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Re: Archaeopteryx feathers and origin of flight based on 11th specimen



On Thu, Jul 3, 2014 10:41 AM EDT Mike Habib wrote:

>However, I would argue that too much is being made of weather asymmetry. There 
>is nothing magical that happens when a feather is slightly asymmetric. In 
>fact, flightless birds often have asymmetric primaries, they just are as 
>asymmetric as in flying >species (on average).

1) asymmetric aerodynamic surfaces (more rigid/heavy on the leading half, 
lighter and more flexible on the trailing half) have evolved many times -- eg, 
insects, airplanes, bats and birds. AFAIK, cross sectional symmetry in nature 
is limited to insects -- if it exists there.

2) if there is no advantage to a symmetrical primary (in extant flightless 
birds), why would an asymmetrical primary not be retained? The implied default 
drift-back-to-the-center tendency is likely non-existent, in the absence of 
selection moving the center of variance.

3) all the extant animals known to have asymmetric primaries are either volant, 
or have volant ancestors, again AFAIK...

Discounting asymmetric feathers as a trait indicating at least the presence of 
volant ancestors seems overly something -- perhaps overly skeptical?