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Re: Summer science quiz #3

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  • Re: Summer science quiz #3

    Dear all,

    Indeed, I must say that this third question is one that I have very
    often broken thoughts about, and I was in fact still wandering about

    Certainly the stability hypothesis does not seem attractive at all I
    must say. The reson for example why our centre of pressure is
    maintained before our ankle is because it is an "L" shaped joint. Not
    the other way around! (Had it been "T" shaped, we would keep a
    different centre of pressure).

    But let me try:

    If, for simplicity we define the "knee" and "elbow" joint as the one
    between the two longest limb segments, then the distinction does not
    seem to be birds versus mammals, because according to that
    definition, most mammals (horses, cat mice kangaroos, mention it)
    like birds do have a backward "knee" in the hind leg. In fact many
    animals have a forward "elbow" in their fore limb. Humans seem to be
    in the "odd" group rather than belonging to the regular ones.

    The hindlegs' most important and general function is forward
    propulsion of the animal. The problem of having a "forward knee" in
    the hindleg is that it has to extend infinitely fast just before
    take-off to keep ground contact let alone to keep on accelerating the
    animal. This problem is not present in a backward "knee".
    Why then do some silly human-like creatures have such a "wrong"
    forward knee? Maybe just a case of unfinished evolution? Fact is that
    we are not terribly good at running, whereas long-legged but
    short-feeted birds, such as ostriches, do not seem to have a problem
    with balance

    Marc de Lussanet


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