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Re: Origin of feathers
On Apr 9, 11:46am, Dinogeorge wrote:
> When pre-feathers first appeared, it is likely (though not certain, of
> perhaps they popped into existence fully structured, with rachis, barbs, and
> barbules!) they were small (like hairs) and thus had little impact on the
> visual appearance of the animals. The visual impact would have come later,
> would have gone hand-in-hand with the enlargement and elaboration of the pre-
>-- End of excerpt from Dinogeorge
Well, I suspect vertebrates with good vision are very sensitive to minute
differences in the appearance of conspecifics - as long as pre-feathers
were visible it is possible that sexual selection had a role. Sexual
selection can be responsible for the spread of a mutant gene which does
not aid survival in any way, and the significance of Michael Ryan's work
on frogs is the demonstration that a female preference can be present
BEFORE the male characteristic evolves.
(Also, are you saying that it is impossible for ANY structure to evolve
purely for display without having had a utilitarian origin?)
It is also possible (via genetic linkage) that this mutation spread via
co-selection with something of genuine utility, ie classic natural selection.
Speculation I know, but plausible, not requiring miracles!
On Apr 28, 4:28am, Dinogeorge wrote:
> I don't maintain an aerodynamic origin for feathers. I currently favor a
> metabolic origin for feathers. This >is< compelling, in that feathers thereby
> fill a prior physiological need of the organism.
>From your previous posts, it is clear that you don't mean a physiological
need to support sustained flight in your descendents - could you elaborate
on the prior physiological need aspect, ie what was the need which other
reptiles did not share?
Just to be clear, I have no strong views on which, if any, of the competing
theories of feather origins is correct - food capture doesn't seem likely,
and I agree with you that flight was probably not the initial function of