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Re: Fw: Dinosaurs and birds
> No, I don't. As the car accelerates (w/in reason), I give a little
> jump, and make some progress, effectively increasing stride length.
Sure, but only within a pretty narrow margin. If you are sprinting at your
fastest speed, the extra pull of the car shouldn't help much. If you start
having to sacrifice stride frequency to increase the stride length, then you
won't really be making any progress. Keep in mind, as well, that the analogy
isn't perfect. If you're very agile, you might be able to keep up with the car
by essentially bouncing briefly off the ground every so often and letting the
car pull you through the air. That's not really running with extra thrust,
though, that's just being dragged with style. I'm impressed that you've tried
though, it would make me a tad nervous.
In any case, the point Jim was trying to make is that the speed of a running
(bipedal) animal is largely limited by mechanics of the hind limbs and their
interaction with the ground. Adding thrust from the forelimbs will only add
speed if the hind limbs can keep up. They generally cannot if the animal is
already at a sprinting gait, so forelimb-assisted speed increases don't tend to
be very feasible for birds. This is one reason why running birds don't deploy
the wings unless they are launching, or engaging in a ground maneuver for which
an additional force vector might be helpful in maintaining balance.
>> BTW-- did you notice that Mike H. actually admitted I was (at least
> in theory) right in that inclines are not essential to wing-assisted
> evo-scenario's? It was buried pretty deep, but it was there. Ha!
> Although 'fore-limb assisted' is a better term, 'wing' being the end
> result of the process...
It was never meant to be "buried". You are most definitely correct that
inclines are not theoretically required for cursorial-based wing evolution.
They *are* required for a WAIR type mechanism; ie. a cursorial mechanism by
which forward progress is directly enhanced by wing oscillation, which is all
my original post was meant to imply. That does not rule out maneuverability
and balance being enhanced by forelimb dynamics over level terrain, and these
will obviously bolster forward progression indirectly.