Re: AAH update (was: Bipe
J. Moore (j#d#.moore@canrem.com)
Tue, 4 Jul 95 12:08:00 -0500
Pa> The recognition that humans probably didn't evolve bipedalism on the
Pa> savannah is relatively recent.
No, the problem is that you equate "savannah" with "treeless, waterless
place". "Relatively recent" that we figured that hominids didn't evolve
in a sort of arid desert? Well, we're talking at least 20-30 years;
I suppose that *is* recent...in geological time.
Pa> If bipedalism is such a great adaptation, why is it restricted to
Pa> just one primate species. I know this comment will set off Nicholls
Pa> in another long-winded exposition about how human bipedalism is
Pa> just a slight exaggeration of an existing ape tendency towards
Pa> bipedalism.
I've never seen him make any comment which said that apes have a
"tendency towards bipedalism", only that bipedalism is one mode
of locomotion among many for *all* apes and monkeys. Bipedalism is
*not* "restricted to just one primate species". This is a fact,
and why this fact should upset you so is beyond me.
Pa> >Pa> Display? No sign of sexual dimorphism.
Pa> >
Pa> >Perhaps you could try using complete enough sentences to make
Pa> >intelligible thoughts as well.
Pa> >
Pa> The idea that bipedalism evolved out of some form of display behaviour,
Pa> similar to the upright displays of male gorillas, fails to account for
Pa> the fact
Pa> that there is little difference between human males and females in their
Pa> size or degree of bipedalism.
Thank you for clarifying your previously-incomprehensible thought; this
shows that your problem in understanding the role of display in
bipedalism is two-fold: (1) you're looking for a single *cause*, rather
than a suite of advantages; and (2) you apparently don't understand that
male humans and female humans are the same species, and that therefore
the changes in basic structure of one are very likely to be changes to
both.
Pa> For the purposes of the discussion, we can ignore small burrowing
Pa> mammals, fully arboreal primates, spiny porcupines and the like. That
Pa> said, we are left with animals that can:
Pa> (iii) have a social organisation that allows them to fend off
Pa> predators
Pa> e.g. chimpanzees and baboons.
Pa> (iv) can run off to the nearest trees and climb rapidly
Pa> e.g. baboons
Pa> Human ancestors could be presumed to adopt some combination of (iii) and
Pa> (iv).
Chimps can do your number iv as well, but they don't ordinarily have to.
So you're saying that we would have to be somewhat like our closest
relatives. I am astonished that you find it so difficult to believe
that we were undoubtedly like our closest relatives, as in fact we still
are.
Pa> It's obvious that the last ape to reach
Pa> the safety of a tree would be
Pa> the first one eaten.
See how chimps take care of the problem in similar environments.
You could get yourself a library card and use it, or just read what's
been available online here. David Burkhead did one or the other,
enabling him to point out to you:
Pa> In such a case, it only has
Pa> to make it to the shallows to evade a shark or crocodile.
DB> It would have to make it to shallows too shallow for shark or
DB> crocodile. For the shark, that would be, at best, no more than knee
DB> deep and even that is uncertain. While sharks don't generally attack
DB> prey in water that shallow they _can_. And crocodiles can follow your
DB> fleeing pre-humans right up onto the shore if they wanted to. The thing
DB> is, they'd not _have_ to. They are so much faster in the water than
DB> humans that from the time the pre-humans would know they are there, and
DB> the time they struck, a pre-human would only go a couple of feet. The
DB> same for sharks in waist deep water. They are _so_ much faster than
DB> humans in water that you don't have _time_ to get to the shallows.
DB> In _real_ shark attacks (as opposed to the ones in movies) the
DB> first sign that anyone has that the shark is even there is often when
DB> the attackee notices that his _arm_ (or leg) is gone!
(My note: crocodile attack too; victim rarely sees it coming.)
PD> >That option is not available to an ape trying to outrun a leopard.
DB> Still clinging to that "treeless, waterless savanna"? Fleeing for
DB> the trees is comparable to fleeing for the shallows--and the race is
DB> _much_ more even. Go look at my numbers again. The fastest human
DB> swimmer there ever was is less than half as fast, compared to typical
DB> swimming predators, as an average runner against the fastest land
DB> predators.
DB> And go look at how chimpanzees _actually_ deal with predators like
DB> leopards. It's _not_, in general, by fleeing. They do, at least on
DB> occassion, band together to _drive off_, or _kill_, the leopard. There
DB> is no reason at all why our putative ancestors could not have done the
DB> same thing.
DB> The idea that an aquatic environment is, somehow, safer from
DB> predators than a savannah environment (not the mythical "treeless,
DB> waterless savannah" but a real one) is patently false.
DB> David L. Burkhead
Pa> >Pa> Tool carrying? Bipedalism predates tools.
Pa> >
Pa> >Actually unlikely; you are confusing "stone tools" with "tools".
Pa> >Again,
Pa> >there's been *some* writing done on human evolution in the last 30
Pa> years.
Pa> You missed the point.
The point is that you said something that is almost certainly untrue.
Pa> Perhaps the sight of chimpanzees rushing down a hillside
Pa> brandishing branches torn off trees inspired that idea.
"Perhaps" it was the observation that bipedal locomotion in non-human
primates is often used when they carry more than can be gripped in one
hand.
Pa> However, chimpanzees
Pa> do not carry such tools around with them; nor do they expend any effort
Pa> refining their tools.
Pa> It is likely the first bipedal hominids used tools in
Pa> much the same way as modern chimpanzees; the brain power was probably
Pa> comparable. But it is long after the evolution of bipedalism that any
Pa> sign of tools that are re-used emerges in the fossil record. If the
Pa> tools aren't being re-used, they aren't being carried around by a
Pa> bipedal ape.
Chimps modify their tools. Chimps re-use tools. Maybe *your* ancestors
weren't as smart as chimps, but *mine* were. Tools "in the fossil
record" (actually stone tools are not "fossils", of course) are, so far,
stone tools, and our ability to recognise non-cutting stone tools, or
wooden tools, grasses, etc., at that time-distance is at present
essentially non-existent.
Pa> >Pa> Food gathering? Lots of problems with disadvantageous intermediate
Pa> >Pa> forms.
Pa> >
JM> >The non-existent "law of disadvantageous intermediates" again. Give it
JM> >up, Pat; it doesn't exist.
Pa> See prior comments re Dawkins. I suppose you believe evolution is
Pa> directed; that the advantages of the final outcome will outweigh
Pa> the disadvantages of the intermediate forms.
Pa> Pat Dooley
Building a strawman, Pat? Let's just look at your idea of "the
principle of disadvantageous intermediates" and how, many many posts
ago, I tried, for the umpteenth time, to get you to understand how it
doesn't exist:
Pa> Evolution doesn't give you a sub-optimal holiday while you evolve an
Pa> optimal solution - the principle of non-disadvantageous intermediates.
There is no such "principle", as has been pointed out to you many many
many many times so far. The idea that evolution produces "optimal"
behaviors or morphology is a popular misconception, but that's all it
is. Evolution does not force "optimal" results, it selects against
ones that don't work "well enough". The sooner you divorce the words
"optimal" and "evolution" from each other, the closer you'll be to an
understanding of evolutionary principles.
Pa> You might try reading Richard Dawkins "The Blind Watchmaker"
Pa> before making such a statement. It is a simple principle of
Pa> evolution that its progress
Pa> is not directed by the desirability of particular outcomes, but
Pa> by the accumulation of small changes that are not, in themselves,
Pa> disadvantageous.
Not *critically* disadvantageous; in other words, not so horribly wrong
that the creature couldn't survive long enough to raise a few kids to
the age where they raise some kids of their own.
Pa> You have to demonstrate that each intermediate form between the
Pa> ancestral
Pa> gait of the human/chimpanzee common ancestor, and the bipedal
Pa> gait of Australopithicenes, was advantageous.
No, you don't show that it was *advantageous*, but rather that it *was
not* horribly disadvantageous. You know, like standing around in
crocodile-infested water 4-8 hours a day would be.
Jim Moore (j#d#.moore@canrem.com)
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