Text 639, 166 rader
Skriven 2004-11-03 22:20:00 av Brett Aubrey (1:278/230)
Ärende: Re: Metabolism Forced
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"tinyurl.com/uh3t" <rem642b@Yahoo.Com> wrote in message
news:cm9meg$1flm$1@darwin.ediacara.org...
> > From: Brett Aubrey <brett.aubrey@shaw.ca>
[snip]
> > But isn't all this still just speculation?
> Correct.
[snip]
> > You write like we *know* that a simple chemical replicator took
> > hold and dominated the oceans and led to life as we know it.
> No. Just that to me it seems plausable and worth researching.
> I try to eliminate the false arguments against this theory, so
> we can concentrate on seriously considering whether it might
> possibly have happened.

Good approach.

> > Panspermia is still a possibility, no?
> Correct,
[snip}
> > And hydrothermal vents without dominating replicators?
> Right at the vent, the environment would be too harsh for a prebiotic
> replicator to survive, but near the vent where the vented chemicals
> have decayed (redox/energywise) a little and the water has cooled a
> little, and where the water is cycling around due to bubbling from the
> vent, is where I expect most of the interesting chemistry including
> catalytic activity would have occurred.

Or course, I mean the area of the vent.

[snip]
> > > But for a fully-formed lifeform to suddenly emerge
> > > out of nothing,
> > Ya came in late.  As stated before, very much *not* "out of nothing",
> > I just don't know out of *what*.
>
> I mean out of nothing that was previously replicating, hence out of
> nothing (except very simple chemicals) that existed in any significant
> quantities, like probably only one molecule of any such complicated
> species in the entire ocean at any time and then it breaks up and
> millions of years pass before one more molecule of the particular
> chemical species is by chance created again.

My chemistry isn't at your level.  I would have assumed that more than "very
simple chemicals" could be cooked up due to solar, volcanic (and vents),
lightning, impacts, etc.(?), and that this might possibly happen far more
often than once every few million years.  How sure are you of the facts you
imply in your para. (above)?

> I consider it unlikely
> that something "alive" in the full sense could spontaneously arise
> under such conditions. By comparison, a simple chemical replicator (a
> catalytic cycle/loop) has some reasonable chance of spontaneously
> arising in this complicated mix of Miller-Urey reactions going on all
> the time throughout the oceans but mostly near sources of concentrated
> energy. So my "bet" is on the simplest replicator as the first
> replicator, which would be a catalytic cycle/loop, as having the best
> chance of spontaneously coming into existance during the first several
> hundred million years of the Earth's (or Mars's) existance.
>
> > As stated before, very much *not* "life as we know it today".
>
> You previously said "I think that 2 rare, complex and overlapping
> events (replication, then life) are less likely than 1 (life, which
> learns how to replicate, as we know it did)."
>
> In that quote, you don't seem to define "life" to be anything which
> replicates,

No. Life replicates but not all that replicates is likely to be life (not
sure of your meaning).  And I specifically said that I think that there
could be chemical replicators.

[snip]
> By the way, I should have blatantly challenged your claim that we KNOW
> that life learned how to replicate. We know no such thing! What we do
> know is that life replicates. But we don't know whether replication was
> already happening before the stuff passed the threshold we'd accept for
> calling it "life" or not.

Agreed.

> My idea is that pre-metabolism, i.e. chains
> and webs of chemical reactions decaying from the high-energy input of
> volcanic vents or UV irradiated chemicals etc., came first, and then
> replication came next as one particular instance of such
> pre-metabolism, whereby I would now refer to it as metabolism without
> the qualifying prefix, and finally mutation and natural selection
> caused the replicators to evolve to what we'd accept as "life".
>
> > Well, the topic *is* OOL, not OOSOO (Origin of Something or Other).
> > So maybe we (well, you, really) need to start with a definition of
> > life (I'm comfortable with my internalized, personal version).  Else
> > it seems there's little point in discussing its origin.
>
> The qnswer to all such questions is a chain of events starting with
> abiotic chemistry and ending with life as we know it today. Depending
> on where you draw the line between non-life and life, the short answer
> to your specific OOL question is the one link in the chain that starts
> with the last point of pre-life and ends with the first point of
> true-life.

Agreed.

[snip]
>
> > I just don't think the replicator sounds too convincing
>
> You don't believe it remotely possible that over a time span of
> hundreds of millions of years, with Miller-Urey experiments going on
> constantly throughout the oceans of Earth and Mars, that sometime
> during all those experiments a simple chemical replicator, possibly a
> catalytic loop, with fecundity greater than one, might form by
> accident?

Well. you're repetitive.  But wrong again with your implied understanding of
my stance.  As I said, I think it is remotely possible.

> Or you don't belive that such a simple chemical replictor,
> once formed and exponetially grown to have so many copies that it
> persists indefinitely,

Yes, this is a big potential stumbling block, IMO.  Especially if we can't
make replicators (and I don't think that's yet been done).

> could then evolve within a few additinal hundred
> million years to fully genomic evolving life?

If it gets past the stumbling block, I think this is possible, but another
hurdle.

> Or you belive the
> accidental creation of a fully formed RNA replicator or other more
> lifelife replicator would happen sooner than a simple chemical
> replicator (that's absurd in my opinion!!)?

No.  As I said, something simpler is more likely (but unknown).

> Or you consider *all* the proposals
> for OOL to be so grossly improbable that you don't
> accept any of them even as just-so speculations?

No, I accept them all as speculations, but again, you talked like your
scenario was the the only one that should be even discussed and that it was
wrong-headed to think of other issues (e.g. that at some point T there was
likely no life on the planet, while at another point T', there was; when T'
> T was undefined).

Or what?

As I said, if I had to make a bet at this point, it'd be for panspermia
(extra solar system).  That is, if Mars is involved, it also was seeded from
outside.  I recognise that this only puts the OOL problem back to some other
planet, but I think life is pretty improbable and likely quite rare if it
has to emerge independently on "each" planet (where it exists).  But I will
say that your agruments (and Tom's and Richard Dawkins') are having an
affect and I'm far more ready to accept your scenario than I was a month
ago.  Thanks.  Regards, Brett.
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