Re: [wingstroke]

["Tim Williams" <twilliams_alpha@hotmail.com>]

David Marjanovic wrote:

> I've read the Burgers & Chiappe paper. I think they make the same, erm,
> improbable assumption as old Baron Nopcsa. Why does _no other_ terrestrial
> cursor, including running birds, use this?

This is an argument often aimed against a "ground up" origin of flight.  
However, the most plausible theory on the origin of flight in insects 
suggests that the earliest stages of flight in this group evolved without 
the assistance of gravity.  Modern Plecoptera display this behavior to some 
extent.  But there are no modern insects which re-capitulate the incipient 
stages of insect flight.  AFAIK, anyway (please correct me if I'm wrong.)

Still, you have a valid point here.  I personally prefer a "trees-down" 
origin of avian flight, with powered flight evolving in a semi-arboreal 
theropod.

> > or in an arboreal parachuter or glider.
>
> Neither needs a wingstroke _for anything_.

They need thrust to stop them from descending.  A glider can generate an 
airfoil to give it lift, but it can't stay in the air forever.  For that you 
need the flight stroke.


Tim





------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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