1). Huh? Can you clarify? Because the statement above sounds like good old-fashioned double-talk, in the context of my "good argument".
Mike claims this is physically impossible, even for humans equipped with high-tech rocket packs, due to something called the "limiting hindlimb mechanic". To quote; "The
animal can point the thrust in any direction it wants, and apply it in any series of pulses or continuous push that it wishes. If the hind limbs are the limiting factor in velocity, then aerodynamic thrust still does not speed them up...." --MH.
"If", indeed. Surely you did not mean to posit your conclusion as a pre-condition to your argument.
--MH
In any case, the hind limbs are NOT the limiting factor, at the rate of forward motion that can be achieved by running; THRUST is the limiting factor.
This conclusion requires only 2 assumptions; 1) the stresses on the leg are less at the front of the stride cycle than at back, and 2) it is possible for the hind limbs to increase cycle frequency when not generating the primary thrust necessary to maintain forward motion. Both assumptions appear to me to be manifestly true.
The maximum speed a biped can generate through unassisted use of the hind limbs does NOT constitute some magical theoretical barrier that cannot be exceeded.
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2). Total power relative to forward motion is not coming from the hind limbs in this situation, yet evidently there is a term in your equation that "...requires higher hind limb power (that we've already limited)". [???] Why is that? In fact, relative to the theoretical situation as posited, NO forward thrust is required from the hind limbs... nor is any aerodynamic lift required, as the legs serve to counteract gravity. Note, that can be done mechanically, w/out thrust generation other than that required to pull a given leg forward into the front of the stride cycle...
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Not quite what I meant. If the animal is supporting its full weight with lift, and doing so by overcoming drag with thrust (from the wings), then it is flying.
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3). Flight requires a flight-control phenotype. Simple thresholds of lift and thrust production do NOT mean FLIGHT-CAPABILITY in any relevant ecological or evolutionary sense. And lift is not relevant to my argument.
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Positive lift is counter-productive for running speed.
====================================== 3). Thrust. NOT lift. Not necessarily counter-productive. ======================================
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4). _If_ my understanding of the hypothesis is correct, WAIR, when advanced as a _primary_ flight evolution scenario, overemphasizes foot traction by oversimplifying lifestyle, substrate issues, and traction enhancing devices, and in so doing discounts the numerous advantages attainable in a vast number of situations in which those simplifying assumptions do not hold, yet forelimb assistance can be postulated. This may be a result of WAIR's use of extant animals w/ a specific life style as models, or natural academic competitiveness.
Sure, I can expand. Sorry for shifting the subject a bit last time and causing confusion. If the normal force on the foot is reduced by producing positive lift, then the foot will both 1) experience lowered friction, and 2) impart reduced force against the ground. Not a particularly useful tool for running rapidly.
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5). That depends on environment, lifestyle and bodyplan. Not a universal law. Reduced foot force against the ground can highly advantageous to many exploits, _especially when it is discretionary_.
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Cheers,
--Mike H.