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



> While I am at it, it is also commonly assumed that the
> previous step is a 
> transition from parachuting to gliding, but whether such a
> thing has ever 
> happened or is even possible is another question that has
> occasionally been 
> asked in the literature. Animals that descend at an angle
> of, or anywhere 
> near, 45° seem to be rare or nonexistent; instead,
> parachuters go down 
> nearly vertically, while gliders move almost horizontally.
> Given the fact 
> that parachuting requires maximizing drag while gliding
> requires minimizing 
> drag, an animal in between might combine the worst of both
> worlds. IMHO it 
> is more parsimonious to assume that parachuting evolved
> from jumping down 
> from a tree, while gliding evolved from jumping from branch
> to branch.

Good point. Though in the case of Archie, "jumping from branch to branch" would 
have been "jumping off of something". In any case, it was not a parachuter. 
Evolution is not something that takes accident prevention seriously (it doesn't 
blunder very often either, but it certainly does not really emphasize 
*intelligent* design), and thus would be little benefit for a proto-Archie to 
drop straight down from a (scarce) high tree it had (impossibly) climbed up all 
the way.

As regards tertials, swifts have them reduced compared to the other remiges. 
But their mode of flight is somewhat unique. In any case, a significant 
contribution of gliding to make it through the transitional phase 
nonwithstanding, to have a theropod like Archie evolve into a full-blown expert 
glider is about as unlikely as to have a proto-colugo into a bat. Possible, but 
neither likely nor, judging from the fossil record, a direction it went.

There are modern birds which make good use of parachuting, screamers for 
example. And there might be a transition between that and gliding - basically 
oblique parachuting. It is not helpful at all when it comes to long-distance 
locomotion, but *if you are capable of powered flight* it may be the best way 
(very effortless and very safe and better control as opposed to pure drop-down 
parachuting) to get down from a tree or whatever. But judging from modern birds 
it can only be realized post facto, not to *gain* flight.


Regards,

Eike

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