Re: Bipedalism in different substrates

From: NA Sides (nas_at_sonic.net)
Date: 07/11/04 

Date: Sun, 11 Jul 2004 15:51:55 GMT

On 9 Jul 2004 22:48:56 -0700, algis@RiverApes.com (Algis Kuliukas)
wrote:

>> >> >In article <d8kqe0pe3oscap2tb3c7tm5p9tbqduiebh@4ax.com>,
>> >> >NA Sides <nas@sonic.net> wrote:
>> >> >>On 7 Jul 2004 21:48:28 -0700, algis@RiverApes.com (Algis Kuliukas)

<snip>

>> So, even though they probably never swam much, those few times they
>> did attempt it proved so deadly that it exerted enough selective
>> pressure to create an instinctive phobia against swimming.
>
>Of course. I'm amazed you have a problem with this. The less they swam
>the more of a risk it would be when they did swim. This is why, I
>suspect, all terrestrial animals tend to have basic swimming
>abilities. The more they swam, the less the risk but the more
>efficient that locomotion would become.

Why was swimming extremely dangerous for apes but not for any other
terrestrial mammals? Why was it apparently safe even for monkeys? You
are aware, are you not, that monkeys can swim and that members of some
monkey species appear do so simply for the fun of it? Why were apes
exterminated by this deadly activity and monkeys were not? Why was it
apparently also safe for aquatic mammals such as tapirs and capybaras?
You are claiming that so many apes drowned while attempting to swim
that an instinctive aquaphobia was instilled. Yet you also claim that
this fear of water and swimming was the product of an ancient swimming
holocaust in which apes continued to forage aquatically even though it
was exacting a terrible toll. You have yet to say why you think apes
were uniquely subject among mammals to drowning and why, in spite of
the terrible mortality inflicted on them by their attempts to swim,
they nonetheless persisted until the aquaphobia developed, then
persisted in wading thereafter, then at some point resumed swimming.
You also haven't explained why you think swimming wasn't so dangerous
this second time around.

>> The
>> ancestors of the modern great apes also dabbled in this deadly
>> activity for a considerable period of time and therefore inherited the
>> same phobia, but then they mostly got out of the water altogether and
>> therefore never became bipedal. When the descendants of the
>> proto-hominins went back to swimming, the activity was no longer so
>> dangerous for some reason. Is that about right?
>
>It wasn't so much that the proto-hominid descendents went 'back to
>water' as much as they never left it, unlike the chimps and gorillas.
>The AAH is saying that our ancestors were exposed to water as an
>agency of selection *more* than the ancestors of the apes. So, yes,
>our ancestors lived in water-side habitats more than theirs did. This
>explains why we're bipedal and they're not. It explains why we can
>swim better than they can. It explains why we're naked and have more
>sc fat. etc etc.

My question had three parts. You attempted to answer only the first -
inadequately - and I await your clarification on that first part (i.e.
why was swimming so much more dangerous for apes than for other
creatures?). The second and third parts you merely avoided. Perhaps I
was being unclear. I also asked how you think the extant great apes
acquired their aquaphobia. Were their ancestors also drowning in great
numbers? If so, why were those ancestors drowning? Were they also
foraging in water? If so, this shoots down your argument that major
human traits are due to human ancestors being exposed more to water
than were the ancestors of the great apes.

Thirdly, I asked, if swimming was so deadly to proto-hominins, why was
it apparently not so deadly later on when their descendants took it up
again? And when do you think swimming resumed? You say above that they
never really left the water, but that wasn't the question I asked.
Soon after my entry into this thread I asked you if you think sc fat
was an adaptation to wading and you denied that was your belief. Yet
here you claim once again that:

 "The AAH is saying that our ancestors were exposed to water as an
agency of selection *more* than the ancestors of the apes. So, yes,
our ancestors lived in water-side habitats more than theirs did. This
explains why we're bipedal and they're not. It explains why we can
swim better than they can. It explains why we're naked and have more
sc fat. etc etc."

How precisely do you think that living in "water-side" habitats
brought about nakedness and sc fat? You claim that swimming was deadly
for proto-hominins, so you must think that these traits developed
later when swimming was no longer deadly. Why was it no longer deadly?

>NAS, do you contend the assertion that swimming is riskier than not
>swimming?

I don't accept your assertion that swimming in waist-deep water is
somehow so extremely dangerous that, although proto-hominins rarely
attempted it, the mortality rate was so high that their pelvis and
spine and legs were reshaped. You claimed that they couldn't *know*
the water was deep unless they were wading bipedally. Yet this would
only be potentially a problem in extremely muddy water where depth
couldn't be accurately gauged. And yet you are also claiming they
foraged in clear water for crabs. This is another inconsistency. Your
"drowning danger" claim falls apart in your only attempt to say how
proto-hominins foraged. How do you think they were foraging in muddy
water? Why were they attempting to swim in muddy water? Why did it
kill them when they attempted it?

>> [Algis]
>>
>> >Regular upright bipedal locomotion is likely to result in the changes
>> >to the lower spine and pelvis. The more they waded the more that would
>> >be selected for. How much clearer could it be?
>>
>> [NAS]
>>
>> But you claim they weren't wading for hours at a time, so I'm not real
>> clear on what the specific selective factors are supposed to have
>> been. Were all the quadrupedally adapted apes being killed by sore
>> backs, tired legs or what?
>
>Sometimes they'd be wading for a long time sometimes not. But the more
>they waded the more likely they'd have traits to support upright
>locomotion - because the ones that had those traits more would move
>more efficiently (even if it was just five minutes a day, it all
>counts) and reduce some of the risks asociated with wading.

It does *not* "all count." You are claiming that water provided some
benefit so large that procuring this benefit outweighed a high risk of
death. If there was no significant danger there was no selection. But
what aquatic foraging activity was so dangerous that five minutes in
the water posed a significant risk of death? What resource was so
easily obtained that it could be secured in five minutes and so
valuable that it made the risk worthwhile? And what was the advantage
that better bipedal adaptation is supposed to have provided during
those extremely hazardous five minutes?

<snip crab grabbing>

>> Of course to get at these oddly plentiful crabs, the bipedal waders
>> would have had to plunge down into the water and grope around on the
>> bottom with their hands. So you have the very situation - heads and
>> arms underwater - that you claimed as primary reasons why quadrupeds
>> would have gone bipedal while wading. For some reason they are not
>> panicking and drowning now. This is a big change since earlier you
>> were claiming that it would have been dangerous for waders merely to
>> get their faces close to the water.
>
>Please stop this facile attempt to pin this idea down to such a high
>degree of specifity. I'm trying to answer your objections with as many
>different examples from different angles as I can but I've repeated
>many times that over seven million years I think that our ancestors
>lived through a mosaic of evolutionary habitats. This is standard
>orthodoxy, so I'm curious as to why you are contesting it. Oh, yeah -
>I know - it's because I'm favouring the dreaded 'a' hypothesis, so
>different rules apply. It's ok for aquasceptic models to be vague and
>talk about 'mosaic evolution' but not the aah proponents. No, they
>have to provide an exact menu item of food eaten. A ethological map of
>behaviours with exact perecentages postulated for wading (at which
>depth), swimming arborealsism and terrestrial locomtion.

You're smokescreening, Algis. You know I wasn't contesting that our
ancestors lived through a mosaic of habitats. I was pointing out a
contradiction between your earlier claim that it was extremely
dangerous for proto-hominins to get their head and arms underwater (or
even close to water) and this current claim that they were foraging
for crabs on the bottom of shallow lagoons. With your crab-grabbing
claim you have refuted your own earlier assertions. Since you offered
those assertions as "evidence" supporting your claim that bipedal
wading is safer, you have undercut whatever argument you think you may
have had. You have never offered real evidence to support any of your
assertions, but even so you should at least try for a little more self
consistency among them.

>This is why I keep saying that it is 'obvious'. Wetland habitats are
>food rich - that's not something I've conjured up from my imagination.
>Miocene apes lived in habitats around the Med/Tethys coasts. They must
>have been exposed to those changing coastlines. Later, in the
>Plio-Pleistocene hominids in East Africa must have been subjected to
>flood-dessication cycles. All of these data place hominoidae and
>proto-hominids closer to water sources that modern apes are today.

Crab-grabbing is all you've offered so far. You've wiped out legions
of quadrupedally adapted apes who plunged mindlessly into the water
attempting to swim after crabs. The only survivors were the clever
ones who refused to succumb to the mad temptation to swim. Meanwhile
monkeys and other terrestrial quadrupeds continued to swim happily and
safely all around the corpses of the foolish apes who had attempted
the same feat. Some of the more clever apes did survive by wading
bipedally, and the crabs were so nutritious and plentiful that a five
minute trip (two and one half minutes each way) made up for the
terrible risk of back-strain that accompanied any venturing - no
matter how brief - of apes into water. So many of these more clever
apes succumbed to back-strain or leg strain during these short jaunts,
or slipped and suffered fatal falls because their wide and manually
dexterous feet were no good for moving in water, that eventually it
led to reorganization of the pelvis, spine, legs and feet. I'm not
sneering at you, by the way. I'm using parody to highlight
inconsistencies and weak claims. I don't mind that you called me a
fool, so you should allow me this small bit of license.

>> >Again, you conveniently forget what we're comparing the early bipeds
>> >with. It's not stated, but clear, that you're comparing them with
>> >Homo. If you compare them with chimps, bonobos or gorillas however,
>> >a'piths already were relatively long legged. Of course we have zero
>> >data about the LCA of all four groups - and yet you just *know* that
>> >this particular pro-wading argument is a non sequitur. Amazing.
>> >
>> >> Yeah, I missed that one. Algis's post tend to contain so many
>> >> unsupported assertions and non-sequiturs that it's easy to let a dozen
>> >> or so slip by unnoticed.
>> >
>> >So, support the comparisons. What are you comparing what with? Not
>> >supporting that assertion I note. More double standards.
>>
>> What comparisons are you referring to? Are you talking about alternate
>> foraging scenarios?
>
>No. Clearly Jason was just talking about the short leggedness of early
>bipeds - an unsupported assertion, since we have no data on the LCA.
>He was comparing to humans, not to extant apes.

Yep, I should have gone back and made sure what point was being
discussed. You have my apologies, sir. I don't know how long their
legs were before and during the transition to bipedalism. Longer,
perhaps, than legs of chimps and shorter than those of afarensis. But
I'm not going to eat too much crow until you at least make some
attempt to clarify how you think they were foraging. Your whole point
seems to be that longer legs would have kept their chests and faces
above the water. But in your crab-gathering claim you would have them
plunging beneath the surface each time they spotted a scuttling morsel
on the bottom of the clear-water lagoon. Your claims are mutually
contradictory.

>> I told you I lean toward the view that
>> proto-hominins were generalists who utilized different foraging
>> strategies and acquired a variety of different food types. I listed
>> some of the foods they could easily have used. I think I forgot to add
>> leafy green vegetables, nuts, seeds, melons, and starchy roots and
>> tubers to the list. I'll probably think of more later.
>
>Yes, but it's meaningless to do that. When, eactly, in the seven
>million years were those food items available? The mosaic of habitats
>was probably so vastly complex that it's silly even to try. I mean,
>would it make you feel better if I drew up a list of fauna and flora
>that live in all the wetland habitats? (Later, apparently, you seem to
>suggest it would.)

You forget that I'm saying they were generalists who foraged for
whatever foods were readily available at any given time. I've listed a
wide variety of foods that generalists could have opportunistically
utilized. Proto-hominins were anatomically, physiologically and
probably behaviorally, able to forage arboreally, terrestrially and to
a certain extent aquatically. This flexible adaptability would have
allowed them to make a living in a variety of different environmental
contexts. You, on the other hand, are claiming they were specialized
aquatic foragers, so you need to specify what aquatic resources were
available at all times and that could be exploited using some aquatic
foraging method or methods that you still haven't adequately
specified. You need to say what methods they might have employed. your
crab-grabbing claim is the closest you've come to presenting a
tangible scenario that can be analyzed.

>> >You're being pedantic. I'm trying different angles to demonstrate
>> >(increasingly, it seems, to someone who is determined not to be
>> >persuaded) how wading through water would be selected for. In seven
>> >million years of evolution I think there's plenty room for times when
>> >our ancestors spent several hours a day wading, other times when they
>> >did so less frequently and other times when they did not do so at all.
>> >I think a mosaic of habitats were inhabited throughout that timescale.
>> >That's why I'm not going to be pinned down to stating that species x,
>> >lived in habitat y where in spend n minutes per day wading in depth l.
>> >I'm sorry if you find this vague but, I note that the orthodox models
>> >you refuse to defend (and in fact impune as 'poor') are even more
>> >vague except in their curious certainty that water was *not* anything
>> >to do with it.
>>
>> Well, if you now accept that proto-hominins inhabited a variety of
>> habitat situations, you've assimilated at least that much of what
>> Pott's was saying in "Environmental Hypotheses of Hominin Evolution."
>
>I've always accepted that.

But you insist on making them specialized aquatic foragers: a claim
that the available evidence doesn't support.

>> Now if you can get past the idea that during drier periods they would
>> have been restricted to gallery forest "refugia" and that they would
>> have had to wade for their lives during the wetter periods of the
>> climate fluctuation cycles, you will be making progress.
>
>I've *never* claimed any kind of exclusivity for moving through
>wetland habitats. I'm claiming (yet again) that our ancestors moved
>through water *more* than the ancestors of the great apes. That's all.
>
>As someone who favours a generalist model, I find it rather
>exasperating to be arguing this point with you. Your 'generalist'
>clearly didn't move through trees as much as chimps do and, it seems,
>you don't like the idea that they moved through water either. This
>doesn't sound like much of a generalist to me.

Sorry Algis, but you have not, in any of your posts to this point,
favored a generalist model. If you think you have been doing so, then
you don't know what a generalist model is. You have claimed
proto-hominins were specialized aquatic foragers and that water
somehow or other imposed selection for major features of hominin
anatomy. You have not yet presented a credible scenario for how such
selection could have occurred. I readily acknowledge that
proto-hominins wouldn't have moved as much or as efficiently through
trees as do chimps, but that's no problem. Generalists typically are
opportunists who perhaps can't utilize some particular resource as
efficiently as could a specialist, but make up for this by being able
to exploit a wider resource base. The same goes for foraging in or
around water. Perhaps they wouldn't have been particularly efficient
at it, but if some easily obtained food presented itself, they
wouldn't have turned up their noses at it. Bears and raccoons do much
the same.

>> Of course you
>> won't have made *much* progress until you realize that the
>> paleoecological data don't support your claim that proto-hominins were
>> specialized aquatic foragers.
>
>See that? Putting words in my mouth. When did I ever say that they
>were 'specialised aquatic foragers'. All I've ever claimed is that our
>ancestors moved through water more than their's did. Now, are you
>arguing that they *didn't* or what?

You *don't* claim they were specialized aquatic foragers? Then why the
heck do you claim they were spending so much time in water that basic
features of their anatomy and behavior supposedly were reshaped?

>> As for other models or scenarios, I've
>> only impugned Lovejoy's male provisioning model. I have told you my
>> own opinion that proto-hominins were probably generalists who foraged
>> widely and in an opportunistic manner for a wide variety of habitat
>> resources. I'm not going to defend any scenario that has them
>> depending solely on some single resource because I doubt they actually
>> did so.
>
>Sorry. It was Jason who said that other models were 'poor'. It's his
>assertion that my criticisms of the other models do nothing to help
>support this one.
>
>And, again, I'm not suggesting that they depended *soley* on any
>single resource - just that they depended on water-side niches *more*
>than did the ancestors of chimps and gorillas.

*What* "water-side" niches? Crab grabbing?

>> >Apes that move through waist deep water *will* move bipedally.
>> >Therefore the more they wade, the more bipedal apes would become. It's
>> >so f&%Ģing obvious anyone with three independent thinking brain cells
>> >can see it.
>> >
>> >All of your objections are the most pedantic bluster I've ever seen.
>>
>> Everyone knows you think it's obvious. You've repeated many times that
>> it's obvious. But through all those repetitions you've failed to
>> support your assertion. Your "sore-back" claim is the closest you've
>> come and it's not credible. Mostly you just continue to ignore the
>> fact that waist-deep water provides buoyancy that would have
>> eliminated the need for bipedal adaptations.
>
>For bipedalism to have evolved don't you think it would be kind of
>useful if the model can, somehow, get these apes to move, you know,
>bipedally? Wading does that. It does it predictably. It causes it to
>happen for as long as the conditions prevail. It does so with 100%
>(not just > 50% as Hunt would define it) of the body weight on the
>hind legs. No other scenario can do that and yet it is the one
>scenario you are, curiously, keen to reject. I wonder why.

Being on land gets chimps walking bipedally twenty times longer than
does wading, with full weight on the legs and with none of that
buoyancy that makes bipedal traits unnecessary.

>In waist deep water they've no choice and the bouyancy makes it
>practically cost-free and there'd therefore be less adaptive pressure
>to change. In shallower water they'd have progressively more choice
>and progressively more cost and consequently there'd be more pressure
>to change. Wading apes, though, (crucially fore this argument) would
>always move through *both* of these depths and, in fact,a full
>spectrum in between dry land and depths where they'd have to swim. It
>is this *package* of locomotor behaviours that, as a unit, would
>favour the evolution of traits which aid a watered down form of
>terrestrial bipedalism such that, eventually, a rubicon would be
>crossed where it would be easier to move bipedally on land too.
>
>Mostly, you just ignore the elegance of this explanation and instead,
>pedantically, try to pin it down to a particular depth, or a
>particular habitat... *anything* but accept that this idea has more
>merit than anything else going.

Elegant, huh? If you say so. Unfortunately you seem unable to support
this elegant speculation with anything other than sub-speculations,
and assertions piled on top of assertions. You seem to think it's an
either/or choice between vague and pedantic. You don't even try to
analyse the logical implications of your own claims or to check those
claims for mutual inconsistencies. You harp on the importance of
to-and-fro trips from shore to waist-deep water, claiming that they
would have entailed selective costs but, beyond your unrealistic
claims about hidden dangers, you can't specify what these costs were.

>> >> >>3) another unsupported assertion. By the way, humans don't have flat
>> >> >>"paddle-like" feet. We have narrow arched-feet good for putting
>> >> >>forward thrust on the ball of the foot and for catching the forward
>> >> >>motion of the stride on the heel. Neither of these adaptations are
>> >> >>much use while wading.
>> >
>> >Compared to chimps, we have *more* paddle-like feet.
>>
>> No we don't. That's just a figment of your imagination. Ducks have
>> flat broad fan-shaped paddle feet. Chimpanzee's feet are shaped more
>> like a duck's feet than are ours. Our narrow arched feet are lousy
>> paddles, but they are well adapted to bipedal striding on dry land.
>
>A fan shape is not paddle-like. A paddle shape is what you find at the
>end of an oar. You've just decided to re-invent 'paddle-like' to fit
>your argument. The gap between the big toe on the chimp foot and the
>rest (without webbing) by definition makes it less paddle-like than
>ours where the big toe is closer and the toe lengths are shorter.

Our *hands* are more paddle-like than our feet. They're flat and the
fingers can be brought together to efficiently push water back. It's
absurd to claim that our foot morphology is adapted to wading or
swimming. It's adapted for bipedal striding. If water had played a
major role in the shaping of an ape foot, the rigid arched structure
wouldn't have developed. Instead the apes would have kept their wide
flat feet and simply developed webbing. Much less morphological change
would be involved and this would have provided a quite large and
efficient duck-foot type paddle as good as any aquatic mammals' webbed
foot.

>> >> >>4) Orangs, with their narrow ilia, have at least as much lateral leg
>> >> >>motion as humans.
>> >
>> >Fine. But look, you asked me for how wading might result in the
>> >selection of traits that would aid terrestrial bipedalism. I gave you
>> >some. Of course you have to attack them and try to swat them down like
>> >flies but the point remains that, clearly, some (although not all)
>> >adaptations that are likely to help wading would also help terrestrial
>> >bipedalism.
>>
>> You claimed wide ilia enable wider lateral leg motion and
>> "paddle-like" feet enhance wading ability or swimming. Both claims are
>> bogus. Apes have good lateral motion and more paddle-like feet than
>> humans.
>
>It wasn't so much wide ilia but iliac blades orientated more
>anteriorly. Again I thought this wasn't in dispute. It's one of the
>key indicators of a. afarensis bipedalism. All climbing primates have
>good ab/ad duction of the thigh for climbing. Terrestrial bipeds need
>some of that too, but I'm claiming that wading bipeds need it more.
>
>You didn't answer my point. All I was trying to do was answer your
>criticism that wading would not lead to traits which were exaptations
>for terrestrial bipedalism. This is clearly not true. I listed a few
>possibilities.

You've presented no evidence ether that hominin pelvic structure
increases the legs' lateral mobility or that such mobility, if it
actually had existed, would have had adaptive value associated with
wading. Once again you offer nothing but fanciful assertions that are
unsupported by available evidence or, as in this case, refuted by such
evidence. Aquaphobic great apes have greater lateral leg mobility than
anyone but human contortionists.

>> >> >[JE]Why does the facultative biped have fewer babies?
>> >> > [than a proto-hominid evolving wading traits]
>> >
>> >It wades less efficiently, it is not able to wade in as deep water, it
>> >is more at risk from losing it's footing and drowning when the water
>> >gets deeper. (Of course.)
>>
>> You make three claims - all unsupported assertions. Then you add that
>> "of course" those claims are true. You seem to think that your own
>> private conviction lends credibility to your unsupported opinions.
>
>1) If ape group (a) has some adaptive traits to help it wade (ie
>longer legs, flatter more paddle-like feet, more upright orientated
>spine and pelvis, more powerful ad/ab duction of the thigh) than group
>(b) it is likely to wade more efficienctly. How can you dispute this?

You're merely asserting that proto-hominins had significantly longer
legs that figured in some viable foraging strategy. You haven't
presented evidence that any such strategy existed. You merely assert
that it existed and resulted in leg lengthening. If you think
crab-grabbing could support hominin populations, present evidence to
support that assertion. You also repeat the false claim that humans
have flatter more paddle-like feet. In fact great apes have flatter
and broader feet.You've presented no evidence - none- zilch - that
morphological reorganization was the product of wading.

>2) If ape group (a) has longer legs than group (b) it is likely to be
>able to wade in deeper water. How can you dispute that?

I don't dispute that longer legs would have allowed wading in deeper
water. You should have said this is what you meant by the phrase "more
efficient wading." Now demonstrate that a viable aquatic foraging
strategy existed and that slightly longer legs would have provided a
significant advantage to proto-hominins foraging in this manner.

>3) The third is, a grant you, a little less certain but I put it to
>you that it's rather likely.
>
>I write 'of course' to counter the smoke screen of pseudo-scientific
>pedanto-babble that culminates in arguing that the very certainty of a
>bipedally wading quadruped precludes it from being cited as an
>argument for the selection of bipedal traits in a proto-hominid. By
>this argument the more causative a factor is, the *less* it can be
>used as an argument for bipedal origins. That is the very essence of
>nonsense, the antipathy of scientific reason.

Quadrupedally adapted apes tend to wade bipedally. That's the only
real datum you've got. Their ancestors have been doing so for millions
of years. That is a reasonable inference. Millions of years of it had
no "causative effect" in terms of making them efficient bipedalists.
You deny the only remotely plausible aquatic foraging scenario that
could have imposed selection on our own ancestors - that our own
ancestors were foraging in shallow water for long periods of time.
Instead you continue to assert the existence of entirely unrealistic
"dangers."

><snip>
>> >For heaven's sake. Oh right - so there are no waterside habitats
>> >anywhere near the Med/Tethys coasts of the Mid/Late Pliocene (you know
>> >where apes lived at that time). Ever heard of wetlands like swamps,
>> >littoral, salt marsh, mangroves? Apparently not. What *is* your
>> >problem? Rather than admit that apes might have inhabited waterside
>> >habitats - far too uncomfortable - you'd rather re-write ecology so
>> >that wetlands cease to exist.
>>
>> It shouldn't be too much trouble for you to list the resources in each
>> of these habitats that you think would have supported populations of
>> specialized aquatic foragers. I've already provided you with a list of
>> resources that I think generalized proto-hominin foragers could have
>> utilized.
>
>So you *do* want me just to dig up a list of food items that live in
>such habitats. What's the point?

I'm trying to get you started on the road toward doing real science.
You should have begun research into this a long time ago.

>> Note that generalists, by utilizing a wide variety of
>> habitat resources, and foraging in different areas, aren't so likely
>> as more specialized foragers to deplete the resource base on which
>> they depend. Since your specialized foragers would have faced this
>> problem, it's reasonable to ask you what plentiful, and not easily
>> depleted, resources you see as the basis of their species ecology.
>
>You're trying to stick this specially exaggerated label 'specialised
>foragers' - but you know I never used that term myself. I agree with
>you that they were generalists but, that includes moving through water
>more than chimps do, right?

I realize that you never use the term. The claim that they were
specialized foragers is *implicit* in your primary claim that water
reshaped hominin morphology and behavior. You apparently have never
analyzed your own claims in sufficient detail to uncover that basic
implication. If they were spending enough time in water to exert
adaptive pressures sufficient to drive those morphological changes,
then they were specialized aquatic foragers.

>> >> >>b) You've presented no realistic risks.
>> >
>> >Odd that. Sometimes you guys say that the crocs would eat up all the
>> >hominids so they'd never get in the water, sometimes you say they'd
>> >never swim 'coz they'd always wade safely, sometimes you ask 'why
>> >would they wade when they could swim?' - *anything* as long as this
>> >pesky idea would just go away. Your scientific objectivity shines
>> >through the mist like diamonds.
>>
>> Try to focus, Algis. If you postulate wading or swimming risks as a
>> factor leading to obligate terrestrial bipedalism, you need risks that
>> distinguish between less bipedally adapted and more bipedally adapted
>> waders. You know that's what we were talking about. Your "hidden-pits"
>> danger was bogus. Your "arms underwater attract crocodiles" danger was
>> bogus. Your "swimming is dangerous, so they waded bipedally, and hence
>> saved their lives and thus became obligate terrestrial bipeds" danger
>> was bogus. It was all bogus from beginning to end. You conflate your
>> own imaginings with evidence and pretend that those imaginings have
>> some kind of scientific significance.
>
>The only imaginings going on here are those that pretend that moving
>through water would incur no extra risk than moving through land, and
>that any animal with a few basic adaptations that helped it wade
>bipedally rather than have to swim would be less at risk.
>
>The only thing bogus here is the bizarre claim that as quadrupedal
>apes would always move bipedally in shallow water it cannot be
>considered as a factor in the evolution of terrestrial bipedalism.

So far as I can tell your claims of hidden dangers really are bogus.
Your "arms attract crocodiles" claim is silly to begin with and
inconsistent with your later "crab-grabbing" scenario. You've also
presented no evidence whatever to support your claim that
knucklewalkers would tend to get their arms caught by underwater
snags. After all this time you still reject the only remotely
plausible scenario, the one Jason and I spoke of: hours long foraging
in water below waist level which would be energetically inefficient
and tiring for quadrupedally adapted apes. If you do eventually accept
that idea, you still will have the problem of outlining what plentiful
and not easily depletable resource could best be exploited in that
way. You seem offended when anyone tries to get you to clarify your
vague speculations and support them with evidence.

>> >> >In waist deep water, the buoyancy assistance of water minimizes the
>> >> >differences between an obligate biped like ourselves and a facultative
>> >> >biped like just about every other primate. This is why "waist deep
>> >> >water" getting them to stand up is a non-sequitur. This is why the
>> >> >exposure to shallower water is the key.
>> >
>> >They didn't wade in water at just one depth, though, *did* they? There
>> >was a *continuum* of depths. It's the *whole package* of wading
>> >through these depths that I'm suggesting caused the changes I'm
>> >talking about. In getting to the waist deep water, they'd almost
>> >certainly go through the shallower water at least twice.
>>
>> The fact is you've failed to support any of your claims that wading in
>> any depth from ankle-deep to chest-deep would have imposed selection
>> for morphological reorganization. Jason and I have helped you out by
>> noting that quadrupedal apes would be inefficient at wading in very
>> shallow water for hours at a time (as they would have been at
>> prolonged bipedal walking on land), so if you could come up with a
>> credible scenario as to why they would be doing that, you would at
>> least be on more solid ground (no anti-aquatic slur intended) than you
>> are now; but you've pretty much rejected these helpful reminders that
>> might have allowed you to hone your ideas into some kind of actual
>> hypothesis. Instead you've simply repeated again and again your same
>> baseless opinions as though they constitute evidence.
>
>The shallower the water, the more 'support' needed and the more likely
>anatomical changes would evolve to provide that support. As wading
>involves movement through a continuum of depths (a point I still
>haven't seen you accept) then, of course, shallow depths would be
>moved through every time they'd move into and out of deeper water.
>
>You stick a convenient qualification onto that shallow wading, though,
>don't you - when you say 'hours at a time.' A qualification designed,
>no doubt, to make you feel more confident that it could never be
>achieved. When I do provide a scenario that would achieve it (wading
>in lagoons and estuaries for crabs as people here in WA do every
>season), however, you sneer at it and rubbish it. This argument, it is
>increasingly clear, just cannot win with some people no matter what.
>It has already been classified as 'wrong' and no amount of evidence
>can change that prejudice.

Extended bipedal wading in shallow water would be energetically
inefficient for quadrupedally adapted apes. It would tire them out. If
they were successfully foraging in this way, selection could occur for
more efficient bipedalism. Do your estuaries and lagoons support
thousands of foragers year round? Do those foragers depend on nothing
else but the food they get while wading?

>> >> >>That's OK with me. You can continue in that mode forever on usenet or
>> >> >>aquatic ape forums. It might present difficulties if you ever try to
>> >> >>publish in peer reviewed journals.
>> >> >>
>> >> >><snip>
>> >
>> >Yes you always snip the argument that the other models are worse,
>> >don't you? Just don't want to go there.
>>
>> I've already presented you with a better scenario: the idea that
>> proto-hominins were generalists who were able to exploit a wider range
>> of resources and habitat conditions than could specialized forest
>> dwelling arborealists.
>
>Oh, and this is better, is it? How is it better? How does a
>'generalist' become a biped? How does 'exploiting a wider range of
>habitats' (whatever that means, as chimps are generalists and you're
>proposing that somehow we became more generalists through losing the
>forest habitat and not gaining the aquatic one) make some apes move
>bipedally more than others? Come on. I want specifics. I want to know
>the cost-benefit equation, which traits are going to be selected for,
>why the non proto-hominids would be at a disadvantage if they didn't
>have these traits etc etc. Just read through all your points you made
>against the wading model and apply them to the 'generalist'
>(whatever-that-is) model. Are you willing to do that, or do you invoke
>the double standard at this point?
>
>> It's not a developed model, but it's more
>> internally consistent and explanatorily powerful than your own
>> grab-bag of opinions and assertions.
>
>Internally inconsistent? So, your 'generalist' is more generalist than
>an ape, yet it has given up the forest habitat and it hasn't stepped a
>toe in the water. How's that internally consistent?
>
>Explanatory power? Can it even give one simple reason why being a
>'generalist' - being more generalist than a chimp, presumably - might
>even lead to one *incident* more of bipedalism than a chimp?

More efficient bipedalism would have allowed hominins to carry weapons
and food and travel farther in a day's foraging than do chimps. More
open habitats could be exploited while retaining a considerable degree
of ancestral arboreality. Meat could more easily be acquired and in
the more open areas grains could perhaps be exploited. This would be
consistent with the observed dental changes and continuous occupation
of sites while the climate fluctuated and conditions changed.

>> The bottom line is that
>> proto-hominins may well have been foraging at times in water, but most
>> evidence is inconsistent with the claim that they were specialized
>> aquatic foragers. They were generalized all-rounders and their
>> descendants inherited and further developed that initial adaptive
>> flexibility.
>
>I never said they were *specialized aquatic foragers*. That is your
>invention.

It's implied by your claim that morphological reorganization was due
to water as the primary "causative factor."

>So, finally, you now admit that proto-hominids "may well have been
>foraging at times in water". Amazing. Ok, good. Let's delve into that
>a bit more.

I've been saying it all along. Go back and re-read from where I
entered the thread.

>Do you, furthermore, accept that proto-hominids may have foraged in
>water *more* than did the ancestors of Pan/Gorilla?
>
>Do you accept that if this was true, that it is pretty much a law of
>biology that a difference in such behaviours is likely to result in
>adapative change to help the wading foragers do so more efficiently in
>the group that did so more?

You haven't framed your question clearly enough that I can agree or
disagree. What "law of biology" do you have in mind?

>Do you accept that if ape group a have traits which help them wade
>bipedally that are not shared by ape group b then ape group a are
>better pre-disposed to terrestrial bipedalism?

That depends on what traits you're referring to. You claim that our
feet allow us to wade more efficiently than would the feet of
great-apes. You have inaccurately described our feet as flat whereas
actually the great-apes have flatter and broader feet that might
better enable them to make their way over underwater sand, mud or
cobbles. We are better adapted for extended wading in water below
knee-depth, but you've presented no valid evidence of any kind that
such wading figured in the proto-hominin adaptive strategy. In fact
you shy away from this scenario while repeating assertions that
selection occurred while going to and fro from shore to waist-deep
water. You claim that quadrupedally adapted apes would suffer greater
mortality during these commutes, but have presented no credible
scenarios of how this greater mortality would occur.

If you ever do manage to clear up the basic inconsistencies, outline a
realistic possible aquatic-based ecology, and find some evidence to
support your assertions, then you will have the makings of a credible
argument. Of course you ought to bear in mind that terrestrially
acquired bipedal traits would also allow for extended shallow-water
wading.

NAS

>Algis Kuliukas

Relevant Pages

  • Re: Bipedalism in different substrates
    ... >> can keep track of the depth of the water you're in and see if you are ... Developing bipedalism as a means of guaging ... Apes are poor ... But the point remains that swimming is the overwhelming ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... >>water into an argument against it being a selective factor then, ... > wading, therefore, would have saved lives. ... > in the thread, nobody was swimming. ... I argued that as apes, generally, are not good swimmers ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... Whether the original bipedally wading apes could swim or not - they'd ... still move bipedally in shallow water. ... Because our ancestors lived by the ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... >>the more of a risk it would be when they did swim. ... > Why was swimming extremely dangerous for apes but not for any other ... Why were apes ... us move in water better than they have. ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... >>the more of a risk it would be when they did swim. ... > Why was swimming extremely dangerous for apes but not for any other ... Why were apes ... us move in water better than they have. ...
    (sci.anthropology.paleo)
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