Re: An alternative to ST and AAT

Phillip Bigelow (
Sat, 30 Nov 1996 16:47:49 -0800

Paul Crowley wrote:
> It is clear from their anatomy that there was no great
> selective pressure on the Australopithecines to develop an
> efficient walking technique,

"Efficient" can mean many things. "Ecologically-efficient", for
instance, is much different in meaning than the term
"biomechanically-efficient". Just because it looks awkward doesn't
mean that it doesn't convey optimal efficiency for that particular

>or that other aspects of their
> niche inhibited it.

Australopithicenes are intermediate in locomotion-adaptation
between other apes and modern humans. They are also intermediate
in time between the split from the LCA (which may have been
an arboreal brachiator) and Homo erectus (a hominid with a human-
like stride).
The reason that Australopithicenes were unusual walkers
is because they were intermediates. Intermediates, by definition,
are going to be different from either end-point.
The longevity of the austrolopithicene clade (slightly over
2 million years) strongly suggests that whatever their
locomotion style was used for, it certainly was used well, and
was better than "just adequate". "Just adequate" invites
evolutionary refinement.
Whatever selection opportunities caused the more human-like
gait of Homo-erectus, these opportunities probably arose
near the end of the australopithines' tenure, not at their beginning.
The only conclusion that can be drawn for most of the 2 m.y. reign
of Australo's is that australopithicene-style locomotion was
highly desirable.