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Re: Bipedalism and Arboreality.
>>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:
In 'human terms' they seem to have come to spend too much time on the
ground too soon!<<
Ouch. I did say that I might be making a fool of myself. Okay, I accept the
point. Humans were bipedal before they got onto the ground and the bipedal
stance was convenient in that is left their hands free to manipulate, and
allowed them to gaze over the savanna to see oncoming predators. That
arboreal/bipedal thing may be the biggest logical hole in my testament on
bird evolution. Bipedalism _is_ a neotonous trait in humans, though. Read
Steven Jay Gould's article about Mickey Mouse (I don't have the book handy
and so can't be any more specific).