RE:Origin of feathers

["Matthew Troutman" <m_troutman@hotmail.com>]

<<Despite the attractiveness of the trees down, parachuting - gliding - 
flying scenario, I lean towards Ostrom's and Caple's cursorial 
theory--particularly if combined with Regal's theory on the evolution of 
feathers.  The initial aerodynamics-related selective pressure on 
feathers on the trailing edges of the arms of a homoeothermic, feathered 
proto-bird would be towards reduced drag and increased lift and thrust. 
Although the "ground up" argument is not without problems, it is also 
appealing to me because it seems to eliminate at least two evolutionary 
steps required by the "trees down" theory--tree dwelling and 
parachuting.>>

     The main problem with this scenario is that it is impossible for a 
teresstrial, cursorial animal with outstretched forelimbs to not have 
strong amounts of drag. There also is the problem about how it will 
develop the proper flight musclature ; most bipedal animals that move 
quickly ( macropodids ) have their forelimbs tuck in so drag is not 
produced. Since, to be able to achieve maximum running potential you 
have to keep the forelimbs tucked in, there is no way that the animal 
could have achieved high speeds or develop strong musclature. 

Tennekes in '96 showed that it requires 4 times as much power for birds 
to take off from the ground. This is another problem for the cursorial 
origin of flight ; it requires animals to assume their maximum muscle 
usage for primitve take-off. Even when the animal runs to get enough 
speed to take off when it jumps it would stall too much for take-off!!!

MattTroutman

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