"Genome Research" Theory Q&A: 1/4

aroger at ac.dal.ca aroger at ac.dal.ca
Tue Apr 11 21:43:55 EST 1995


In article <3m3f8p$757 at fullfeed.msn.fullfeed.com>, Periannan Senapathy <sena at genome.com> writes:
>   No evolutionist that I know of--and I have searched
> hard--has ever proposed a mechanism for the origin of the genes and
> genome of the first cell.  Even modern evolutionists do not explain
> the origin of the first cell, and begin their explanation assuming
> that the first ancestral cell "somehow" originated on earth.
> 
Then you haven't looked very hard. For starters, please
read an article by Tom Cavalier-Smith published in Cold Spring
Harbour Symposia on Quantitative Biology, Vol LII, Evolution
of Catalytic Function, 1987, called "The Origin of Cells:
A Symbiosis between Genes, Catalysts and Membranes." pg 805.


> It should also be noted that my theory is able to explain the
> presence of utterly unrelated genes in distinct organisms -- a
> phenomenon that evolution theory cannot explain at all.
> 

This statement is not correct.  First of all, any reasonable theory
of molecular evolution suggests that with time the sequences
of genes will change by mutation.  If genes are separated by
a speciation event then each resulting group of organisms will
contain genes which will be changing independantly  as time goes
on.  It does not take much of an intuitive leap to realize
that given enough time homologous sequences will drift to the
point where it is no longer possible to detect their relationship.
This is what is presumed to happen, for instance, for portions
of non-coding DNA such as introns.  For coding regions, this
also  occurs (at an albeit slower pace).  For a description
of molecular evolutionary models of these processes please
check Li and Graur's text, The Fundamentals of Molecular Evolution,
1991, Sinauer Associates.  Look specifically at chapters 3 and 4.
In addition there is no reason why new genes could not evolve
from what was originally non-coding DNA in an ancestor of a 
modern organism.  Perhaps the ORFs would start out small,
but they could grow by selection operating on variants which
were a little longer (for instance where a mutation changed
a stop codon into something else like a glutamine codon-
NOTE- this requires only a SINGLE POINT MUTATION).  And given
enough time they could become a decent sized gene.  What the
hell is the matter with this kind of explanation of the evolution
of novel genes?  I just don't get it.

I would also like to make a general comment on the form of
Senapathy's argument.  

A and B are different organisms belonging to different
phyla.  We cannot fully explain how to get (using evolutionary steps)
 from group A's form (assume A is ancestral to B) to B's form. 
Therefore an evolutionary explanation is wrong.  The problem
with this sort of argument is that the lack of a currently
exhaustive explanation for an evolutionary transition is not
necessarily evidence that none exists, it is evidence that either we
need more data or we need to think harder about how to get from
A to B. An analogy springs to mind.  Does the fact that no
person or computer currently existing could give an adequate
description of a brain working in terms of particle physics
(such that future states of tha brain could be predicted accurately)
mean that the laws of physics are completely wrong?  Furthermore
does this mean that an alternative theory that argued that
the states of the brain are determined by non-physical (non-material)
forces is to be automatically preferred?

Andrew Roger
aroger at ac.dal.ca




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