Originally posted by: Throckmorton
I listened to a David Attenborough BBC radio documentary on the aquatic ape hypothesis. The theory makes a pretty good case for itself.
It does so only if the person making the case leaves out info and twists the facts. Sad to say David Attenborough did that in this case. He usually does a pretty good job on nature/science stuff but with the "aquatic ape" idea he falls down rather badly; it seems he has a blind spot there.
I should introduce myself. My name is Jim Moore and I've been examining the claims of AAT/H proponents for over ten years now; I have a web site on the theory (actually a hypothesis, but the distinction between theory and hypothesis, while important in science, is not terribly important here). My site has been used as a source many times, both for university courses as well as popular media, such as The Fortean Times and the Straight Dope column you linked to. I've also recently written an entry on the subject for the
Sage Encyclopedia of Anthropology. The site is
Aquatic Ape Theory: Sink or Swim? and I have a page there specifically dealing with the
Attenborough BBC Radio4 show.
The site is rather large and covers both the many errors of fact and misunderstandings of evolutionary science the idea's proponents make, as well as engaging in a number of logical fallacies. Since most things are covered in greater depth there, I'm going to just point out the errors in the statements here. I know these aren't your fault, so please don't think I'm picking on you; you've just been misled by people who really shouldn't do that.
Originally posted by: Throckmorton
Some things that really got me are:
Humans are the only primates with a layer of fat stuck under our skin.
This is a consequence of being fat relative to many other animals, and that is almost certainly due to a relative lack of predation. Animals which have little predation can get fatter than their relatives who have to have more mobility to escape predation -- this is a well established fact -- and humans have created for theselves a relatively predator-free environment ever since they developed fire use and "advanced" weapons (spears, for instance). That is to say, for the past million years, maybe more. This environment is also portable, which is one of the unique things about humans. Other primates which are allowed to get fat in captivity get that same fatty layer under the skin (BTW, all animals have their fat deposits anchored to internal depots, unlike another common AAT/H claim).
Originally posted by: Throckmorton
Humans can have aquatic births.
Not surprising, considering the infant, like virtually every other mammalian infant, has spent its life to just before the moment of birth in an underwater environment.
Originally posted by: Throckmorton
Young babies hold their breath and can swim instinctively (although the swimming may just be quadripedal motion a la dogs and horses).
As do all mammalian infants that have been tested. Again, not surprising in an infant which has spent its entire life underwater up until birth. The way this is said by AAT/H proponents -- without mentioning it's a common, apparently universal, mammalian trait, shows they are not trustworthy sources of info. This came from a 1939 paper, quite short and readable, which clearly mentioned all the other infants tested (opossum, rat, kitten, rabbit, guinea pig, and rhesus monkey) right on the first of its five pages. Other money quotes from that paper (which go unmentioned by AAT/H proponents): "these rhythmical movements of the human infant are quite similar to those of other young quadrupeds in water" and "at no time did any baby show himself capable of raising his head above the water level for the purpose of breathing".
Originally posted by: Throckmorton
Humans are the only land mammals born covered with a layer of grease that would serve to insulate from the cold water. The only creature I know of like that is the harbor seal.
Let me just quote from my site:
Now we get into something interesting, and something I haven't researched thoroughly. It's the vernix caseosa, which is a white substance composed of sebum (the excretions of sebaceous glands) and sloughed off skin cells in babies which are either preterm or at term (it's gone in postterm babies). It apparently has antibacterial properties, and it was supposedly found only in humans.
Attenborough's research crew apparently found a researcher in Nova Scotia, Don Bowen (the way they put it makes it sound like Bowen found them), who says he's found something which he assumes is similar in newborn harbor seals, and to a much lesser extent in grey seals, but although "we always assumed that it was analogous to the vernix that humans are born with; we never pursued it systematically."
This is interesting, but what does it mean? On my site I go on to ask the relevant questions that Attenborough didn't. Could it be that other animals have this but we just haven't examined enough in detail to know? Is it like the hymen, which happens to be present in various unrelated mammals (humans, lemurs, guinea pigs, and fin whales) apparently by chance? These are relevant questions, and I think they're interesting; Attenborough apparently doesn't.
Originally posted by: Throckmorton
Humans are the only primate with fat babies which help with buoyancy and insulation.
We also are unique in the amount of post-parnum brain development, which seems to be driven by the need for fat. Sounds suspiciously like a good reason for fat babies.
Originally posted by: Throckmorton
We have some webbing between our fingers.
Some of us do, as do our close relatives siamangs and gorillas. Actually, this is an interesting example of faulty thinking on the part of AAT/H proponents: webbing between digits is controlled by small genetic changes during development. This means it's a fairly easy developmental change, seen in mammals, birds, reptiles, and amphibians. If it were useful to us -- as the AAT/H suggests -- we would expect it to be ubiquitous, but instead it's rare. This suggests that there were strong selection pressures
against[I/] it rather than for it.
Originally posted by: Throckmorton
Some brain chemists recently said that in order to evolve such developed brains we needed a lot of iodine and omega 3 fatty acids. He also pointed out the iodine deficiencies that are common in poor inland regions. Iodine is readily available in seafood, but even here in the food-rich USA we put iodide in our salt to supplement our diets.
Not brain chemists, nutritionists. We don't need "a lot", but we do need "enough", and modern nutrition is often crappy in that area as well as many others. Iodine is available in many natural food sources, for instance many plants as long as the area isn't iodine deficient. AAT/H proponents often say, or at least imply, that omega-3 fatty acids are only available in seafoods, but this is not true. Wild game has it, especially brains, and we can synthesize enough from vegetable oil sources (the Mayo Clinic says "One tablespoon of vegetable oil easily meets your daily requirements.").
Originally posted by: Throckmorton
We are the only primates that can consciously regulate our breathing.
This may be so, although I wonder if it's really been tested (I know that AAT/H proponents have never tested it). For instance, when a crab-eating macaque dives underwater, does it really not take a breath just before doing so? At any rate, we do have a much greater degree of concious control over our breathing than most other mammals. This is a side effect of not using our forelimbs for locomotion; it freed up the muscles around our chests to be used more freely and independent of locomotion. A lucky break, that bipedal locomotion allowed for better breath control and therefore better and more varied vocalization, leading to speech. Evolution is full of lucky breaks like that.
Originally posted by: Throckmorton
Spleens apparently store oxygen like a corresponding organ in some marine mammals.
All spleens do that, they store blood and the blood stroes oxygen. It's a physiological universal. However, the spleens of actual diving animals such as seals and whales store far more blood than can the spleens of humans. This partly because their spleens are much larger for their size and due to the fairly radically different composition of their blood (far more hemoglobin).
Originally posted by: Throckmorton
But I kept thinking that those are just a few picked and chosen traits and could have other causes.
And some arguments just don't make sense, like walking upright being an adaptation to semi-aquatic lifestyle. Catching fish while wading is not really easy.
Our babies also can't surface and breath on their own, and the human body is very bad for this.
Swimming is awkward for us compared to quadripeds whose noses are naturally above water when swimming. Water birth doesn't seem like it would be an evolutionary development just because a species spends a lot of time by shores, but then again it may be safer than dropping a baby out onto a rock.
The cause of our ability to regulate breathing could be that it was part of the evolution that allowed us to speak the way we do, and had nothing to do with holding breath underwater.
But what's so unbelievable about living on shores and evolving significant semi-aquatic traits?
The objections you raise to the AAT/H are all good ones, and I want to commend you for thinking about it sensibly. That may seem like not much of a complimnet, but I've seen so many people just swallow this stuff whole without any apparent indepent thought. It's refreshing to see it.
Your closing question brings up another problem, one specifically tied to the more recent AAT/H claims. As the theory went along, the supposed aquatic period because less and less aquatic, and for shorter time periods. Yet the things they claim are still the same. And the biggest ones are traits they claim we share with aquatic animals, which they are typically very careful not to specify. The reason they don't want to specify which aqautic mammals they're talking about is that they are whales, serenia (dugongs and manatees) and seals, all fully aquatic mammals which have been so so tens of millions of years -- longer than hominids have existed. The problem is twofold. One is that they describe these features inaccurately, so their facts are wrong to start with; these traits are not actually similar to aquatic animals. The other is simple: how do you develop the traits of a whale, a manatee, a dugong, a seal, by walking along the shoreline and taking an occasional dip? The answer, of course, is you don't.
So check out my site if you're interested in the idea, and if you have questions or comments, there's a feedback mailto at the bottom of each page. I'll be travelling soon and may not see entries here (I try to keep up with threads in forums when I can) but I do answer emails, albeit with some delays.
It probably had nothing to do with aquatic ancestry. The people just preferred to live in places which minimized the risk of dying.
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