Text 1048, 71 rader
Skriven 2004-12-16 12:30:00 av Perplexed In Peoria (1:278/230)
Ärende: Re: Biochemical evolution
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"Maarten D. de Jong" <this.address@is.invalid> wrote in message
news:cppsj3$2qbq$1@darwin.ediacara.org...
> During a discussion about primitive forms of life, someone popped the ques-
> tion why there is so little biochemical variation around. His argument ran
> that most life on Earth has some form of DNA or RNA inside it, and that there
> is little evidence for anything more primitive. He then proceeded to say that
> regular biological evolution breaks down at the biochemical level, and that
> you would need a different theory (but not any form of creationism, he was
> quite emphatic about that) in order to explain all sorts of basic biological
> structures, like for example DNA.
>
> My first reaction was to dismiss the idea entirely, despite the fact I am
> not a biochemist. Nevertheless, I decided to hunt around if I could find some
> information on this particular subject. But most hits Google turns up
> (including those of the much more limited scholar's edition) are poisoned
> with creationism, and the library at my university does not have the
necessary
> literature for a biochemical search.
>
> Is there any truth to what this person claims? Any links to informative
> articles would be most appreciated. (I vaguely recall that a recent edition
> of the New Scientist featured an article about a quantummechanical spark of
> sorts to begin it all, but I don't have the print edition at hand. Something
> like that.)

If what your friend was saying is that Darwin's theory of evolution by
natural selection does not and can not explain the origin of life, then
he is obviously correct, IMHO.  Darwin's theory begins with the assumption
that we already have life-forms capable of reproducing themselves.  We need
a different theory to explain how reproducing organisms (with heritible
variation) came to exist.

Now if what he is saying is that we need new theoretical principles comparable
in profundity to Darwin's NS, then, well, the jury is still out on that.
The issue is how to account for the "progress" that evolving quasi-life
made in becoming suitable for true Darwinian evolution.

There are basically three possibilities:
(1).  If genetics arose early and easily, as in the theory of Cairns-Smith,
then no new principles are needed.  Just some clever ideas, most of which
Cairns-Smith has already provided.  Personally, though, I find this idea
unconvincing.
(2).  There may have been some not-yet-appreciated self-organization principle
at work.  Perhaps it was based on non-equilibrium thermodynamics as the
Brussels school proclaims.  Or perhaps it is based on complex systems
theory as Stuart Kauffman seems to think.  Again, I am unconvinced.
(3).  Or perhaps there is no over-arching principle to explain the apparent
"progress".  Perhaps life arose "by accident" or as a result of a series of
accidents.  This idea is unsatisfying to the scientifically inclined, but,
IMHO, it is probably correct.  (Yes, Mr. Hendricks, I know you disagree.)

But regardless of what "drove" the origin of life, we still have to work out
the path that was followed.  And until we have a theory that describes that
path in detail, and draws on supporting evidence ("molecular fossils") in
present-day life, then no one's opinion is going to convince anybody.

The origin is a tough problem, and an unsolved problem.  Francis Crick, a
fairly militant atheist, is quoted to the effect that the problems with a
mechanistic origin are so great that an honest man would have to say that
it would almost require a miracle.  I think that is still true today.  But
I expect that the problem will be solved sometime during this century.
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