Re: Bipedalism in different substrates
From: NA Sides (nas_at_sonic.net)
Date: 08/09/04
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Date: Mon, 09 Aug 2004 18:28:56 GMT
On 7 Aug 2004 06:21:36 -0700, algis@RiverApes.com (Algis Kuliukas)
wrote:
>NA Sides <nas@sonic.net> wrote in message news:<n2ksg0ph2ckg624bsr8uh63bltcpqdr7ad@4ax.com>...
>> On 30 Jul 2004 20:43:25 -0700, algis@RiverApes.com (Algis Kuliukas)
>> wrote:
>[snip]
>
>- Part Two
>
>> Unfortunately, even in the unlikely eventuality that you can someday
>> show that such a niche could have existed, you will continue to run up
>> against the embarrassing fact that, if proto-hominins were generalists
>> foraging in a variety of areas and employing different foraging
>> strategies, and if they were foraging quadrupedally on land and in
>> trees, the selection for quadrupedal traits would outweigh any
>> selection for bipedality that might lead to enhanced water-based
>> foraging. Your only realistic option would be to have them foraging
>> bipedally both on land and in water, but this would shoot down your
>> claim that wading was the primary "causative factor" for bipedalism,
>> so you can't do that without abandoning the faith.
>
>That's just nonsense. First of all, it's not an unlikely event.
>Wetland habitats are here and they always have been. As 3 out of 5
>extant great apes feed in such habitats today, at least sometimes,
>it's doesn't take a great stretch of the imagination (at least for
>those of us who possess such a thing) to envisage a scenario where
>hominoid ancestors could have done so *more*. Add to that imagination
>the facts that Miocene apes of Europe & SE Asia must have lived around
>the Med/Tethys coast and that Pliocene hominins of E Africa certainly
>inhabited riparian forests prone to wide flood/dessication cycles and
>that pushes it enough in the direction I'm talking about.
As usual you have responded with your standard assertions and ignore
the point that generalists would be foraging for most of their food on
land and that (1) selection for terrestrial quadrupedalism would
outweigh any putative selection for aquatic bipedalism or (2)
selection would be occurring for terrestrial bipedalism and sustained
shallow water wading would at best be a contributory factor rather
than the main "causative factor of bipedalism" as you so frequently
claim.
>A generalist - by anyone's defintion but your own - means more aquatic
>than an arboreal primate but I understand that would be just too
>controversial to contemplate for some of you guys. So 'generalist' to
>you, in reality, just means 'not arboreal'.
It's you who are trying to impose your own idiosyncratic and
uninformed definition of ecological generalization. I've told you what
the term means, but you insist on using your own strawman definition.
A generalist species has a broad ecological niche. It will be
omnivorous, though some species, like black bears and coyotes, belong
to the order carnivora. It will be able to exploit a variety of
different habitat resources and usually can employ at least several
different foraging strategies. Ecological generalization is usually
reflected in morphology. Thus canid cheek teeth, with their
combination of shearing and crushing surfaces, are less specialized
than felid carnassials and this generalization matches a usually more
varied canine diet. Same with bears. Specialists, on the other hand,
usually employ some narrow range of foraging methods and tend to have
morphological and behavioral specializations that limit the types of
resources they can utilize.
>All primates and especially more generalist apes have all sorts of
>pressures on their locomotor repertoires. I'm suggesting that as
>wading is the most likely to induce bipedalism, then any generalist
>that practiced *more* wading would, undoubtedly, practice more
>bipedalism. It wouldn't take much extra wading to push apes over a
>threshold where they moved bipedally on land too.
And you continue to ignore the fact that a generalist would be
foraging mostly on land and in trees and that terrestrial selection
would be either for quadrupedal speed or bipedal weapon use and
endurance. If the first situation obtained, then the facultative
bipeds would remain facultative bipeds. In the second situation
obligate bipedalism would eventually emerge but it wouldn't be due
primarily to "movement through water."
<snip>
>> If you know of evidence that women's less dense body hair does provide
>> them with a relative advantage over men in terms of drag reduction,
>> I'm more than willing to consider it. You haven't presented it yet.
>
>Until someone does that experiment which actually measures the body
>hair that's been shaved off and tracks the drag reduction as the hair
>regrows we just don't know. But, 100% body hair reduction does give
>around 11% drag reduction in water. It's interesting that you seem to
>have convinced yourself that this an argument *against* the part of
>the AAH explanation for human nakedness that suggests it was to help
>our swimming abilities (another part, which you always conveniently
>forget about, is of course that it aids water-powered sweat/dip
>cooling.) Self-delusion knows no bounds.
If experiments have been done with both men and women, and if both
show an 11% drag reduction with 100% hair removal, then this in itself
constitutes evidence that relative hair reduction has no significant
effect (unless the men and women were equally hairy before shaving).
And I haven't forgotten about sweat cooling. I think it was probably
the main factor in hair reduction. This has nothing to do with the
subject of hydrodynamic drag. I do agree that self-delusion knows no
bounds, but you won't be surprised to learn that I think you're the
one who is delusional.
<snip>
>> >'It wouldn't be difficult' and yet no-one bothered to do it. Still,
>> >you require me to do so before you allow your mind to be openned to
>> >the outrageous possibility that hominins moved through water much.
>> >Can't you see how this argument wreaks of double standards?
>>
>> I have only your word that no one has done it. Have you exhaustively
>> researched the relevant literature?
>
>I've read all the major relevant papers on bipedal origins and I don't
>know of a single mention of 'optimum foraging strategy' or any general
>attempt to justify their model in such precise terms. I put it to you
>that as you are the one suggesting that this is so important a
>requirement, all of a sudden, you point me to some model of bipedal
>origins that has done so, so that I might try to emulate their high
>standards. I suspect, however, it is just yet another case of double
>standards.
>
>> But even if no one has applied
>> optimal foraging models to their scenarios, this doesn't mean much if
>> the scenario posits an ecology similar to ecologies that we know, from
>> studies of modern humans or apes, can support populations of
>> hominoids. Do you get it?
>
>So, you're covering your arse, already. I see. You must realise
>already that you're just being hypocritical requiring that the wading
>hypothesis fulfills this requirement, then.
So you don't believe that apes can survive on land? You don't believe
they forage for a wide variety of plant and animal foods? You don't
believe that proto-hominins could have survived on a similar menu? You
don't seem to understand that we *know* such resources exist and that
both apes and human can and do utilize them. You, on the other hand,
want us to believe that human ancestors occupied a wading-based
ecological niche centered on utilization of resources that, from all
available evidence, do not exist. You don't understand that extant
apes don't occupy such a niche. When you claim that they do, you just
demonstrate your ignorance of ecology.
>Extant apes (bonobos, w l gorillas and orang utans - that's 3 out of
>5) live in wetlands, at least some of the time - and so do many
>humans. I've just come back from the excellent Museum of Western
>Australia, here in Perth, and I was interested to read that Perth city
>centre is built on a former wetland zone on the banks of the river
>Swan. Apparently the very area where the city centre is was used for
>thousands of years by the local Noongar people for foraging for food
>because it was so rich in wildlife. This is, remember, just 170 years
>ago. Of course all over the world people have done the same thing but
>you're too blinkered to see it.
Australian aborigines also survived in other habitats. That's one of
the benefits of being a generalist: the ability to exploit a wide
variety of habitat types. I've told you this, but apparently you
haven't understood.
>> You're the only one positing a radically
>> different niche from any that we know exist.
>
>No.
>a) it's not so radically different, is it? Why do you gape in horror
>at the prospect of humans and apes getting their toes wet to get food
>and to keep cool from time to time? Look at a population density map
>of any country in the world and look where all the cities are.
>b) They do exist and they always have.
I don't believe you're stupid, Algis, but your rhetorical sallies
about your critics "gaping in horror at the prospect of humans and
apes getting their toes wet" are both repetitive and stupid. You know
I have acknowledged all along that proto-hominins probably waded at
times. The fact is you've presented no evidence whatever that a
wading-based hominoid niche could have existed. The occasional wading
of chimps, bonobos and gorillas doesn't constitute evidence for any
such niche.
Then you bring in the irrelevant fact that cities tend to be situated
near water. Do you think this is because their inhabitants want to
wade or swim? It's because trade and commerce has always been carried
out mostly by means of water transport. In regions where cheaper water
transport wasn't possible, cities sprang up along caravan or other
overland trade routes.
>> We know, in fact, that no
>> hominoids, and not even monkeys, exploit aquatic resources in the way
>> you claim proto-hominins did.
>
>Rubbish. Gorillas wade, bonobos wade, chimps wade, orang-utans wade
>and humans wade. Gosh that covers all of them. It's just a question of
>degree. I'm proposing that our ancestors waded *more* than theirs did.
>Get it?
I was referring to the fact that no hominoids obtain a major part of
their food by wading. You haven't demonstrated, or even made a serious
attempt to demonstrate, that a wading-based niche could have existed.
You expect people simply to take your word for it. We're supposed to
believe that you have infallible intuitions about this subject and
that we should accept as evidence your fantasies about 5 to 20 minute
crab-grabbing jaunts that supply a day's food. But I don't accept your
intuitions as infallible. You claim that "wetlands" provide a
sustainable resource base that extant apes could, but for some reason
don't, fully utilize. You also claim that our own ancestors did fully
utilize this mythical resource base. Well, actually you never made
claims this specific. You merely recited your mantra that "wetlands
are rich habitats." But when others pointed out to you some of the
implications of your claims, you responded by making still more
baseless claims and ignoring still more contradictions.
>> It's incumbent on you, therefore, to
>> support your claims that an adequate resource base exists and that
>> hominoids could only have accessed those resources through wading.
>
>Bonobos today in the Congo have been documented wading bipedally for
>algae in shallow pools and have been reported wading bipedally whilst
>foraging in streams too. Western lowland gorillas have been reported
>wading bipedally whilst navigating flooded beis (swamps) in the Congo.
>If extant apes can do this today why do you doubt that their (and our)
>ancestors could have done so in the past? If their wetland habitats
Nobody doubts that their ancestors could have done so in the past. But
those ancestors didn't become obligate bipeds. You have presented no
evidence that a set of sustainable resources exists anywhere that
could support a wading-based hominoid way of life.
>where more dominant that those in the tropical rainforest of the Congo
>today - such as coastal/island/river delta forest on the Med/Tethys
>coasts in the Miocene - you know where Miocene apes must have lived as
>they passed to/from Africa to Europe - and if riparian forest in East
>Africa were inhabited by their descendants in the Pliocene - where the
>water's edge/area ratio would have been much greater than the Congo
>wetlands - then WHY, apart from wishful thinking on you part - can you
>not accept that their ancestors must have been exposed to greater
>selection from moving through water than extant apes today?
Oh yeah, that's a clincher alright. Here is where I'm supposed to say
"Gosh, there was a lot of coastline. That means apes were wading for
most all their food!" If I don't accommodate you in this respect, you
will doubtless think I'm displaying mock incredulity.
>> >> Both chimps and human hunter-gatherers were utilizing known
>> >> resources in known ways. The proto-hominins may have employed novel
>> >> foraging methods, but if the scenario merely posits increased
>> >> distances between resource patches, then not much extrapolation is
>> >> needed. You probably could apply with little modification the same
>> >> sorts of models that are applied to human h-gs.
>> >
>> >How does this contradict the wading model? Why does this 'increased
>> >distance' (based on the bizarre notion that trees would have just been
>> >ever more thinly spread out, as opposed to clustered around water
>> >sources) imply bipedalism? And why is that no problem for the foraging
>> >strategy but if they stepped into water it would be?
>>
>> Who said the resource patches must be individual trees? If clumps of
>> trees become separated due to increasing aridity, then the distance
>> between clumps becomes a factor. These clumps wouldn't necessarily be
>> all clustered around open water sources. You'd have broken and clumpy
>> forest margins merging into woodland-grassland mosaics.
>
>Not *necessarily* but overwhelmingly likely. The vast bulk of evidence
>is that tree cover is highly correlated with the water table. This is
>itself highly correlated with precipitation (including that from
>higher altitudes) and, of course, proximity to water courses. Any
>ecologist knows this. Gallery forests are well known to act as refugia
>for flora and fauna species in times of aridity. (See, e.g. Meave et
>al 1991)
Once again you lost track of what I was saying. Mosaics of forest,
open woodland and scrub or wooded savanna apparently did prevail over
large regions during the late Miocene, with areas of wooded savanna
spreading between clumps of denser forest. If apes were relying
primarily on chimpanzee-like food of the deep forest, then foragers
might have to travel greater distances between small forest clumps
where these foods were most plentiful. So it's no great extrapolation
to add in the additional costs of traversing the areas between
resource patches. No new ecology was involved; merely an additional
stress on apes who had to travel somewhat farther to obtain food. This
is much different from your
>Meave, Jorge; Kellman, Martin; MacDougal, Andrew; Rosales, Judith
>(1991). Riparian Habitats as Tropical Forest Refugia. Global Ecology
>and Biogeography Letters Vol:1(3) Pages:69-76.
>
>Orang utans live in very lowland, swampy forest *because* that is
>where most of the fruit trees grow. The species diversity there is a
>function of the proximity to water courses and precipitation. See, for
>example...
>
>"... Even in the lowlands the orang-utan is not evenly distributed. A
>review of the available literature on orang-utans, supplemented by
>survey data from many different sites in Sumatra and Borneo (Rijksen,
>unpublished), indicates that the ape is more commonly found close to
>streams, rivers and in swamps; it is found in greater densities in
>(alluvial - deposited by running water) forest patches in river
>valleys, and in the (flood-plain) peatforest near swamps or between
>rivers. One is less likely to come across the ape in any numbers
>further away than 10-15 km from a watercourse or a swamp with open
>water. No doubt the main reason for such preference is the higher
>incidence of preferred fruit trees close to rivers, but an additional
>reason may be that rivers and streams are the best geographical
>landmarks for spatial orientation. It seems that the ape is as rare or
>absent in extensive, relatively uniform lowland forests on well
>drained 'dry' flat ground, as it is in some mountain complexes above a
>certain altitude." Rijksen & Meijaard (1999:68.)
>
>Rijksen, H D; Meijaard, E (1999). Our vanishing relative. Kluwer
>Academic Publishers (Wageningen)
Yet, despite the fact that orangutan ancestors apparently have been
living for millions of years in what you would call wetland
conditions, they get no significant portion of their diet from wading
and no subpopulation has diverged off to take advantage of the food
opportunities you claim are there for waders. Orangs don't support
your claims. They provide more evidence that no such niche could be
formed by hominoids. The same goes for other extant apes. None
supports your claims that proto-hominins could have occupied a
wading-based niche.
>> If bipedalism
>> allowed penetration into the more open habitats, perhaps because it
>> allowed for weapon carrying and the porting of tools and foods, then
>> bipedal traits would be favored. It's no problem for terrestrial
>> scenarios because there would have been no great change, at least
>> initially, in foraging strategies - just a gradual penetration, over
>> periods of many generations, into the more open habitats. No radically
>> different ecological relationships would be presumed. You, on the
>> other hand, are positing a wading-based niche that doesn't exist now
>> and without evidence that any such niche ever existed. .
>
>This is a bizarre concept: bipedalism *allowing* weapon carrying.
>Perhaps this is part of your problem. You seem to imagine these apes
>'wanting' to carry weapons before the advent of bipedalism. For twenty
>million years they wanted to but were prevented from doing so by their
>damned ancestry. Finally, they broke through. Evolution, with magical
>prior knowledge of the advatnages that would follow, 'broke through'
>and bipedalism was finally achieved *allowing* them to carry things.
>
>Perhaps I've misrepresented your point of view there, but I think it's
>instructive that you use the word 'allow'. You see the wading model
>needs no such concept because in water they move bipedally - as a
>matter of course.
You indeed have grossly misrepresented what I said. I stated it
clearly enough, but, as usual, you miss what's there and substitute
your own strawman. The ancestral Miocene apes were *already*
facultative bipeds. How many times do you have to be told this? They
could carry weapons for short distances, but they had to go
quadrupedal when traveling over long distances. Therefore they
couldn't carry weapons over long distances. However, due to long-term
aridification, some regions that had been deep forest were becoming
fragmented and interspersed with open forest or forest-grassland type
areas. Apes may have had to travel farther between forest clumps in
order to get their preferred foods. Since climbable trees would be
more widely spaced, they may have had more need of weapons. Bipedalism
could have aided with both these problems. It could have allowed them
to travel farther in a day's foraging and also allowed them to carry
weapons and port food items.
>So, taking away this 'desire' to be bipedal so they can carry weapons,
>please explain why on earth an ape 'penetrating more open habitats'
>would start to move bipedally? Can you give me a tiny scrap of
>evidence from any extant ape that supports this? I think you'll find
>that the evidence is for quite the opposite view. Chimps live in more
>open habitats than bonobos but they're the ones with traits which
>indicate less bipedality.
See above for advantages. I can't think, right offhand, of evidence
from extant apes to support it, but the evidence isn't "for quite the
opposite view." You have claimed that bonobos are more bipedal, but it
is my understanding that captive chimps and bonobos are about equally
bipedal. You have claimed that bonobos' lower intermembral index,
associated with their occupation of deep forest and their observed
instances of bipedal wading, support the idea that they are "on a
trajectory" toward greater bipedalism. Your claim is weak. The
ancestors of bonobos have apparently inhabited the same sort of deep
forest habitat for eight million years. There has been plenty of time
for greater bipedality to evolve, but it never happened. And the whole
intermembral index argument falls apart when applied to those other
waders, the gorilla and orangutan. They have *higher* intermembral
indexes than do chimps.
>"Morphological differences between chimpanzees and bonobos, including
>more centrally positioned foramen magnum (Shea 1984), longer thigh
>bones (Zilhman 1984), lower intermembral index (Coolidge & Shea 1982;
>Napier and Napier 1985), heavier lower limb muscle (Zihlman 1984),
>loner feet (Fleagle 1988) and different distribution of body weight
>(Zihlman 1984) have led to the claim that bonobos demonstrate a
>greater predisposition for bipedal locomotion (Susman 1987). Myers
>Thompson (2002:66) Also, she doesn't note that bonobos have more
>anteriorly flared iliac arches.
>
>But never mind the evidence, eh Norm - you stick to your guns mate!
>Bipedalism happenned on the open plains of Africa. Dart is dead, long
>live Dart!
Like I said before: your rhetoric is stupid. Why do you pretend that
I'm claiming bipedalism occurred on "the open plains." You know it's
not what I've said, yet you repeatedly make these little speeches
featuring gross misrepresentations.
>Wetlands do exist now, they always have and hominoid and hominin
>ancestors almost certainly were *more* exposed to them than extant
>great apes are today.
Trouble is, you've failed to show that wetlands provide a sustainable
set of habitat resources that could support a hominoid wading-based
niche. Since no extant apes fully utilize the resource base that you
claim, without evidence, is there for the taking, it appears likely
that in fact no such set of resources exists and that you are just
engaging in idle fantasies.
>> >> The point here is whether there might have existed a viable
>> >> specialized wading niche potentially exploitable by apes. You have
>> >> presented no evidence that any such niche existed or could have
>> >> existed.
>> >
>> >Yes I have. bonobos, w l gorillas and orang utans exploit such
>> >habitats today - at least some of the time. Therefore if their habitat
>> >changed to have *more* exposure to wetland and less tropical rain
>> >forest - they're almost certianly going to survive. It's just mock
>> >personal incredulity again. It's all you have. Pathetic.
>>
>> Try to calm yourself, Algis. Maybe you'll be able to think more
>> clearly. I'm going to explain this again. Bonobos, gorillas and
>> orangutans wade occasionally but no extant ape occupies any sort of
>> wading-based niche.
>
>That's right. That's why.... wait for it.... they're not bipedal like
>we are. That's the point.
The *real* point is that despite the fact that (as you say) wetlands
have always existed, no evidence exists that any hominoids have made a
living by wading.
>> Bonobos, gorillas and orangutans don't provide
>> support for your claim that such a niche once existed. If anything,
>> they constitute counter evidence. If such a niche could exist in areas
>> they inhabit, then populations of their ancestors had plenty of time
>> to exploit that niche. This never happened, and it constitutes
>> evidence that there exists no sustainable resource base in ape habitat
>> that could have supported a wading-based species ecology.
>
>What? Such niches *do* exist in areas they *do* inhabit and they *do*
>exploit them. IT DOES HAPPEN. The claim is that our ancestors did so
>*MORE* than they do today. The claim is that the habitats on the
>Med/Tethys coast exposed the ancestors of the Hoominoidae to greater
>wading pressure resulting in an 'aquarboreal' (wading/climbing)
>ancestor for all great apes. Their descendants that came to Africa
>either settled in the tropical forests to the west (as their habitats
>became *less* exposed to wading they became *less* bipedal) or in the
>east (as their habitats became exposed to wide fluctations in climate
>their riparian habitats continued, in fact intensified, their exposure
>to wading and ultimately to tree loss).
Take some elementary courses in ecology and evolutionary biology. You
need them. If you don't flunk out, maybe you'll learn what the concept
of niche means. It has been explained to you here by both Jason and
myself, but you haven't understood it. Extant apes sometimes utilize
aquatic resources as a relatively minor component of their diet.
Chimps and bonobos eat mostly terrestrial herbaceous vegetation and
fruit.
>> >> Some mammals, including apes, do forage in water for aquatic
>> >> resources, but they tend to fall into two classes: generalists and
>> >> specialists. Generalists can utilize a wide resource base and some
>> >> species can forage arboreally, terrestrially and by wading or
>> >> swimming. All evidence I'm aware of supports the idea that our own
>> >> ancestors were in fact generalists.
>> >
>> >Yes generalists that left the trees but didn't take one step in the
>> >water. Doesn't sound much like a generalist to me.
>>
>> As much as possible, you should try to keep track of your
>> corespondents' real arguments and positions, not strawman versions
>> that you yourself make up. You haven't done a very good job of that in
>> this thread. No one has said that proto-hominins "didn't take one step
>> in the water." In the very paragraph you supposedly were responding to
>> I say that some mammals, including apes, do forage in water for
>> aquatic resources. Don't you think that should have provided a clue?
>> I've said that proto-hominins were probably generalists who foraged
>> primarily terrestrially, but also arboreally and perhaps to some
>> extent also in water.
>
>Ok, I apologise. 'didn't take one step' was an exageration. But then
Your apology would be worth more if you hadn't repeated the same
misrepresentation in this very post: claiming that I "..gape in horror
at the prospect of humans and apes getting their toes wet.."
>answer me this this... if you accept that as generalists they did move
>through water sometimes and, to be precise, more than did the anestors
>of the apes and, presumably, you agree that whilst doing so they were
>bipedal pretty much all of the time - why then do you resist the idea
>that this extra wading might have contributed in any way to the
>evolution of hominin bipedalism? Aren't you flying in the face of the
>laws of natural selection?
I *don't* necessarily accept that they moved through water more than
did the ancestors of extant great apes. Possibly they did so, but I've
seen no evidence that they did. Contrary to what you apparently want
to believe, not all ecological generalists forage much in water. Of
course I haven't actually said, as you also seem to think, that extra
wading couldn't have contributed to the evolution of hominin
bipedalism. I've said a number of times that I think sustained shallow
water wading could possibly have been contributory, but that wading
couldn't have been (to use your own clumsy phrase) the main "causative
factor." I've explained why I think this. It has to do with the fact
that, if proto-hominins were foraging quadrupedally on land or
arboreally for most of their food, then selection for terrestrial and
arboreal quadrupedalism would outweigh any selection for bipedalism
associated with sustained shallow water wading.
>> >> Proboscis monkeys and long tailed
>> >> macaques seem to be the only primate species who can inhabit mangrove
>> >> forests. The proboscis monkey is a specialized leaf eater that is more
>> >> or less restricted to mangrove forest by its own dietary
>> >> specializations while the long tailed macaque is an omnivorous
>> >> generalist who can live not only in mangrove forests but in a variety
>> >> of other habitat situations. In almost every respect except size, we
>> >> are more similar to the long tailed macaque than to the proboscis
>> >> monkey. Our generalist ancestors wouldn't have been restricted to
>> >> mangrove forests. I've pointed this fact out to you previously and
>> >> you've ignored it. Also hominins are morphologically adapted to
>> >> bipedal striding; not wading or swimming.
>> >
>> >Once again - I've never said they were *restricted* to any habitat.
>> >I've pointed this out to you hundreds of times but -again - you ignore
>> >it.
>>
>> Yes, and I've repeatedly pointed out to you a contradiction between
>> your claim that wading was the primary "causative factor" of
>> bipedalism and your other claim that proto-hominins were generalists
>> who weren't restricted to a wading-based foraging strategy. If
>> proto-hominins were inhabiting different habitats during certain
>> phases of the Miocene climatic fluctuations, and if they were foraging
>> quadrupedally in trees and on land, then selection for quadrupedal
>> traits would wipe out any bipedal traits that interfered with
>> efficient quadrupedal foraging and defense behaviors.
>
>Why? Extant great apes are pretty much quadrupedal in their usual mode
>of terrestrial locomotion 97% of the time. It doesn't stop them moving
>bipedally when they're in water and it doesn't stop them moving
>bipedally sometimes (about 3%) on land too. Surely, if an ape moved
>through water more and therefore it was more bipedal generally, it
>would be more likely to move bipedally on land too. It's this
>correlation, which you have to pretend would not apply, which is the
>clinching argument here. Bonobos (cf chimps) provide very strong
>evidence of such a correlation.
I was assuming that morphological reorganization of the pelvis, legs
and spine would rule out knucklewalking. I'm also assuming that
everybody is right when they say that chimps can, for a short
distance, move faster than a human can run. Thus quadrupedal speed
would lost and there must have existed some compensating advantage *on
land* to make up for what otherwise could be a deadly disadvantage. I
suggested that this advantage consisted of ability to use weapons in
defense, to travel farther while foraging and to port foot and tools.
But if such terrestrial advantages existed, and if proto-hominins were
generalists doing most of their foraging on land, then there's no
reason to think that water was the primary "causative factor" for
bipedalism. I've said this all before but you never seem to get it.
But, to play the Devil's Advocate here, I have myself argued in back
in 2003 in the thread "Thermoregulation and predation in Homo" that
proto-hominins could possibly have been fairly efficient bipedal
walkers and knuckle-walkers too. By the time we get to relatively long
legged species like afarensis, efficient knuckle-walking would no
longer be compatible with hominin type legs, but I don't remember that
anyone posted any convincing arguments that, for a somewhat shorter
legged species, this dual locomotory strategy would be
bio-mechanically impossible.
If it's biomechanically feasible, and if the critter could still
maintain good knucklewalking speed, then it's perhaps possible that
morphological reorganization of the pelvis, legs and spine could have
come about through sustained shallow water wading and then turned out
later to also be useful on land. But then you have to explain why such
creatures would be restricted to wading in water and not foraging
bipedally on land for equivalent or greater periods of time during the
period when the morphological reorganization was occurring.
>> >I agree that we are generalists and that our ancestors were too. But
>> >you see that's a problem for you because being generalist means, by
>> >definition *more aquatic* and 'more aquatic' is all Hardy was ever
>> >talking about, right? It's all I am arguing for - as I've made clear
>> >at least a hundred times.
>>
>> Being a generalist doesn't necessarily mean "more aquatic."
>
>Well it does if we're talking about a more-generalist-than-a-chimp
>type of ape, which i think we are. You're contradicting yourself. A
>moment ago you were claiming that of course you too agreed that our
>ancestors moved through the water somtetimes - now you're... what are
>you claiming?
You've got water on the brain, Algis. You don't know what ecological
generalization means. Chimps post-split ancestors moved through water,
too. Our own post-split ancestors could have been more anatomically
and behaviorally generalized without necessarily moving through water
more. Some populations perhaps did while some populations perhaps
waded less.
>> Chimpanzee-like hominin ancestors would already have been relatively
>> generalized, foraging mostly in trees but also on the ground and to
>> some extent in water. Bipedalism may simply have allowed their
>> descendants to inhabit the more open habitat that was gradually
>> replacing large areas of what had been deep forest.
>
>This 'allowed' word again. Why on earth, tell me, does quadrupedalism
>'prevent' or even slightly inhibit any move towards more open
>habitats? Is there *any* evidence for this? No - not one jot. The more
>open the habitat, the more committed the quadruped, in fact. It is in
>trees that upright posture is promoted and it is only in waist deep
>water that bipedal locomotion is guarranteed.
In more open habitats predators might be more a problem because
claimable trees are spaced farther apart. Thus the possible need to
protect oneself with clubs or spears. There is also the fact that
hunter-gatherers do travel farther (on average) in a day's foraging
than do chimps. Humans can cover more ground without tiring than
chimps. Early hominins weren't humans, but they did have some features
of human-type bipedalism, so it's plausible that they also could
travel somewhat farther without tiring.
>This notion is a pure fantasy. You really are clinging on to the
>savanna theory even now in 2004. Amazing.
No I'm not, Algis. You are engaging in pure fantasy when you say I am.
Most people can understand that terrestrial habitats are not limited
to deep forest and savanna. Apparently you cannot.
>> Coatimundis,
>> coyotes and English sparrows, for example, are relatively generalized
>> non-aquatic species, though like any species they have their own
>> species-specific characteristics.
>
>We're talking about apes.
I was talking about characteristics of ecological generalists. Our own
ancestors appear to have been ecological generalists. Is the concept
too abstract for you?
>> >Your generalists, though, bizarrely never exploited any aquatic
>> >resources at all. Your generalists left the trees but only moved onto
>> >the more open grasslands to, presumably, explout a purely terrestrial
>> >hunter-gatherer lifestyle. Some generalists, those.
>>
>> Is it an organic memory deficit, unconscious repression, or do you
>> deliberately attempt to ignore and forget what people actually say? If
>> I repeat a few dozen more times that I think proto-hominins probably
>> sometimes foraged in water, do you suppose the information will begin
>> to penetrate your brain? Perhaps you could tape it to a corner of your
>> monitor screen. I'm going to try to say this clearly. Please try to
>> focus this time. Generalists can exploit a wide variety of habitat
>> resources. Proto-hominins probably still foraged to some extent in
>> trees and also sometimes in water.
>
>But you just said: 'Being a generalist doesn't necessarily mean "more
>aquatic."' Ok then. I accept you accept that proto-hominins foraged in
>water sometimes. Great. So, did they do so more than the ancestors of
>apes? Yes or no? Did they do so bipedally? Yes or No?
It's unlikely that any population of early hominins foraged more in
water than extant apes. There's no reason to think they did because
there's no evidence that more wading would provide sufficient returns
for time and energy invested. Lord knows you haven't provided any
evidence despite being repeatedly asked to do so. If more wading
provided such returns then one would expect extant apes and monkeys to
wade more than they do and to derive a larger percentage of their food
in this manner.
<snip>
>> >And what about the marine food chain? When did that come in?
>>
>> You tell me. This is your area of interest.
>
>Ever heard of omega 3 essential fatty acids - heavily implicated in
>healthy human infant brain growth? They are largely found in the
>aquatic food chain?
So you figure that coastal peoples had healthy brains while inland
peoples did not?
>> >> If proto-hominins were ecologically similar to chimps, then present
>> >> models can be applied with small modifications. You, however, are
>> >> claiming the existence of a wading-based niche in mangrove forests.
>> >
>> >Why chimps? Why not bonobos? Bonobos appear to be, at least on a
>> >trajectory towards bipedalism compared to chimps. And where do they
>> >live? In wet and wooded habitats.
>>
>> Both chimps and bonobos subsist mostly on fruits and terrestrial
>> herbaceous vegetation. They both are quadrupedal knuckle-walkers and
>> facultative bipeds. There's no evidence that either is "on a
>> trajectory" toward obligate bipedalism. If a subpopulation of bonobos
>> were going to become bipedal, they've had more than adequate time to
>> do so. It never happened.
>
>Of the two, it is the bonobo that anecdotally (e.g. de Waal & Lating
>1997) or anatomically (see above quote from Myers Thompson 2002) is
>the more bipedal. It is the bonobo which has less fear of water and
>greater exposure to the need to wade. But, of course, this extra
>pressure has still been sub-optimal to cause a switch to fully
>obligate bipedalism. Our ancestors, it is argued, had still greater
>exposure than the bonobo.
>
>> >> You've presented no evidence that any such niche could have existed.
>> >
>> >Astonishing. Bonobos, w l gorillas and orang utangs *DO* live in such
>> >habitats today - at least some of the time. Wetlands *DO* exist today
>> >and before modern humans exploited the more favourable of those
>> >habitats they were even more common in the past. Loo at the
>> >paleogeography of Miocene apes and their proximity to the Med/Tethys
>> >coasts...
>>
>> I know you don't like this to be pointed out, but your claims of a
>> wading-based niche aren't supported by bonobos, gorillas and orangs
>> living in deep forest and sometimes wading. In the perhaps 12 million
>> years since the hominin-pan LCA, the ancestors of extant apes have
>> apparently been primarily living in wet forest conditions, yet none
>> has diverged off to fill a wading-based niche. This would seem to
>> indicate that no viable such niche existed (or could be formed).
>
>The ancestors of extant apes have been living in wet tropical
>rainforest forest conditions - but this was not sufficient to drive
>*them* to bipedalism. It needed an extra shove. That was provided in E
>Africa by wide swings in climate from very arid (forming gallery
>forest refugias, where the water's edge/area ratio was very much
>higher) to very wet (where such valleys would become flooded exposing
>hominin ancestors to even more need for wading.) Get it?
I get the fact that you're repeating your standard unsupported
assertions and that you've provided no evidence that tropical
rainforest, gallery forest, mangrove forest or any other habitat
supplies a sustainable resource base that hominoids can only access
through wading. I understand that the evidence we do have of wading
hominoids is inconsistent with your claim and that, in order to move
it from the realm of baseless opinion, you need to document that such
resources exist. I understand that you've so far made no effort to do
so and that for genuine empirical research you've substituted just-so
stories about five minute crab-grabbing jaunts that supply a full
day's food.
>> >If you can post one reply when you don't just stone wall my
>> >explanations with something like 'I've asked you for x and you've
>> >never given it'. If you can show one microgram of objectivity that you
>> >are actually open to evidence then I'll cut the rhetoric. I'm not very
>> >hopeful I'm going to be able to do that, though.
>>
>> Yeah, I know the pattern. I ask for evidence and you respond with
>> assertions. I point out that your so-called evidence consists of
>> nothing but assertions and you respond with pejorative rhetoric ;0)
>
>Ok - so let's call it a day and just agree to disagree then. I'm tired
>of going round in circles. If you have nothing more to say than (yet
>again) 'you've only given assertions' - when that's all I could
>possibly give and that's all any of the models have ever given - then
>just don't bother.
Whatever. It's not like I'm going to convince you to do good science
rather than your usual assertion and rhetoric.
NAS
>Algis Kuliukas
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