Re: Dissecting the Aquatic Ape: Bipedalism
Gerrit Hanenburg (ghanenbu@inter.nl.net)
Sun, 7 Jul 1996 12:20:47 GMT
rfoy@netcom.com (Richard Foy) wrote:
>>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?
>I don't know if it is a common feature or not but my fingers are like
>that as well.
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.
None of the above features are found in fossil hominids.
Shouldn't we concentrate on these fossilizable characters when it
comes to assessing locomotor behaviour of extinct ancestors,instead of
relying on such practically untestable features as lack of hair on the
median segment of the fingers?
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.
And btw,I *do* have hair on the median segments of my fingers.
Gerrit.
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