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Re: square-cube law
J E Hawcroft (J.E.Hawcroft@shef.ac.uk)
Wed, 08 Jan 1997 15:18:28 +0000
morphis@niuhep.physics.niu.edu wrote:
>
> Hello,
> I know this isn't quite on topic but since paleontology often makes
> use of knowledge about skeletons I thought I would ask... does anyone
> here know what how tall/heavy a bipedal hominid could get before the
> square-cube law would provide limits.
Hmm, I don't know a lot about sums but I do know that for a human biped
to stand up requires suprisingly little effort on the part of the
muscles. The fact that the head, spine, pelvis and knees are located
directly about the feet means that the body is in perfect balance rather
than having to be held there by muscles. Of course there is some muscular
input, chiefly from the gluteal group, and these are multipennate, short
wide muscles that do not tire very easily.
The weight of the body runs down the femurs to the knees, and then runs
directly down to the ground. This is the most efficient possible route of
transmission so the force is minimised. In the foot, transverse and
longitudinal arches direct the force into the ground via the pressure
points at the heel, MTP joint 1 and MTP joint 5. So perhaps this
square-cube thing has already presented a problem sometime in evolution
and these pressure-dispersing gadgets evolved to take care of them. After
all, hominids who were not stacked as straightly as us, such as Lucy and
her ilk, were much smaller than us. They were also more gracile - I guess
if you were as slim as Lucy and six foot tall, the wind would blow you
over!
Jennie
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