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Re: Why insulation = endothermy



>Rob Meyerson wrote...
>> This is true for "end members" of each group, yet for the intermediate forms
>> it may not be that big of a problem.  Just like Rome, full endothermy is
>  not made in a day, or even in a generation; so there is likely to be a
>  number of partially endothermic/partially insulated forms.  What I see
>  is a snowballing effect, where a generation adapts to a higher
>  metabolism (with those animals possessing adequate insulation surviving
>  to the next generation), and so on down the line until the species
>  reaches full endothermy.  Looking back on the trend, we would see that
>  the amount of insulation was proportional to the metabolism.  Therefore,
>  the "chicken and egg" scenario is avoided (and also provides an answer
>  to the old question of "which came first?").
>
>     How reasonable is this scenario though?  Did those first few little
>pre-feather bristles offer even a TINY bit insulation for increased
>development and isulating ability to be selected for?  This is similar to
>the "half a wing won't do" problem of flight evolution; it has to have
>already developed PAST a certain point before it is useful for a
>particular function.  What was it being used for in the meantime?

        Which came first, flight feathers or down?  Maybe down came first,
then some of those got adapted for display purposes, then the flight
feathers came.

>    Which brings me back to a question I asked a while ago; does the
>presence of a rachis, barbs, and barbules on plumaceous feathers make them
>better insulators then hairs?  Are the nodes on plumaceous feathers
>atrophied barbicels, or are barbicels on contour feathers derived nodes?
>Which came first, the plume or the contour feather?  Is there any evidence
>that neossoptiles (which lack a rachis altogether) are phylogenetically
>more ancient then teloptiles?  When IS that frigging Sinosauropteryx paper
>coming out?
>
>LN Jeff
>O-

bruce

        "The more television I watch, the more I wonder why I'm not already
supreme ruler of earth."  --Dogbert