[Oops, I sent this privately first by accident, sorry.]
Steven P Crawford writes
in message <20000808.094726.-74557.0.stevenpcrawford@juno.com>:
>
> I see another problem with this explanation for why abiogenesis does not
> occur today.
>
> The advent of the first lifeform would have indeed placed pressure on the
> population of pre-biotic molecules. But this predator-prey dynamic
> theoretically would have been naturally selective. Yes, many of the
> biomolecules would have perished in the process, but conceivably a few
> (or more than a few) should have survived due to their randomly mutating
> self-replication. This is especially true since mechanisms for
> self-checking replication would not have existed back then. RM would
> have been running wild, and so possibilities should have existed where
> prebiotics would have biochemically escaped the hunger of the new
> lifeform. Perhaps the apparent ability of viruses to elude bacteria is a
> modern-day analogy to this hypothetical situation.
>
> Those that did have mechanisms for escaping the new life species would
> have kept on replicating, and thus the population of predator & prey
> should have reached some type of equilibrium. This would last until the
> next development of evolution, in which case the whole process would
> theoretically repeat itself until a new equilibrium is established.
That's sounds right, but I can't see how this particular situation
would match anything today. The critical difference is what
has already been mentioned: life's ubiquity ensures that prebiotic
elements are quickly eaten.
> So, then, if my logic is not mistaken, evolution does predict that a
> population of prebiotic molecules should exist in equilibrium with
> present-day species.
But only as long as there is a life "vaccum", allowing prebiotic
molecules to exist for lengthy periods of time --maybe years--
without being broken down into waste products by living organisms
-- which is nothing like Earth today.
Each square centimeter of your skin averages about 100,000
bacteria. A single teaspoon of topsoil contains more than
a billion bacteria. A single gram of sand on the seashore
contains a billion bacteria. Where can you go on Earth today
to escape life and still have the conditions for life? No where,
it would seem.
[From your previous post:}
> My post even mentioned how that biomolecules would probably not
> remain intact for very long. Yet, what kind of fragments do
> bacteria leave behind after they're through?
I assume you're not talking about waste products. Dead
bacteria and fragments of dead bacteria are eaten by other
protozoa, other bacteria, etc.
> If these remnants
> are more complicated than the most basic elements and compounds,
> then it seems that rudimentary, first-step self-organization of
> molecules (as Darwinsts envision) should be observable in today's
> world.
But not if they get eaten.
> Likewise, we could be doing laboratory experiments where the
> absence of microbes could be ensured. We could place a bunch
> of bacteria in a test tube, wait for all of them to die, and
> watch the remaining biomolecules under differing circumstances.
> Has any experiments like this ever been done?
Assuming that you can get a test-tube full of bacteria fragments
(instead of a test-tube full of bacteria waste products), the
next requirement before anything could happen would be energy
input and catalysts (since we know molecules rarely do anything
interesting otherwise).
Now with biomolecules, catalysts, and energy input this *is*
starting to look like modern abiogenesis experiments in general.
But while there have been many interesting results in this area,
it is now clear that not just any biomolecule or catalyst will
do the job.
(Nor do I see a good reason to assume that evolutionary advanced
biofragments will be more capable of self-assembly than the much
more primitive precursors postulated to exist on early Earth.)
http://exobio.ucsd.edu/issol99/sci_summaries.htm has some
summaries of current, ongoing research in abiogenesis.
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