Re: Bipedalism in different substrates

From: NA Sides (nas_at_sonic.net)
Date: 07/09/04 

Date: Fri, 09 Jul 2004 15:25:00 GMT

On 8 Jul 2004 21:38:49 -0700, algis@RiverApes.com (Algis Kuliukas)
wrote:

>NA Sides <nas@sonic.net> wrote in message news:<dj1re0p7ii9mk286peend47n06n44tlar0@4ax.com>...
>> On Thu, 8 Jul 2004 16:57:50 +0000 (UTC), jae@vidi.ucdavis.edu (Jason
>> Eshleman) 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]
>
>In the intrests of brevity I'm going to try to reply to your reply,
>Jason's reply to your reply and your reply to Jason's reply to your
>reply all in one go.

Each post would have been more brief and readable if you had responded
to mine and Jason's comments in separate posts. But no matter. In
order to avoid a monstrously long post I'm going to snip most of your
remarks addressed specifically to him and he can respond to your post
separately if he so desires.

 I note that you've snipped away all my questions regarding what I
called "the ancient swimming holocaust." Those questions were aimed at
clarifying your ideas about swimming as a selective factor and your
views as to why modern great apes seem to share the same swimming
phobia that you claim forced proto-hominins into a pattern of bipedal
wading which somehow then brought about morphological reorganization
leading to obligate terrestrial bipedalism.

Perhaps you think the questions were flippant or trivial, but they
offered you an opportunity to clarify your ideas about hominoid and
hominin phylogeny while perhaps dispelling what appear to be basic
inconsistencies in your explanation of how this phobia arose in the
different hominoid lineages. You have accused me of snipping away some
of your own questions that you think I don't want to deal with.
Although those questions concerned other models and weren't directly
relevant to your own claims, I have offered my own current opinion as
to the probable proto-hominin adaptive strategy. You, on the other
hand, ignore questions that must be answered in order to assess the
plausibility of your own claims and even to determine more precisely
what those claims are. So I'm going to reinsert them:

[Algis]

>My argument is not a non sequitur, your's is. How anyone can claim
>that the fact that quadrupedal apes move bipedally in water, when many
>quadrupedal mammals do not, as an argument *against* bipedalism being
>selected for in apes regularly moving thtough shallow water is one of
>the most crazy, illogical points I've ever seen. I understand,
>however, that when arguing against the AAH, because you know you're
>right, sometimes you have to argue that black is white and white is
>.black.

[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. 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?

[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?
 
<snip>

>> >>>3) Apes that have flatter, more paddle like, feet are going to be more
>> >>>stable whilst wading on the sands.
>> >
>> >Ape feet are flatter than our feet. We have longitudinal and medial
>> >arches. Our feet are not flat.
>> >
>> >>>4) Apes that have iliac blades that are more anteriorly orientated
>> >>>will have more efficient wading propulsion through water - for lateral
>> >>>side-to-side motiion
>> >>>
>> >>>Even if they do not swim there is still some extra risk of moving
>> >>>through the water which group (b) would not encounter. This risk might
>> >>>manifest itself as freak tides, flash storms, floods (if in river
>> >>>suystems) etc etc.
>> >>>
>> >>>So, you have both increased risk and selective advatnage from moving
>> >>>through water and you have adaptive traits which clearly would favour
>> >>>that behaviour.
>> >>>
>> >>>What more do you need?
>> >>
>> >>1) If you could demonstrate that apes had some compelling reason to be
>> >>wading in water deeper than they could easily manage, then longer legs
>> >>might indeed be useful. Unfortunately, you haven't demonstrated that
>> >>any such need existed. What valuable resource did waist-deep water
>> >>supply?
>
>I just gave you one - wading for crabs in a lagoon.

You've given up on rivers, huh? You think that crabs on the bottom of
a lagoon would have been a sufficiently large and steady food source
to support populations of specialized aquatic foragers? They must have
been very plentiful crabs and the water very clear. This water clarity
would totally eliminate the possibility of hidden deep spots as a
danger that proto-hominins avoided by going bipedal. But since that
claim was bogus anyway, it won't be a big loss if you dispense with
it. I note also that you must be assuming a very slight depth gradient
in order for the proto-hominin's marginally longer legs to
significantly increase the available foraging area. Are you now
claiming by any chance that proto-hominins inhabited coral atolls?

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.

>> >And he has ignored that the great shift in the intermembral index didn't
>> >occur until after significant adaptations for bipedalism had occured.
>> >"Longer legs for better wading" is a non-sequitur in terms of the origins
>> >of bipedalism.
>
>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? 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.

>> >>2) You've claimed now that proto-hominins were both wading long enough
>> >>to reorient the spine and reshape the pelvis and that they weren't
>> >>wading for hours at a time. When asked for a ball-park estimate of how
>> >>long they *were* wading, you've switched back to your claim that
>> >>"hidden dangers" were the primary cause of selection. You haven't
>> >>supported any of these claims. They remain mere assertions.
>
>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."
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. 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. 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.

>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.

>> >>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.

>> >>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.

>> >>>> >I dispute that they'd have to wade for hours if hominid ancestors
>> >>>> >lived in water-side habitats for 7 million years. Even very slight
>> >>>> >selection multiplied by that number of generations is very
>> >>>> >significant. The point about the depth gradient, which you keep
>> >>>> >missing, is that for every bout of waist deep wading there are going
>> >>>> >to be at least two phases of even shallower wading where a watered
>> >>>> >down bipedalism will be practiced.
>> >
>> >Slight selection in any given generation can accumulate (though,
>> >importantly, it can also be swamped by drift). But there must be a
>> >selective differential in each generation. This hasn't been demonstrated
>> >beyond conjecture and assertion. Why does the facultative biped have
>> >fewer babies?
>
>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.

<snip>

>> >>a) You are claiming that there existed an ecological niche open to
>> >>hominins that involved a specialized aquatic foraging strategy. You
>> >>have made no attempt to document that any such niche could have
>> >>existed.
>
>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. 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.

>> >>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.

>> >>c) Having failed to support your major premises, you have no basis
>> >>for your conclusion.
>
>Rubbish.

Your imaginings don't constitute valid support.

>> >>>> Once you get around to specifying
>> >>>> distances, it will be an easy matter to double them to get total
>> >>>> distance traveled. You haven't responded thus far. Since you have now
>> >>>> clearly denied that you think they were wading for hours at a time in
>> >>>> shallow water, you should give us a ballpark estimate of how long you
>> >>>> think they *were* wading at a time, and you should say why you think
>> >>>> this time was sufficient to increase mortality among quadrupedally
>> >>>> adapted apes and thus to favor more bipedally adapted apes.
>> >>>
>> >>>Look, I can see that you're trying to pin me down to saying that they
>> >>>never swam and that they only waded for 43 minutes and that they lived
>> >>>in Rhizophora mangle trees with a depth gradient of 0-35cm within 0.8m
>> >>>of the water's edge - so that you can then try to twist more
>> >>>ambiguities out. But, excuse me but I'm going to resist that
>> >>>challenge. I do not know how much they waded, what food sources they
>> >>>lived on - but I think that waist deep water is *obviously* simply the
>> >>>most predicatble causative factor that causes an ape to move
>> >>>bipedally. Water-side ecosystems are food rich and so - hey - use your
>> >>>imagination.
>> >
>> >"Waist deep" is not an environment likely to select for the traits we see.
>> >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.

>> >>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. It's not a developed model, but it's more
internally consistent and explanatorily powerful than your own
grab-bag of opinions and assertions. 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.

<snip>

NAS

>Algis Kuliukas

Relevant Pages

  • Re: Bipedalism in different substrates
    ... >> sustained terrestrial bipedalism. ... >to adopt in waist deep water than quadrupedalism. ... When apes are in water approaching waist deep, ... Bipedal wading doesn't ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... >kind of statement that proto-hominin x ate food source y in habitat z ... parsimoniously infer that proto-hominins may have eaten a wide variety ... underlie selection leading to obligate terrestrial bipedalism. ... >wading they did, the more bipedal they would become. ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... > morphological changes necessary for efficient terrestrial bipedalism. ... Apes will already do this on land, no water required. ... Requires millions of years of wading for one thing... ...
    (sci.anthropology.paleo)
  • Re: poor runners (Re: Is Oreopithicus the Aquatic Ape Link?
    ... in waist deep water the stresses that compel bipedalism are ... >> changes that result from upright posture) and in very shallow water ... What's the difference between standing up and wading as ...
    (sci.anthropology.paleo)
  • Re: Bipedalism in different substrates
    ... >>yet the anatomical adaptations for bipedalism preceded longer legs. ... As wading is relatively costly ... persuaded) how wading through water would be selected for. ... the more bipedal apes would become. ...
    (sci.anthropology.paleo)