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Proof or counter-proof... this is how to do it.

Ludvig Mortberg Agneta.Guillemot at historia.umu.se
Wed Jul 12 15:41:17 EST 1995


Thanks everyone for responding to my sceptical article on the  
molecular clock. Your opinions are valuable. Thanks to them I  
think I'm closer to defining methods of proving or disproving the  
theory of the molecular clock, as I prefer to call it. 
 
The following criteria should be satisfied if there is a clock. If not,  
the clock is in trouble. 
 
(1) Phylogenies, divergence dates etc, obtained by the clock,  
should conform with fossil data. 
 
(2) When different parts of the genome are used in an analysis the  
results should be the same. Different chromosomes, protein  
sequences etc should give the same divergent dates or  
phylogenies. Of course  it may not be possible to draw conclusions  
from data from a very slowly evolving protein. Histones for  
example. 
 
(3) The Wilson relative rate test should be positive when applied  
to three reasonably closely related species. See illustration below: 
 
      / A 
    /  
  / 
/\    / B 
   \/ 
     \ C 
 
We have determined that B and C are closest. The distance from  
B to A, be it nuclear substitutions or melting temperatures for  
DNA-DNA hybrids, should of course be the same as the distance  
from C to A. Otherwise B and C have evolved with different  
speeds. 
 
The last test may be the one that is most useful in determining  
wether there is a clock or not. 
 
Now what does the data say?  
 
Ludde 





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