From: CurtAdams@aol.com
Date: Tue Jul 16 2002 - 19:40:19 MDT
In a message dated 7/16/02 9:34:29, kevin.bluck@mail.com writes:
>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.
Yes, *but* - chimps and gorillas knuckle-walk, while the ancestral state
is palm-walking. This strongly suggests chimp and gorilla ancestors were
bipedal at some point. Since all the African ape fossils from about 2 to 6
million years ago were bipeds, I think that was the primitive
state for all African apes. Human went all-the-way upright, and other
apes almost-all-the-way knucklewalking.
Gibbons, incidentally, are bipeds too. It's not a human-only characteristic.
We're just the best at it.
>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.
No; knuckle-walking has lots of speed advantages, it's just hard to carry
things.
The spectacular expansion of Erectus could have driven all the
australopithicines
out of their niches. Indeed, it's about when Erectus shows up that the
australopithicines-that-look-like-gorillas go "poof" and the gorillas appear.
>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.
Based on gibbons, it seems a natural ground transportation method for
a suspensory climber. If the australopithicines needed to climb, they had
good reason to walk that way.
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