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Re: Science feather strength debate




On 11/4/2010 10:09 AM, Don Ohmes wrote:

Also -- if some flightless birds retain asymmetrical vanes, while others
don't, and those birds that do not have them are "further" from their
earlier volant state -- then that would tend to support the notion that
asymmetrical vanes evolve under flight conditions, would it not?

On 11/4/2010 2:26 PM, Augusto Haro wrote:

Non necessarily, because you may have assymetrical vanes appearing
before or together with flight. Someone knowing more about pennaceous
feathers in non-avialians may tell us if the assymetrical vanes are
actually derived with respect to symmetrical ones or not.

Sorry, I was less than clear -- I meant in living birds. While you are right in theory, I am skeptical that the geo-record can ever inform us in this regard, due to it's incompleteness -- should asymmetrical vanes be found on an early and clearly non-volant animal, even one pre-dating all other known feathers, I could still say that this animal might be secondarily flightless, or even be creating aerodynamic effects to some other purpose such as making noise or cooling...

And I probably would, barring an absolute mountain of evidence to the contrary -- I accept that feathers in the general sense likely appeared pre-flight, but doubt as extremely non-parsimonious that flight feathers evolved to serve some other purpose and then "just happened" to be flight-worthy.

More simply -- if asymmetrical vanes appear to be derived relative to symmetrical vanes in extant birds, that is good enough for me...

Although anything is possible.