Re: book reviews, parsimony and some loose ends

[Jeffrey Martz <martz@holly.ColoState.EDU>]

George Olshevsky wrote:

> Well, you can support BADD theory, in which the origin of avian flight is
> presented as a miraculous event resulting from the accumulation of numerous
> specific adaptations, all of which appeared for reasons other than flying. Or
> you can support BCF theory, in which flight slowly originates on a particular
> lineage of arboreal archosaurs wherein the adaptations occur as systematic,
> incremental improvements to a volant lifestyle. 

     BCF proposes exaptation as well, whether you realize it or not.  You 
have feathers originally evolving as padding for dino-birds falling out 
of trees.  This is not flight.  Neither is using long grasping 
fingers and claws as climbing tools.  Later using these long CLIMBING 
fingers to control feathers in FLIGHT would however be a primo example 
of exaptation.  Saying that that falling (not parachuting or gliding) 
and climbing abound in trees are early stages of flight just because the 
animal's feet aren't touching the ground is bogus.  Arboreal animals like 
monkeys and squirrels are NOT in the early stages of flight.  However, 
if they chose to modify characteristics used for an arboreal lifestyle 
for flight later on, this would then be exaptation.  BCF and BADD both 
have the same problem: taking a GRAVITY BOUND creature and getting it 
airbourne, and both probably aren't going to find a solution without 
exaptation.       
     There is nothing particularly "miraculous" about exaptation.  It is 
a logical way of getting from A to C.  Just about any trait used by a 
living organism for more than one purpose is a potential source of 
exaptation. 
 
LN Jeff
"We're going down, sir."
"I know.  Thank God I'm stoned."