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Re: The Aerodynamic Origin of Bird Flight (2)

Much has been written about how birds evolved from dinosaurs. The discussion
today revolves around two theories, the "ground-up" and the "tree-down",
both I feel are hopelessly flawed. This is another way! Please read my essay


Replace "(dot)" with "."

Why didn't you spell it out and add http://? That way it would have shown up as a link in our e-mail programs/browsers.

Anyway, I've read it now. Commented quotes follow:

"What good is a micro wing?"

Certainly not for flying! But -- apart from WAIR! -- it's easily imaginable that wings evolved for reasons that had nothing whatsoever to do with aerodynamics. Sexual selection comes to mind. Another possible reason is brooding (remember how the *Oviraptor* and *Citipati* skeletons sit on their nests). I'm sure you can come up with more. Once a wing of a reasonable size is present, it can be exapted for aerodynamic uses. The same, of course, holds for the tail.

"Parachuting could lead to gliding. And gliding could lead to flapping. Both statements, I believe, are true."

Why do you believe that?

"Protobird was a diver! Protobird dove for a fish, swam back to shore and climbed back up to the spot from where it dove, and waited for another fish to come by."

Difficult to imagine with theropod body shapes. Also remember you just said birds don't climb and used this as an argument against trees-down. Why isn't it also an argument against cliff-down?

"Protobird's species were waders. We know there must have been waders three ways. 1. They exist today and are very successful. They feed in countless numbers taking huge amounts food."

By that logic, all ancestors of anything must have been waders! Why does anything but waders exist today?

"2. We know vertebrates came out of the seas. They would have fed in the transition zone for countless generations until they only came back for water."

And? Those countless (but calculable) generations were over for our ancestors by the middle of the Carboniferous.

"3. We know that mammals returned to the sea. They also would have fed there. There is a tremendous amount of food here that can be exploited from above."

How does it follow that the first birds were waders? And don't wading and diving require different adaptations?

"Protobird was warm blooded and feathered."

That's old news: *Sinosauropteryx*, *Sinornithosaurus*, *Beipiaosaurus*, *Dilong*, *Sinocalliopteryx*...

"They also need something to help keep their eggs warm and shade them from the sun."

This is enough to explain the evolution of full-sized wings, isn't it?

"Warm blooded protobird would attack at dawn, as soon as it could see. The pterosaurs would have to warm up."

Then why did the pterosaurs have bird-style super-efficient lungs? Clearly they were warm-blooded, too.

"Buoyancy is another use for feathers. Feathers would help to float and swim even if temporally."

Not necessary. All saurischians had bird-style lungs.

"This is also why the fossils are so rare."

Fossils are common in river sediments.

"Flapping will begin to increase the effectiveness of the forelimb fin. Flapping will actually precede level gliding! Protobird is still in a dive and cannot yet generate enough force to raise its glide slope much. A 1 to 1 glide slope ratio is a 45 degree angle. Modern gliders have glide slope ratios in excess of 40 to 1."

And why should it try to not dive? The fish are down in the water...

The air cushion has already been addressed.

"This is why the third lift clinches my theory."

Theories aren't clinched, they are disproven if anything. So are hypotheses -- and yours is a hypothesis because it's way too small for a theory. Learn what these terms mean: http://www.dinosauria.com/jdp/evol/evolfact.htm


Conclusion: Nice try, but it doesn't work.