On Wed, 1 Sep 2004 15:45:13 +0000 (UTC), 
Tim Tyler  wrote:
> Anon.  wrote or quoted:
> 
>> Criminality is social - is there really a gene for smoking in 
>> an Irish bar?
> 
> Definitely - according to conventional biological usage.
> 
> If you have any doubt about the matter, I refer you to the section
> on "genes for tying shoelaces" - in The Extended Phenotype - p.22.

Here's another point of view .....
 

  "So to biochemists, if not geneticists, there is no longer any
   gene 'for' eye colour. Instead there is a difference in the
   biochemical pathway that leads to brown and blue eyes, for
   in the latter one particular enzyme, which catalyses a chemical
   transformetion *en route* to the synthesis of the pigment, is
   lacking. So in blue-eyed people, the gene for this particular
   enzyme is either missing or non-functional for some reason.
   A gene 'for' blue eyes now has to be reinterpreted as meaning
   'one of more genes *in whose absence* the metabolic pathway
   that leads to pigmented eyes terminates at the blue-eye stage.'
   Similarly, the reason for the difference in colour between
   Mendel's yellow and green peas is that the yellow ones have 
   an extra enzyme in the metabolic pathway that leads to the
   breakdown of the green pigment chlorophyll. But this of course
   is just one of the many enzymes involved *en route* from the
   complex chlorophyll molecule to its end-products, to say 
   nothing of the sequence of enzyme-catalyzed reactions by which
   it is synthesized in the first place. This rephrasing yet 
   again exposes the distinction between a developmental and a
   genetic approach. For the developmental biologist, what is
   of interest is the orchestrated biochemical route that leads
   to pigmented eyes. The mutation or absence of particular 
   genes may help reveal that route ... but it is not of interest
   in itself; we are not dealing with one gene, one eye. But the
   geneticist is still interested in the difference between
   brown and blue eyes, yellow and green peas, and is still
   prepared to use the - misleading to the rest of the world and
   sometimes to geneticists themselves - shorthand of genes 'for'
   such colour differences.

   Of course, all biologists know that this is true, and that the 
   phrase 'genes for' is merely a convenient shorthand. Dawkins,
   in THE EXTENDED PHENOTYPE, explicitly makes the same point,
   before going on to discount it as irrelevant provided the
   system behaves *as if* such 'genes for' existed. That is, his
   genes are purely theoretical constructs, combinations of
   properties which may or may not be embedded in specific enzymes 
   or lengths of DNA, but which can be used to play mathematical 
   modelling games.

   You may think this doesn't matter, that to complain is merely
   pernickety pedantry on my part, but I assure you that it is
   not. Thinking of genes as individual units which determine 
   eye colour may not matter too much, but how about when they
   become 'gay genes' or 'schizophrenia genes' or 'agression
   genes'? Sloppy terminology abets sloppy thinking."


   Rose, S. (1998) Lifelines: Biology Beyond Determinism.
            Oxford University Press, p. 116


             -------------------------------------------

  "Complex organisms cannot be construed as the sum of their
   genes, nor do genes alone build particular items of anatomy
   or behavior by themselves. Most genes influence several aspects
   of anatomy and behavior - as they operate through complex
   interactions with other genes and their products, and with
   environmental factors both within and outside the developing
   organism. We fall into a deep error, not just a harmless
   oversimplification, when we speak of genes 'for' particular
   items of anatomy or behavior.

   No single gene determines even the most concrete example of
   my physical being, say the length of my right thumb. The very
   notion of a gene 'for' something as complex as 'intelligence'
   lapses into absurdity. We use the word *intelligence* to 
   describe an array of largely independent and socially defined
   mental attributes, not a quantity of a single something, 
   secreted by one gene, measurable as one number, and capable
   of arranging human diversity into one line ordered by relative
   mental growth.

   To cite one example of this fallacy, in 1996 scientists 
   reported the discovery of a gene for novelty-seeking behavior
   - generally regarded as a good thing. In 1997 another study
   detected a linkage between the same gene and a propensity for
   heroin addiction. Did the 'good' gene for enhanced exploration
   become the 'bad' gene for addictive tendencies? The biochemistry
   may be constant, but context and background matter."

   Gould, S.J. (2002) "The Without and Within of Smart Mice"
            in I HAVE LANDED, Harmony Books, New York  p. 234




Larry Moran
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