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Re: Bipedalism and other factors
David L Burkhead (r3dlb1@dax.cc.uakron.edu)
22 Jun 1995 16:17:43 GMT
Newsgroups: sci.anthropology.paleo
Subject: Re: Bipedalism and other factors
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Organization: The University of Akron, Akron, Ohio
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In article <3sabc8$srn@newsbf02.news.aol.com> sircpu@aol.com (Sir CPU) writes:
[ 8< Chimpanzees and natural predators >8 ]
>
>-Odd that you manage to suggest that, despite the fact that chimpanzees
>-manage to deal reasonably well with their potential predators, such as
>-lions and leopards, early hominids of similar size and brainpower would
>-be incapable of doing so.
>
>Well, I think chimps have a better opportunity to climb trees in the
>wooded environment which they live. I think that if early hominids were
>out on the open savanna, as the savanna theory states, they would have
>much less of a chance to escape from a predator, especially a lion, to a
>tree.
Several things here. First, climbing trees is not a terribly
effective escape strategy from leopards (a more serious threat in
wooded environs than lions, which are savanna creatures). Leopards
climb quite well, and being lighter than the chimps, they can travel
onto any branch which will support a chimp's weight. But that's
really a side issue. Check how chimpanzees _actually deal_ with
leopards. The footage I have seen did _not_ involve the chimps
fleeing, at least not all of them. A group of them gathered to throw
sticks and stones at the leopard to drive it away.
>
>JM> You gave a quote about how much water can be lost by active humans in
>JM> the desert, which has nothing whatsoever to do with australopithecines
>JM> unless they were in the desert. So your quote has nothing whatsoever
>JM> to do with the subject at hand. (Question: How much water would, say,
>a
>JM> wildebeest use in "an hour of walking in a hot day in the desert"?
>JM> Answer: who cares? the desert has nothing to do with its actual
>JM> habitat.)
>
>Tk> The point was still that hominids do not conserve water very well, IN
>Tk> ANY KIND OF HABITAT. I understand that they do not live in the desert
>Tk> but I was merely pointing to their unusually high water consumption
>Tk> rates. Did I not make that clear?
>
>-All that matters is whether or not they do *well enough*; that's how
>-evolution works. We see that in fact australopithecines did well enough
>-to survive in their environment for millions and millions of years. And
>-in fact even chimpanzees do well enough in relatively dry areas, similar
>-to those used by australopithecines.
>
>The point is, however, if hominids were evolving on the savanna for the
>millions of years that they were supposedly, how come their evolution
>didn't bring them up to the level of other savanna creatures. It is that
>simple. I mean, don't you find it the least bit odd that the human body
>temperature of 98 degrees is more like that of a dolphin or a whale than
>that of other savanna creatures? And don't you find it odd that we expend
>a tremendous amount of energy and resouces to keep our body temperature
>constant, again like aquatic creatures, instead of allowing our internal
>body temperature to rise? Again, if we were on the savanna for the
>millions of years as you say, and did not have an interviening period of
>"aquatic-ness", instead evolving with the other savanna creatures, why
>then did we not end up evolving the same way?
Sigh. This point has been answered _repeatedly_. Evolution
works with what's at hand. Pre-humans did not have the same starting
point as other savanna creatures. Thus, to expect the same results is
fatuous nonsense. All that matters is if human survival mechanisms
worked _well enough_. They patently did since they _did_ survive for
millions of years on the savanna. This savanna period also happened
_after_ any postulated aquatic period, so your arguments about
"intervening period of "aquatic-ness" is totally empty. There's no
_time_ after the known savanna and later periods for this hypothetical
aquatic phase.
Why don't humans let their body temperature rise? My guess would
be because we don't have large snouts to keep the _brain_ cool (as do
other large savanna mammals) and so have to keep the entire body cool.
Why the "coincidence" of body temperature? Well, why not provide some
_data_ on that? Just what body temperatures are found in various
animals--woodland primates, savanna dwelling large mammals, aquatic
mammals. A vague, arm-wavey "more like aquatic animals" says nothing
of substance.
>
>Tk> If you really think I don't understand "how walking in the desert
>Tk> differs from foraging and resting in a wooded savannah mosaic
>Tk> environment" then I don't think you understood the point I was trying
>Tk> to make at all.
>
>-Your point was, and is, irrelevant to the subject of australopithecine
>-adaption to their environment. Contrary to what you continually insist,
>-they just flat out worked in that environment; well enough to last there
>-for millions and millions of years.
>
>You point of "well they were there, on the savanna, and they mananged to
>survive well enough to get us to were we are today"; I don't think is a
>very good one. Sure we were there, but we ended up taking a different
>evolutionary path from the majority of animals there, now the question is
>why? If you want to say, "well we did, and we made it ok, and that is
>that, fine". But as a scientist, don't the peculuarities of our
>anotomical structures make you wonder what causes us to be that way? And
>then look for a SIMPLE explaination to cover all aspects of our unusual
We "ended up taking a different evolutionary path" because we
started from a different point. As has been pointed out to you time
and again evolution works with the material at hand. (Okay, that's
anthropomorphising the process but it will work as a metaphor, I guess.)
>physical structures?
>
>Tk> > I don't think there is really any question, no matter what quote you
>Tk> > come up with, that the susceptibility of early hominids to
>Tk> > dehydration
>Tk> > was probably pretty high. If you look at any other creature on the
>Tk> > savanna, the ways in which they conserve water resources are far
>Tk> > superior to the human/pre-human model. Their body temperatures are
>Tk> > generally higher, they allow their internal body temperatures to
>Tk> > rise in response to heat and they don't sweat, they pant.
>
>-Evolution works on what is there; it can't just build a whole new system
>-from scratch.
>
>I agree. And this is why I think you see the strange human configuration.
>Because evolution worked on an aquatic ape that was suddenly living on the
>african plains.
Sorry, but "aquatic ape" is _still_ an unjustified assumption.
There is enough difference between woodland ape going savanna and
other savanna creatures that the different evolutionary path is
sufficiently explained that way. We have only assertions and
whole-cloth creations of hypotheses to claim otherwise.
>
>
>-As I pointed out above, you can't just evolve whatever "takes your
>-fancy"; evolution works with what is there in the organism. So no, we
>-didn't survive there like antelopes do, or like warthogs, or by
>-burrowing and coming out at night, or by digging into the ground and
>
>Again, I think you are supporting my claim again. Evolution worked with
>what it had in the organism, and aquatic organism, and came up with some
>unusual strategies to cope with life on the savanna.
No. He did nothing of the sort. "Different from other savanna
animals" (which leads to different solutions to survival problems)
does _not_ necessarily support _your_ particular claim.
> This is not a good arguement to defend our evolution on the savanna. To
>say we were there, and we made due with our evolutionary circumstances,
>does not cover the unusual aspects of our evolution that separate us from
>other savanna creatures. I think the AAT goes a long way to help explain
>these peculuarities, even if I don't know enough about crocodile habitats.
Not at all. AAH has some _serious_ problems. Main of these is
that it picks and chooses. There are enough properties of any living
thing that you can find cross correllations between different types.
Yet we have AAH making claims that are totally unsupported. For
instance, the claim is made that the aquatic phase is what led to our
becoming bipedal. Yet, when asked, its proponents cannot point to a
_single_ bipedal aquatic mammal. Not one. Where, then, did this
extraordinary claim come from? Whole cloth creation.
Likewise, the claim is made that an aquatic environment provided
a refuge from predators. This is nonsense. For one thing, the
weakness of humans in comparison with terrestrial predators (on a
purely physical level) is even worse for humans in water wrt _aquatic_
predators. I can (or could before my knees went to pot) run with a
speed 25-30% of the _fastest_ land predator. An olympic swimmer
would not make more than 5% of the fastest aquatic predators, and not
more than 10% of more "typical" predators. Then, in the water, it is more
difficult to see predators coming and avoid them. Likewise, it is more
difficult to band together to drive off a predator (as those chimps did).
Also, aquatic predators are _stupid_ and unwilling to be driven off by threat
displays (unlike land based mammals).
Plainly, the AAH doesn't hold water.
David L. Burkhead
r3dlb1@dax.cc.uakron.edu
d.burkhead@genie.geis.com
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