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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)
--- On Sun, 9/28/08, Jaime A. Headden <email@example.com> wrote:
> What concensus on bats?
That: a) bats are arboreal in origin, and b) probably went from gliding to
flapping. Don't blame me, I didn't know that consensus was reached either. I am
sure it is not 100%, anyway.
> <I already pointed out the error, which is failing to
> consider the various points of various glide sequences at
> which selection on incipient flapping can occur. Nothing to
> do w/ falsifying equations.>
> Not to insert my own foot into my mouth here, but if the
> arm is incapable of developing a flapping motion while
> retarding drag during descent -- and no extant glider
> performs such an action so as to test this (to my knowledge)
> -- then one cannot dismiss this to simply barge ahead and
> say a portion of the gliding development can lead to
> flapping. I am not arguing for or against a particular
It seems to me you are understandably confused as to the chain of claim and
Mike stated that arm oscillation in mid-flight will not improve a gliders
performance due to reduced vorticity. I do not argue that point.
I will dispute the conclusion(s) that *therefore*, a) passive gliders cannot
transition to powered flight, and b) gravity-driven flight origin in birds is
falsified -- if and when such claims are made. I frankly do not remember if
such claims WERE made. I THINK they were at least implied by someone, but am
not sure at this point. My contention that there are places in the glide
sequence that selection can act upon other than midflight to create an
incipient flapping module was made as counter-point, and stands as such, imo.
If you are really interested in who claimed what, and when, and what the
obligations of evidence are, and the sum of evidence offered, perhaps you will
have to re-read the thread. It is a pain, but it seems to be part and parcel of
the posting system decreed by "netiquette". Not that there is anything wrong w/
In any case, I have spent all the time I can on posting for now, although I owe
Jim C an explanation re "appealing" ptero's. Maybe later this week.
> but it seems to me to argue that if the arm can
> flap, then it must overcome the forces that are acting
> against it, and it is to this that Mike addressed his
> comment. Thus, to propose YOUR argument, Don, you must
> falsify his.
> <I merely pointed out that small terrestrial bipeds
> could easily exploit the morphology of cycads, positioning
> themselves for a gravity-driven first step, and that the
> 'lack of flapping' in extant gliders was easily
> explained by competitive constraints.>
> The nature and existence of cycads are really irrelevant
> to this argument. A two-meter tall rock or a cliff can serve
> just fine. But the argument here MUST propose the mechanism
> whereby leaping about leads to gliding structures in the
> limbs, and then from there to flapping structures, and then
> to powered flight without gliding. Your cycad proposal, Don,
> makes only an argument towards climbing, but not to getting
> back down aside from jumping, and at that point, there was
> no reason to go that should lead to gliding behavior.
Again, the "cycad proposal" was advanced as a counter-point; specifically,
counter to the idea that a lack of 'hard-core' arboreal adaption in proto-birds
falsifies a gravity-driven evolutionary path to flight in birds.
It was not advanced as a hypothesis in and of itself, being (imo) only a
cartoon*, although it is certainly possible that it occurred, assuming a
gravity-driven path is possible at all. I think most will agree that
'gravity-drive' is at least possible, and if so, even "jumping" can get the
ball rolling, although there is more to it than that...
* -- cartoon ~= "detailed but untestable hypothesis, compelling just-so story,
realistic scenario, arm-waving, etc, etc, ...". I find them sometimes quite
useful, often entertaining, and don't consider the name "cartoon" to be
derogatory in the least.