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Re: FW: The ground-nowhere hypothesis on the origin of bird flight

 dale mcinnes <wdm1949@hotmail.com>

> A proavian can not be working both against/for gravity at
> the same time? Why not use the wings as spoilers to pin
> yourself against the substrate while running up a tree thereby
> defying gravity?

Yep, excellent point.  This is the basis of WAIR, by which excursions of the 
wings supply improved hindlimb traction, allowing birds to run up inclined and 
even vertical surfaces.  However, when applying WAIR to pro-avians as part of 
the evolution of flight behavior, at what evolutionary stage does the pro-avian 
become airborne - and for what reason?  It's this shift to aerial locomotion 
where we need to look at the role of gravity - and whether the pro-avian is 
using gravity to its advantage, or working against it.