Re: An alternative to ST and AAT

Paul Crowley (
Sat, 30 Nov 96 20:46:59 GMT

> > "Rohinton Collins" wrote
> >
> >> The only thing we know for sure is this: Lucy's bipedalism is more
> >> efficient than ape quadrupedalism only during walking.

> (Paul Crowley) wrote:
> >We do NOT know this. In fact, everything indicates the opposite.

In article <57nurn$> "fsflowers" writes:

> Why do you say we do not know this? . . . . . . . I
> don't agree that everything indicates the opposite, at least
> with my inexperienced and unprofessional opinion.

This has been debated extensively in this thread. Gerrit posted
the following a while back:

> Christine Berge in her paper "How did the Australopithecines walk? A
> biomechanical study of the hip and thigh of Australopithecus
> afarensis" (J.of Human Evol.26 (1994):259-273) concludes:"Not only did
> Australopithecus have less ability to maintain hip and knee extension
> during the walk,but also probably moved the pelvis and lower limb
> differently. It seems that the australopithecine walk differed
> significantly from that of humans,involving a sort of waddling
> gait,with large rotatory movements of the pelvis and shoulders around
> the vertebral column. Such a walk,likely required a greater energetic
> cost than does human bipedalism."

It is clear from their anatomy that there was no great
selective pressure on the Australopithecines to develop an
efficient walking technique, or that other aspects of their
niche inhibited it. IOW it's unlikely that Lucy walked a lot.
Getting around in the most effective way was not one of her
priorities. Roh's assumption is commonly made because it
is the obvious one: "early hominids became bipedal to get
about more efficiently than when they were quadrupedal".
But it is not borne out by a study of their anatomy.

Its falsity would also be realised with a moment's thought.
A quadrupedal animal gets about quite well; if it is going
to adopt an unaccustomed stance, it is going to get about
less well. After many generations, it will adapt to the
new stance and become better at getting around in the new
way. This may or may not be better than the old way.

But it did not become bipedal to get around faster or more
efficiently. It is the old, old problem in evolution of
intermediary stages. Birds did not learn to fly because it
was a better way to migrate long distances. An intermediate
stage usually implies some diminution in the normal
capability and it requires a special explanation. Maybe
birds started jumping to catch insects. Similarly, the
origin of bipedalism needs some explanation other than
getting about more efficiently.