Re: Which Came First


"Tom Hendricks" <tomhendricks474@xxxxxx> wrote in message news:dp57d9$187q$1@xxxxxxxxxxxxxxxxxxxxxx
>
> > > It is not obvious. It's groundbreakingly original.
> >
> > I haven't the slightest Idea why you might say this. Honestly.
>
> I know and that's the problem.
> >
> > >
> > > Look at this quote from Lovelock. If you think what I have said is
> > > obvious
> > > then you will see how wrong this quote is:
> > >
> > > "At some early time organisms discovered how
> > > to tap the abundant and inexhaustible energy of
> > > sunlight to make their own food." (Ages of Gaia)
> > >
> > > If what I said was obvious, then no scientist would say anything like
> > > that quote.
> >
> > I don't see why not.
>
> And that's the whole problem. Lovelock is putting the energy source
> after replication not before.

I think that Tom is close to making an important point here, though I'm
not sure that it is quite as clear-cut as he thinks. Let me try to put
it into my own words.

Theories of the origin break pretty cleanly into heterotrophic theories
and autotrophic theories. Lovelock, in the quote, is pretty clearly
buying into the standard heterotrophic theory. Organisms arose in a
'soup' and lived by getting their carbon-carbon bonds and their energy
from pre-formed molecules. Pre-formed how? Well, from Miller-Urey
processes taking place in the atmosphere driven by the uv flux from
the sun. But once life got going, the 'soup' would be depleted pretty
fast, so, in an heterotrophic theory, life has to invent photosynthesis
pretty quickly - thereby getting its continuing energy needs directly
from the sun, rather than the original situation of getting energy
from the sun indirectly via Miller-Urey chemistry.

In an autotrophic theory such as Wachtershauser's, however, there is
no nutritious soup. Organisms get energy directly from a geochemical
source such as a vent, and they construct their own carbon-carbon
bonds. Sooner or later, these organisms too will invent photosynthesis
and shift their energy source from geochemistry to sun-driven photochemistry.

Tom's theory seems to be a hybrid. He is happy enough to get his
carbon-carbon bonds from a 'soup', as in a heterotrophic theory.
But he thinks that the energy supply must have come directly from
the sun from day one - not indirectly from the sun via Miller-Urey and
the soup. He has recently been promoting some interesting ideas in
which RNA strands act as light harvesting complexes and chromophores
in a primordial uv-driven kind of photosynthesis or photo-phosphorylation.
In a sense, he is saying that there was an 'autotrophic' origin for
energy, if not for carbon.

I am far from convinced, but I do like the idea that the first nucleic
acids (which I assume appeared long after the first 'life') were
involved in collecting uv energy. And, to someone who insists that
anything before RNA must be classified as prebiotic (because life=genetics
'by definition'), Tom's ideas are indeed 'groundbreakingly original'.
He is promoting a phototrophic origin theory, to compete with the
heterotrophic and autotrophic theories.

(Well, maybe not completely original. He did get his ideas about uv
photon collection by RNA from a published paper.)


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