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Re: ABSRD BAND on Sinornithosaurus feathers
<< 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 >>
Maybe so, but this doesn't get past your concept that structures don't evolve
with foreknowledge of their ulimate use. In this case, why would peach fuzz
evolve? There would need to be several genes responsible for even this simple
change, and they couldn't arise for no reason. There must have been -- not a
future use -- but a present use, at the time.
Sure, I can see HOW feathers or fuzz would excrete sulfur, but WHY is still
relevant. Kidneys are very adaptable to the levels of various body
constituents. If an evolutionary line of species ate more and more sulfur
rich materials, the kidneys would at first react WITHIN A SINGLE INDIVIDUAL
to compensate. Then, if the increasingly sulfurous diet demanded, mutations
would be fixed over time to up-regulate the sulfur secretion mechanisms of
kidneys. These regulatory and mutational mechanisms are well understood in a
variety of metabolic systems and known to be widespread even among humans
(alcohol dehydrogenase variations, diphosphoglycerate variations in high
altitude peoples (sherpas, aboriginal peruanos)) so it's a tough sell to
start invoking complicated fuzz-generating mechanisms when simple metabolic
alternatives are well known.
In a nutshell:
Metabolic mechanism= a LEVEL adjustment to an old metabolic system.
Fuzz/feather mechanism= a whole new structure and the NEW GENES to make it.
The former is REAL, well known, and trivial for the body to accomplish, the
latter is not without precedent perhaps, but still only hypothetical and
requires new gene creation, a very complex process.
WHY fuzz developed remains elusive, but I am absolutely sure it wasn't to
replace an already existing, highly effective and adaptable mechanism.
Thomas P. Hopp