Re: Bipedalism and theorizing... was Re: Morgan and creationists
Gerrit Hanenburg (ghanenbu@inter.nl.net)
Wed, 2 Oct 1996 21:20:03 GMT
"John Waters" <jdwaters@dircon.co.uk> wrote:
>>What I meant was that regular "genuine" long distance walking
>>(say 200 yards or more) requires a reorganization of the pelvic region
>>and lower limbs.
>>As you probably know,when chimps stand or walk bipedally,they
>>do so with flexed hips and knees in order to retain maximum lever
>>advantage for the hamstring muscles.This requires a lot of energy and
>>leads to rapid fatigue.
>JW: I agree with all of this, but it seems to make Paul's
>arguments concerning the putting down of the infant all the
>stronger. If Faben could only manage thirty yards, how far could
>a chimpanzee mother with a three year old infant manage? Thirty
>inches?
That's why I think that reorganization of the pelvic region and lower
limbs is crucial,and happened early in hominid evolution.
It may have started during a stage when the main function of
bipedalism was postural and not yet locomotory.
>I assume that you accept that the Hominids eventually became
>fully bipedal, and that the Gorilla/Chimpanzee/Bonobo have two
>types of ground level locomotion, namely: knuckle walking and
>bipedalism. However, I am not sure where you stand on the other
>aspects of the matter. Can we clarify a few things?
>1. Do you accept that the Gorilla/Chimpanzee specie became
>knuckle walkers after their collective split from the Hominids?
I wish I could say yes,but I remain sceptical because of conflicting
data.Morphological data seems to point to a Gorilla/Pan clade with
Homo as the sistergroup.
For example,a cladistic analysis by Groves and Paterson,using the
PHYLIP-package,consistently found a Gorilla/Pan clade with their
largest dataset of morphological characters (114) and
applying several different parsimony methods.(Groves,C.P.and
Paterson,J.D.(1991),Testing hominoid phylogeny with the PHYLIP
programs.Journal of Human Evolution 20:167-183).
But molecular data seems to point to a Homo/Pan clade with Gorilla as
the sistergroup.
This leaves us with several possibilities:
-In case of a Pan/Gorilla clade,the LCA of humans and African apes was
a knucklewalker and the character was secondarily lost by the
hominids,or the LCA was not a knucklewalker and the character was
acquired later by the LCA of the African apes after the split from the
hominids.
-In case of a Pan/Homo clade,The LCA of humans and chimps was a
knucklewalker and the character was secondarily lost by hominids,or
the LCA was not a knucklewalker and the character was acquired
independently by Gorilla and Pan.
>2. Using retrospective analysis, do you accept that before the
>Gorilla/ Chimpanzee specie developed knuckle walking, their only
>means of ground level locomotion was bipedalism?
They could have used another kind of quadrupedalism (palmigrade or
fistwalking) but I agree that the only likely option for all possible
forms of quadrupedalism on the ground is a form of bipedalism.
>3. From this, do you accept (by extension) that the common
>ancestor of the Gorilla/ Chimpanzee and the Hominids was bipedal
>on the ground?
No,see answer to 1.
>4. By deduction, do you accept that the Hominids inherited
>bipedalism as the sole means of ground level locomotion from the
>common ancestor?
Only *if* the LCA was bipedal,but that may not have been the case (see
1).
>5. Do you accept that the Hominids were never knuckle walkers?
So far the fossil record does not indicate any knucklewalking
adaptations in early hominids,but I don't know what the future will
bring.I accept it for the time being.
>6. By extension, do you accept that Hominids developed from
>short distance bipedal walkers to long distance bipedal walkers,
>without any intervening quadrupedal stage of locomotion?
Yes.
Gerrit.
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