Re: bauplan convergence

[Stanley Friesen <sarima@friesen.net>]

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

> Stanley,
>      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