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Re: flapping from gliding



George Olshevsky writes:

> But if feathered arms, or similar structures, evolved as air brakes,
> perhaps we should see more of this behavior among living animals
> than we do.

First off, as we went through back in December, this sort of argument
is weak.  Just because something happened (or may have happened in
this case) doesn't mean it should happen multiple times.  If it did
happen multiple times you can conclude it's easy, but if it didn't,
the best you can do is say that it's hard, or the right set of
circumstances just didn't present themselves more than once.  In this
particular case it seems we're talking about a group of vertebrates
that flaps its arms (as opposed to its hands or its fingers) to fly,
and that mode of locomotion (irrespective of its genesis) also appears
to have arisen only once.  Clearly there are precedents for biological
uniqueness in this sense.

Secondly, among what vertebrates would you propose to see this sort of
air-braking?  I submit that *this* was your key misunderstanding back
in December.  By claiming that human marathoners are good models for
running theropods you completely miss the boat.  No other animal past
or present ran like theropods do (i.e. two legs, a horizontal spine, a
sigmoidal neck and a long counterbalancing tail).  Sometimes the
specifics are important...

--
Mickey Rowe     (mrowe@indiana.edu)