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Re: feathers as N2 excretors



Jerry D Harris wrote:

                                   (SNIP)

 >       My problem with this idea (at least, as Reichholf has written it)=

is that I fail to understand why evolution would guide early feathered
"protobirds" into a position where they are producing excess sulfate (or
anything else, for that matter) in their bodies, thus requiring the
excretionary adaptation (for which feathers seems excessive).  It doesn't=

make much sense to me that a population of organisms would evolve into a
position where they are producing toxins to themselves.  Also, given that=

the vertebrate body has evolved an elaborate system of organs for
eliminating wastes, producing a wholly new (and rather complex) one seems=

excessive (that is, not very parsimonious).  <


     I haven`t read Reichholf, but as far as an ecological, and evolutionary
reason as to why this might have happened, perhaps these "protobirds" took
to an arboreal enviorn to escape competition and predation from other
species on the ground. I imagine water might be scarce, (at least not
regularly available) in the arboreal enviornment. To seek it on the ground
would engender risk from predators. Those which could do without the longest
would tend to survive to produce offspring. Hence the development of
concentrated urea , and excretion into scales and feathers of toxic wastes
would have developed. As far as EXCESS waste produced to form elaborate
feathers, once the feather became a highly necessary feature to survival of
the animal, this waste elimination mechanism would have turned into a
necessary one of feather production. Hence, .....perhaps these S and N
compounds shouldn`t be reguarded as "waste" products any longer. At any
rate, this is  (of course) speculation on my part. It seems to me though a
viable explanation.
     Of course this would indicate that the feather actually evolved in an
arboreal enviornment!