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Evolution & the 2nd law?

Robert Solomon Bioc rgs at mole.bio.cam.ac.uk
Thu Nov 23 05:04:02 EST 1995

Mark Fry <wmfry at morgan.ucs.mun.ca> writes:

>The other day a physicist friend of mine said that he does not believe 
>the theory of evolution, based on the laws of physics.  His argument went 
>something like this:
>The theory of evolution, as it is generally presented, states that 
>billions of years ago, some proto-organism arose from the primevil ooze.  
>It presumably had some genetic material, encoding but a few "genes".  
>Since then, more complex organisms have "arisin":  each of these more 
>complex organisms contains more information in its genetic code.  This 
>represents an accumulation of information and energy, or a tendancy towards 
>more order in the universe.  This is in direcyt conflict with the second 
>law of thermodynamics that states "the entropy of the universe increases 
>in all natural processes".
>Even if the case of natural selection is considered (the differential
>survival and REPRODUCTION of those individuals with greater fitness) we
>still have an increase in proportion of genes that optimize survial in a
>given environment.  This again represents a tendancy towards more order. 
>Extinction is consistant with the second law.
>His argument is not that of a crackpot, but seems to be based in the laws 
>of physics.  I'm not sure if the basis of his argument (ie information = 
>energy) is strong enough to support his argument.
>I know this a little out of the scope of this group, but I know that most 
>of you are knowledgable about molecular evolution.  I would like to know 
>what others think of this argument.
>"What does a physicist know anyway?"  ;)

Well, a physicist should know a couple of things, I'd have thought:
One being the Second Law.  Which refers to an isolated system.  It does not
refer to the entropic state of part of an isolated system.  How does this
apply to your friend's argument?  Evolution of life on earth, and any attendant
decrease in entropy, does not necessarily decrease the universal entropy.
To put it another way, if the entropy of a system (not isolated) decreases,
the entropy change in it's surroundings must increase in compensation (and
I think it may be argued that in the case of evolution of life on earth, a
little compensatory increase in the surroundings' entropy might have occurred).

Rob Solomon

Thanks to P. W. Atkins (Physical Chemistry, 2nd edition) for his excellent
handling of this topic, from which I hope I have borrowed correctly.

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