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:

* Dawkins is actually talking about the DNA
  content of a species - not an individual -
  and that rescues his argument. (Jim)

* Mutation (meaningless error) quite obviously
  decreases the "true information content" of
  the program, to use Dawkins' phrase. (Wirt)

* Mutations are mostly in junk DNA - and Dawkins
  says he is only attempting to describe the
  information content in the "meaningful" section
  of the genome [Inman].

* Adopting the correct observer's position is critical
  when measuring information.  The correct observer in
  this case is the gene pool itself [Inman].

In turn:

* Whether Dawkins is talking about species or
  individuals is totally irrelevant.  Either way,
  mutations add large volumes of information to the
  genetic message, and natural selection (mostly)
  removes it again.
  
* Wirt appears to have missed Dawkins definition of 
  "true information content".  Dawkins clearly states in
  his essay: "The true information content is what's
  left when the redundancy has been compressed out of
  the message, by the theoretical equivalent of Stuffit."
  I.e. he is talking about Chaitin-style information
  content at that point.  Mutation certainly *increases*
  this information content - by introducting random
  noise into the message - and making it less compressible.

* Inman is correct to point out that Dawkins deliberately
  confines his attention to the functional region of
  the genome.  However *even* there I claim that it
  is mutations that are primarily responsible for
  increasing the information content of the genome.

* Inman's criticism that the correct observer is the
  gene pool seems to make little sense to me.  Gene
  pools are not observers - unless you get into some 
  rather strange and twisted metaphors.

  The whole point of Dawkins' essay is that
  he is addressing the question of whether
  evolutionary processes can increase the
  information in the genome.
  
  The observer in that case has surely got to be
  an *external* observer, examining the genome
  and measuring its information content.

To give some more technical details of why
I think Dawkins is saying something which
is basically wrong - or at least _very_
misleading in this essay:

Basically I agree with Larry Moran - that
genetic drift and random mutation are
the main forces in evolution as far as
molecular evolution go - and when
talking about the information content
of the genome, that has realisitically
*got* to be the perspective you take.

I don't dispute that natural selection
transfers *some* information - about how
to survive - from the environment to
the genome.  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.

Natural selection removes whole individuals
from the population, destroying *all* the
information represented my the chance events
that occurred during meiosis and any mutations
or other information that has accumulated
in them since they were born.

What information does an individual death
add?  At the very *maximum* it adds the
information required to identify that
individual in the population.  That
can typically be a number between 1
and the size of the population, assuming
the population is ordered by birth date.

There is no way this latter volume of
information can possibly compete with
all the information lost during the
destruction of an individual.

The lost information doesn't just
include mutations.  It includes
details of where recombination events
occurred during meiosis.  The death
of an individual represents a *gigantic*
loss of information, combined with a
*miniscule* information gain.

For Dawkins to therefore claim that
it is natural selection that adds
information to the genome - and that
mutation (if anything) *reduces* it
is so *hugely* far of the mark that
the reality inversion field surrounding
these comments needs pointing out.

There can be no dispute that contingent
events totally dwarf natural selection
when considering raw DNA sequences.

There can be very little doubt that contingent
events massively dominate natural selection
when considering non-junk DNA (one base
pair in three is nearly neutral).

Dawkins gets into special pleading - 
by attempting to further minimise the
effect of mutations on the information
content of the genome - by asking us to
consider only mutations that have an 
effect on the phenotype.

However, *even* in that domain, mutation
is *bound* to add many more bits of
information to the genome than natural
selection does.

Overwhelmingly, natural selection's role
is that of *destroyer* of information.
Its primary action is destroying whole
genomes full of large volumes of information
added by meiosis and subsequent mutations.
The information it adds is piddling - both
by comparison with what it destroys, and
by comparison with the information added
by mutations.

In my book, Dawkins cannot be allowed to get
away with perpetrating this sort of gross
distortion.

It totally mis-states the relative effects
of natural selection and mutaton on the
information content of genomes.

We'll wind up with the next generation
believing mutation destroys information
and natural selection adds it in (pretty
much an exact inversion of what's really
going on).

Organisms are mostly *accidents*. If one
is asked to describe them (to practically
any level of detail) the accidental
outweighs the functional many to one.

This is *especially* true when discussing
the information content of their genomes -
since there are a fantastically huge number
of ways of writing what is basically
functionally the same program.
-- 
__________
 |im |yler  http://timtyler.org/  tim{at}tt1lock.org  Remove lock to reply.
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