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Re: Flight



The cursorial (ground-up) model for the origin of avain flight does have
merit. A bipedal insectivore has much to gain from an increase in
stability while running after its prey. The arms and tail are held
outstretched from the body, not to serve as "insect nets" or anything
similar (I have never thought that the insect-net model was in any way
viable) but instead to stabilize the body while running.  This is what the
feathers, and proto-feathers of hypothetical intermediates did. If the
scales on the arms and tails became elongate, they would have functionally
stabilized the body while running. Thus we have our selective pressure:
those animals which run more stably than others will be more successful
hunters, and therefore reproductive fitness will be higher.  Feathers thus
evolved as a modification for flight, not for insulation or endothermy, as
there are no feathers on the body, only the flight surfaces of the arms
and tail. 


Jason P. Schlumbohm
s-mail: 211 NW 29th Street, Corvallis OR 97330-5344 U.S.A.
e-mail: schlumbj@ucs.orst.edu