Re: warm/cool/cold blood

[Stan Friesen <swf@tdat.ElSegundoCA.NCR.COM>]

Vicki Rosenzweig vr%acmcr.uucp@murphy.com wrote:

 > I can't refute Ralph's theory entirely, lacking the background, but
 > the idea that "nature does not like to invent the same idea
 > twice" is not a valid generalization. Flight has been invented
 > several times: birds, bats, and many insects evolved it
 > independently (even leaving out pterosaurs for the moment, lest
 > I appear to be arguing from my conclusions). There are probably
 > other, equally good examples--flight is just what comes to mind
 > first.

Oh, indeed there are other examples.  Convergent functionality is
common in evolution.  There are whole books written on the subject.

For instance, no matter *how* you slice it, endothermy has to have
evolved at least 4 times independently:
        Archosaurs (birds and pterosaurs and maybe dinosaurs)
        Mammals
        Certain fish (e.g. Tuna)
        Certain insects

And, it *may* have evolved more than once within the Archosaurs.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.