From: rwallace@unix1.tcd.ie (russell wallace)
Subject: Re: trivial self-replication
Organization: Trinity College, Dublin
Distribution: sci
Date: Fri, 31 Jul 1992 05:11:54 GMT

In <1992Jul30.204712.278061@cs.cmu.edu> 18084TM@msu.edu (Tom) writes:


>>>Simple molecules in solution can reproduce
>>>themselves, given favorable conditions.  RNA, in particular, does this.
>>>Not well, and not quickly, by itself... but it does do it.

>>Again, if it is replicating by itself, it is performing *trivial*
>>self-reproduction, because it is not carrying any genetic information.

>So what if it isn't carrying genetic information?  Self-replication is
>self-replication.  Evolution will favor more complex forms, and eventually
>it won't be 'trivial' anymore.  BTW, what is the definition of 'trivial'
>in this context?  And no, evolution does not require DNA.  In this context
>(usually called chemical evolution) it is just the process by which those
>structures that replicate (whether 'trivially' or not) come to dominate.

Basically the problem with not having genetic information is that that
chemical substance which tends to form most easily and be most
persistent will certainly come to be the most abundant, but unless it
has a blueprint for its own construction, which can be mutated to create
a more complex version of the substance, this is a dead end. This is why
reproduction without genetic information is termed "trivial".

>>If the only machinery required is the stuff floating around all over the
>>place (free amino acids etc.) then you have trivial self-reproduction
>>which does not count, because even if RNA can replicate in this context,
>>it is trivial self-reproduction because the RNA does not have or need
>>any genetic information.

>By what standards are you deciding that it 'doesn't count'?  If it can be
>demonstrated (as I think it has, both in my own studies and in the
>synopses offered here of late) that life processes can arise on their
>own, without the infamous hidden watchmaker, or without the improbable
>'protien of the Ninth Configuration', then what exactly, does 'not
>counting' mean?  That we aren't here?  Ps- it's been mentioned already,
>but RNA doesn't need genetic material, because it IS genetic material.
>If we could talk to a piece of DNA, it might say that we existed for IT.

Well, by "not counting", I meant that that wouldn't get you any closer
to cracking the key problem, of forming something capable of non-trivial
self-reproduction (see above for the reason why you need non-trivial
self-reproduction).

However, it has been suggested that a strand of RNA can act as an
enzyme, its activity being determined by the sequence of bases; and that
as such it can moderate its own replication, and produce protein enzymes
which can assist with this process. If it could work, this would seem
the most promising way to solve the problem, because then the RNA
strand would be doubling as blueprint AND machinery, thereby solving the
problem of requiring the two to form together. Does anyone know exactly
how far the research on this has got (i.e. what capabilities of RNA in
this area have been demonstrated)?

>Aaaaand, as long as you have such a great handle on the defintion of life...

>1)  Are viruses alive?  They reproduce non-trivially (by what I can get
>    of your defintion from context)

A virus by itself is not alive because it does not reproduce
non-trivially or indeed at all (it has the blueprint, but lacks most of
the machinery). I would be inclined to say that a virus is somewhat akin
to a computer virus, having a sort of pseudo-life.

>2)  If humans built self-sufficient space colonies, would it mean that
>     Gaia (the entire biosphere) had reproduced?  Evolved?

>3)  Is human culture, as a whole, an organism?  It feeds, makes wastes,
>    evolves, etc...

Hmmm... these are interesting questions :-). I think proponents of the
Gaia hypothesis would say yes to 2), perhaps with some justification;
and there's a book a read a while ago called "Bionomics" in which the
author draws parallels between human culture and an ecosystem; which
would seem to be an argument in favour of 3).

--
"To summarize the summary of the summary: people are a problem"
Russell Wallace, Trinity College, Dublin
rwallace@unix1.tcd.ie