Oolon Colluphid

Nope, doesn't work either. In aquatic animals, the nostrils tend to be towards the top of the head (or a snorkel like an elephant's ), ie out of the water, not in it but at a different angle. Far more likely would be the ability to close off the nostrils. There are muscles that could do this, but they're pretty pathetic -- ie they don't work. We'd expect that if something like hairlessness and subcutaneous fat were left-overs from being under water, then there should be other obvious adaptations like nostril-closing muscles, or even nostils on our foreheads.

And anyway, water doesn't go up your nostrils if you hold your breath, and easily can if you're not careful in the shower, despite their angle. So I'm not sure what the point of our noses is (it's for supporting spectacles, no? ), but an improvement in swimming isn't it.

I'm happy to consider the idea that wading might be involved in bipedalism (though it is not necessary, and things like the position of Australopithecine big toes implies trees rather than lake beds), but I don't see why we would need to learn to swim -- it sure doesn't come even a bit naturally -- if there were more than the vaguest aquatic element in our ancestry.

And actual swimming, rather than wading, is a horizontal activity, not a vertical one. If we were aquatic, it would cause selection pressure against the bipedalism that was so crucial in our evolution. We'd be better off as a quadruped, with our body already angled to go through water. Our foramen magnum would be -- is -- ill-placed for swimming. We're face-down in water, and so have to raise our heads further than quadrupeds to get our breathing equipment into the air.

Cheers, DT

Nic Tamzek

This describes most drowning accidents, actually.

Well, you know what they say about natural selection being a statistical thing...sometimes the dumb survive despite themselves.

Vampyric

I seem to remember seeing in some documentary (probably in biology class in school) that (in support of an AAT) infants when immersed in water automatically held their breath and lowered their heartrate.

Although I can see this has advantages regarless of an AAT and do not consider AAT at all likely myself (though new evidence may change that). I was wondering if anyone else had heard of these adaptations?

Also thought I woudl toss them in to see if they had any interest to this debate.

Sorry for lack of sources and all but it must have been close to a decade ago now and I seem to remember having other interests at the time

Oolon Colluphid

I’m also wondering where this swimming might have taken place. It has to be Africa. So, coastal? Then why is it so easy for us to get swept out to sea, even if we are good swimmers? And what of sharks and so on? We’re not talking wandering along beaches, remember, but actually swimming out in it. Shark attacks are nearly all in wading-to-shallow-swimming depths. Sure, leopards ate their share of Australopithecines, and that doesn’t mean that our ancestors weren’t on African plains. But then, we don’t drown in air, and it has to be pretty drastic air to even blow us over. A not-very-good swimming creature is a sitting duck.

Rivers and lakes, then. But any animal that ventures near water, from migrating gnus to monkeys, does so very warily, and with good reason: crocodiles. How long might a swimming ape last in an average African lake, I wonder, if it stayed in the water? Can you imagine the delight of the crocs: ‘no more waiting and skulking for something to come near enough to be rushed upon -- they’re coming out to meet us! Yum!’

Also, thinking of being in the water, if we’re aquatic, why does out skin crinkle up and go white if you’re just in the bath for a bit? Note how easily such soggy finger flesh is damaged, and how it loses sensitivity (it’s no good fumbling for clams if you can’t feel them -- cf raccoons ‘washing’ their food). We’re not talking just having a paddle: it is alleged that we were in water long enough and often enough for significant evolutionary changes to take place. Just doesn’t make sense.

And another thing: just why -- what significant evolutionary advantages -- were these apes swimming in the first place? Catching fish... with fingers and teeth like ours? Just about everything else can be got from shorelines, without going out into the water. It looks to me as if Morgan and co have found some aquatic-like characteristics and worked backward from there, without wondering why the apes would bother.

One might also look for answers in embryos and babies. In the same way that our embryos have tails because our ancestors did, shouldn’t there be something indicating ‘watery lifestyle’ in our foetuses? If one can deduce that an African elephant had an aquatic ancestor from its embryo, surely we could do the same for humans. But as far as I know, there’s no unambiguously aquatic signs in our development.

Finger and toe webbing is now a developmental abnormality, but one that should have been an obvious advantage in water. (It could have evolved easily, since divisions between fingers -- as between eg radius and ulna -- are a result of a separation of the tissues into distinct bits. Fingers start off ‘webbed’, and divide, it’s not a case of having to grow more tissue to web them.) Why is it not more common, or even standard? A bit of webbing need not interfere with grip -- the only grip it might affect is the scissor grip (think holding a cigarette), and even then only if the webbing went right to the finger-tips -- and could assist no end with swimming. Or was piano-playing ability also a selection pressure keeping it from happening?

Cheers, DT

pz

The diving reflex is real. Unfortunately for the silly aquatic ape hypothesis, the same reflex is present in virtually all mammals.

Celsus

No you see, back in Noah's day (and Noah was probably a hairy bugger), there was this great big flood. So what happens is the Great Rift Valley became the Great Big Swimming Pool. The giant Nephilim (see Numbers 13:33 and Deuteronomy 1:28), who survived the flood, had to microevolve features (but only through the loss of information--and the loss of hair is a loss of information surely), and then became hairless. After they got chased out of Canaan by the Israelites, they evidently fled east, to China, and set up a Chinese civilisation with no memory of the flood because they weren't killed in it. Which explains why Chinese people are more hairless than everyone else. Meanwhile, people from the Middle East are the most hairy, because they've bred the least with us Nephilim (Chinese people). And as proof that we will eventually return to normal size, there's Yao Ming. It all adds up! Convert heathens!

/me runs off to write his Nobel prize acceptance speech.

Mageth

Just to pick a nit here: elephants are actually rather good swimmers. I’d never have believed it till I saw the BBC nature programme on Indian wildlife, 'Land of the Tiger', a few years back, where they had some incredible below-surface footage of elephants crossing a river.

Good point. Yes, elephants are excellent swimmers; I didn't mean to characterize them otherwise. I've seen such films myself, including a large herd of African elephants swimming across a broad, deep river, trunks extended above the water (just one of the many uses of this amazing, versatile adaptation). I was countering the allegation that doing so made them "semi-aquatic." While excellent swimmers, swimming is a relatively rare activity among elephants, and is used to get from one place to the other, not to gather seafood. (Though they sometimes wade to eat aquatic vegetation in freshwater ponds etc., not in the ocean AFAIK).

Of course, I don't think their swimming ability has anything to do with them being (relatively) hairless, which is why Baidarka brought them up. (note: I'm using "hair" as a shorthand for fur/hair, of course). One only has to go back a few thousands of years to see quite hairy elephant relatives (think woolly mammoth). Elephant hairlessness appears to be an adaptive advantage in the warm climate they live in. When it was much colder, their near relatives evolved hairiness. As did the rhino's relatives, among others. It seems relative hairiness is one of many traits that can be adapted fairly rapidly to fit changing climactic conditions in many species. And, of course, also can be adapted to fit changing from terrestrial to aquatic environments, if it provides survival advantage for the particular species.

And don’t forget that it seems elephants did have an aquatic stage in their ancestry... and that they are nearest to the Sirenia -- dugongs and manatees -- too.

Good point, as did many (if you go back far enough, all) species, whether furry, bald, fat, thin, floaters, swimmers or sinkers.

Oolon Colluphid

Yup. And IIRC, baby elephants are rather hairy.

Note too that there's plenty of hairy semi-aquatic mammals. In fact, off-hand I can't think of any semi-aquatic (and I don't think Morgan and co claim we were completely aquatic!) mammal except hippos that isn't hairy. From otters to tapirs, beavers to voles, hair is a pretty good insulator in water too. Trapped air, you see. Since we're not whales, I don't see why we'd need to lose our hair even if we were semi-aquatic.

DT

Baidarka

quote:

Originally posted by VonEvilstein
I must say, I've always been fond of the AAT - it's thought provoking, if nothing else. However, there's a point you may have missed.

Human nostrils, positioned as they are, allow us to swim without the water we're swimming into going strait up our noses. I am not aware of other great apes with their nostrils positioned "downwards".


Our cousin the proboscis monkey is another excellent swimmer and diver with down turned nostrils.
I guess we would be better swimmers if we had noses on the back of our heads, webbed fingers and toes, transparent eyelids and the ability to close our nostrils and ears but this does not stop our down turned nostrils from being a better arraignment for swimming than the wide open nostrils of chimps and gorillas.
Huge mounds of oyster shells found from North America to Terra del Feugo is mute testimony to our species ability to exploit sea food as a staple.

ps418

Sea-food? Eckk! The only sea-food I like is fish, but even then it has to be baked and blackened, or fried and on a bun with tarter sauce. I'd much rather dine on steak or chicken. I guess that clinches it -- my ancestors were land-lubbers!

Patrick