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Re: courses

On Thu, 5 Dec 2002 16:54:08   
George Olshevsky said:
>>>I would say that evolution >always< takes the easiest course, >which is 
>>>determined by the raw material available. This is because >the chance of 
>>>finding the easiest course is much greater than that >of finding a harder 
>>>course. That, indeed, is the definition >of "easiest course."<<

Dan Bensen then responded:
>I would say that trying to designate between "easy" are "hard" >courses will 
>not get you anywhere.  Random mutation and selection >are based upon so many 
>different variables that I don't think we >can ever determine the path of 
>least resistance for change in an >organism.

Well, yeah, "easy" and "hard" are probably too simple in this context.  But, I 
think George was arguing something akin to entropy, where there are countless 
different possibilities, but probability dictates what actually happens.  As a 
result, *most* of the evolution that actually happens results from random 
mutation that, because of probability, follows an "easy" path instead of a 
"hard" path.  I'm sure there are many mathematical models that exhibit this 
idea better than my words (or George's words) can.

Technically it is possible for a coin to come up tails 50000 times in a row.  
But, it's not probable.  I think this is what George is saying.  There are 
probable paths ("easy") and very improbable paths ("hard").  The improbable 
paths are possible, but very rarely will they be seen, because nature is so 
complex, as Dan said.  So, perhaps "probable" and "improbable" are better terms 
for "easy" and "hard."

Does evolution *always* follow the probable paths.  Well, that probably depends 
on where you draw the line between probable and improbable.  But, like the laws 
of thermodynamics, I would say that it is a fairly good bet that evolution 
follows the most probable path and very rarely, or ever, improbable paths.  I 
mean, has anybody *ever* flipped a coin 50000 times and seen all tails?


Stephen Brusatte
Geophysical Sciences
University of Chicago
Dino Land Paleontology-http://www.geocities.com/stegob

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