Newsgroups: talk.origins
Subject: Re: Thermodynamics FAQ
From: sbishop@desire.wright.edu
Date: 24 Jul 92 22:51:03 EST
 <schinder.711942290@leprss.gsfc.nasa.gov> <henley.920724101706@wilbur.eng.auburn.edu> <henley.920724122410@wilbur.eng.auburn.edu>
Organization: Wright State University 

In article <henley.920724122410@wilbur.eng.auburn.edu>, henley@eng.auburn.edu (James Paul Henley) writes:
> In the preparation of my FAQ on Thermodynamics and Evolutionary Biology, I
> have found some striking parallels to solution thermodynamics.  Before I
> complete the FAQ, let me throw out a few idea about analogies.  These
> particular analogies are not for the purpose of debunking any evolutionary
> theories, but rather an attempt to understand mechanisms such as Genetic
> Drift, Narrow Sense Heriditability, Sexual Selection, and Random Mutations
> from a microscopic and macroscopic thermodynamics point of view.
> 
> First analogy:
> 
> Miscibility is the ability of two liquids to form a solution.  There are
> systems of complete miscibility - such as ethanol and water, which will remain
> in one phase at all concentrations.  There are systems of partial miscibility
> - such as butanol and water, that will remain in one phase at high 
> concentrations of either butanol or water, but in certain concentrations will
> form two separate phases.  Now miscibility seems to be analogous to sexual
> selection.  Take dogs.  When you put two breeds of dogs together, the breeds
> will interbreed, and you will end up with a composite breed - complete
> miscibility.  As far as I know, interbred dogs don't tend to form distinct
> breeds by natural sexual selection.  Does anyone have any information on
> this?
> 
> Second analogy:
> 
> What about horses and donkeys?
>     It is possible to interbreed the two, but I believe that if they
> were allowed to mate by natural sexual selection, you would definitely see
> distinct horse and donkey populations.  Most of the offspring of horses and
> donkeys are sterile, but a few are not.  Does anyone know what happens when
> you mate mules?  Do you get a homogeneous population, or do you see distinct
> horse and donkey populations?  If the population is like a partially miscible
> system, then you would see populations that were primarily donkey, but with
> some horse traits, and a population that was primarily horse, with some
> donkey traits.  If it was a completely miscible system, then the population
> would be homogeneous.  If you changed the environmental conditions - analogous
> to change the temperature and pressure of a solution, then the equilibrium
> point should change.  Does anyone have any information on this?
> 
> 

Jim, I've had horses most of my life.  YOu are working from a deeply flawed
analogy here.  Horses and donkeys are different species.  The vast majority
of offspring from a cross are sterile.  Very, VERY rarely a mare mule might
have a foal.  These offspring are so rare that you *might* get a foal out
of one in ten thousand mare mules.  Genetic testing on a foal or two that
were born in the last 10 or 20 years showed that they were genetically 
a donkey, evidently the mare mule was producing ova that only carried the
donkey genes she had inherited from her sire.  
Once again, since horses and donkeys have different chromosome numbers, the
mule inherits an uneven number of chromosomes.  This almost universally
causes sterility.  
Horses, and donkeys are divergent species.  In other words, they have a 
common ancester but have evolved in slightly different directions and are
no longer able to produce fertile offspring.

Sue
> James P. Henley Jr.
> Chemical Engineering Department
> Auburn University
>