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From: alexis@reed.UUCP (Dimitriadis)
Newsgroups: net.bio,net.origins,net.philosophy,net.sci,net.sf-lovers
Subject: It doesn't take that much to self-reproduce
Message-ID: <696@reed.UUCP>
Date: Sun, 11-Nov-84 00:43:58 EST
Article-I.D.: reed.696
Posted: Sun Nov 11 00:43:58 1984
Date-Received: Tue, 13-Nov-84 00:43:39 EST
References: <241@hocsj.UUCP>
Organization: Reed College, Portland, Oregon
Lines: 50
Re: The missing step -- self-reproducing organisms


> That was my thinking up to this morning.  Now it strikes me that I have
> been glossing over a pretty complex step, one which is likely to have a
> lower probability than either of the ones mentioned above.  That is the
> step of going from something that is merely alive to a self-reproducing
> (SR) cell.  This, it seems to me, is the biggest step of the three.  It
> is one thing for the amino acids to form something that in some abstract
> sense is alive, it is quite another for this thing to be an SR organism.

    Actually, I think it is not a low-probability event at all.
Isolated DNA can self-replicate in the test tube. An organism would need
to feed itself in order to be (and stay) alive, wouldn't it? That means
assimilating matter from the outside. Thus it can also grow (by
assimilating more than it uses up). An incerase in size could cause a
primordial organism to fragment, much as a drop of oil will if shaken.
If there were enough copies of the genetic material in an organism
(and the restriction in the number of copies in higher organisms is no
doubt artificial) then all the pieces will probably get a full
complement of genetic material, QED. That is, a simple organism does not
need specialized structures for replicating.

    Of course, it sounds so simple because DNA does self-replicate.
That is probably why it is the "genetic material".

   The improbable event in the origination of life seems to be the
establishment of a functioning genetic code: The association of the DNA
with certain proteins that it "codes for", and which can "read" the
code, that is, produce the proteins coded for in the DNA.
(The process of transcription is enzyme-dependent, and enzymes are coded
for on the DNA).

   The improbable event is the origination of a self-maintaining
DNA-protein system. That may sound like what you had in mind to begin
with, but the production of molecules peculiar to an organism is a
fundamental part of being (and staying) "alive". I don't think I begged
the question.

    I should also mention that there is a difference between an event
like the origin of life and the evolution of intelligence. The origin of
life seems to have been a one-step, low-probability single event. (At
least, no one has come up with a multi-step mechanism for the crucial
part). Intelligence, on the other hand, is a product of evolution,
subject to the mechanisms of survival of the fittest etc. The one-step
origination of eyeballs would be hardly less improbable than the
one-step origin of intelligence.

                        Alexis Dimitriadis
                          alexis@reed

			  ...