Time to abandon the 'progenote' idea?

arlin at ac.dal.ca arlin at ac.dal.ca
Sun Oct 31 10:54:43 EST 1993


In article <01H4OQ2RTUDY8ZEECI at DBV>, DRBH at DB1.CC.ROCHESTER.EDU writes:

> As for formally rejecting the proenote hypothesis, Arlin first asks
> "Hasn't enough evidence accumulated...?", then cites not evidence,
> but an ARGUMENT that existence of homologous DNA-polymearases with
> proofreading functions "rules out the possibility".  Let us not
> confuse evidence with one person's interpretation of some data.

You lost me here with your proposed distinction between 'argument' and
'evidence'.  What else do have in evolution but i) fossil evidence;
ii) inference based on comparative biology and an understanding
of mechanisms; and iii) manipulative experiments to elucidate mechanisms.
It seems our evidence/argument is mainly limited to type (ii) in the 
present case.  To call into question the technique of inference used to infer 

if A, B and C have DNA genomes, then their most recent common ancestor 
had a DNA genome

is to call into question much of evolutionary biology.

> The argument may be persuasive to some, but "rules out the possibility"
> is such a strong statement that I would surely require more than
> one line of evidence to be persuaded.  I might be willing to accept

That's why I gave more than one line of argument.  Circular DNA genomes,
long genes, operons, DNA pols, proofreading, complex ribosomes-- all
of these would be independently inferred (with varying degrees of 
certainty) for the most recent common ancestor of all cells, and each 
would contradict the progenote hypothesis.

Barry suggests a more conservative statement, such as:

> "Given our current assumptions and understanding the findings concerning
> homologous modern DNA polymerases makes the progenote hypothesis seem
> unlikely"

> Barry Hall

I don't object to this at all, except I would include the other lines of 
evidence and might say 'extremely unlikely'.  

Arlin



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