Re: Birds of a Feather....

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

> 
> Aside from just being a darn intersting thing to know, the answer to this
> question would seem to have implications in both the evolution of feathers
> and the evolution of birds themselves.
> Regarding the evolution of feathers:  If the F.T. evolved after feathers,
> then it would follow that feathers mos tlikely evolved for some purpose other
> than flight, and were later co-opted into that role.  If the F.T. evolved
> before feathers, or roughly at the same time (though I know this is difficult
> to determine), then it is possible (probable, even?) that feathers evolved
> for flight, and were later modifed for their other uses, such as insulation,
> among others.

      I think it is safe to assume that if you follow Archaeopteryx's 
family tree back far enough, you would come to an unfeathered ancestor.  
Considering that conseiderable development and refinement for flight 
characterizes he avian feather, and that it is unlikely that a naked 
skinned dinosaur (or basal archosaur or whatever) one day gave birth to 
an animal with fully developed, fully functional flight feathers, it is 
probable that it took a number of intermediate stages before feathers 
were developed enough to permit flight. Species do not "plan ahead" when 
developing a trait; they are concerned with immediate results.  If the 
earliest feathered archosaurs could not fly, they certainly developed 
feathers for some other purpose.  
     S.J. Gould has a paper an essay in Bully for Brontosaurus called Not 
Neccesarily a Wing, in which he discusses the principle of this issue a 
little further, focusing on the pre-flight function of wings rather than 
feathers.  This is an interesting point that comes a little bit further down 
the evololutionary tree.  You start out with a naked skinned archosaur 
that develops rudimentary feathers for some purpose, then these 
feathers on the arm become larger and more developed, but still not 
developed enough for flight, until soemtime down the road the animal 
realizes that it can generate lift with these things.  Perhaps origanally 
the animal could only make longer hops in order to escape predators 
or catch food, then on to gliding, and eventually true flight.  This 
is all speculative of course; the point is that feathers, and wings, 
probably did not originally in birds for flight.          
     I haven't read the Gould article all the way through in a while, so 
my recollections of his arguments might be a little distorted.

LN Jeff