Re: On influencing factors

Fri, 6 Nov 1998 15:56:30 -0500 (EST)

Subject: Re: On influencing factors
Date: Fri, 6 Nov 1998 15:56:30 -0500 (EST)

Mark was thinking about analogies between signal transduction
between cells, and signalling between individuals.

I replied:

> I'm not sure that signal transduction research can tell us
> >much that would be applicable to memetics.

and Mark responded:

> Perhaps there is more than meets the eye. Memes are often described as
> 'units of imitation.' Imitation is a form of signal transduction.

Signal transduction has a very specific meaning in molecular
biology. It describes the processes by which ligands bind to
receptors, how those receptors change conformation upon ligand
binding, how SH2 domain proteins are activated, how G proteins are
activated, how MAP kinase cascades are then switched on etc. I
could go on at length (in fact I go on for precisely 14 hours of
lectures most years).

So I can't swallow the analogy that imitation is a form of signal

> I
> don't think it a huge jump to suggest DNA is involved in signal
> transduction and hence imitation, too.

Well all the signal transduction proteins are gene products which
themselves have to be transcribed in response to other signal
transducion pathways etc.

> Does a suggestion that DNA is involved in imitation at the
> microbiological level seem reasonable?

Well, I'd say there is no imitation at the microbiological level.
Imitation is a highly specific subset of social learning which is
confined to humans, birds and possibly dolphins (maybe chimps
too). I don't see that we can stretch the definition of imitation
to more than that without dislocating ourselves from the
mainstream of psychology.

> Genetics involves DNA sequences planted in a sugar
> substrate. Memetics involves neural tissue. In both cases, we are
> interested in signal transduction.

No again you can't say this because you are misusing terminiology
which has a highly specific meaning in biology. If you read that
book by Hancock that I mentioned in a previous post, you'll get
some idea of what signal transduction is.

> I'm puzzled by your use of the term 'genetic blueprint.' The notion of
> 'blueprint' implies the existence of a self contained plan. It's a
> Platonic notion and easy to understand. I thought the Darwinian
> revolution dismantled this paradigm, though.

Is it Platonic? I'll need to think about that. It's certainly a
common colloquialism among geneticists. Hmmm......

> The notion of 'ball and groove' model fits the Darwinian paradigm better
> than 'blueprint.'

Yes, on reflection I agree entirely here.

> There is no particular
> plan to the set of grooves.

Ah, but yes there is, and it's quite rigid.

> Reproduction randomly rearranges the grooves for each new generation.

No, any rearrangement will be minor. Only very long periods of
evolutionary time will rearrange the grooves. For instance, one
of the startling things that molecular embryology has revealed is
that the same basic blueprint/groove set is used by almost all
metazoans. It's called the phylotype. See "The zootype and the
phylotypic stage" a classic Nature article by Slack and Graham
around 1992 (sorry, not in office so don't have it to hand).
Back in 1989, Robb Krumlauf at MRC in London and Denis Duboule in
France were investigating the expression of homoeobox genes in
mice and simultaneously realised that the order of expression of
these genes was the same in mammals as it is in flies. I
vividly remember the sound of jaws dropping as we viewed that
months copy of Cell.

> Each groove is catalytic, providing a lower energy path for chemical
> processes.

No, don't press the analogy. It's just an aid to
conceptualisation. The metabolic energy theories of embryogenesis
went out in the late 60s.


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