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Re: ABSRD BAND on Sinornithosaurus feathers

In a message dated 3/20/01 10:11:40 AM EST, TomHopp@aol.com writes:

<< A question: if variations in your sulfur-wearing protobird's diet led to 
 normal or deficient sulfur levels, did it stop growing feathers? >>

The reason I find the sulfur-excretion hypothesis attractive is that it gives 
a proactive reason for the existence of feathers. Evolutionarily speaking, an 
animal cannot know that feathers will be good for insulation until after it 
evolves them; thus insulation cannot be the >reason< for the evolution of 
feathers. Likewise evolution of feathers for flight, display, brooding, 
camouflage, and pretty much all the other uses for which feathers were 
exapted once they evolved. (This assumes that feathers are not homologues of 
scales, of course, but are genuinely novel dermal structures.)

The reason I find the sulfur-excretion hypothesis unattractive is that, as 
you say, it is simply not necessary to go to all the trouble of evolving 
feathers when so many other pathways for sulfur excretion are already 
available (and used by featherless animals). Of course, the first feathers 
were probably like peach-fuzz, and evolving that kind of very simple dermal 
structure as part of sulfur excretion seems to be a lot more likely than 
evolving fully formed feathers. More intricate feathers are likely the result 
of feather evolution after exaptation of the peach-fuzz for other functions.