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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 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