we got some chimps to practice holding their breath from a very young age to see what they could do if they grew up like those people in certain places who have this as part of their culture.

    We may well have better abilities in this regard but there are two things that have to be considered:

    1) Human activity is generally more aerobic than chip activity, so maybe we have slightly enlarged lulngs.

    2) If we do have enlarged lungs it doesn’t show up as far as I know when we compare ape and human organ sizes (though maybe a little, I’m not sure, but certainly not a lot) but what is different is our relative muscle mass. It is very very low, so maybe we have much less minute-to-minute demand on O2 from the lungs for that reason… but…

    3) Our brains are very demanding of O2, which probably counteracts that.

  6. #6 Keith M Ellis
    Kansas City, MO
    January 7, 2013

    Thanks, Greg.

  7. #7 Jeffrey
    Canton
    January 7, 2013

    My 2 cents worth is that as suggested above hairless ness evolved along with persistence hunting. I’m a bit amazed that our muscle mass is relatively low compared to other primates. Makes sense tho since they workout every day as part of their daily lives, and we typically don’t need much muscle mass especially since machines do most of the work for us. What I really find weird is that primates lost the ability to make their own vitamin C. Could it really be so expensive to make that evolution weeded it out, considering how important C is? I guess so….. Another point for Darwin !!!!

  8. #8 Greg Laden
    January 7, 2013

    Vit. C production (not all of it, just some of it … it is used in different systems) did not have to be expensive to go away, it just has to be totally obviated by diet. The cost may have been an issue, but I’m guessing not.

  9. #9 sailor
    January 7, 2013

    The Aquatic theory was always a crock. But the fun of Elaine Morgan’s original book was its take down of the Naked Ape which was hilarious.

  10. #10 anthrosciguy
    January 7, 2013

    A few bits on hair and evolution. First, the AAT/H claim has never really made sense; it’s always been a naive and unsupported speculation based on a naive and faulty analogy — that we’re similar to (usually unnamed) “aquatics”. But our hair characteristics aren’t like those animals at all, and the fact is that we’re extremely dissimilar to any of the hairless aquatic and semiaquatic mammals. It also turns out that hairlessness is a relatively unusual condition for semiaquatic mammals, and even more so when you look at how often it evolved in such mammals. A couple years ago I did a page on my website dealing with that subject: Aquatic and semiaquatic mammals.

    On how and why we evolved the hair characteristics we have, I’ve been an adaptationist as most people are when they start thinking about this, but I’ve realized (thanks to Larry Moran’s constant prodding) that this is something that needs proving beyond just looking at what we think are good reasons for doing “X”. We do find that our body hair is good for efficiency in sweatcooling, due to the simple effect of physics — sweat cools better than if it evaporates closer to the skin. And we see differences between the sexes that suggest sexual selection. But these things being true doesn’t necessarily mean that this is why we are as we are. It could be drift. The helpful effects regarding sweatcooling could be a spandrel. This is not something I accepted easily, but the more I’ve thought about it the more I see the possibility.

    First, we have some idea now about when our body hair changed from studies of lice genetics, and it’s approximately a million and a half years ago (there are some other much later lice dates as well that may show the use of clothing by our ancestors). And my first thought was that this indicated selection, going along with a generally rangier body and much more widely ranging hominids. All suggesting heat tolerance via getting rid of heat better. But it was also, due to brain size increases around the same time, probably when our secondarily altricial infancy popped up. I used to think this clinched the adpatationist scenario, showing the mechanism and the heat business (and at some point sexual selection) as the selection. It’s possible that this is it, but I no longer think it’s a sure thing, because I’ve thought more about drift.

    If our secondarily altricial infancy led to a mosaic of neotenous features (and it did, didn’t it) it could rather easily include hair changes. These hair changes could have nothing to do with selection for them, but rather a side effect of birth, infancy, and bigger brains. The changes in development would cause changes in hormonal control and this could easily affect a big change in hair without actual selection for that specific change, just as a spandrel from our becoming secondarily altricial and resultant (mosaic) neoteny (both our altricial features and our neoteny are mosaic, affecting some features and not others). This could also mimic sexual selection due to sex differences in hormones, a point I didn’t grasp in the past.

    Hair changes are simple and easy in an evolutionary sense. For instance, all the variations in dog’s coats texture and length is due to just three genes, and there are indications that this is also so in mice, cats, and humans. We also see how easy and quickly these things vary by looking at the variation in our own species.

    Bottom line: our hair characteristics could be due to selection, but using the null hypothesis of drift we can easily build a scenario where drift caused these changes, and any helpful effects are a spandrel. So to determine that it is due to selection requires more proof than we have so far, and frankly, more than people seem to be trying to provide (Larry Moran’s basic ongoing rant on the overall subject of drift and selection).

  11. #11 Jeffrey
    OH-
    January 9, 2013

    Makes sense – the ability to lose C was lost with an abundance of citrus fruits etc. for early man to ear. I always assumed a cost had to be involved so this may explain some other similar instances for me. Thanks, Greg

  12. #12 PitPony
    January 10, 2013

    The clue to your scepticism is in your last sentence.
    You do not need anyone to teach you to swim.
    As a 9 year old I started going to the pool with a some other non-swimmer kids. As we got confident in the water the swimming thing just came naturally.

  13. #13 Stephen Munro
    Australia
    January 10, 2013

    Greg, I think it’s interesting – your three year old son can perform tasks that could probably allow him to collect shellfish in relatively shallow waters, and yet you see this as evidence that humans could never have evolved by performing such activities.

    You base this on the fact that since your son has had regular swimming lessons, been taken to the pool regularly by his mother, and enjoyed several days a year by a lake, and he doesn’t yet swim as well as a dolphin, the AAT must be wrong.

    Well, I did some quick calculations, and not counting the half of his life when presumably he’s been sleeping (or at least you and your wife have wanted him to sleep), and allowing two hours every single week of his life for swimming lessons and pool visits, and five hours for seven days of his life every summer, he has spent approx. 3% of his waking time exposed to water, and I guess that’s probably an over estimation. Now, that of course means he’s spent close to 97% of his waking time on a terrestrial substrate. So, my questions to you is, what’s your son like at endurance running? Surely, with close to 100% exposure to terrestrial substrates for his whole waking life, he’d just about be ready to chase down antelopes on the open savannah by now, wouldn’t he?

    But seriously, you say: “Had Amanda and I been aquatic apes, Huxley would not have survived to this ripe old age.” But I really don’t understand this statement. Why wouldn’t you and your wife be able to look after your son on a tropical beach? Surely while you or Amanda were foraging for food in the shallows or along the beach, the other could be minding Huxley, and even when he went into the water you or your wife could surely be there to make sure he didn’t get into trouble, couldn’t you? And if you did live 100% of the time on a tropical beach, rather than the 3% of time he’s been exposed to water as a modern child, perhaps Huxley would have spent closer to 50% (perhaps even more?) time in the water, and since there is evidence that Homo erectus (according to the comparative data, probably the most aquatic hominin: google, e.g., pachyosteosclerosis archaic Homo), developed significantly more quickly than Homo sapiens, there’s a good chance that Huxley would have been significantly more advanced physically at this age than he is as a modern child, and therefore would have been even more adept in terms of floating, swimming and diving.

    In short, I don’t see any reason why your son’s inability to swim like a dolphin at age three after being exposed to water for about 3% of his waking life, is a nail in the coffin of the idea that human ancestors once foraged part time in relatively shallow waters along tropical beaches for sessile and slow moving foods such as shellfish.

    The aquatic theory need not be as radical or extreme as you imagine. Regular part-time foraging in relatively shallow waters for foods that don’t run or swim away. I’m sure even Huxley can see the logic in this.

  14. #14 Greg Laden
    January 10, 2013

    Stephen, yes, I did think of that and you are right that a true aquatic family would have the little one in the water all the time. Nonetheless, he didn’t show the kind of innate skill I would expect if there was a behavioral fingerprint from an aquatic ancestry. Do note that I pointed out that this does not disprove AAT, but it does fail to support it.

    I’m not actually imagining the AAT as being anything in particular. I’m going off of how it has been characterized by its supporters.

    I do think that if the AAT suggests that humans need water to drink and that some populations also foraged for aquatic food or resources that tend to be riverine, it isn’t in any way a departure from “non AAT” thinking.

  15. #15 Greg Laden
    January 10, 2013

    We are hoping, by the way, that Huxley will grow up to be a great swimmer so we can live off his endorsements following his Gold Medal wins. When that happens, he’ll probably enjoy looking back at this conversation!

  16. #16 anthrosciguy
    January 12, 2013

    Note that AAT/H proponent Munro engages in extremely blatant strawmanning while simultaneously falsely accusing others of it . Sadly, in my experience this is normal from kost of the idea’s proponents.

    Also note that it’s certain ly true that most human three year olds “can perform tasks that could probably allow him to collect shellfish in relatively shallow waters” since this is called “walking (or even crawling will do it). Most shellfish collection isn’t done in shallow waters at all, but on shorelines near them. How this then provides selection for convergent evolution to gain us (supposedly) the characteristics of cetaceans, pinnipeds, and sirenia is unexplainable.

  17. #17 Stephen Munro
    January 12, 2013

    I sincerely hope so, Greg, on both counts :-)

  18. #18 Stephen Munro
    January 12, 2013

    :-) No, anthrosciguy, how ‘drift’ explains characteristics of cetaceans, pinnipeds, and sirenia is unexplainable.

  19. #19 Radical Rodent
    January 13, 2013

    By the time I was three, I could “swim like a fish” (according to my mother, but she may have been biased). We lived on a tropical coastline, so I was in the sea if not daily, certainly for several hours a week. I had no fear of water, and was quite competent at getting about, mostly underwater, as I had yet to learn the techniques. It has been shown that new-born babies have no fear of water, and know to hold their breath underwater; in other words, human DO have an inherent ability to swim (granted, not as well as dolphins – but they do have a design advantage).

  20. #20 Greg Laden
    January 13, 2013

    Radical, the newborn behaviors of humans in water is the same for mammals generally.

  21. #21 somitcw
    January 13, 2013

    Greg Laden, I can’t comment about all mammals but our three closes relatives are bonobo, chimpanzee, and gorilla.
    They don’t swim. They don’t have human-like breath control.
    They don’t have a fat layer that allows them to float.
    If you drop any in a pool, they sink like a stone.
    The Congo river has kept bonobos and chimpanzees apart for hundreds of thousands or millions of years.
    Unlike them, humans can swim seconds after birth.

  22. #22 Radical Rodent
    January 14, 2013

    I do enjoy learning new things, even if it shows that what I thought I knew was wrong.

  23. #23 marc verhaegen
    January 14, 2013

    Some comments in a hurry:
    - Human newborns in & outside the water behave very differently from most other mammals, eg, google “Dirk Meijers Homo litoralis” (Dirk is one the speakers at our conference in London May 8-10, see link below). Moreover, human premature newborns have a “vernix caseosa (google), which is elsewhere only seen in common seal pups. Moreover, human newborns have “renculi” (google), which are typically seen in aquatic mammals. Etc.
    - Gorillas can swim very well (at the surface), eg, google “gorilla Mbeli bai” or “gorilla Ndoki bai” or so. Early hominoids were “aquarboreal” (google), ie, they lived in flooded/swamp/mangrove/coastal/gallery forests, where they spent part of their time in the branches & part in the water, but they were predom.surface-swimmers (lowland gorillas & sometimes chimps still feed on floating vegetation), whereas our Pleistocene ancestors were excellent divers for bottom foods, when they dispersed along the coasts (& from there along rivers) to different continents & even islands.
    - Fat layers are not for floating, but rather for thermo-insulation in medium-sized non-tropical mammals. In fact, they hinder diving in littoral mammals (therefor slow & shallow divers need heavy skeletons to descend & to stay below, just like human divers (after we lost this “pachyosteosclerosis” (google)) often carry weights.
    - I’ll soon send here a brief but +-complete picture of ape & human evolution IMO.
    http://tech.groups.yahoo.com/group/AAT
    Human Evolution Past, Present & Future
    Anthropological, Medical & Nutritional Considerations. London May 2013.
    http://www.royalmarsden.nhs.uk/education/education-conference-centre/study-days-conferences/pages/2013-evolution.aspx
    Was Man more aquatic in the past?
    http://www.benthamscience.com/ebooks/9781608052448/index.htm

  24. #24 somitcw
    January 14, 2013

    Marc Verhaegen, I could not find your reference to a gorilla swimming but suspect that it is just a definition difference.
    Chimpanzees love to soak in the river but they stay next to the shore and hold onto branches so they don’t drown. Just like the Congo river that has kept chimpanzees and bonobos separated for possibly one or two million years, it has also kept gorillas on the chimpanzee side of the river. Zoos use moats to enclose gorillas and chimpanzees and it appears to work well. Human fat is lighter than chimpanzee muscle and bone so humans are less likely to drown.
    The only great ape that normally swims is human. Well there was one island great ape in Borneo or Sumatra that was seen swimming but that wasn’t a bonobo, chimpanzee, or gorilla. It also had some breath control and air sacs.

  25. #25 Calli Arcale
    January 15, 2013

    somitcw:

    They don’t have a fat layer that allows them to float.
    If you drop any in a pool, they sink like a stone.

    Humans do too, unless they have been taught to swim. You have to be pretty obese for the fat layer to make much of a difference; it’s really your *lungs* that provide the most buoyancy. So if you didn’t get a good breath before going under, bye-bye…..

    I trained as a lifeguard; they teach you just how shockingly fast drowning happens, even in people who *do* know how to swim, and that it is completely unlike what you see in the movies. Humans do have a drowning reflex. It is extremely powerful, and also extraordinarily counterproductive (being mostly “flail about to try to find something to climb”), so I don’t think there could’ve been much evolutionary pressure to develop a good drowning reflex.

    marc:

    Fat layers are not for floating, but rather for thermo-insulation in medium-sized non-tropical mammals. In fact, they hinder diving in littoral mammals (therefor slow & shallow divers need heavy skeletons to descend & to stay below, just like human divers (after we lost this “pachyosteosclerosis” (google)) often carry weights.

    Divers wear weight belts because they are wearing wetsuits, which are very buoyant. It’s very hard to dive while wearing one. Meanwhile, human fat layers do not offer much insulation — which brings us to why the divers are wearing those wetsuits. It’s not just because they look snazzy. It’s because it’s cold down there.

  26. #26 hobgot
    January 15, 2013

    Firstly I think that humans are aquatic apes, because we are easily the most aquatic of apes. However I also think it highly probable that we are aquatic because we were bipedal and not the other way around.

  27. #27 marc verhaegen
    January 15, 2013

    I not necessarily disagree, Calli, only a few comments:
    - Japanese shellfish divers (Ama) held weights during descent (with a helper in a boat), but did’t wear wetsuits (eg, Hong & Rahn May 1967 Scient Amer).
    - Human SC does offer a lot of insulation, esp.in trained swimmers (eg, Pugh & Edholm 1955 Lancet 6893:761-8).
    - Our littoral ancestors (before the sapiens LCA) probably lived at warmer coasts, eg, Red Sea or Ind.Ocean (but Neandertals lived at more temperate seas & rivers).

  28. #28 somitcw
    January 15, 2013

    Calli Arcale, You posted:
    >somitcw:
    >>They don’t have a fat layer that allows them to float.
    >>If you drop any in a pool, they sink like a stone.
    >Humans do too, unless they have been taught to swim.
    >You have to be pretty obese for the fat layer to make
    >much of a difference; it’s really your *lungs* that provide
    >the most buoyancy. So if you didn’t get a good breath
    >before going under, bye-bye…..

    I have always been able to lay back, cross my arms, and float for as long as I felt like. Perhaps I could try an exhale enough to clear my lungs to sink? I have normal weight and breath normally to float.

    If I needed to swim twenty feet down quickly, carrying a stone or pulling on a rope would be much faster than using my arms and legs for propulsion so would give me more time down there. Japanese divers knew what they were doing.

    If none of our ancestors were littoral, when did we morph to become so well adapted to water? Did we get the breath control, floating ability, natural swimming muscle coordination, nose shape, and other adaptations at the same time or separate? Could it all be convergent evolution to become aquatic?

  29. #29 anthrosciguy
    January 17, 2013

    “No, anthrosciguy, how ‘drift’ explains characteristics of cetaceans, pinnipeds, and sirenia is unexplainable.”

    Of course I said nothing of the sort. Yet another case where Munro strawman’s another’s comments while falsely claiming AAT/H views are being strawmanned.

  30. #30 OHSU
    USA
    January 18, 2013

    Since this is a science blog, let’s talk about the scientific method a little.

    In its most common form, the AAT is adaptationist and environmentally deterministic. In other words, it proposes that various human features are specific adaptations to a specific environment.

    The null hypothesis for any adaptationist hypothesis must necessarily be exaptation. In other words, if you want to test the idea that feature X is an adaptation, you have to generate an experiment to test and falsify the idea that feature X is just an evolutionary spandrel.

    And the null hypothesis for a proposal of a specific environment would be that the feature is not specific to that environment. In other words, the null for the hypothesis of aquaticism would be that the proposed feature are actually terrestrial adapations.

    No AAT proponent has ever shown the tiniest hint of grasping the scientific method or how to go about providing evidence for their fantasy. Specifically, none has ever shown any understanding of null hypotheses or falsification.

    Like all good pseudoscientists, their arguments are full of methdological flaws, psycological biases, and circular reasoning. Most obviously, they rely heavily on confirmation rather than refutation. Specifically:

    – Many of their assertions do not admit the logical possibility that they can be shown to be false.
    – And many AAT proponents take the angle that any of their claims that can’t be shown to be false must be accepted as true.
    – Many of their “predictions” are things that the theory doesn’t logically predict.
    – Proponents rely on “testimonials”, or untestable first-hand anecdotes or personal experiences.
    – Proponents engage in selection bias; presenting only details that seem to support their claims and completely ignoring the vast majority of the evidence (such as the entire fossil record) which doesn’t support their claims.

    All of their arguments boil down to:

    1) Feature X looks aquatic to me. Therefore it is.
    2) I can imagine scenarios in which feature X might have evolved for aquaticism. Therefore it did.
    3) You can’t prove that feature X isn’t aquatic. Therefore it is.

    One of the most obvious ways in which the AAT is pseudoscience is the circularity of its argumentation:

    “Humans swim better than chimps because we went through an aquatic phase. Evidence that humans went through an aquatic phase is that we swim better than chimps.”

    It never gets any more sophisticated than that.

  31. #31 Stephen Munro
    January 18, 2013

    OHSU, you say:

    “And the null hypothesis for a proposal of a specific environment would be that the feature is not specific to that environment. In other words, the null for the hypothesis of aquaticism would be that the proposed feature are [sic] actually terrestrial adapations.”

    My question to you is why should the null be terrestrial? Isn’t this being equally “adaptationist and environmentally deterministic”?

  32. #32 Stephen Munro
    January 18, 2013

    Sorry anthrosciguy, when you said “Bottom line: our hair characteristics could be due to selection, but using the null hypothesis of drift we can easily build a scenario where drift caused these changes, and any helpful effects are a spandrel.” I assumed you were advocating a scenario where drift caused our nakedness (a trait we share to a certain degree with some, but by no means all, aquatic mammals).

    You say drift may have caused the change, OHSU says the null hypothesis should be terrestrial, AAT proponents say water is a better explanation. Perhaps we’re all wrong, but only one model, as far as I can see, is backed by any comparative data. In other words, while the AAT uses the scientific method (Hardy OBSERVED that humans had a combination of traits similar to certain mammals that spend considerable time in the water – more subcutaneous fat and lack of a functional fur covering – and asked if human ancestors may have also spent more time in the water), the idea that drift caused the changes by its very nature ignores the comparative data, and the terrestrial model is even less supported (no fully terrestrial mammals are fat and naked to my knowledge).

    I’m not concerned that you disagree with the part-time underwater foraging model, anthrosciguy and OHSU, but if you want to put forward alternatives such as drift or terrestrialism, at least put forward some supporting evidence to back your arguments up.

  33. #33 somitcw
    January 18, 2013

    OHSU, I am adapted to water. I can swim faster, swim longer, swim deeper, float longer, and hold my breath longer than any non-human great ape on the planet. Sixty years ago I could do the same. I’m not a good swimmer compared to most other humans.
    How did I become so well adapted to water?
    Was it because:
    1. All of my ancestors were blocked from getting near water?
    2. Because some ancestors did have access to water?
    3. For some other reason that is unknown at this time?
    I cannot prove that the theory about how we became more aquatic than other great apes is the most reasonable speculation or not. If it is not a reasonable theory, is there a rival theory that would explain it? I’m not a scientist so please keep the description simple.

  34. #34 Chak
    January 20, 2013

    Interesting post on your first-hand observations. I also wonder why we need so much training (I am a poor swimmer), while other mammals can do that instinctively? Doesn’t it contradict the very premise of the AAH?
    But I think comparing to dolphins is unfair (I know you said that jokingly), that’s like saying that sea otters don’t swim as good as dolphins and thus cannot be considered aquatic. Also saying something “happens in mammals generally” is only part of the story.

    Here are the facts about our swimming / diving abilities as I know.

    - Most mammals (e.g. monkeys, dogs) can swim instinctively because when afloat, their head is already above the water surface. Apes, due to anatomical changes for bipedality, have no such advantage, and the logical consequence is to drown. So we are relatively poor swimmers (need much training) not because we are humans, but because we are apes.

    - Comparing to other apes, we are already good swimmers. There are reports of gorillas and orangutans swim in their natural habitats, chimps trained to dive in a pool to retrieve stuffs at the bottom (a major breakthrough!), but that’s nothing compared to humans, who can swim across the English Channel and free-dive to the depth of abyss.

    - We are excellent divers even among the aquatic mammals. With the physiology equipped, an average human can dive down to 20m (ask any one in a coastal nomadic tribe), and some dedicated free-divers can descend to 100m, all done without any equipment. Can you imagine that with a chimp or a dog?

    - Human infants (up to 6 months old) are protected by a reflex that allow them to dive easily – hold their breath in water, open the eyes, and move forward with rhythmic movements. Chimp babies have this reflex too, but only last for like 10 days. After this period, human babies will switch to another reflex that turns their body upward and their face above water to breath, this is not observed in other mammals (except otters, perhaps). These reflexes altogether (plus water birth) enable us to learn swimming / diving since the very moment of birth.

    - The so-called diving reflexes (plural) actually have 3 components: (1) bradycardia (slowing of heartbeat) when immersed in water, (2) peripheral vasoconstriction (restricted blood flow to limbs) in deeper water, and (3) blood shift (plasma fill in cavities) in extremely deep dives. So far (2) and (3) are only observed in aquatic mammals, and human. (1) does exist in all mammals, but human is in the range of otters and beavers. (Don’t be fooled by Jim Moore, he likes to say “all mammals have diving reflex”, and he meant bradycardia).

    Except Darwinian natural selection and adaptation, I can’t think of other logical reasons for these.

  35. #35 somitcw
    January 21, 2013

    Chak, are you changing the question from:
    “how did humans gain aquatic abilities without water access”
    to:
    “how did humans retain aquatic abilities without water access while all non-human great apes lost most of their aquatic abilities even though they lived on islands like Sumatra or Borneo or on either side of the Congo river and some love soaking and playing in the water”
    or:
    “a combination of both”?
    It takes me a few seconds to get up from a chair but I can probably out-swim most monkeys and most dogs too.
    Humans are adapted to a littoral environment. Whether it started three millions years ago or thirty million years ago, I couldn’t tell you. If the adaptation or trait retention occurred because some of our ancestors lived in the desert, rain forest, or near water, I have my suspicion but I can’t prove either way. If not what I suspect, what is a rival theory?

  36. #36 Algis Kuliukas
    Perth, Australia
    January 21, 2013

    Interesting discussion.
    Chak has made the key point, in my opinion. Although the ape clade is peculiar in being comparatively poor at swimming (e.g. Wind 1976), there can be little doubt that the evidence suggests that of the ape clade, the odd species called Homo sapiens is the best of that group at that form of locomotion. So how might this phylogeny be explained?
    Three ways, to my mind.
    1) It could be the result of a spandrel-like exaptation.
    2) Random genetic drift.
    3) The result of some natural selection.
    On 1) several have been suggested, most notably as a consequence of our bipedality, or as a consequence of our improved intelligence. These are as much “just so” stories as any other and in addition can be accused of special pleading and convenience. What other mammal has become good at swimming as a consequence of its bipedality?
    On 2) if this trait were purly a matter of drift, how come humans have so many other traits, different from the chimps and gorillas, which are also all potentially explicable in terms of selection from wading, swimming and diving? Drift might be the null hypothesis, but it can easily be rejected on this basis.
    3) Makes most sense as long as one is careful not to “straw man” the argument to dolphin-like proportions. Run any population genetics simulator (e.g. http://evolution.gs.washington.edu/popgen/popg.html) andd you’ll soon see that even very slight regimes of selection can and do cause fixation of alleles in very short evolutionary timescales.
    If one considers Stephen Munro’s scenario (above) and postulates a population living on the coast, one need not invoke very much swimming in their locomotor repertoire at all in order to arrive at a regime of selection that would quickly have a profound effect on the phenotype.
    Hardy merely asked “Was Man More Aquatic in the Past?” but few seem to have wondered “… and if so, how MUCH more?” The answer, it turns out, is not much at all.

    Algis Kuliukas

    Wind, J. Human Drowning: phylogenetic origin. Journal of Human Evolution 5:349-363, (1976).

  37. #37 somitcw
    January 22, 2013

    The article main questions have not been answered.
    Has the aquatic ape theory being nailed into a coffin?
    My list below implies that the nail is premature until some other explanations are picked. There could be a combination of factors influencing genetic selection or single ones like what was used to make a list.

    Humans have thin hair because of genetic selection reinforced by:
    1. Sexual selection.
    2. Some human ancestors went through a littoral phase.
    3. Naked bodies might communicated better.
    4. Wearing clothes in colder environments stifled hair.
    5. …

    Humans control breathing because of genetic selection reinforced by:
    1. To vocalize better.
    2. Some human ancestors went through a littoral phase.
    3. To be able to eat quicker.
    4. …

    Humans have subcutaneous fat because of genetic selection reinforced by:
    1. Living in colder climates.
    2. Some human ancestors went through a littoral phase.
    3. For better protection from injuries.
    4. Sexual selection.
    5. …

    Humans are bipeds because of genetic selection reinforced by:
    1. Seeing over tall grass.
    2. Some human ancestors went through a littoral phase.
    3. Efficient travelling like Bonobos do on long trips.
    4. Walking on tree limbs like Orangutans.
    5. Wading like Gorillas.
    6. Carrying objects a few steps like Chimpanzees.
    7. Retained from the Great Ape last common ancestor.
    8. …

    Humans children instinctively swim because of genetic selection reinforced by:
    1. Instinct was retained from before the Great Ape last common ancestor.
    2. Some human ancestors went through a littoral phase.
    3. Children can’t swim without a swimming “instructor”.
    4. …

    Humans swim deep in water because of genetic selection reinforced by:
    Humans swimming speed because of genetic selection reinforced by:
    Humans swimming duration because of genetic selection reinforced by:
    1. Genetic drift convergent evolution coincidence.
    2. Some human ancestors went through a littoral phase.
    3. Other adaptation gave synergy.
    4. …

    Humans nose shapes are because of genetic selection reinforced by:
    1. Held humidity to be able to live in the desert.
    2. Some human ancestors went through a littoral phase.
    3. Preheats air for sinuses and lungs in colder climates.
    4. …

    There are many other human traits that could be related to littoral and aquatic-like differences between humans and other great apes.

  38. #38 Chak
    January 23, 2013

    Algis: Drift is out of the question here. It’s the null hypothesis only for neutral traits “invisible” from selection forces, like the color of iris, the loopiness of fingerprints, or non-coding regions in DNA. Otherwise natural selection is the default answer. I think Darwin will agree on this!
    The idea of spandrel is compatible with the ideas, most “aquatic” features may have been serving other purposes, or already there in the mammalian LCA, but in human they’re enhanced and cooperated to make underwater foraging possible.
    There is also 4) Sexual selection. It’s like “because the females like this” and can’t quite explain WHY.

    Somit: Nice list of alternatives… but I think we need more details on every point 2:
    Thin hair — Naked skin makes a *smooth surface* that lower the energy in water locomotion (same principle for both hairless and furry aquatics)
    Breath control — Better planning of inhalation between dives
    Subcutaneous fat — Streamlined body and keep warm in water (by means of insulation and lower surface:volume ratio)
    Biped — Early hominids foraged in shallow water, later diving favor a straight body plan
    Children swim/dive instinctively — Reflexes to avoid infant drowning before they can learn the real skillz
    Speed/duration/depth in swimming and diving — Selected for foraging in coastal area
    Nose shape — Prevent water splash in

    If the AAT has ever been nailed into a coffin, it was due to ideological and social disagreement (John Hawks said something like this), not because of evidence.

  39. #39 Algis Kuliukas
    Perth, Australia
    January 24, 2013

    Chak. Agreed. Sexual selection is often offered when nothing better can be considered but in a sense everything could be explained as sexual selection in the sense that having two eyes, ears, a nose and mouth, rather than not, is proabably in one’s favour when hoping to attract a mate. It’s only where there is clear sexual differentiation where a good case for sexual selection could be made. Even there, they are not necessarily incompatible with other (e.g. waterside) factors.

  40. #40 somitcw
    January 25, 2013

    By “sexual selection”, I was thinking in the other direction. Males would find well rounded and therefor healthy females more worth pursuing and maintenance than either females with no fat showing or females with excessive fat showing. Fat under the skin with none on internal organs would be selected for. I do understand that “sexual selection” and “healthy, visual, and beauty selection” have little meaning but none of my points were meant to be complete descriptions.