Re: Bipedalism in different substrates

From: Algis Kuliukas (algis_at_RiverApes.com)
Date: 07/14/04 

Date: 14 Jul 2004 01:44:57 -0700

NA Sides <nas@sonic.net> wrote in message news:<dpl2f05vabf2qf3pevjukoad6ndr81ula3@4ax.com>...
> On 9 Jul 2004 22:48:56 -0700, algis@RiverApes.com (Algis Kuliukas)
> wrote:

Sorry I missed this one until now, NAS.
 
> >> 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?

Ok, they're good questions. It's odd that apes are, generally, so bad
at swimming, isn't it? But they are. According to the literature
orangutans do not swim and neither do bonobos. There is one anecdotal
incident of a chimpanzee swimming once (maybe, or maybe it was just
wading with style) a few metres at Conkuoati but, apart from that,
niente. Gorillas are the only ape that apparently swims quite
comfortably, according to the literature.

Look, I think you're exaggerating the point (again). It's ok, Norm. I
know this is what you have to do when you're arguing against the AAH.
I realise that if you agree to play the game I'm playing - toning down
the proposed level of aquaticism - your objections start to seem a bit
trivial and silly. But anyway... 'why were apes exterminated by this
deadly activity'? Of course the answer to that is that they weren't.
It's just that our ancestors were more exposed to the dangers of
drowning that their's were - hence we evolved traits that tend to help
us move in water better than they have.

Perhaps our ancestors displaced theirs from the richest water-side
habitats - that would explain why they're worse than most terrestrial
animals, wouldn't it? Certainly it is consistent with the AAH
definition that water has acted as an agency of selection in our
evolution more than it has in their's, right?

> You are claiming that so many apes drowned while attempting to swim
> that an instinctive aquaphobia was instilled.

No. Actually the opposite. Enough of our ancestors drowned to
eliminate genes that built proto-hominins that were not very
profficient at moving through water. This gave our ancestors a love of
water (compared to apes). The great apes' (apart from gorillas)
undoubted aquaphobia is the result of so few of their ancestors being
exposed to the dangers of drowning compared to ours.

> 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.

Blimey, Norm. 'swimming holocaust'? What are you on about? I'm really
shocked that, even at this late stage in our debate, you're still not
clear on even the basic point I'm trying to make. I must be doing a
terrible job of explaining myself.

Let's try to clarify the proposed model...

1) Mid Miocene hominoidae living in coastal mangroves and other
wetlands around the Med/Tethys seas and associated river systems.
They're already wading-climbing (aquarboreal) apes and, due to their
wetland habitat they are more often bipedal when wading than they are
on solid ground. These are the LCA of Gorilla/Pan/Homo. They may or
may not have swimming abilities. It's probable, in my mind that, they
have but it is irrelevant to the idea that they'd wade bipedally
through the shallows.

2) Late Miocene. Two groups of these apes split off away from
mangroves into more 'traditional primate' forest habitats. First
gorilla ancestors around 7-8Mya, followed by chimp ancestors 5-7Mya -
leaving the third group, Homo ancestors, still in a predominently
water-side niches. Clearly, the move away from water-side niches would
have reduced the selection pressure of moving through water from
chimps and gorillas, compared to proto-hominins but, as gorillas
retain their swimming abilities it is likely that gorilla ancestors
may have returned to some wetland habitats and were, generally, more
terrestrial than were the chimps.

3) Pliocene. Homo ancestors now living in E African riparian forest
habitats subject to wide (and ever widening) swings in climate from
very arid to very wet. Hominins therefore became more 'generalists' in
the sense that they had to cope with both. In dry spells efficient
migratation (by efficient walking) along dried up river beds and lake
sides to find water and food sources was selecetd for, and in wet
spells wading, swimming and diving *more* than their ape cousins were
doing elsewhere - resulted in traits that gave us better aquatic
abilities than the apes. Hence out ancestors' swimming abilities were
never lost, they just gradually evolved.

Note that this three stage picture is a gross simplification of what
probably really happened. I suspect that there was actually a very
complex mosaic, with some groups having short spells closer to water
sources than others at different times. I also have the view that Homo
sapiens is the result of a hybridisation event of two hominis, meaning
that, contemporaneously, one group of our ancestors could have been
going through a 'more aquatic' phase at the same time that another
group of our ancestors were going through a 'less aquatic' phase. But,
*in general* our ancestors were exposed to water as an agency of
selection *more* than were the ancestors of the apes, *since the
split*.

Please tell me where I can make that any clearer.

> >> 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?).

It wasn't but swimmign is more dangerous than not swimming for any
animal that is not fully aquatic.

> 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.

Probably because their ancestors moved away (perhaps displaced) from
water-side habitats.

> Were their ancestors also drowning in great numbers?

Not as much as our ancestors since the split.

> If so, why were those ancestors drowning? Were they also
> foraging in water?

Not as much as ours.

> 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.

Not so, so no it doesn't.
 
> 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?

It wasn't 'so deadly' - just 'more deadly' than not swimming - as with
any animal that is not fully aquatic.

And it was just as deadly later as it was earlier. I'm suggesting that
homo ancestors, generally, continued to live in water-side habitats
for at least the last seven million years and, through the undoubted
selection going on from the greater (compared to ape ancestors)
movement thtough water, their swimming abilities have gradually
improved over that timescale.

> And when do you think swimming resumed?

I don't think there was ever a significant break which required any
such resumption. Some later groups of homo, I propose, lived in island
coastal/marine habitats and became even more aquatic relative to other
homo groups which were less aquatic. I propose the Homo sapiens
speciation event around 250-500kya was a hybridisation of two groups
such as these. Since then, our aquaticism and level of swimming
abilities have been, I propose, somwhat intermediate between those two
putative groups.

> 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?

It was never 'no longer deadly' - where did you get that idea from? We
do not know when nekedness and sc fat evolved, since they do not leave
a trace in the fossil record. We do know bipedalism evolved at least
4Mya and probably much earlier. We do know that we're more naked than
apes, have greater sc fat and that we can swim and dive better than
they can. We know that we move on land like they do in water.

Moving through water (wading, swimming, diving) provide simple
explanations for these three (and more) ape-human differences. Wading
for bipedalism, swimming/diving for nakedness and sc fat. The exact
order those traits came in our lineage is unknown but a generally more
water-side living ancestry for Homo is absoilutely consistent with
that view.
 
> >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?

It was a simple enough question. I was kind of hoping for a 'yes' or a
'no'. Well, actually, if you had an ounce of objectivity - it has to
be a 'yes'.

As someone who's recently found out about the joys of snorkelling in
the beautiful clear coastal waters of WA I can tell you that it's not
obvious how deep the water is even when you can see everything really
clearly.
 
In seven million years I suspect our ancestors lived in water side
habitats that were muddy sometimes and were crystal clear at others,
don't you? In muddy waters (singing 'I'm a Man!!!') they might have
been foraging riverside vegetation or perhaps crossing over river
deltas at low tides for new food sources like getting access to birds'
nests etc. In clear water they might have been wading through lagoons
looking for crabs. It's all posible and none of it contradicts the
need to wade.

Why did swimming kill them? Because - my original point - swiming is
more risky than not swimming, so, if you can, it's better to wade
bipedally than to swim.

> >> [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?

You're exaggerating again. Some risk is riskier than less risk. Wading
in water is riskier than walking on land. It's also costlier but if
there's sufficient reason to do it - getting access to food sources
that would be otherwise inaccessible, or perhaps there's simply no
choice because the river is flooding and you decide to wade away
towards higher ground. You're trying to pin me down to five minutes -
I don't know how long they spent wading, right? It's totally
unreasobale that you expect me to give this kind of detail. Wading in
a lagoon for a crab could, however, take less than five minutes and
provide a day's worth of food.
 
[..]

> >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.

No, I'm not refuting my earlier assertions, Norm. In a mosaic of
evolution I'm suggesting that sometimes they waded for crabs,
sometimes they waded to get across rivers, sometimes they waded to get
access to marshy birds' nests, somtimes they waded to get across river
deltas at low tides etc etc. Whatever they were wading for it was
undoubtedly an advantage to do so - access to food that they couldn't
have accessed otherwise. It's also undoubted that they'd do so
bipedally if they could. It's also undoubted that if they couldn't
they'd have to swim or drown. It's also undoubted that swimming is
riskier than not swimming and therefore wading makes selective sense
in habitats of those borderline depths.
 
> >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.

Do you think that hyping up the language of ridicule is making your
case any stronger? I don't.

I called you a fool only because you repeated, blindly, and in fact
exaggerated Bob's web citation that chimps often walked 1km (you said
1 mile) when anyone that knows anything about chimps would have been
very sceptical of that figure and checked it out before posting. It
turned out to be 50 yards, less than one twentieth of that claim.
Otherwise I don't think you're a fool at all. I get the impression
that your a very nice and clever guy. I welcome your critical eye, but
not your sneering (which is clearly what you're doing here.)

[..]

> >> 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.

Accepted.

> 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.

There's no contradiction. Storks have very long legs and yet they have
to get their heads wet when grabbing a fish, don't they?
 
> >> 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,

No I'm not. You're putting words in my mouth. I'm saying (again) that
our ancestors wree *more* aquatic than the ancestors of the apes.

> 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.

Wetlands are food rich. Use your imagination.
 
> >> >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.

I make no such insistance.

> >> 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.

Generalist: Able to draw upon resources on more than one niche. I
propose hominins were able to draw upon at least three niches -
wetland habitats, riparian woodland and those on the edges of those
forests.

> You have claimed
> proto-hominins were specialized aquatic foragers and that water
> somehow or other imposed selection for major features of hominin
> anatomy.

Putting words in my mouth again. A typical Mooreism.

> 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.

They would have been more efficient at it than chimp ancestors, right?
If you can accept that, you're on the way.
 
> >> 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?

'So much time' is subjective. I'm saying, yet again, they spent *more*
time in water thahn did the ancestors of chimps, get it?

> >> 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?

Many. In seven million years I suspect there were few water-side
niches they didn't exploit.
 
> >> >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.

But... again... our ancestors were not chimps, right? I mean you do
understand that point, at least, right?
 
> >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.

I give up.

> >> >> >>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.

It's adapted to bipedal striding too. But how many other terrestrial
animals have *anything* like our feet, whetehr bipedalor not?
 
> >> >> >>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.

Many PAs have noted that A afarenisis seemed to have stronger ad/ab
ductive abilities than apes and humans.

> >> >> >[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.

Yes, I'm asserting - but answer the question. group a, with those
traits would wade better than group b, right?

Look. I'm getting a bit tired of this 'oh yes it it... oh no it isn't'
kind of debate. We've both got better things to do. Let's just agree
to disagree about paddle-like feet, ok?

As to the notion that I've presented no evidence... no, no evidence
except that waist deep water is the most predictable place on the
planet for ape upsupported bipedalism to be practiced for as long as
the situation prevails. (And which other models can do that? Remind
me... none, zilch, nieko, nada) no evidence exept that Miocene apes
must have lived around the ever changing coastlines of the Med/Tethys
and that proto-hominins must have inhabited gallery forests in the
wet/dry cycles of the Pliocene.
No evidence other than moving bipedally is kind of likely to produce
morphological changes that allow bipedalism.
 
> >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.

It's rather likely that aquatic foraging would have been part of their
lifestyle given the proximate paleohabitats of the time and places
they lived in.
 
> >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.

But, once again, ooops! just disect out the main point, don't you?
Extant apes *aren't* bipedal. We ARE. The hypothesis is that our
ancestors moved through water *more* than their ancestors did. I'm
going to keep repeating this point until you get it.

> 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."

I do *not* deny that! Tell you what - why don't you just write out my
ideas for me until they become satisfactorily easy to dismiss, you're
practically doing that already. Another Jim Moore clone.

Honestly, it's all the aquasceptics can do. Hardy asked 'Was Man more
aquatic in the past?' And the response - 'That bloody fool Hardy - he
thinks our ancestors were aquatic.' And it's still exactly the same
response 44 years later. The mild idea that our ancestors were
slightly more aquatic than theirs is so bleeding obvious your brains
can't cope with it, you have to push it, extend it, exaggerate it into
some neat little pigeon hole you've got pre-prepared for 'wacky ideas'
and, no matter what, you're determined to squeeze it in there, aren't
you. Well, it's not going to fit. It's not a wacky idea at all.

You keep trying to pin me down to one and only one habitat, one and
only one depth, one and only one food source. I'm just not going to
allow that, sorry.

Your argument that the complete predictability that apes will move
bipedally in shallow water is an argument *against* it is just peverse
and, in fact, demonstrates the absurdity of your objection.
 
[..]
> >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.

Yes, of course - but only the wading model has to do that, right? The
others are somehow exempt. I don't do it, because it's bleeding
obious. Wetlands exist, they're food rich. Proboscis monkeys, bonobos
and western lowland gorillas all feed in such habitats. Next.
 
> >> 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.

No it isn't. Perhaps this is where you're binary thinking just can't
cope.

Let's try another tack...

Which is more arboreal? A chimp or a human? (easy, right?)
Ok which is more arboreal a chimp or a gorilla?
Which is more arboreal a chimp or an orangutan?

See? Things aren't black and white. Why does a species have to be
either a 'specialist aquatic forager' or *not*.

There are *many* grey areas areas in between the black and white that
you only seem to be capable of seeing.

For example:

a) In between dry land and deep water there are lots of habitats in
between: wetlands, littoral, salt marsh, river deltas, islands,
beaches, riparian woodland etc etc.

b) In a single habitat there are many microhabitats. Ina gallery
forest ecosystem you have possible deep and wide rivers, shallows,
river shore line, perhaps mud flats, marshes, grassy banks, mangroves,
dense woodland, more open woodland and open grassland all within a
couple of km.

c) In a single day a putative water-side dwelling hominin might spend
time in the trees, on the ground moving quadrupedally or bipedally or
wading or swimming.

d) In an evolutionary timescale a group of apes might get marooned on
a swampy island, isolated ina dry mountain range, find themselves next
to rivers and lakes etc etc.

This all goes into the melting pot. It's not so simple as to say that
'our ancestors were specialist aquatic foragers' - although i can see,
obviously, you'd love that to be the case. That way you can probably
defeat it.

> 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.

Rubbish. More time in water provides *more* selection. It's as simple
as that.
 
[..]
> >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.

You missed my point completely.

[..]
> >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?

It's one scenario that might have worked.

> >> 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?

Nothing to say there, I notice.

> >> 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.

Why would they want to do that?

> More open habitats could be exploited while retaining a considerable degree
> of ancestral arboreality.

What would they exploit in those open habitats?

> 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.

Meat eating? In Miocene apes? How does that help you?

> >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."

Ooooh no it isn't!!
 
> >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?

That species adapt to their niches.
 
> >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.

Pass

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
    ... >> pressure to create an instinctive phobia against swimming. ... >the more of a risk it would be when they did swim. ... Why was swimming extremely dangerous for apes but not for any other ... this fear of water and swimming was the product of an ancient swimming ...
    (sci.anthropology.paleo)