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Flight again (was Re: The Lizard of Oz)



> David Marjanovic wrote:
>
> >This implies that either bird ancestors dropped from low heights -- 2 m
or
> >less, I guess -- or that they already had something to retard their
> >descents.
>
> Both are possibly true.  Feathers could serve to create drag, in addition
to
> their insulatory properties.

IMHO the first is rather improbable because a jump from such a low height
lasts too short for selective pressure for steering structures to occur --
any steering except the direction of the jump, which would probably suffice,
would have little to no effect.

> I never ever said that feathers FIRST evolved for drag.
> Insulation came first, and was most likely the primordial function of
> feathers.  Their "fluffy" structure pre-adapted them for drag, useful in
> gravity-assisted leaps (incipient parachuting).

A testable opinion of mine that has AFAIK not been tested: Downy feathers
are much too short and not stiff enough to exert measurable drag.

> Then the feathers on the
> forelimb and tail  became longer and stiffer and wider.

Why not on the neck and flanks? Or even on the thighs?

> This design
> pre-adapted the symmetrical vaned feathers for lift.  The wing feathers
then
> became asymmetrical.  Evolution of flight by successive exaptations.

Of course by successive exaptations!

Feathers for S excretion --> for insulation --> wings and maybe semilunate
carpal for brooding --> underwater flight, tail feathers for steering, wing
feathers slowly more asymmetrical --> flight in air? Lots of exaptations
here.