New(ish) paper

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

Charles A. Long, G. P. Zhang, Thomas F. George & Claudine F. Long. (2003) 
Physical theory, origin of flight, and a synthesis proposed for birds.  
Journal of Theoretical Biology 224: 9-26.

Abstract
Neither flapping and running to take-off nor gliding from heights can be 
disproved as the assured evolutionary origin of self-powered flight observed 
in modern vertebrates. Gliding with set wings would utilize available 
potential energy from gravity but gain little from flapping. Bipedal 
running, important in avian phylogeny, possibly facilitated the evolution of 
flight. Based on physical principles, gliding is a better process for the 
origin of powered flight than the "ground-up" process, which physically is 
not feasible in space or time (considering air resistance, metabolic energy 
costs, and mechanical resistance to bipedal running). Proto-avian ancestors 
of Archaeopteryx and Microraptor probably flapped their sparsely feathered 
limbs synchronously while descending from leaps or heights, with such 
"flutter-gliding" presented as a synthesis of the two earlier theories of 
flight origin (making use of the available potential energy from gravity, 
involving wing thrusts and flapping, coping with air resistance that slows 
air speed, but effecting positive fitness value in providing lift and 
slowing dangerous falls).

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