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
