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Re: Why insulation = endothermy

Jeffery Martz writes;

>     This is an interesting chicken and egg problem indeed: insulation
>intereferes with ectothermic thermoregulation but an endotherm
>needs it to keep all that metabolically produced heat.

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?").

Rob Meyerson
Orphan Vertebrate Paleontologist

When the going gets wierd, the wierd turn pro.