Re: First Mutation Was Biggish
From: tinyurl.com/uh3t (rem642b_at_Yahoo.Com)
Date: 11/15/04
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Date: Mon, 15 Nov 2004 03:57:06 +0000 (UTC)
> From: an588@freenet.carleton.ca (Catherine Woodgold)
> Right from the beginning, except perhaps for a few generations
> supported by luck, Life had to be substantially better at replicating
> than was anything in the vicinity that was using the same resources and
> being spontaneously generated at a substantial rate.
It depends on your meaning of the word "substantially". See the
simulation of randomly-generated fecundities, and the calculation of
chance of passing the threshold into assured exponential growth, which
I posted a few days ago:
http://www.google.com/groups?selm=cmounv%24vm%241%40darwin.ediacara.org
With a fecundity of only 1.1, there's appx. one chance out of three,
starting with just a single molecule, of passing that threshold, while
the next lower fecundity of less than 0.95 has no chance at all of
having any measurable consumption of resources, so that tiny difference
of fecundity is significant in a rather major way. Does that tiny
difference satisfy your definition of "substantially better"
> One could have a theory that there was replication going on before
> RNA was replicating. I'm not sure that this would be refutable. One
> could perhaps try to show that no other known substance (or set of
> substances) has the required replicating and mutating properties; it
> would be more difficult to show that no possible substance has such
> properties.
I suspect it would be impossible to prove no such chemical can exist,
even if it's in fact true. And I suspect it's not true at all. But a
better question is whether any other substance which might occur by
chance event (from chemical cascade from high-energy source) within a
reasonable time could possibly be a replicator. It may be easier to
answer a more general question, namely to generate the statistics for a
whole series of expected times between spontaneous production of
various lengths of catalytic chains, and to generate the probability
that such a chain of any particular length would close to form a
catalytic loop, and then put the two together to get the expected time
to get the first catalytic loop by that means. So need experiments to
produce data to compute those two sets of statistics, and then more
experiments to verify the statistics.
> Perhaps one could try to show that if some other substance had such
> properties and was the beginning of life, that there would be only a
> very low probability that all such life would have switched over to
> using RNA.
If we can show a way that the first replicator would surely be created
within a reasonble time, and if we can show a way that first replicator
could have evolved within a reasonble time to genomic-evolving life,
where the genome codes somehow for manufacturing proteins to implement
arbitrary biochemical pathways, then at that point just about any kind
of biochemical pathway would be possible for subsequent evolution,
including the manufacture of RNA, and the mapping of the genome to RNA
and back again, and the direct coding from RNA to proteins in lieu of
coding from the original genome, loss of the original coding method,
etc.
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