Path: utzoo!utgpu!watserv1!watmath!uunet!snorkelwacker!bionet!lhc!ncifcrf!fcs260c2!toms
From: toms@fcs260c2.ncifcrf.gov (Tom Schneider)
Newsgroups: bionet.population-bio
Subject: Re: Average Fitness, Evolution of Sex and Others
Message-ID: <1910@fcs280s.ncifcrf.gov>
Date: 17 Oct 90 14:01:53 GMT
References: <3347.2719f222@cc.helsinki.fi>
Sender: news@ncifcrf.gov
Organization: NCI Supercomputer Facility, Frederick, MD
Lines: 37

In article <3347.2719f222@cc.helsinki.fi> xia@cc.helsinki.fi writes:
>
>          Average of Fitness, Evolution of Sex and Others
>          ===============================================
>
>In case that someone forgets, let me remind you that the average 
>of fitness of a gene over generations is represented by geometric 
>mean, not by arithmetic mean. Allow me to use an example to 
>illustrate the reason behind this.

I have two problems with this thesis.  The first is that the concept of
fitness is ill-defined (flame away!!!), however much it may be discussed.
How do you measure fitness?  What are the units?  I think that it is an
arbitrary measure that assumes that the organism does not affect the
environment it is in.  But every organism strongly affects its environment!

   "We" made oxygen!  We made oil!  We put the oil back into the atmosphere!
   The oxygen precipitated iron and uranium from the oceans (correct me if I'm
   wrong on this) so we were the cause of the uranium deposits that allow us to
   spread radioactive particles all over...

The idea of 'fitness' ought to be dropped and replaced with better measures.

>If a population of a gene makes 100 copies of itself in one generation, 
>but 0 copies in the next generation and become extinct, then the 
>average fitness of the gene is 0 (=square root of 100*0), not
>50 (=(100+0)/2).

My second objection is that if fitness is the time geometric mean, then
highly successful animals like the dinosaur and (yes) humans AND ALMOST
ALL SPECIES have zero fitness, since most species die off eventually!

  Tom Schneider
  National Cancer Institute
  Laboratory of Mathematical Biology
  Frederick, Maryland  21702-1201
  toms@ncifcrf.gov