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  • Bipedalism -- another problem

    From Paul Crowley@21:1/5 to All on Sun Mar 13 04:07:37 2022
    " . . . Alternatively, it could come down to anatomy, and pig hearts may not be up to the job in a human body. Our hearts have to work much harder to fight gravity than a pig's because we walk on two legs rather than four. . . "
    https://www.bbc.com/news/health-60708120

    If an animal can proceed quadrupedally
    (as our ancestors before ~5 ma could) it
    will continue to do so for a whole variety
    of reasons -- including this one -- unless
    there are compelling circumstances that
    bring about the change.

    (Failure to identify those 'compelling
    circumstances' is the most obvious
    defect of the various theories around
    here.)

    Walking or running bipedally is much
    harder on the heart than proceeding
    quadrupedally. Assuming that the animal
    has a choice, it will get tired much more
    quickly in the upright posture.

    This is a powerful argument against the
    notion that bipedalism evolved to chase
    after prey on the savanna. Our basic
    design is hopelessly inappropriate for
    fast or sustained running.

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  • From Paul Crowley@21:1/5 to Paul Crowley on Sun Mar 13 04:49:00 2022
    On Sunday, March 13, 2022 at 11:07:38 AM UTC, Paul Crowley wrote:

    " . . . Alternatively, it could come down to anatomy, and pig hearts may
    not be up to the job in a human body. Our hearts have to work much
    harder to fight gravity than a pig's because we walk on two legs rather
    than four. . . "
    https://www.bbc.com/news/health-60708120

    The standard chest shape for terrestrial
    animals -- including cercopithecoids -- is
    "narrow and deep", whereas in apes it's
    "broad and shallow".

    See Figure 7 (about half-way through) in: https://onlinelibrary.wiley.com/doi/10.1111/joa.12454#

    Monkeys follow the standard mammalian
    pattern, and have their hearts in the
    optimum position. The change to the ape
    chest form abolished this position, meaning
    that the ape heart is badly located and less
    efficient than it was among its ancestors.
    That loss came about for major reasons,
    which yielded great compensating benefits.

    What were they?

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  • From [email protected]@21:1/5 to All on Sun Mar 13 06:09:10 2022
    Op zondag 13 maart 2022 om 12:07:38 UTC+1 schreef Paul Crowley:

    " . . . Alternatively, it could come down to anatomy, and pig hearts may not be up to the job in a human body. Our hearts have to work much harder to fight gravity than a pig's because we walk on two legs rather than four. . . "
    https://www.bbc.com/news/health-60708120

    :-DDD

    Thanks, Pauli.

    Early hominoids perhaps 20 Ma were already orthograde (upright, vertical),
    - not for running after antelopes as some incredible imbeciles still believe,
    - but simply for wading bipedally & climbing arms overhead in forest swamps & mangroves.

    Google "aquarboreal ancestors".

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  • From Paul Crowley@21:1/5 to [email protected] on Sun Mar 13 11:34:09 2022
    On Sunday 13 March 2022 at 13:09:11 UTC, [email protected] wrote:

    Early hominoids perhaps 20 Ma were already orthograde (upright,
    vertical),

    - but simply for wading bipedally & climbing arms overhead in
    forest swamps & mangroves

    Why the fundamental design changes
    in anatomy from monkey to ape?
    A large baboon would seemingly be
    better designed for " . . wading
    bipedally & climbing arms overhead
    in forest swamps & mangroves . . ".

    You're not getting to the heart of
    the matter (deliberate pun).

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  • From I Envy JTEM@21:1/5 to Paul Crowley on Tue Mar 15 20:38:26 2022
    Paul Crowley wrote:

    If an animal can proceed quadrupedally
    (as our ancestors before ~5 ma could)

    We find evidence for bipedalism going back 7 to
    9 million years.

    Chimps split off from our line far more recently than
    5 million years ago. Even going by just the y-chromosome
    "molecular clock" it's less than 5 million. Factor in other
    areas of the genome and you're looking at less than 4
    million... like 3.7 million.

    I'd give a margin or error of AT LEAST a million years more
    recent than that. Molecular dating assumes a constant
    rate of change (mutation) when we all know for a fact that
    it's not true. Our mtDNA has been under HEAVY selective
    pressures. Cold weather, moving north was a big selective
    factor, as mtDNA helps us to produce warmth. But mtDNA
    also slows down with age, so the longer it lasts the older
    we can get. It also seems related to our ability to fight off
    cancer.

    If you're born in a warm environment, if your mtDNA helps
    to keep you warm then it likely would be selected AGAINST.
    It won't change. But move a population to a new environment
    and such a mutation is selected FOR.

    Mutations are the furthest thing from clock like. All the
    molecular dating greatly exaggerates age.

    Chimps evolved AWAY from upright walking and TO knuckle
    walking. It never happened the other way around.




    -- --

    https://jtem.tumblr.com/post/678757006186889216

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