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The Punctuated Clock

Bert Gold bgold at itsa.ucsf.edu
Fri Jan 10 11:57:25 EST 1997


If it is true that our scientific theories must prove accurate in their
predictions of real world phenomena in order that they be upheld, then I
would suggest that our simplistic conception that the pacemaker of
evolution; mutation, occurs as a stochastic process, is in real need of 
modification.

Advances in molecular genetics have recently revealed a large number
of different mechanisms responsible for mutation.  Perhaps foremost
among these are oxygen radical damage, DNA methylation and repair
and numerous higher level alterations in chromosomal structure
including deletion, insertion, inversion and retrotransposition.

To my way of thinking, there is no way a base specific 'molecular
clock' which attempts to measure evolutionary time as a consequence
of point mutations, even begins to grapple with the magnitude and
diversity of known mechanisms by which gene changes are founded and
proliferate in expanding populations.

My belief is that there is room for an incredible amount of work
to be done in population genetics in order to understand the ways in
which profound genetic changes occur in populations over time.

And my wonderment is why, rather than addressing this very real and
important question of how it is that the 'new genetics' applies to
the older ideas of mutations and populations, do we keep having the
same old arguments about whether or not Darwin was correct.

It appears to me that it is much like asking whether Newton was
correct.

To a first approximation, it is clear that the laws devised by each
were accurate descriptors of the observables at the time they lived.

It is equally clear, however, that the Darwinian approximation is
sorely in need of adjustment; because the clockwork-like mechanism
it proposed to account for the source of variation, does not tick evenly
through time, as was first supposed.





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