From: dsiebert@icaen.uiowa.edu (Doug Siebert)
Newsgroups: sci.nanotech
Subject: Re: Evolution and nanotech
Date: 28 Aug 92 01:32:02 GMT
Organization: ISCA

In article <Aug.26.21.59.27.1992.1069@planchet.rutgers.edu> JoSH writes:
>
>[Rats.  I thought I had a paper by Drexler addressing this subject
> in that directory, and it's not there.  I gave you a bum steer.
> I will send you a copy as soon as I find it.  The "understanding"
> I'm speaking of is from CS, genetic algorithms in particular.
> Early researchers found, not surprizingly, that making small 
> random changes in computer programs almost always caused them 
> simply not to work.  The probability of getting from one 
> working program to another working program is no better than 
> arriving at the second program in one fell swoop from alphabet
> soup.  Evolution doesn't work that way.  It works when small
> changes in structure produce small changes in system performance,
> as in the "classifier systems" that G.A. research actually uses.
> These have many higher-level cognates in biological systems, 
> including diffusive transport, pattern (shape) directed control
> of primitive operations, and so forth.
> --JoSH]

I don't think the comparison you make is valid.  I don't think that a genetic
mutation corresponds to changing a computer program, but rather a change in
the memory of a computer somewhere.  Many genetic changes are essentially
"random" and don't increase an organism's chances for survival.  They might
look different, in color or form, for instance, but act (i.e., are programmed)
the same.

And many programs WILL work correctly if you change a random bit or byte of
data somewhere in the computer.  Some will have no effect at all, some will
make only cosmetic changes, (maybe it prints "Hell{ world!" instead of "Hello
world!") some will cause them to not work (changing an instruction to an
illegal instruction) but some can have a profound effect on the operation of
a program.  What if a loop is interated 5 times instead of 50, or 500 times
instead of 50?  Or is skipped when it otherwise wouldn't be?  What if the
direction of a branch operation is reversed?  There's a big difference between
changing a line of source code and changing a memory value in an actual
(compiled/assembled) product.  I suspect Drexler was thinking more along the
lines of changing source code, which I don't see as correct.

And making a change to the memory while a program is running can have further
effects, and parallels some changes in nature which occur before an organism
is fully developed.  Such as a mother taking some kind of drug that causes a
problem with her infant's development to be altered in some way.  While not an
actual genetic mutation, it can seriously alter the way that single organism
works.

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[Minor damage to mechanisms happens all the time, and does indeed change
 their appearance and degrade their functionality.  However you will never
 find a car that has accumulated enough dings and scratches to convert
 it into a piano.  Evolution requires a *long* sequence of cumulative
 changes, and and needs a fairly complex structure in the evolving
 organism to support it (including sex).
 On the other hand, the equivalent of genetic damage, causing perhaps
 the sort of problem Ian originally mentioned (i.e. suppressing the
 useful function of a self-replicating device) could certainly happen.
 However, it would not lead to evolution.  It would be more like cancer
 in the (self-reproducing) cells of an individual organism.  
 It is a useful avenue of discussion to explore methods of preventing
 this; but don't confuse it with evolution.  It isn't.
 --JoSH]