Inman Harvey  wrote or quoted:
> Tim Tyler wrote:
> > Tim Tyler  wrote or quoted:

> >>I observe that there are some simple factual errors in:
> >>
> >>''The Information Challenge''
> >>
> >>http://tinyurl.com/4eqbh
> >>
> >>This bit:
> >>
> >>``Mutation is not an increase in true information content, rather the
> >>  reverse, for mutation, in the Shannon analogy, contributes
to increasing
> >>  the prior uncertainty.''
> >>
> >>...is not correct.  Mutation typically *increases* the
information in the 
> >>genome, by increasing its suprise value.
> > 
> > I'm suprised - and rather disappointed - to
> > find that several of you are defending Dawkins :-(
> > 
> > To attempt to summarise your main criticisms:
> > 
> 
> > * Adopting the correct observer's position is critical
> >   when measuring information.  The correct observer in
> >   this case is the gene pool itself [Inman].
> 
> No, this is a totally misleading reading of what I said. I gave the 
> example of the sports report on a crackly radio with the sports fan 
> (scores is the information wanted, crackles are noise) and the 
> meteorologist (crackles from lightning is the information wanted, score 
> reports are noise) to emphasise that there is *NOT* "A SINGLE correct 
> observer", there are many possible equally correct observers with 
> different interests. To avoid ambiguity you need to specify which one 
> you are referring to.
> 
> (D) For the most part, Dawkins makes it clear he refers to something 
> like (metaphorically) someone overseeing the gene pool of a species and 
> uncertain about what information is needed to specify fitter 
> individuals. In this context, rounds of Natural Selection do indeed 
> provide this information.

He talks about "information in the genome" and about "information in
the body" - which he claims is a better metric.

The only place I can see him talking about the information needed
to provide fitter individuals is in the section:

``If natural selection feeds information into gene pools, what is the 
  information about? It is about how to survive. Strictly it is about
  how to survive and reproduce, in the conditions that prevailed when 
  previous generations were alive.''

I don't really have any problem with this section.

My criticism is that Dawkins portrayal of mutation is the reverse of the 
truth.  Mutation adds information during the process of evoultion.  It 
qualifies as both "information in the genome" and about
"information in 
the body" - the sorts of information goes to some length to 
describe - and are what he seems to be talking about.

Dawkins - totally incorrectly - characterises mutation as decreasing 
information during the evolutionary process.

>   However, the *main* role
> > in evolution - as far as making changes
> > to the information content of genomes goes
> > has simply *got* to be given to random events.
> > 
> > Mutation *totally* swamps natural selection
> > in terms of introduced information content
> > by just about every metric I can imagine.
> 
> No! Mutation *provides* the variation, Natural Selection *chooses* from 
> the available variation, and in doing so provides information to the 
> gene pool (under perspective (D).
> 
> In the game of Twenty Questions, if I ask you "Is it an animal with more 
> than 4 legs?" and you answer Yes or No, then it is I who provides the 
> variation to choose from, and you who does the choosing. You provide the 
> information, not me. Natural Selection provides the information, not 
> mutation.

In *that* game the possible answers are only yes and no - and the
question itself provides no information.

That is certainly not true in evolution - there mutation does not
generate all the possible alternatives and ask natural selection to
choose between them.  Instead it generates a tiny subset of the
available possibilities and asks natural selection to choose between
what it does offer.  In doing so, it mutation provides information to
the evolutionary process.  The exact mutations available affect
the whole course of the evolutionary process.

I would claim that such information is more voluminous - in terms
of bits - than the information added by natural selection.

This is obviously true if you consider the organism's genome - but
I reckon this is still true even if you ignore all mutations that
don't contribute to the phenotype - and instead just consider the
ones that actually affect the organism's gene expression profile -
what Dawkins refers to as "information in the body" (which is
what Dawkins *says* he is talking about).

Mutation dosen't /just/ provide variation to the evolutionary
process.  It itself provides information - the information
about which mutations and (combinations of mutations) were
tried in the first place.

To view variation as not providing information, and natural
selection as giving information by choosing among the
available variation misses out the whole process whereby
mutations themselves provide information - by failing
to occur uniformly.

Dawkins writes:

``Mutation is not an increase in true information content, rather
  the reverse, for mutation, in the Shannon analogy, contributes to 
  increasing the prior uncertainty.''

It's simply not correct.  *Before* an observer witnesses the mutations 
they have no idea which mutations were going to arise.  *After* seeing
the mutations they know which mutations actually *did* arise.

So: witnessing the mutations results in an *increase* in their
knowledge, a transmission of information to them - and a *decrease* of 
the observer's uncertainty - not an *increase* of it as Richard claims.

The fact that Dawkins says "true information content" makes no
difference - since he defines "true information content" to
be what remains after redundancies in the data have been
squeezed out.

This problem of mis-conceiving the role of mutation in evolution
does seem quite in line with Dawkins playing up the role an importance
of natural selection - and minimizing the significance of random
processes (such as drift) in evolution.

However, when talking about the information content of genomes,
there's no getting away from the very large significance of
chance processes - and claiming that mutations decrease - rather
than increase - information in the genome is just plain wrong.

I would not say natural selection's effect was to increase
the information content of the genome either.  Most of the
time natural selection spends its time weeding out deleterious
mutations.  It is *destroying* information introduced by mutations.

The rare bits of information it adds are rare by comparison with all the 
information loss associated with deleterious mutations which it destroys.

So - from this perspective - Dawkins has it wrong on both counts:

He claims mutations decrease information - they actually increase it;

He claims that natural selection adds information - which is true -
but it destroys a *lot* more information than it adds - since it spents
most of its "quota of death" destroying information added to unfit 
individuals by mutation - so the net effect of natural selection on 
information content in genomes should normally be portrayed as being 
negative.
-- 
__________
 |im |yler  http://timtyler.org/  tim{at}tt1lock.org  Remove lock to reply.
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