Re: Dissecting the Aquatic Ape: Bipedalism
Paul Crowley (Paul@crowleyp.demon.co.uk)
Sat, 13 Jul 96 20:49:22 GMT
In article <Du6ACE.9B1@inter.NL.net>
ghanenbu@inter.nl.net "Gerrit Hanenburg" writes:
> >>I have hair on the backs of my hands and on the proximal phalanx
> >>of each finger, whereas the last two phallanges of each finger are
> >>hairless. These latter would have been in contact with the ground
> >>and possessed knuckle pads had my ancestors ever knuckle-walked.
> >>Is this a common hss feature? If so, is it evidence of a knuckle-
> >>walking lca?
> Skeletal features associated with knuckle-walking are:
>
> -dorsally extended articular surface of the head of the metacarpals
> associated with hyperextension of the metacarpophalangeal joint.
> -a transverse bony ridge on the dorsum of the metacarpals to prevent
> the joint from collapsing under the weight of the body.
> -widest diameter of the metacarpal heads located dorsally.
> -proximal phalanges short relative to length of the metacarpals in
> relation to humans and orang-utans.
> And further:
> -distal articular surface of the radius deeply concave.
> -bony ridges on scaphoid and dorsal distal radius stabilizing the
> wrist joint.
Thanks for the technical information. Someday, maybe, I'll get
around to studying it myself. My speculation was an especially bad
one and I half suspected it at the time. The hair on our fingers
is clearly a form of insulation against cold and is not needed on
the median or terminal phallanges of our fingers as on cold nights
or in freezing weather these would be curled up into fists which
would be held under the arms.
> On the basis of the above mentioned skeletal features associated with
> knuckle-walking we can at least make the testable prediction that if
> the LCA was a knuckle-walker,fossils of it will show these features.
Hopefully, definitive fossil data on this whole area will be available
within a year or two.
Paul.
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