From newshub.ccs.yorku.ca!torn!cs.utexas.edu!sdd.hp.com!ux1.cso.uiuc.edu!mp.cs.niu.edu!rickert Wed Aug 12 16:52:23 EDT 1992
Article 6560 of comp.ai.philosophy:
Newsgroups: comp.ai.philosophy
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>From: rickert@mp.cs.niu.edu (Neil Rickert)
Subject: Re: Memory and store/retrieve.
Message-ID: <1992Aug4.165958.17775@mp.cs.niu.edu>
Organization: Northern Illinois University
References: <1992Aug3.151610.21034@puma.ATL.GE.COM> <1992Aug3.200351.3632@mp.cs.niu.edu> <1992Aug3.220654.20920@beaver.cs.washington.edu>
Date: Tue, 4 Aug 1992 16:59:58 GMT
Lines: 89

In article <1992Aug3.220654.20920@beaver.cs.washington.edu> pauld@cs.washington.edu (Paul Barton-Davis) writes:
>
>I'm a little troubled by some of the appeals to evolution I've seen
>appearing in this thread.

  I guess that's me you are questioning.

  I've avoided giving detailed explanation of my assumptions on evolution,
and have used rather simplistic language in describing them, because I
sense that most readers of this group are more concerned about the issues
relating to intelligence.

>	1) there still is no good consensus on the neutrality of
>	   most mutations. I have been quite suprised to find 
>           a dearth of simulations for this; although there are
>           plenty of theoretical position papers, my searches so
>           far have not shown up anyone who has actually demonsrated
>           that for mutations to persist, they must be beneficial.

  I don't believe anybody even claims that to be true.  Harmful mutations
will tend to die out, or at best persist at a very low level set by the
rate of new mutations.  Neutral mutations will tend to just become part
of the genetic diversity of the species.

>	   For my part, I actually wrote a small test program to
>           try this out. Its appalling simple, but it confirmed my
>           own intuition - mutations that affect reproductive fitness
>           have to have a *very* dramatic effect in order to affect
>           their own (rather then a system of which they later become
>           a part) survival, in the presence of environmental 
>           noise (weather, predators, disease, etc.)

  I'm not sure what is your definition of "*very* dramatic".  Evolution
takes place over very long periods of time, so that even very small
statistical advantages can have effects.  I believe there are plenty of
natural experiments which demonstrate that beneficial traits will tend
to persist at levels higher than could be explained by their mutation
rate.

  However, all this is beside the point.  You are raising the question
"if a genetic change is beneficial, what is the probability that this
change will result in evolution toward a new species?".  I suspect the
answer is that the probability is very low.  But this is not the important
question.  You should be asking "what is the conditional probability,
given that evolution did occur, that the genetic change involved was
beneficial?"  This is a quite different question with surely a much
higher probability, although the probability is still likely to be less
than 1.  Yet even this is not the question of importance for my
assumptions.

  Here, then, are my assumptions:

  It is generally agreed that intelligence has evolved, and that it is
beneficial.  I admit the possibility that perhaps intelligence is not
beneficial at all, and it is due to mere homocentric hubris that we
assume that there is a benefit - but I intend ignoring this extreme
view.

  I am assuming that most genetic changes are simple.  Of course a simple
change can sometimes have a dramatic effect, as when a slight change in
a growth hormone might have an enormous effect on body size.  But small
changes are unlikely to result in the development of complex new
structures.

  Now if we look at the evolution of intelligence, say from primitive
fish through primates, we seem to have two possible explanations:

   (a)  There were many small genetic changes, most of which were
	beneficial to the species.

   (b)  There were many small changes most of which had little
	beneficial effects, but by random luck just happened to contribute
	toward development of a highly complex intelligence structure.
	Finally, at later stages all the parts fell together and the
	combination suddenly became highly beneficial.

  Personally I find (b) highly implausible, and (a) quite plausible.
This plausibility argument is all I am depending on.  I don't claim this
proves anything.  We will prove something only when we either fully
understand the workings of the brain, or we have truly been able to
mechanically replicate human-like intelligence, or preferably both.
Think of my plausibility argument as an intuition pump to suggest
direction of further investigation, and as an attempt to reduce the
tendency toward over-reliance on introspection.

  Certainly the above plausibility argument is an atheistic view.  If
you believe in the existence of a God guiding evolution, then (b) might
become quite plausible.



