Re: An alternative to ST and AAT

Rohinton Collins (
20 Nov 1996 23:29:28 GMT

> > (Paul Crowley) wrote:

> Striding, in this sense, rules out waddling, which as you say,
> involves excessive lateral displacement. Chimpanzees and gorillas
> cannot stride when they walk bipedally; nor,

*** I BELIEVE ***

> could Lucy or
> male A.afarensis. Surely the development of the bipedal stride was
> the major change with H.erectus morphology?

Remember Paul, there is much evidence for a striding gait in the
australopithecines. This evidence at least calls for differentiation when
describing the locomotion of the African apes and the australopithecines
(as you have above).

1. They were fully adapted bipeds, and is so unreasonable to first assume
that they waddled, but looking closer at the anatomy:

2. They had a valgus angle similar to a modern human and dissimilar from an
ape, indicating that the feet were closer beneath the centre of gravity
than in an ape. This means that during locomotion, lateral movement of the
body would be reduced.

3. The iliac blades are flared laterally when compared to an ape, which
suggests that the gluteus muscles were acting in a new capacity, as
abductors of the thigh, which would action the lateral movement necessary
for balance during the swing phase.

4. Lastly (that I can remember now) the Laetoli footprints describe more a
modern style of bipedalism, rather than an ape one - the footprints are
close together laterally, not like an apes who are wide apart laterally.

Feel free to add to this list Susan, Gerrit, anyone,