From: Kevin Bluck (kevin.bluck@mail.com)
Date: Tue Jul 16 2002 - 10:28:22 MDT
>Not necessarily. There's some fetish in paleoanthropology which drives
>paleontologists to call anything more human than a current ape a human-
>only ancestor. As a result, even through chimps are the main line of
>hominids, there are (supposedly) no chimp fossils older than 1.5 million
>years. This is just plain silly. Some of the Australopithicines are human
>ancestors, but some must be chimp and gorilla ancestors too in spite of
>the fact that everybody calls their discovery a human ancestor. It's
>particularly outrageous with the "Robust Australopithicines" which have
>a blizzard of gorillla features but relatively human dentition and slightly
>larger brains. (Their skulls look astonishingly like gorillas, too) According
>to conventional wisdom, several branches of robusts disappear suddenly
>and are replaced by the very similar gorillas who supposedly had been
>hanging out for 6 million years without leaving any fossils. Riiigghhht.
>
>The melange of human, nonhuman ape, and primitive characters of the
>new skull is *exactly* what you expect from a common ancestor. This
>thing could easily be the ancestor of humans, chimps, gorillas, or even
>all 3.
You are exactly right about the "every find is an ancestor" attitude. That
is precisely why this and other recent finds are so important --- it makes
it pretty much impossible to construct a viable "family tree" in which
*every* paleontologist's pet find is a direct ancestor. As you say, some
of them may actually be ancestors of other apes such as chimps, and still
others may be extinct dead ends.
The best hallmark of direct human ancestry in a fossil in my mind is the
presence of an upright two-legged gait. The other apes are all quadrupeds,
although they can move awkwardly on two legs for a limited distance. "Lucy"
and the other Australopithicines appear to have had this upright gait, and
so in my opinion are unlikely to be direct ancestors of the chimp/gorilla
line. Too much "unevolution" would have had to occur. Something as
fundamental to survival as efficient locomotion is not going to change
without strong pressures. For such pressures to produce a bipedal gait and
then opposite pressures to revert later descendants back to knuckle-walking
quadripedalism seems to me vanishingly unlikely. It is still to early to
tell whether this new find was bipedal or not, since they have failed to
find other parts of the skeleton.
In my opinion, the answer to the question of human origin all begins with
our wacky habit of walking exclusively on two legs. It's ridiculous, when
you think about it. Damn poor engineering. It exacts an enormous physical
price. Few other animals have problems with bad backs, knees, high blood
pressure, hemorrhoids, and a host of other ailments that can be traced
directly to our upright posture. It makes us inefficient walkers and slow
runners. Injury to a single leg is crippling, rendering us nearly immobile.
Practically every other land mammal has the sense to adopt a nice, stable
four-legged gait. No animal, prohominid or otherwise, would just start
walking around on two legs for the hell of it. Even highly preadapted
species like primates find it difficult and unwieldy, and will do so only
during threat displays or if they are artificially trained. We humans have
a two-legged bias. To us, walking upright seems obvious and easy, but
that's only because we're born to do it. The fact it, it is incredibly
unusual, due to its obvious disadvantages. We are the only land mammal
species to do it. (Before anybody mentions kangaroos, those are tripedal,
as the strong tail effectively forms a third leg. Without it, they couldn't
balance.)
It is now apparent that humans didn't "become" bipedal to use technology,
as many school-age science texts (and not a few college texts) confidently
proclaim. It is clear that bipedality long precedes use of technology.
Millions of years before the first stone tool was chipped, there were wild
animals walking about on two legs. Why? Most anthropologists have no good
answer. What answers they do supply seem curiously predictive. Virtually
all of them have humans becoming bipedal to gain some future perceived
advantage. Surely they know better. Evolution is not "forward looking".
Species change because some trait helps them reproduce better *now*.
Various excuses: we did it to free our hands to use tools. (Bipedality
precedes tool use.) We did it to see farther while hunting. (Why didn't
cats, dogs, etc. do this if its such an advantage? Baboons just climb a
termite mound to see farther.) We did it because its lets us walk more
efficiently. (Every other mammal species would disagree.)
I think there is one, glaringly obvious reason why we adopted an upright
posture. We stood up so that we could breathe. We were forced to stand up
because we were wading in deep water.
At one shot, that completely eliminates the mystery of bipedality. Avoiding
drowning is certainly the sort of immediate incentive that will enhance
reproductive success. What is more, while immersed in water it is much
easier to balance in an unconventional posture. I doubt many of us here
could balance on our hands on dry ground, not without a great deal of
practice. But practically anybody can do it easily in four feet of water.
Wading in deep water is precisely the sort of environment that would make
adaptation to a bipedal gait for an ape not just practical, but nearly
inevitable.
To my mind, it all fits. The naked skin. Very rare among land animals.
Quite common among aquatic species. Most apes avoid water. We love it.
We'll irrationally pay 2-3 times as much for a house that happens to be
near water. We bathe constantly. We're pretty good swimmers, much better
than the average ape who, if thrown into deep water, prove mainly to be
pretty good drowners. We can voluntarily hold our breath, almost unique
among the primates. The subcutaneous fat layer, again rare among land
mammals (nonexistent in the other primates) but common in water/wallowing
mammals. Our propensity for obesity. Even the curious thatch of hair on top
of our heads. (That was the only part sticking out of the water most of the
time.)
There was even a plausible site for these species to arise. The Afar
triangle, a depression at the head of the Rift valley, was suddenly
inundated by seawater at just about the right time. Small populations of
apes would have been trapped, cut off from each other --- a perfect
environment for rapid evolution of numerous related, but separate species.
This could certainly explain the wide variety of dead-end hominid species
being discovered. The suddenly marine environment would have required them
to enter the water to move around, thus overcoming the natural apely
reluctance to get wet, and eventually favoring an upright wading posture.
As time went on, they became so accustomed to walking upright that they
continued to do so even when out of the water, although that was less and
less of the time. Pro-humans were well on their way to becoming a
completely aquatic species.
Then, disaster struck again. The climate shifted once more, and Afar dried
up. Our animal ancestors, now fish out of water, were forced to take their
strange adaptions and make the best of it on dry land. The bipedality, so
useful in water, worked OK on land too, so it remained. The naked skin was
a bigger problem. Very hot in the sun, cold at night without water covering
it to filter the sun and moderate the air temperatures. Could that naked
skin have been the first impetus pushing us toward technology, as our
now-maladapted ancestors struggled to survive by covering themselves with
"artificial fur"?
All this is based on the work of Elaine Morgan, author of the "Aquatic Ape
Theory". For a long time, she was regarded as a kook, dismissed out of
hand. Although still considered fringe, the final demise of the Desmond
Morris-esque "Savannah theory" now means people in the field at least
listen to her ideas. I just don't understand how mainstream anthropology
can continue to cling to thin, illogical excuses for humanity's utterly
bizarre construction as land animals and disregard the fact that every one
of the features that makes Homo Sapiens so unusual as a land mammal are
perfectly commonplace among a variety of water mammal species.
--- Kevin
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