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Re: Campbell's even crazier than a MANIAC? (archeopteryx climbing)

At 2:05 PM -0700 9/4/08, Jaime A. Headden wrote:
>The problem here is that *Archaeopteryx* doesn't appear to even be that 
>important of a player on the direction toward birdiness. The problem lies in 
>several elements, including the apparent "half of a wing". What use is such a 
>structure on the evolution towards flight? There is no actual direction just 
>as there is not actual destination, so what features we peg as "towards 
>flight" have to operate under a paradigm while the animal was alive. WAIR can 
>help explain this, but it doesn't answer everything.
To borrow an idea from WAIR -- of observing baby birds -- 'half of a wing' also 
helps a baby bird to survive falling out of a nest by easing its impact on the 
ground. That fits into at least two possible scenarios where ancestral birds 
made some use of trees:

Flight originated with feathered theropods who used trees (or some other 
elevated objects) as hiding places for nests. They didn't live in the trees - 
they just nested there. Partial wings helped them flutter down without injury. 

Flight originated with feathered theropods who used trees as a refuge to escape 
predators -- like a housecat chased by a dog. Cats are among critters who can 
get up trees easier than they can get down, but that behavior presumably 
evolved because it was worth the risk of getting down to avoid the (presumably) 
greater risk of getting caught by the predator. Partial wings would have helped 
the theropod get down the tree. 

That strategy might have worked best for a small Microraptor-like animal, which 
could dash up the tree or into the shrub when danger threatened, then get back 
down quickly when danger left. 

I doubt that was the only advantage -- once feathers started to evolve to 
larger size, they probably offered more advantages including, eventually, 
powered flight.  
Jeff Hecht, science & technology writer
jeff@jeffhecht.com  http://www.jeffhecht.com
525 Auburn St., Auburndale, MA 02466 USA
tel. 617-965-3834