jae{at}veni.ucdavis.edu (Jason Eshleman) wrote 


> >Okay. Would it take a text book to tell me why drift occurs (feel free 
> >to recommend one if it would ;-)?
> 
> Drift is simply sampling error.  It's change due to chance and chance
> alone, blind to the genetics.  If you have a population that is 50-50 for
> 2 alleles at a locus, in the next generation, it may not be 50-50 just
> because one or two individuals with one genotype reproduced more simply
> due to chance.  Or because a disaster wiped out a ton with one genotype
> (the disaster being blind to the genotype--thus it's not selection for
> that type).  
> 
> Chance is always a factor.  

To even discuss genetic drift as a factor in speciation is 
to demonstrate one's ignorance of speciation.  

I'm going to make my argument by way of analogy:

Suppose that instead of being concerned with speciation we 
were concerned with the level of the oceans and changes 
thereof.  If one went out to measure the level of the ocean 
one would observe that their measurement went up and down 
on a second by second basis.  Why?  Because of waves.  So 
the observation that the level of the ocean changes on a 
second by second basis is confirmed by observation.  However, 
if you were to attempt to gain an understanding of why ocean 
levels change over thousands of years the fact that oceans 
have waves would be perfectly useless.  Levels of oceans 
change depending on inputs (melting of glaciers) and outputs 
(formation of glaciers).  

likewise genepools (populations) change over time due to 
natural selection not genetic drift.  Genetic drift is nothing 
but the OBSERVATION that gene totals change due to random 
factors over time.  Like waves on an ocean the changes in gene 
totals that result from genetic drift are irrelevant to 
understanding why new species emerge.  To say otherwise is 
equally ridiculous as saying that sea levels rise and fall as 
a result of waves.

One must be extremely careful about the truths that one 
extracts from college level text books.  Half of it is 
superstition and the other half is half superstition.

Unfortunately this is just the state of the current paradigm 
in evolutionary biology.  

Jim
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