Bipedalism and Arboreality.

[luisrey <luisrey@ndirect.co.uk>]

>In a message dated 9/25/99 7:23:10 PM EST, dbensen@gotnet.net writes:
>
><< NOOOOO!  Well, I don't know about tree kangaroos and the climbing
>hypothesis
> makes sense, but humans did not become bipedal as an adaptation to
>arborality.
> Humans became bipedal AFTER they descended from the trees. >>

This assertion goes against all current knowledge and research. Early
Australopithecines spent a lot of time in the trees and  modified pelvis
and adopted a bipedal posture while still being pretty much arboreal.
The latest reconstruction of semi-prehensile toe of afarensis feet
demonstrates this. They combined modern pelvises and fully erect stance
with prehensile toes.
In fact, the more we go backwards in hominid evolution the weirder the
locomotion gets. Tim White was working on a model of anamensis and
specially Ardipithecus ramidus that he said "was going to challenge
everything we ever thought about locomotion".
So bipedality indeed seems to have a rather complicated origin in the
trees, not on the ground.
If we see the way Chimpanzees walk around: it seems they resorted to a
mid-way compromise solution in an evolution race towards full bipedality:
Knuckle-walking.
In 'human terms' they seem to have come to spend too much time on the
ground too soon!


Luis Rey

Visit my website on http://www.ndirect.co.uk/~luisrey