phillip smith  wrote in
news:bv23b3$25op$1{at}darwin.ediacara.org: 

> in article but4kr$lgo$1{at}darwin.ediacara.org, William Morse at
> wdmorse{at}twcny.rr.com wrote on 24/1/04 7:51 PM:
 
>> But perhaps evolution is better thought of as changes in phenotype.
>> We typically say that horseshoe crabs are "unchanged"
after millions
>> of years, even though their gene frequencies today are almost
>> certainly significantly different from their gene frequencies 
>> millions of years ago. 
 
 
> I couldn't agree more. But changes in phenotype are so often taken as
> changes in  a gene that we confuse the issue.
 
> Returning to Joe and Fred. Fred meets a sticky end. This we know, what
> was the cause of death? He was eaten by a tiger. Was it a fast tiger?
> If Fred had met the tigers slower mate ginger would Fred be here
> today. Does that fact that Fred was only 4 years old and Joe was in
> his early twenties and if compared age for age Fred would have been
> much faster. Or perhaps Fred was actually faster but was not bright
> enough to realise he was being chased by a tiger or perhaps was
> running in the wrong direction. There are so many possible confounding
> factors. What we do know is that the experiment will never be repeated
> again. Never again will two individuals with exactly those two
> genotyoes at that age will meet exactly the same tiger in exactly the
> same situation. So we must be very careful what conclusions we extract
> from such data. 


But we do get non-contingent results. And in evolution we have had 
experiments repeated. On three continents we have had mammals evolve in 
the presence of the potential food resource of anthills. The result is 
spiny anteaters, pangolins, and south american anteaters. They are 
totally unrelated, but share numerous features in common. Now they are 
not identical, because evolution _is_ contingent. But they are similar, 
because evolution is also statistical - even with the confounding factors 
there is enough equivalent comparison (Fred is 22, Joe is 20, both turned 
as the tiger started its charge, often enough that differential speed 
alone made a difference in survival) to give evolution some typical 
directions. These directions represent possible niches  - large size and 
low reproductive rate, small size and high reproductive rate: speed, 
armor: camouflage, toxicity and bright colors:  etc. So we cannot talk 
about an overall direction for evolution, but we can make predictions 
despite contingency.

Yours,

Bill Morse
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