Re: Postural bipedalism may have preceded and not causally connected to walking.

mclark wrote:
>
> "rmacfarl" <rmacfarl@xxxxxxxxxxxxxxxx> wrote in message
> news:1132789950.960881.98580@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> Philip Deitiker wrote:
> > American Journal of Physical Anthropology
> > Early View: Published Online 15 Nov 2005
> >
> > Arboreal bipedalism in wild chimpanzees: Implications for the
> > evolution of hominid posture and locomotion (p NA)
> > Craig B. Stanford
> [...]
> >
> > "
> > Most observations of bipedalism were made when the animals
> > were in treetops and the observer at eye-level across narrow
> > ravines. This suggests that wild chimpanzees may engage in
> > bipedal behavior more often than is generally appreciated.
> > Models of the likely evolutionary origins of bipedalism are
> > considered in the light of Bwindi bipedalism data. Bipedalism
> > among Bwindi chimpanzees suggests the origin of bipedal
> > posture in hominids to be related to foraging advantages in
> > fruit trees. It suggests important arboreal advantages in
> > upright posture. The origin of postural bipedalism may have
> > preceded and been causally disconnected from locomotor
> > bipedalism. Am J Phys Anthropol, 2005. © 2005 Wiley-Liss, Inc.
> > "
>
> Thanks Phil. So possibly a chimp-like, knuckle-walking ancestor becomes
> postural biped in an arboreal context, then later moves to a
> terrestrial context where it adopts obligate locomotive bipedalism
> (with vestigial signs of knuckle-walking). Convoluted, but not
> implausible.
>
> 179 instances of bipedal stance of 5 seconds' duration or greater. Data
> overkill? :-)
>
> So now all we need is some reference to Crompton and
> the circle will be complete. Rich, I think that's your cue...

Me? *blush*

Yes, this is not a new idea.

http://www.trussel.com/prehist/news283.htm
...
But now a group of scientists has proposed a controversial theory which
maintains our upright ability is far more ancient than supposed. They also
claim we picked up our two-footed prowess while living in trees. ...

"Trees were an ideal nursery for the learning of human walking," says Robin
Compton of Liverpool University. "They enable an animal to balance itself.
They can reach out in any direction, above and below themselves, and find
branches. Orangutans do just this sort of thing."

And having got our bipedal act right, we were then perfectly placed, when the
climate changed 2 million years later, and forests thinned, to walk out on the
savanna with our hands free to make tools and carry food to caves.

This startling evolutionary idea has been put forward by scientists led by
Martin Pickford, of the College de France, and Brigitte Senut, of the National
Museum of Natural History in Paris. As they claim in "Secrets of the Dead: The
first human?" on Channel 4 television in Britain, their discovery of ape-men's
bones in Kenya last year provides evidence we could walk on two feet at least 6
million years ago, although most scientists believe our bipedal expertise did
not appear for another 2 million years.
...
.

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