Re: An alternative to ST and AAT
Gerrit Hanenburg (G.Hanenburg@inter.nl.net)
Sun, 17 Nov 1996 19:30:22 GMT
"John Waters" <jdwaters@dircon.co.uk> wrote:
>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.
The efficiency of locomotion depends on the entire anatomy of the
organism,not just the tendons. The arch of the foot,the lumbar
lordosis,the shape of the thorax,the position of the shoulder,etc. all
make a contribution to the overall efficiency of locomotion.
>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.##
Lucy had a relatively wide pelvic inlet,and as result of this also a
relatively long bi-acetabular width (distance between the hip-joints).
Because the hip joint acts as the fulcrum of the lateral balancing
system she has a long body-weight lever arm resulting in a greater
pelvic tilt during the stance fase of walking. The abductor muscles
(gluteus medius and minimus) have to work harder to counteract this.
To compensate for the mechanical disadvantage of the abductors Lucy
has a wide laterally flaring iliac blade and a long femoral neck.
So,contrary to the above,a longer femoral neck would make the lateral
balancing system in Lucy more efficient.
But why did she have such a wide pelvic inlet?
Gerrit
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