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Re: Origin of feathers



Norton, Patrick wrote:
> 
> I'm not speculating on the evolution of homeothermy. But to speculate
> just a bit on the topic of this thread----I believe that the origin of
> feathers will eventually be found to have a thermoregulatory explanation,
> not aerodynamic. 

Never underestimate the importance of display structures. Many modern
animals seem to have sacrificed their physical manoueverability in
the name of display (especially sexual display). It has even been
said that the permamently swollen breasts of human females is an
attempt to create a buttock-like cleavage at the front of the
body as well, specifically as a form of sexual display (and let's
not mention the fact that human males have the largest relative
sexual organs of any primate). Both adaptations are probably taking 
advantage of the display potential of a bipedal gait.
        The thing is, often these form of displays may actually
slow a creature down. It seems that it is more important biologically
for a creature to reproduce than it is for it personally to live
a long trouble-free life. If that is the case then feathers may have
initially developed as display structures (even if they did slow
the creature down a bit via air resistance while running). Once they
were present then perhaps homeothermy and flight were secondary
biproducts. More speculation of course.

> I also believe that the vertebrate record will
> eventually document at least two roads to flight; one that included a
> tree (or cliff) dwelling phase and one that did not.  The first led to
> the quadrupedal non-cursorial bats and pterosaurs, and the second to
> birds.

Only two? Perhaps you should give nature more credit. I suspect
that there were many situations that led to flight. Let's not forget
insects as well, they were flying before vertebrates left the water!
The fact that microbats and flying foxes don't seem to be closely
related seems to suggests that flight may have been more common
than we think (ie. it evolved at least twice in mammals). Flying
creatures tend to be light-weight and fragile and not the sort of 
things easily fossilised.
-- 
____________________________________________________
        Dann Pigdon
        Melbourne, Australia

        Dinosaur Reconstructions:
        http://www.geocities.com/capecanaveral/4459/
        Australian Dinosaurs:
        http://www.alphalink.com.au/~dannj
____________________________________________________