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Re: bauplan convergence

At 07:48 PM 6/16/00 -0700, Ken Kinman wrote:

I see no big problems with such a sequence, but I believe protofeathers first evolved for either display or insulation, not both at the same time.

The problem I have with this is that natural selection does not act on functions or uses, nor even, really, on individual organisms. It is a population process. This means that there is rarely a clean separation of functional effects with regard to selection.

In short: separate selection for one of a set of function is *very* rare. Selection for an amalgam of functions within the context of the local ecological situation is the general rule.

Significant changes *rarely* happen for just one reason.

Thus display and insulation are not separable features with respect to the evolution of proto-feathers.

Nor are brood insulation and display separable with respect to proto-wings (aka extended feathers attached to arms).

May the peace of God be with you.         sarima@ix.netcom.com