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Re: FEATHERS



George Olshevsky wrote:

> Feathers are the most complex structure to have grown out of vertebrate skin
> _ever_. To argue that this structure _just happens_ to have been, later on,
> usefully exapted for flight is illogical. The only way to explain the initial
> appearance of feathers is to say that they evolved for aerodynamic purposes. 

      Hold on there.  It is exceedingly unlikely that feathers 
could evolve for flight WITHOUT preadaptation.  Unless you are speculating 
that one day a completely unfeathered theropod produced a theropod with 
fully formed flight feathers large enough and designed for aeorodynamics, 
you have to go through a series of intermediate stages between nekkid 
coelurosaurs and flying birds.  Evolutionarily, those feathers are going 
to have to get fairly large before they can start being used 
for flight, or even giving ANY signifigant aeorodynamic advantage.  A 
If the original function of feathers was for flight, then that means that this 
unfeathered lineage of coelurosaurs was thinking ahead to the day when 
feathers would be useful, and all the intermediate stages were in 
preperation for that day.  Natural selection works on the NOW.  Those 
first unaerodynamic feathers must have had some sort of use before they 
got large enough for aerodynamics.  All guesses are pretty thin on evidence, 
but my personal B.S. is that they orignally devloped for insulation, THEN 
were modified into larger structures of the arms that were used for 
display or some odd and esoteric purpose.  After that, it was found that 
these structures could also have some sort of aerodynamic function 
(manuvering, parachuting, exta speed al a chickens).  Or soemthing like 
that.    
      Greg Paul says the Berlin specimen has body contour feathers, and 
that drawing that was sent to Marsh definitely seems to show them, 
particularly on the legs.  Has anyone with direct access to a good cast, 
or even the original, have anything to say?  Whos says Archaeopteryx lacks 
contour feathers in the first place?   
      
LN Jeff
0-
     "Air doesn't make good ice unless it its mixed with water."