[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

Don Ohms wrote:

<Not to the point of falsifying a gliding-to-powered scenario. That was the 
assertion (or at least implication), remember? Remarkable it was, considering 
the consensus on bats.>

  What concensus on bats? We don't even know their closest genetic or 
morphologic sister taxon, much less the method by which they attained a dynamic 
flapping system in the arm, or flight, or whatever. And you cannot apply the 
same conditions by which it is proposed bats arrived at their condition as to 
birds simply because the bauplans are so distinct from one another, especially 
the membraneous extent to legs and tail versus feathered arms and tail but free 

<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 position, 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. 


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)