The Physics of Leaping Animals and the Evolution of Preflight

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Abstract
After careful examination of the physical demands of pre-powered flight, Ostrom''s (1974) arguments that Pro-avis developed the capabilities for powered flight from a bipedal cursorial habit are supported. A running and jumping bipedal animal that used its forelimbs for balance could be the precursor of animals with powered flight. The evolution of the modern avian wing is best explained as having passed through a series of adaptive stages concerned with the body orientation of a jumping insectivore. Extended forelimbs possessing minute increments of lift offer significant advantages to this jumping animal. Mass movements used for control of the body during a jump are very similar to the aerodynamic movements for control and propulsion used during powered flights. There is no need for the development of new and different neuromuscular pathways to perform powered flight as must be the case if an arboreal glider is to make the transition. A compact, rigid, lightweight body would be most responsibe to distally developed lifting surfaces. Lift and thrust probably developed distally prior to the medial development of lifting surfaces. Primary feathers developed before secondary feathers. This model also predicts that the rate of evolution to powdered flight was rapid.

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