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RE: When New Met Papers



--- Tim Williams <twilliams_alpha@hotmail.com>
schrieb:

> 
> Dawid Mazurek wrote:
> > An intermade stage from scales to feathers? :o
> :o indeed!  This heterodox hypothesis has come up
> before.  It proposes that the elongated, ribbon-like
> rectrices of certain primitive birds reperesent an
> intermediate stage in feather evolution.  The
> alternative hypothesis (which is much better
> supported) holds that this particular feather
> morphology is highly derived, and has nothing to do
> with the origin of feathers, or of flight.  It might
> help to add that the _Paraprotopteryx_ paper cites
> Feduccia's _The Origin and Evolution of Birds_ in
> support of the former hypothesis.

Yeah, but it's actually just too simplicistic.
Apparently feathers *did* evolve from "scales" - but
not "lizard" scales. It has been shown that a simple
mutation and some fine-tuning can transform the scales
on chicken legs into feathery integument.

It needs some serious tweaking of keratin metabolism
to work out as proposed though. That however should
still be doable (they had >50 million years) building
upon simple gene duplication. That again is not really
unlikely to happen in such a timespan. 

(We don't know how *often* it happens really. Most is
missed because it is selected away too quickly. In
this case it is likely to have caught on more quickly
than average. Modest fuzziness or a back frill would
have been as good as neutral, and that's all that's
needed for starters)


Regards,

Eike


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