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Re: Fw: Dinosaurs and birds



No, I don't. As the car accelerates (w/in reason), I give a little jump, and 
make some progress, effectively increasing stride length. 

Actually, the quoted statement stands on it's own merits in the general case. 
It could be argued that it is impossible for animals to increase their maximum 
speed by generating aerodynamic thrust w/ forelimbs. Or, it could be argued 
that increasing speed does not convey advantage. Other than that... :D

What is frequently ignored in the ground-up debate is the fact that the process 
of turning fore-limbs into wings is not likely to start w/ the fastest bipedal 
animal around. This is because it would take (as has been pointed out) a 
sophisticated and efficient forelimb morphology to convey locomotive advantage 
to such an animal, hence there is no valid selective scenario for development 
of a fortuitous structure(s) into a wing. It is the losers, nerds and outcasts 
that have the chance of getting lucky, and finding a new way to 'skin the cat'.

BTW-- did you notice that Mike H. actually admitted I was (at least in theory) 
right in that inclines are not essential to wing-assisted evo-scenario's? It 
was buried pretty deep, but it was there. Ha! Although 'fore-limb assisted' is 
a better term, 'wing' being the end result of the process...

Don

----- Original Message ----
From: jrc <jrccea@bellsouth.net>
To: d_ohmes@yahoo.com
Cc: dinosaur@usc.edu
Sent: Thursday, April 5, 2007 9:39:41 AM
Subject: Re: Fw: Dinosaurs and birds


----- Original Message ----- 

> An animal that increases it's maximum speed by generating thrust w/ it's 
> forelimbs as it runs gains an advantage.

An animal that can generate wing forces while running gains a distinct 
advantage, but additional forelimb thrust does not necessarily allow it to 
run faster.  As a visual analogy, imagine yourself running behind a car as 
fast as you can.  Now, attach a rope to the car's bumper and grab the rope 
with your hands.  Have the car accelerate.  You will find that you do not 
gain the ability to run faster; you just go fanny over teakettle.  The 
running advantage is primarily in being able to generate force vectors that 
assist maneuverability. Even ostriches use their wings to that purpose.  It 
seems to me that increasing running speed with wingthrust is more of a 
derived ability than a basal one.
JimC