Re: An alternative to ST and AAT

John Waters (
17 Nov 1996 14:48:47 GMT

Gerrit Hanenburg <> wrote in
article <56n198$>...
> "John Waters" <> wrote:

> >Modern humans gain their bipedal efficiency from the
ligaments of
> >the lower leg which attach to the ankle via the achilles
> >tendon.
> It is the muscle group composed of M.soleus and
M.gastrocnemius that
> inserts via the achilles tendon into the posterior
> Contraction of these muscles causes plantar flexion of
the foot in
> which the calcaneal tuber functions as a lever arm and
the talar body
> as a fulcrum. The morphology of the australopithecine
calcaneus does
> not indicate that this was much different in A.afarensis.
> Gerrit

JW: My word Gerrit, where would we be without you? Despite
my misdescription of the muscles and tendons involved, do
you agree than it is the tendons which create the element
of bipedal efficiency needed for effortless long distance
walking. There is an analogy here with the Kangaroo which
gains its efficient long distance locomotion in this way.

Clearly, I cannot prove that the Australopithicenes lacked
well developed tendons, and frankly I'm not concerned to do
so. However, since my note to Susan I have read some recent
research which suggests that it was the relatively long
femur neck which reduced the australopithicene's bipedal
efficiency. The research has not yet been published (as far
as I know), but it states the following.

## With a long femur neck the angle of the femur from the
hip to the knee is greater. Modern humans have less of an
angle. The lateral support system is a series of muscles,
the gluteus medium and minimum, that run from the crest of
the iliac blade to the greater trochanter of the femur. As
we lift one foot off the ground, the lateral support system
fires and pulls our trunks toward the supported side so we
don't fall over.##

The modern short femur neck increases the efficiency of the
lateral support system, allowing a more balanced style of

The long femur neck could be the cause of the lurching gait
mentioned by Jolly & Prog.