Re: An alternative to ST and AAT
Thomas Clarke (clarke@acme.ucf.edu)
11 Nov 1996 05:58:42 GMT
Phillip Bigelow <bh162@scn.org> writes:
>Thomas Clarke wrote:
>>
>> than either is to a human's bipedal locomotion.
>That was my point, also. A human's locomotion is very closely similar
>in
>terrestrial locomotion to that of a brachiating primate on the ground.
>Similarly, chimpanzeees are (in general) quite similar in locomotion
Then I misunderstood your original point. I thought you were lumping
humans with saltators with birds with two-leeged dinosaurs into a
class of bipedal animals.
We still differ about the degree of uniqueness of human versus primate/chimp
however.
>> Do they have locking knees?
>No, but they still walk bipedally. Remember that we are talking about
>terrestrial bipedalism in general. Locking knees is an apomorphy of
>hominids (a matter of degree away from the more primitive condition in
>other anthropoids).
No. You are talking about bipedalism in general.
I want to talk about bipdealism in man specifically.
I am being speciocentric.
Yes, I know that the general principles of evolution
can explain LCA -> man, just as they can explain whatever -> velociraptor,
but I am a member of Homo sapiens, and I would like the LCA -> man
transition explained in detail. It interests me. If I were a
velociraptor, then I would be concerned about how the four legged
carbonierous (is that the right era?) ancestors beame bipedal in the
style of velociraptors.
Returning to knees. They are very important. They allow humans tpo
stand around more or less indefinitely without strain to leg muscles.
>> This type of discussion is, of course, a matter of degree.
>> Can a brachiating arboreal primate walk twenty miles?
>Hell, Tom. We don't even know if A. AFARENSIS could walk 20 miles!
>You are damn-right it is all a matter of degree! That was my point.
We know they could walk a couple of hundered feet. There are footprints
to prove that. The anatomy is more like a man than like a chimps, so
_I_ would favor longer distance capability.
>> I just perceive a larger difference than you do, I guess.
>You apparently haven't done a lot of comparative anatomy then.
You apparently haven't done a lot of factor analysis (;-)
>> Actually, as I think about this, I will concentrate on the
>> knee. I think the human (australopithicene?) knee is unique.
>You think wrong.
>This knee-joint style isn't unique in the animal kingdom. It is
>just an apomorphy in primates. Curiously, though, that in the other
>animals that have a graviportal, lock-knee style posture, these
>animals are all terrestrial. Not an aquatic one in the bunch! :-)
When did I ever mention aquatic in this thread? I think it may
be in the title, but I have not mentioned it.
>You want a REAL example of a "unique" morphology? The maniraptoran
>manus.
>The feature is not shared by any other member of the animal kingdom, yet
>all
>members of the clade have a *roughly* similar hand.
_ALL_ members of the clade! Now you make my point.
Why other members of the clade containing H.s contain a locking knee.
Is the clade defined by the locking knee?
>> Now my question can be more precise. Do ostrich's and storks
>> have unique anatomical features related to their style of walking?
>Of course. But the plesiomorphy in this situation is that, in spite
>of their different locomotion styles, they all had an ancestor that
>was bipedal. Only their *specific* style of walking is unique
>to each bird.
Again you make my point. Only H.s has an ancestor that is bipedal.
>> I would argue that number of toes and stride length/pattern
>> are not essential differences.
>And I would argue that primate stride style is similarly not
>that different enough to propose that one of their members (hominids)
>has a "special" origin.
So we differ.
>> Even the human brain can be seen as just an enlarged
>> primate brain.
>> Howeever, the human foot and human knee are a lot
>> different from the corresponging primate features.
>Only in degree. As I noted above, you apparently haven't
>done a lot of comparative anatomy. The differences between
>the two are large IN CERTAIN ways, but it's only a matter of degree.
>In gross morphology, a human foot still roughly approximates a
>chimpanzee
>foot. Remember what I wrote about cladistic analysis (above)?
>Similar differences can be found between other closely-related species.
>There are significant differences in hyal morphology between two
>species of sloth. The sloths in question are (Bradypus and Cloepus).
>Countless other examples can be given.
Sigh. You are too much the paleoontologist.
You can't see the tree for the forest.
Sure, there are just as many bones in the human foot as in the chimp
foot. There arrangment is slightly different and relative sizes
are different. However, there is a very large difference in the
function of the two appendages. And it is the function that
evolution acts upon, not the anatomy and morphology.
>> If the circumstances leading to the unique species of which I am
>> a member were not unique, then why did it not happen before?
>How can you be so *sure* that it hasn't happened in other fossil primate
>taxa before? How many more Miocene and Pliocene primate fossils
>remain to be discovered?
If it did happen, it was abortive.
I think we would find things like fossil pyramids if they had been
built in the Miocene and Pliocene. Remember it is only a couple
of million years from the Australopithecenes to the pyramids.
Tom Clarke
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