A New Twist on the Aquatic Ape Theory

[JeffLee]

Rationalrevolution, although there is certainly a lot of speculation on this thread, not all of it is absurd. However, what would be absurd is for sexual selection to reverse the gender difference in hairiness. Do you know of any species where reversal could have occurred for purely sexual selection reasons?

actually, that specific point falls under the 'absurd speculations'.

sexual selection didn't reverse anything, male humans simple don't have enough hair to make much of a difference. for that matter, women most certainly are not attracted to hairy men[as a fairly hairy individual, you'll have to trust me on this. i don't pick up much girls on the beach ^^] so there isn't even a trend towards more hair!

For that matter, have you even considered testostrone? do you have data stating that the differenc ein hair levels excedes the level hormonohal differences between the sexes would produce? do you have any support for this beyond "oh look men are hairier"?

BTW, the early part of the aquatic period would not have involved much mud, once a beach had formed (after the presumed catastrophic flood of the Afar depression had given way to a normal marine coastline). Sure, wading would have preceded swimming, but swimming could have followed.

ah yes, the sea of afar situation that should have left a whole butt load of geological evidence but no one seems to have found / presented evidence for.

[DavidMcC]

BTW, the early part of the aquatic period would not have involved much mud, once a beach had formed (after the presumed catastrophic flood of the Afar depression had given way to a normal marine coastline). Sure, wading would have preceded swimming, but swimming could have followed.

ah yes, the sea of afar situation that should have left a whole butt load of geological evidence but no one seems to have found / presented evidence for.

I don't know when anyone last went to Afar without a gun, but it is known to have a depression in more senses than one. How would a depression fill when the outside sea levels rose to the top of it?

[DavidMcC]

actually, that specific point falls under the 'absurd speculations'.

sexual selection didn't reverse anything, male humans simple don't have enough hair to make much of a difference. for that matter, women most certainly are not attracted to hairy men[as a fairly hairy individual, you'll have to trust me on this. i don't pick up much girls on the beach ^^] so there isn't even a trend towards more hair!

Hardly absurd, and topmum will tell you that she likes the "silverback gorilla" she's married to.

[anthrosciguy]

Jim, you previously argued that if a man shaves his body hair, it makes little difference to his swimming efficiency, now you claim our body hair is a problem. You can't have it both ways!

You're misunderstanding what I've said. First, it's true that the difference is actually small -- 3-4% of what, at best, is a pathetically slow swimming speed. (Olympic atheletes in the fastest shortest swim events manage to go slightly faster than a quick walking speed -- less than 6 mph). But there is an improvement -- as much as 1/4 of one mph. But that's shaving from what we have to a condition that's not typically human. And then there's the body suits which are often used now, and which also give some improvement over what we have as the human condition by mimicking a full coat of hair like a seal or otter (or the dermal ridges of a dolphin). The thing is that the one thing competitive swimmers never do is go with what is the typical human condition -- which, if that condition was the result of millions of years of evolution for swimming efficiency as AAT/H proponents claim, seems absurd.

So yes, the amount of body hair we have doesn't fit with the idea that the amount of body hair we have is due to convergent evolution and swimming. It fits beautifully with the idea that our hair patterns are due to sexual selection instead, and the pattern of differences between the sexes and changing radically right at puberty also makes sense if it's sexual selection and no sense if it's due to environment and swimming.

(And thinking about one claim further back in this thread, one wonders why competitive swimmers don't grow beards for their swimming if that's really good for swimming efficiency.)

[anthrosciguy]

I didn't write that, I quoted it and then responded to it with info more accurately describing our hunting techniques -- those which were likely to be used by "early-ish" hominids -- for instance, no nets or snares or deadfalls, which are great hunting innovations but probably fairly far into erectus times.

Quick question. Would you compare the early hominid to the Hunter-Gatherers of today in that they hunted and gathered? I'm not trying to compare techniques, instead I just want to know if thats the lifestyle you would prescribe to them?

No, modern gatherers and hunters have better tools. But actually there are some comparisons that can be made, like the prevalence of veggies in the typical gathering-hunting diet (except where you just can't get them, like the far north), the small groups. And you can look at chimps and see what they do. When you see both chimps and modern gatherer-hunters doing the same things you can figure that action was also within the abilities of even very early hominids.

I don't know what Crawford thinks he's doing with that info, but it seems he's once again tripping himself up due to being a nutritionist rather than an evolutionary scientist, which wouldn't be a problem if he did the study he needs to do before making pronouncements based on evolutionary science.

Actually its extremely relevant. When he is looking at DHA he is looking at homo sapiens, not other hominids so stating that we come from this area, although it originates from a bottleneck phase means that its generally correct. You could just read the article, I gave a link on page 2.

It's just that it has nothing to do with his thesis. First, it doesn't even mean what he thinks it does, but beyond that the bigger problem is that so what? We already know from fossil evidence that that general area is where hominids first developed and were even pretty sure from fossil evidence that that general area is where sapiens evolved. It says nothing about lifestyle or what environment they were using, yet he hints that it does. (BTW, I have read it long before you linked to it, as I have most things written by AAT/H proponents, but I do like to get pointers to articles by the idea's proponents anyway just in case I've missed one.)

It also ignores that if this were true, we would expect to see all seals being very large brained (and they aren't), as well as herons etc. This is one of those instances where nature has already performed the experiment for us, and it just doesn't work the way Crawford and friends want it to.

And you are possibly ignoring the ideas that our evolution of the brain was encouraged by DHA and additional factors which I mentioned in the last post.

No doubt DHA played a part in our brain evolution, since we need a certain amount to have proper brain development. This is like saying that vitamin D played a part, since we need that too. And fat played a part, and salt, and iodine, and on and on the list goes. Bottom line on DHA: you don't need to go near water to get enough; studies show there's plenty enough in terrestrial places like those we find our early ancestors in. Like other nutritional things, adding more than needed doesn't make development boom, any more than fitting a larger gas tank to your car will make it go faster.

BTW, we also know now from studies of fossils that a significant portion of early hominids' diets was eating either grasses or animals which ate those grasses. Couple that with the fact that plenty enough DHA was available in those grassy areas, and that other required nutrients were easier to get there than at the shore, and you have a bunch of facts which are very inconvenient for the AAT/H.

Well, that's another good reason to stay away from arguing for the AAT/H, since it is primarily an environmentally deterministic idea. The idea that social interaction, that is the idea that virtually all mainstream paleoanthropologists accept to a large degree, is far more sensible and fits the facts, so I think you should go that route. It entails dropping the AAT/H, but that's not a bad thing to do.

Ummm, I'm not arguing for AAT/H, I'm more of a fan of Bailey's ideas to be honest.

Could've fooled me, but then perhaps I've confused who said what.

[
[edit]
Oh yeah, just to say something on the swimming, to teach an athlete how to swim competitively, takes years of training, etc. However, to teach a normal kid to swim efficiently (as I used to do in my job) takes less than 5 years. Bearing in mind, when I was teaching these kids to swim in those 5 years I spent only 30 minutes a week with a class and taught up to 20 children. Give me a single child at the age of 5 and I could probably teach them by myself to swim correctly and efficiently much quicker, at least a quarter of that time I would imagine. Also, I have never had a kid, even the ones with special needs, that could not swim. The only times I have had problems is when the child will not listen to you (which I blame more on the parents fault) so will not learn.

Just to fill in the background there, I am 19 and have been assisting and teaching for over 6 years. I have the ASA Swimming Teacher's level 1 certificate and I taught for Swim Stockport for a few years. I am also considered a good teacher as well. Just so you know about these things.

Kids learn lots of things extremely quickly. You shouldn't use that ability as evidence for a swimming stage in our evolution any more than the fact that you can easily teach a kid to ride a bike is evidence of a bike riding stage in our evolution. One point to consider; if in your classes the kids were replaced with young macaques, you'd have your students swimming and diving even quicker... although I'd grant you that discipline and cleanup would be a bigger problem.

[anthrosciguy]

The point is that we would expect to see one of two things --hair-wise -- if we were adapted to swimming:

1. no hair
2. lots of hair (and probably no philoerector muscles)

What if, as has been suggested before, it was only or mainly the females who did the swimming (as gatherers), bearing in mind that there are limits to sexual dimorphism in mammals.

This is sometimes used by AAT/H proponents, and it's one of their worst methods, because it highlights the internally inconsistency of the idea. Over the years I've heard people say that one or the other sex was more aquatic (Morgan started this claim decades ago) but look at what that means (I'll quote from my site):

Another major problem the AAT/H has arises from its ad hoc reasoning: the theory is internally inconsistent. For instance, the aquatic ape needs to be in salt water to evolve its radically different salt excretion system, but it needs massive amounts of fresh water for this system to be even remotely possible. Babies need to be aquatic to explain their fat, and non-aquatic to explain their larynxes; later, as children, they need to be non-aquatic again to explain their lack of fat and sebaceous glands, and aquatic to explain their larynxes. Women need to be far more aquatic than men to explain their fat and hair differences, but men need to be far more aquatic than women to explain their sebaceous glands. Although these things are contradictory, generally AAT/H proponents use them all at once, or all in the same book or article. This means the theory is not only contradicted by facts, but by its own claims.

BTW, women are confiend to gathering, although there was no doubt some division of labor between males and females on much gathering and hunting, esp. later on in erectus times. The recent discovery that female chimps make spears and use them in hunting highlights this.

[anthrosciguy]

Just wanted to do yet another post (I've got a few in a row now) that if I've been too harsh with someone please accept my apologies; I know I sometimes get snarky. Same if I've missed someone's point in replies or gotten attributions mixed up.

[DavidMcC]

BTW, we also know now from studies of fossils that a significant portion of early hominids' diets was eating either grasses or animals which ate those grasses.

We ate grass?? So they spent most of the day on all fours, grazing? I suppose you are referring to the robust hominins, but these were later than the aquatic period, later even than Lucy, and are not generally considered to be human ancestors, in any case.

[DavidMcC]

For that matter, have you even considered testostrone? do you have data stating that the differenc ein hair levels excedes the level hormonohal differences between the sexes would produce? do you have any support for this beyond "oh look men are hairier"?

I don't need to, the point is that, as I understand it, hormones can only produce a relatively small effect between the sexes, but what difference there is would make more sense if it was consistent with natural selection, rather than relying on some ad hoc idea of sexual whim reversing the effect of natural selection.

[Largenton]

No, modern gatherers and hunters have better tools. But actually there are some comparisons that can be made, like the prevalence of veggies in the typical gathering-hunting diet (except where you just can't get them, like the far north), the small groups. And you can look at chimps and see what they do. When you see both chimps and modern gatherer-hunters doing the same things you can figure that action was also within the abilities of even very early hominids.

Less evasion next time. I asked if the lifestyle was similar in that they hunted and gathered, tools were something I stated that didn't need to be mentioned.

Now this is why I asked that question. We are both in agreement that the act of gathering is more important than hunting, as even with the techniques and advances that modern H/G people have, gathering is the main priority. Now what I would propose is perhaps the most likely form of action is Bailey's hypothesis which I mention earlier.

I do not argue for AAT/H, I think its too extreme and I don't like the idea of water being an apparent safe place, it isn't, we drown too easily, plus there are other dangers. Instead I would perhaps argue that we lived on the basalt enscarpments, providing a safe haven for us to eat, make tools, etc, all without fear of predators, as well as perhaps using those features to drive animals into traps occasionally. Bailey argues quite strongly for this view and his only problem that he can personally see with it, is that the Rift Valley, happens to be that its the best place for fossilisation. I agree with him there, but since he's my tutor, I would.

However, one thing that he taught me was that hunter-gatherers don't move if there is enough resources to supply them with food throughout the year. The Rift Valley was incredibly fertile, the volcanic ash keeps it that way and although it is dangerous sometimes with active volcanoes, its never stopped modern humans from living in these regions.

Shellfish are an all year round resource. It is possible in that respect that to perhaps suggest that the women gathered those shellfish and other gatherable items such as vegetation whilst the men went on the "manly" hunting activities in order to try and capture wild animals. They won't always be successful, in fact, I would perhaps be more confident to state the gatherers would be the more successful and bring home the more food (btw, I am basing these ideas on the San Bushmen because of certain aspects that we were agreeing on).

This does quite a few nice things. Firstly, it brings into Crawford's idea of DHA advancement quite nicely, encouraging intelligence. The second thing is that it brings in a pressure for the intelligence, the hunting and social co-operation aspect. It also doesn't favour the AAT/H or the savannah hunting (which I've never liked due to the fact we are very vunerable whilst sleeping and at night) and instead provides a different model which favours our bipedalism in rough terrain as well as bringing in an idea that we can carry things back to a safe haven (can anyone remind me who came up with this, I remember it being mentioned in Lewin).

Admittedly, there are some factors I still need to consider, bias towards that region for fossils is one. However, its an idea I favour because of the fact it fits nicely with other hypotheses.

Could've fooled me, but then perhaps I've confused who said what.

Indeed, read my line of reasoning from the start tho, I advocate Bailey more than others.

Kids learn lots of things extremely quickly. You shouldn't use that ability as evidence for a swimming stage in our evolution any more than the fact that you can easily teach a kid to ride a bike is evidence of a bike riding stage in our evolution.

Pretty irrelevant. My point was to counter-argue this statement.

Swimming efficiency for humans is terrible; most of competitive swimming coaching is
how to decrease the naturally poor efficiency of human swimming.

The fact I can say that to swim efficiently is quite easy to teach to young kids and the fact you agree with me, means my idea is valid.

BTW, we also know now from studies of fossils that a significant portion of early hominids' diets was eating either grasses or animals which ate those grasses.

From what sorts of tests exactly?

[gwolf]

I've still not seen good "if X is true then the amphibious ape never existed" evidence. And I want to add one more piece to this puzzle. In humans, why is the female sexual scent reminiscent of fish? If it has nothing to do with being amphibious, then if nothing else it is a most remarkable coincidence. Are there examples of other apes or even other primates with this feature?

As it now stands, h. sapiens is to me a transitional species; many times more amphibious and with more traits adaptable to water than other apes or primates, yet because of the transitional nature, not by any means as well adapted as other amphibious or aquatic tetrapods, all of which appear to have been in the water far longer.

It may be that this transitional form is "just right" for people; the sensitive hands that felt the lake bottoms for forage are just the ticket for fine tool work. Throwing shellfish to shore, was exapted first to shoving branches down the throats of crocodiles, and later into throwing spears at other prey. Less emphasis on gesture language meant more highly developed speech and so on.

George Wolf

[anthrosciguy]

BTW, we also know now from studies of fossils that a significant portion of early hominids' diets was eating either grasses or animals which ate those grasses.

We ate grass?? So they spent most of the day on all fours, grazing? I suppose you are referring to the robust hominins, but these were later than the aquatic period, later even than Lucy, and are not generally considered to be human ancestors, in any case.

We eat grasses now -- grains, for instance. And I do think my saying "or animals which ate those grasses" is pretty darned clear. And the grasses part includes tubers and seeds.

Also, while Hardy and Morgan both claimed an early aquatic period, other proponents claim we've been semi-aquatic all through human evolution, despite the fossil evidence.

[anthrosciguy]

No, modern gatherers and hunters have better tools. But actually there are some comparisons that can be made, like the prevalence of veggies in the typical gathering-hunting diet (except where you just can't get them, like the far north), the small groups. And you can look at chimps and see what they do. When you see both chimps and modern gatherer-hunters doing the same things you can figure that action was also within the abilities of even very early hominids.

Less evasion next time. I asked if the lifestyle was similar in that they hunted and gathered, tools were something I stated that didn't need to be mentioned.

Since chimps do both eat both veggie and meat foods, as do modern gatherer-hunters, it's virtually certain that our early ancestors did so too. I thought this was so obvious I didn't mention it (wasn't trying to be "evasive"). It's unlikely they did as much as modern gatherer-hunters until they had better weapons and carrying devices (the carrying things, such as simple slings, could have been early but probably weren't, but since they'd most likely be made of materials which wouldn't survive well in the archeological record we may never know exactly when that happened). Tools are basic to the question of hominid gathering and hunting, which is why I immediately mentioned them.

Now this is why I asked that question. We are both in agreement that the act of gathering is more important than hunting, as even with the techniques and advances that modern H/G people have, gathering is the main priority. Now what I would propose is perhaps the most likely form of action is Bailey's hypothesis which I mention earlier.

I do not argue for AAT/H, I think its too extreme and I don't like the idea of water being an apparent safe place, it isn't, we drown too easily, plus there are other dangers. Instead I would perhaps argue that we lived on the basalt enscarpments, providing a safe haven for us to eat, make tools, etc, all without fear of predators, as well as perhaps using those features to drive animals into traps occasionally. Bailey argues quite strongly for this view and his only problem that he can personally see with it, is that the Rift Valley, happens to be that its the best place for fossilisation. I agree with him there, but since he's my tutor, I would.

Would you briefly summarise (a paragraph or two) what you see as "Bailey's hypothesis"?

Kids learn lots of things extremely quickly. You shouldn't use that ability as evidence for a swimming stage in our evolution any more than the fact that you can easily teach a kid to ride a bike is evidence of a bike riding stage in our evolution.

Pretty irrelevant. My point was to counter-argue this statement.

Swimming efficiency for humans is terrible; most of competitive swimming coaching is
how to decrease the naturally poor efficiency of human swimming.

The fact I can say that to swim efficiently is quite easy to teach to young kids and the fact you agree with me, means my idea is valid.

I've lost track -- what idea of yours do you feel is valid because kids are able to be taught to swim (as they can be taught to do so many things -- unsurprising in an animal which is one of the world's great generalists)?

BTW, we also know now from studies of fossils that a significant portion of early hominids' diets was eating either grasses or animals which ate those grasses.

From what sorts of tests exactly?

Tests of tooth enamel and C4. Here's a link to a news story about it from a while back (news story and a rather long blog entry which has that and other good info (blog entry). You'll have to scroll down quite a way -- over halfway down the page -- to get to the relevant part, sorry.

[anthrosciguy]

I've still not seen good "if X is true then the amphibious ape never existed" evidence.

While, contrary to common belief, it is sometimes possible to prove a negative, it's not usually a sensible way to do things. What you want is some actual good evidence that the idea makes sense, based on facts that are real facts rather than falsehoods. What we do see is the AAT/H proponents constantly claiming falsehoods as fact, reporting researchers saying the opposite of what the researcher actually said, misquoting researchers, ignoring information that contradicts their claims (even when the info is in a source they use; sometimes on the same page), and mangling evolutionary theory. So, for instance, it's possible that horses went through a bipedal phase that left no evidence, but claiming that is crazy unless there were actual evidence. Countering that by expecting others to come up with proof that horses could never ever possibly have done so is not just impossible, it's silly. Sorry.

[gwolf]

Also, while Hardy and Morgan both claimed an early aquatic period, other proponents claim we've been semi-aquatic all through human evolution, despite the fossil evidence.

I see nothing has been said about the female sexual scent. Does this mean it is unique to humans? Also, if modern humans are the most amphibious of the hominids, wouldn't this make it less likely that we'd find fossils in lake bed strata? If your family lived around and fished in a lake for a really long period of time, you'd watch anybody capable of drowning -- the very young, the very old and the infirm -- pretty closely. There's a good chance that even if they did drown, the corpse wouldn't stay in the water for long because other members of the band would attempt a rescue. Were it any other way, nobody would have the courage to fish.

I still haven't seen a good rebuttal to my comments about croc-killing. Instead I get general arguments along the lines of, "Oh, it's too dangerous, and besides, people would have exterminated them if they were that easy to kill." However as your posts have pointed out, crocodiles are quite prolific, and would have spread back to any lake where they'd been killed off after a few years. As to the danger, how is being killed by one animal any different than being killed by another? If modern "stone age" hominids are capable of killing healthy adult elephants -- something lions have a difficult time doing -- why would there be any problem killing crocs?

Finally, we keep going round and round about the fact that a submerged croc would be very dangerous. There has been no reply to my suggestion that the time to attack a crocodile is when it is torpid and basking on the beach, trying to warm up.

That people without herpetology degrees are capable of learning what exactly the dangers with crocodilians are in great detail is demonstrated by the late Steve Irwin, who was trained as a diesel mechanic, yet had enough confidence around these animals to hand feed one while holding his infant son in his other arm! For Irwin, that performance was mostly illusion since he knew that the crocodile he fed was close to exhaustion, and couldn't have charged him even if it wanted to. Jared Diamond characterized hunter-gatherers as having an almost encyclopedic knowledge of their environment. I doubt that this would exclude crocs!

George Wolf

[gwolf]

While, contrary to common belief, it is sometimes possible to prove a negative, it's not usually a sensible way to do things. What you want is some actual good evidence that the idea makes sense, based on facts that are real facts rather than falsehoods. What we do see is the AAT/H proponents constantly claiming falsehoods as fact, reporting researchers saying the opposite of what the researcher actually said, misquoting researchers, ignoring information that contradicts their claims (even when the info is in a source they use; sometimes on the same page), and mangling evolutionary theory. So, for instance, it's possible that horses went through a bipedal phase that left no evidence, but claiming that is crazy unless there were actual evidence. Countering that by expecting others to come up with proof that horses could never ever possibly have done so is not just impossible, it's silly. Sorry.

I have done my best to stay within the constraints of whatever evidence that really exists, and have modified my hypothesis based in part on what those opposed to it have said. My case is that the most amphibious hominid is the one now extent. On the other hand, specific parts of my case remain unrefuted and still point to amphibiousness; swimming, and those relating to fish such as the mimicry of the female sexual scent to it, and the fact that humans have less trouble digesting fish than either avian or mammalian meat. See my previous post regarding crocodile hunting. It has been pointed out that humans are not as well adapted to water as other amphibious tetrapods, but the actual argument is that humans appear to be much better adapted to water than the other apes, and as far as I know, most other primates too. This is precisely to be expected with h. sapiens' less than one million year reign. There hasn't been time for a lot of adaptations, and sure enough, those adaptations that exist bespeak incompleteness.

I don't think it was complete adaptation, but then our species' current success simply hasn't require that. In becoming more amphibious than other apes, humans became better generalists. H. Sapiens has proven pretty good at exploiting a large variety of habitats. The plunge -- no matter how brief -- prepared the way.

George Wolf

[Marios]

Note - the hominids for which the evidence (criticised as questionable by John Hawks) for vegetarian tuber diet has been put forwards are 2 million years old. From what I remember of Morgan's hypothesis, that would be well post-aquatic.

Why are people whittering about crocodiles? I don't remember there being a single reference to crocodiles in the AAH. Do anthropologists favouring a savannah-mosaic hypothesis have to justify why we wouldn't have all been killed by savannah lions and tigers?

Marios

[DavidMcC]

Note - the hominids for which the evidence (criticised as questionable by John Hawks) for vegetarian tuber diet has been put forwards are 2 million years old. From what I remember of Morgan's hypothesis, that would be well post-aquatic.

Correct. The supposed period in which apes could have been trapped on "Danakil Island" was 6.7-5.4Mya. NB, the "island" wasn't literally surrounded by water, part of its biological isolation (as far as apes are concerned) was due to "flood basalts". (I have the book in front of me as I write.)

Why are people whittering about crocodiles? I don't remember there being a single reference to crocodiles in the AAH. Do anthropologists favouring a savannah-mosaic hypothesis have to justify why we wouldn't have all been killed by savannah lions and tigers?

The fact that she ignored the issue of crocodiles is one of the main criticisms of Morgan's version of the AAH. As you may have noticed, it has been a significant part of the debate on this thread.

[DavidMcC]

Finally, we keep going round and round about the fact that a submerged croc would be very dangerous. There has been no reply to my suggestion that the time to attack a crocodile is when it is torpid and basking on the beach, trying to warm up.

Good point!

[Combine_Dave]

I personally favour the idea of human's having an aquatic ape stage.

Unfortunately there doesn't appear to be a lot of evidence for this belief though.

Many features humans possess are not common amongst aquatic or semi-aquatic mammals:

large ears
long limbs
inability to see under water effectively long hair on top of head which interferes with streamlining

Combine_Dave

Ref:

http://www.straightdope.com/mailbag/maquaticape.html

http://www.aquaticape.org/

http://en.wikipedia.org/wiki/Aquatic_ape_hypothesis

[Combine_Dave]

The plunge -- no matter how brief -- prepared the way.

Perhaps this was more of a brief wade?

I don't recall any earlier homids being shaped like torpedos afterall.

Combine_Dave

[DavidMcC]

I personally favour the idea of human's having an aquatic ape stage.

Unfortunately there doesn't appear to be a lot of evidence for this belief though.

Many features humans possess are not common amongst aquatic or semi-aquatic mammals:

large ears
long limbs
inability to see under water effectively long hair on top of head which interferes with streamlining

The problem with comparing humans with "typical" aquatic mammals is that you have to take into account the specific pre-adaptations in each case. No other aquatic mammals had universally jointed limbs, and therefore lost them. Our early attempts to swim (slow as they were relative to fully aquatic anmimals) would have been aided by universal joints, without which you are limited to paddling.
The hair probably had to stay on our heads even though it would have been a drag in water, to act as a UV protection in the absence of skin pigmentation (which apparently only appeared about 1.7MYa, as mentioned in a reference that Oolon Colluphid gave in the first aquatic ape thread). NB, UV protection on the head would have been very important, as the head is particularly vulnerable in that respect, and UV exposure in women can give rise to anencephalic babies!

[Marios]

The fact that she ignored the issue of crocodiles is one of the main criticisms of Morgan's version of the AAH. As you may have noticed, it has been a significant part of the debate on this thread.

What are the grounds for thinking this would have constituted a serious selection pressure?

I personally favour the idea of human's having an aquatic ape stage.

Unfortunately there doesn't appear to be a lot of evidence for this belief though.

It's an interesting hypothesis - while chasing it up she's brought up a lot of interesting phenomena which no one else seems to have deemed worth even trying to explain.

It's true that it's all terribly circumstantial - but the same seems to true/truer for all other similar human genesis theories of that period.

I don't think there's any point criticising scientific theories relative to an absolute that science doesn't provide or support - the value/lack of value of a theory is entirely relative to the alternate theories. If the evidence for the AAH is weak - then what theory is it strong for? If the AAH is circumstantial, then what theory is it not circumstantial for?

AAH didn't strike me as credible in an absolute sense - merely credible in comparison to the other theories I'd seen - the fact that it sticks it's neck out more is a _good thing_. Scientific theories are supposed to go out of their way to make themselves clearly vulnerable. Previous theories simply don't seem to have done that (or formally defined themselves as theories/hypotheses - 'savannah theory' seems to have been just a collective assumption - I can't even find a clear link to when it is that people believe Africa _had_ a savannah!).

Marios

[DavidMcC]

The fact that she ignored the issue of crocodiles is one of the main criticisms of Morgan's version of the AAH. As you may have noticed, it has been a significant part of the debate on this thread.

What are the grounds for thinking this would have constituted a serious selection pressure?

You should ask anthrosciguy about that.

[Marios]

http://en.wikipedia.org/wiki/Savanna_theory

http://en.wikipedia.org/wiki/Aquatic_ape_hypothesis

Marios