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Re: Origin of feathers



In a message dated 98-05-05 15:23:24 EDT, TomHopp@AOL.COM writes:

<< Dinogeorge also suggested that exaptation from flight to brooding is
 easier than from brooding to flight.  Not necessarily.  A wonderful book
 entitled "The Roadrunner," by Wyman Meinzer shows how an Archaeopteryx-sized
 cursorial hunter escapes counterstrikes from its prey by leaping into the
air,
 then flapping to stay aloft a short while longer.  Think small.  The smaller
 an animal is, the more its large arm feathers can make a difference in "hang
 time."  Given a fully lengthened set of feathers used only for brooding, it
is
 not at all hard to see how Archaeopteryx's immediate ancestors could have
 exapted them for flight.>>

Well, the roadrunner's behavior as cited here is probably best explained as a
holdover from the roadrunner's more volant, less cursorial ancestor. I agree
with thinking small; the smaller an animal is, the more difference feathers on
it will make in any kind of aerial behavior, whether predation by leaping into
the air or simply flying. But the physics of the situation strongly
controverts a strictly cursorial, non-aerial origin for flight in theropods.
If you pretend that wings actually evolved for the purpose of lengthening hang
time in leaping, cursorial predation, you're still left with the problem of
explaining how this behavior could develop into powered, long-distance flying
(ornithoptering, or whatever) against the force of gravity, etc., without some
kind of arboreal stage in there. But if you assume that the flying came first,
a whole lot of rather peculiar behaviors (feathers for brooding, shading,
leaping-predation, etc.) may be easily exapted through secondary
flightlessness.
 
 << So George, perhaps BCF actually stands for BROODING CAME FIRST.>>

Well, I'll take your word for it...