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Re: Arms into wings



In a message dated 3/3/99 1:47:18 PM:

<< Tim Williams wrote:
Makes perfect sense.  Except for the bit about the transition from brooding
 to flight.  Long arms: check.  Long feathers: check.  Now, what was the
 proto-bird doing with its arms immediately before its descendents began
 flapping them.>

<DinoGeorge wrote: Exactly the right question. Note, however, that if the long
arms and long feathers (and presumably flying) come first, then exaptation for
brooding follows easily and naturally. >>

The roadrunner stays landborne until it's sparring with prey causes it to leap
into the air. Then it flaps to stay aloft. It would be easy for a brooding
biped to utilize its feathers for this, because the feathers must already have
evolved a streamlined, rigid form just to perform their brooding function and
keep tucked out of the wind when not needed.
    It's just as arbitrary to insist that flight came first as it is to
suggest brooding first. Flight adaptation does not automatically provide a
brooding-capable wing, so George's argument is relying on some self-satisfying
requirements (that a flight wing is "just right" for exaptation to brooding).
    I am willing to meet half way. Maybe brooding and flight co-evolved at
precisely the same rate, given that they are both critical survival issues for
birds.
    Tom Hopp