[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Birds of a Feather....
> 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.