Sunday, February 04, 2007

Arguments FOR "Aquatic ape"

From a fellow graduate student, check out this story at BBC on "The role of floods in ape evolution". I'm not familiar with all the counterarguments, but this is pretty compelling. I did post one very recent counterargument against "Aquatic Ape" here.


anthrosciguy said...

This BBC article is, I see, either largely or mostly copied from a 2000 BBC article; virtually all its points are simply false, and none provide support for the AAT/H. Are are dealt with on my site (and most were deal with on the earlier version of my site that dated from 1996). I'll provide some corrections and points and quote the BBC article in italics:

If it's true that the reason for the divergence between the hominids and their ape-like relatives was due to a long semi-aquatic phase of history, then it follows that there should be many other modifications of the human body that fit such a lifestyle - remnants that Morgan calls the 'scars of evolution'.

True, yet we see none of the features that actually are indicative of aquatic or semi-aquatic lifestyles; features which are ubiquitous in aquatic and semi-aquatic mammals. None. The fact that we don't, and that we have many medical problems which arise in diving and swimming people (the sports and medical literature has a whole subfield dealing with them) is actually some of the most damning evidence against the AAT/H. If we'd spent any appreciable time being aquatic or semi-aquatic we'd expect otherwise (for instance, polar bears show there features compared to their nearest relatives the brown bears, and they've only been separated for about 300,000 years, far less time than any AAT/H proponent has ever said we were semi-aquatic.

No modern primate has a brain as large as the earliest hominids, once body size is taken into consideration, and none has lost the dagger-like canines. Marine mammals such as cetaceans, on the other hand, do have relatively large brains in relation to body size, and appropriate modifications to their teeth.

The earliest hominids had brains about the size of chimps; in fact most all their bodily proportions are very similar to chimps and bonobos. There was a reduction in canine size, although nowhere near as great as later hominids, but they are nothing like those of whales and serenia, the only marine mammals which fit the above claim (and the vast majority of marine and aquatic and semi-aquatic mammals have large canines, contrary to the above claim).

Also, the vast majority of aquatic and semi-aquatic mammals do not have bigger brains than their terrestrial counterparts. Only a very few species of dolphins (not even all dolphins) have relatively large brains.

Added to this, seafood industries worldwide show how modern humans seek out this source of nutrients, sometimes to the exclusion of nearly all other foods. In addition, researchers have shown that long chain fatty acids present in seafood, and particularly fish oils, play a vital role in the development of human babies.

But we know that these fatty acids are plentiful enough in terrestrial environments, as well as that other required forms of nutritional energy that we need are in short supply in seashore environments. As for invoking Inuit and Eskimos, which is what they're doing in the first sentence of this quoted section, come on, that's nonsense. In every environment where there exists non-seafoods, and certainly in every environment our ancestors lived in until Homo sapiens at least, all hominids ate many things other than seafoods.

As already mentioned, one of the possible throwbacks to the past is our love of swimming. If babies are allowed to swim from a very early age, they show no fear of water. Asthma sufferers - and particularly young children - seem to become liberated when immersed in water. We show obvious enjoyment of showers, baths and the seaside. Pearl divers illustrate the human capacity to stay under water for long periods and to exercise voluntary control of breathing. When in water, human heart rate and metabolic rate are lowered (the diving reflex), and the ability to stay under water improves with practice.

Yes, showers and bathtubs are evidence of an aquatic past -- come on again, is anyone that stupid? Well, okay, I happen to know that some people actually are that stupid -- I've been told that water piped into my home is evidence of an aquatic past. The diving reflex, and the humanlike reactions to it, are found in all animals, except that this reflex is more pronounced in those animals which have evolved in an environment with lots of diving, and that humans fall into the "terrestrial" end of the scale. What highly trained humans can do is fascinating, but does not tell us much about our past, except that we can do a lot of amazing things well, not so surprising perhaps in the mammalian world's premier generalist. BTW, if you look at untrained humans and compare them to other mammals (a more reasonable comparison if you are looking for adaptations) you must deal with the fact that untrained dogs can hold their breath longer than untrained humans.

All these attributes are similar to those of aquatic mammals, but are not shared by our closest-living relatives. Professor Robert Winston, remarking on the diving abilities of babies, has said, "The truth is, we don't even understand the origins of this unusual ability. For the moment, it remains a delightful mystery."

The first part is simply untrue, both the first and second parts of the first sentence quoted in this section. And I have a short page on the babies in water story; this is a feature found in all mammals tested, including opossum, rat, kitten, rabbit, guinea pig, and rhesus monkey. This has been known since 1939, so you'd think they'd have heard about it by now. :) But then why also is Robert Winston commenting on this at all (we can see he doesn't know the facts) -- he's apparently an excellent researcher on IVF and reproductive biology and genetics, but he's way outside his field here (and as I said, he's wrong on the facts here). He's a well-known BBC science presenter so i guess he was easy to get hold of for a quote, but shouldn't one quote someone who knows something about the subject?

In human babies, as in all other primates and non-marine mammals, the windpipe is quite separate from the oesophagus, and they can therefore breathe and swallow at the same time. As the child develops, this arrangement changes. The larynx descends in the throat until the windpipe and foodpipe are lying side by side.

In the past, anthropologists have linked this to the evolution of speech but now most of them agree that this explanation is unlikely. In fact, a similar arrangement can be found in sealions and walruses, and its purpose from an evolutionary point of view is that it allows them - and us - to inhale great lungfuls of air through the mouth. Apes, which breathe almost entirely through their nose, cannot do this.

Again, wildly wrong on several levels. First, the descended larynx of those few aquatic beasts who have them is quite different from ours, and in fact other primates, such as chimps, also have a descended larynx. Now when I first started looking up AAT/H stuff, I thought that humans were unique among terrestrial mammals in this feature, but that turns out to be because we didn't have the technology to look at living creatures, or didn't have that tech cheap enough to use for other than human health concerns. There were still problems with the idea that this was an aquatic adaptation: one is that our descended larynx is not much like that of aquatic mammals; another is that this would require young to be not aquatic for several years at least (while other AAT/H claims, for instance fat, require those young to be highly aquatic during that same period). And this sentence is... well, to be kind, let's say unfortunate:

This theory is far more likely than the largely discredited idea that speech itself somehow caused a dramatic rearrangement of the larynx.

In fact, during the last 10-15 years researchers, especially W. Tecumseh Fitch, have shown that many non-human, non-aquatic mammals have either flexibly descending, or permanently descended, larynxes. These include chimps, as I've already mentioned, howler monkeys, red deer (and their North American cousins, elk), as well as a number of flexibly descending larynx animals, such as the big cats (and similar features in many birds). In all these cases, the number one hypothesis, based on when this feature is used, as well as reactions of other animals to calls, is that it's to exaggerate body size while vocalizing. In humans this is further bolstered by the fact that the larynxes of males descends further at puberty (that's why the deep voices).

If you or anyone else has any questions or comments about the AAT/H, there's a feedback email link on my site, Aquatic Ape Theory: Sink or Swim?. Sorry for the length of this comment (and any typos -- for one thing, I often transpose the "a" and the "u" in "aquatic", and spell "larynx wrong probably 75% of the time :))

aquape said...

This anthrosciguy apparently has no knowledge of recent views & disucssions on AAT (sea/lake/riverside adaptations of human ancestors after the human/chimp divergence c.5 Ma). For instance, laryngeal descent is now known to be composed of 2 elements: larynx descent vs hyoid bone (in all apes) + hyoid descent vs mandible (only humans). Comparative data suggest the first has probably to do with sound production, the 2d with suction feeding.
For an update of AAT, please see or google "aquarboreal"

Anonymous said...

athrosciguy: it is admirable the amount of work you do discounting everything about AAT, and it does appear you have done your homework. However, throughout your writing there is a clear bias. The key to scientific criticism and dialog is (in my opinion) being objective and factual (there is no comedy and as soon as you get aggressive it shows weakness in your own research, it shows bias). It seems you have fallen into the same hole that you criticize AAT proponents, you want so bad to prove your point you lose an objective frame of mind, which to predict your retort, is chiefly present in how you present your argument as opposed to the argument and facts themselves. If your writing was more objective and professional it would be much more powerful. Instead it reads as angry and self righteous. That and it doesn't help not having any degree in biology, anthropology or the like....( and yes I know Morgan doesn't either). ;)

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