Date: Tue, 21 May 1996 12:04:14 -0600
Subject: Re: TREE - reply to Terry's of 4-19, part 2 -Reply



>>> Terrence Mc Donough <TERRENCE.MCDONOUGH-AT-UCG.IE>  5/20/96, 09:52am
My position is that five 
fingeredness  is inherited and is not changed because there is no 
compelling reason for it to change.  Natural selection is passively 
letting five fingeredness through.  Yours is that natural selection 
is actively pursuing five fingeredness as an optimal solution.
-----

I think you are unnecessarily exaggerating the difference in
emphasis.  "Active" vs. "passive" NS is a false dichotomy.  

The differential reproduction in each generation, if any, shapes the
following generation.  Diff. Repr. can occur in a variety of ways. 
If 5 fingers were a problem, i.e. if one more or less had better
results, that is the definition of "selection", i.e. that is DR
itself.  

The degree of DR, i.e. the amount of force of selection can be zero. 
One selective force can be opposed by another.  Both tails of a
distribution may be less successful than those in the middle, so no
change due to selection would be expected in that case.

Part of my point here is that active vs. passive "selection" is not a
helpful way to conceptualize the process. 


BTW, "flying pigs" suggest to me that my intended point was entirely
lost.  Sorry if I was unclear.  

However powerful in the short run [say 10 gerations or less] are the
constraints of present structures upon the slight variations that can
possibly succeed, in the very long run [half to one billion years]
5-fingered primates descended from critters that had _no_ fingers at
all.

So if you want to invoke inherited constraints upon possible future
developments, it may be helpful to be clear about what time scale you
are talking about.  It's a sensible concept only within a relevant
context.  [Well, that's what they taught me in school.]

Regards,
Lisa



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