Re: An alternative to ST and AAT

Susan S. Chin (susansf@netcom.com)
Tue, 19 Nov 1996 16:22:03 GMT

Paul@crowleyp.demon.co.uk (Paul Crowley) wrote:
: >But any serious thought on Lucy's morphology should lead to
: >the same conclusion. If you can't stride, you must waddle.

Gerrit Hanenburg (G.Hanenburg@inter.nl.net) wrote:
: You are confusing concepts.
: Both Lucy and modern humans have what is called striding bipedalism.
: Striding bipedalism refers to the kind of locomotion in which the body
: is supported by first one leg and then the other,and as the body
: passes over the supporting leg,the other leg swings forward in
: preparation for the next support fase. During transfer of the body
: from the trailing to the leading leg there is a brief period when both
: feet are on the ground.
: Waddling only refers to the an excessive lateral displacement of the
: body during striding. Waddling does not exclude striding.

: Gerrit

I'm glad the striding/waddling "dichotomy" was brought up. Strictly
speaking, one could interpret a biped such as Lucy as a less efficient
biped than later Hominids, yet not categorize her and other afarensis as
"waddlers." If waddling, for those who subscribe to that idea, only means
a less efficient form of bipedalism, with *some* lateral displacement of
the body (upper or lower or both?), then that means something very
different than what the term itself implies.

For what it's worth, this is how I'd define the two:

Bipedal locomotion
striders - an exclusive hominid form of locomotion involving major
changes in the pelvic, hip, knee and foot anatomy (this includes both the
hard evidence, bones, and soft tissue). Progresses forward in a
straight ahead direction.

waddlers - type of locomotion found in non-habitually bipedal apes while
on the ground. No changes in anatomy required (aside from using the
forelimbs for balance vs. as another pair of "legs"). Progresses forward
in a lateral direction.

There are other types of bipedal locomotion, but for the hominoids, this
about covers it, IMO.

Susan

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                                             susansf@netcom.com