Text 599, 111 rader
Skriven 2004-10-31 16:56:00 av Tinyurl.Com/uh3t (1:278/230)
Ärende: Re: First Mutation Was Bi
=================================


> From: an588@freenet.carleton.ca (Catherine Woodgold)
> Right at the very beginning of Life, there must have
> been a sudden, substantially beneficial mutation.

I don't agree with this conclusion, unless you allow that a mere chance
closing of a catalytic loop to form the first replictor would qualify
as a "mutation". I would prefer to restrict the use of that word to a
change in something that was already replicating, in which case I would
disagree with your claim.

> But the very first Life had to face a hurdle none of
> the rest of us has had to face since:  direct competition
> from non-Life.

Per my catalytic-cycle scenerio for the first replicator, I don't
regard that competition as very severe at all. Per my scenerio:
There were at least three main sources of high-energy meta-stable
molecules: (1) geothermal vents, (2) UV irradiating the surface
chemicals, (3) hot bodies from crashed comets/asteroids cooking the
nearby chemicals. From these sources, there was a flow of such
molecules out into the general prebiotic soup, forming chains of
chemical reactions that branched out to form very many species of
chemicals. Occasionally a chemical loop would form, whereby some
chemical that went into a chain of reactions would re-appear at the end
to start the chain all over again. I.e. a catalyst would occur, a
chemical that is not consumed in a particular set of chemical
reactions. The appearance of a catalyst would enhance a particular set
of reactions, extending the chemical-reaction chains from it. If by
chance an output product of a catalyzed reaction was itself a catalyst,
the second set of catalyzed reactions would be *greatly* enhanced,
resulting in large quantity of reaction products from it, and large
variety of downstream reaction products, and greater chance of another
catalyst appearing somewhere in that mix extending the catalytic chain
to a third etc. set of catalyzed reactions. If by chance a catalytic
chain were to close the loop, producing one of the catalysts that was
used earlier in the chain, we have a catalytic loop, the first
self-replicator. The first replicator would quickly grow exponentially
to consume all available resources needed for its reactions, which
would actually *reduce* competition by greatly reducing the high-energy
foodstocks available for any alternative type of chemistry. So by
consuming resources so effectively, that first replicator almost
entirely eliminated its competition. It could then survive for a very
long time with virtually no competition and hence with no need for any
mutation to keep it surviving. In conclusion, it's very UNlikely that
any mutation would be needed for a very long time, the opposite to your
claim.

> Suppose one replicand had, by good fortune, some characteristic that
> made it one percent better at surviving and replicating than the
> other, run-of-the-mill, spontaneously generated molecules.

That one molecule, exponentially replicated to exhaust all resources of
active chemical input such as hydrogen sulfide from geothermal vents,
would be quadrillions of quadrillions better at surviving than
something that was just appearing by chance rather then by
self-replication.

> it might happen to have a dynasty of 4 molecules instead of 3.

No, it'd have a dynasty of macroscopic quantities of that single
molecular species, perhaps tons of all that same molecule, diffusing to
fill all the oceans, compared to individual molecules of any potential
competitor. Many many orders of magnitude difference in quantity.
"No comparison" as they say.

> the descendents of that first would-be Life had only one way of being
> created:  by replication.

When such replication by catalytic cycle is so many orders of magnitude
more effective than any other mechanism, who needs anything else??

In fact the first replicator might still occasionally be created by
spontaneous generation, but the quantity of such would be so small as
to be insignificant compared to the large amount created by the
catalytic cycle.

> But the rather similar molecules they were competing with had two
> ways of being created:  replication, and spontaneous generation.

Except that any other molecule chancing upon replication likewise is a
fact not in evidence, and spontaneous generation is insignificantly
small compared to the existing replication of that first replicator.
Given the exhaustion of resources caused by that first replicator, it's
unlikely any second replicator would chance into existance for a very
long time. More likely the first replicator would produce a large
amount of waste product, and subsequent reactions among those waste
products might possibly create a second replicator that consumed those
first-replicator-waste instead of consuming original high-energy
chemicals. That second replicator wouldn't be competing with the first
replicator for resources. And given that it consumes low-energy
chemicals that are "waste" to the first replicator, it has a lot less
available energy to work with, so wouldn't dominate the energy flow as
the first replicator did. Unless that second replicator used both waste
from the first replicator and some untapped high-energy chemical. Still
it wouldn't be competing with the first replicator for resources.

> I would call the appearance of that first strand the major mutation
> I'm talking about.

Like I said at the beginning: I would restrict the use of the word
"mutation" to refer to a change in an already replicating molecule, not
the very first appearance of anything that replicated.
---
ū RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info@bbsworld.com

---
 * RIMEGate(tm)V10.2á˙* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 10/31/04 4:56:11 PM
 * Origin: MoonDog BBS, Brooklyn,NY, 718 692-2498, 1:278/230 (1:278/230)