Guy Hoelzer  wrote in
news:blciii$177j$1{at}darwin.ediacara.org: 

> in article blad15$l0b$1{at}darwin.ediacara.org, Anon. at
> bob.ohara{at}SPAMMERS.SOD.OFF.helsinki.fi wrote on 9/29/03 3:51 PM:
> 
>> Guy Hoelzer wrote:
>>> in article bl1v21$1fov$1{at}darwin.ediacara.org, Anon. at
>>> bob.ohara{at}helsinki.fi wrote on 9/26/03 11:03 AM:



I have to start out by thanking Guy for a nice explanation of why meiosis 
negates the gene as a unit of selection - this was present in an earlier 
follow on this thread but is no longer in the current follow - as it 
accords with my criticism of the Selfish Gene (Dawkins recognizes it 
himself in the book) that the selfish gene hypothesis cannot account for 
meiosis.

 
>>> IMHO, Dawkins presents the appearance of a logical argument, but his
>>> intensely subjective interpretation of the basic ideas is logically
>>> flawed. The terms he chooses to use, replicators and vehicles, are
>>> rhetorically loaded and help him to guide the focus of his followers
>>> to the gene as the foundation of the process and the individual as
>>> some sort of auxiliary construction of the genes when he provides no
>>> real basis for this sort of asymmetry.  On what basis does he think
>>> that replication can occur at one level (genes) while selection can
>>> occur at another (the individual)? 
>>> 
>> One could equally well turn the question around and ask why shouldn't
>> it.  Clearly DNA replicates, but with meiosis, not the whole strand,
>> so for sexual organisms the individual can't be the unit of
>> replication. Conversely, it's individuals who life and die (as a
>> unit), so in the main they are the units that selection acts upon.
> 
> I will attempt to answer your reflection of my question, but I want to
> be clear that I do not think that you began to answer the question on
> behalf of Dawkins' view.  The facts that DNA replicates and
> individuals live and die does not constitute a logic for selection
> acting as Dawkins claims.  I assert that there is no such logic, and I
> would like to see a substantive argument to the contrary if it exists.
> 
> OK.  Here is my quick answer to why it does not make sense.  I think
> the most concise way to explain it has been frequently argued by John
> Edser. [Note that I have always agreed with John on this aspect of his
> arguments, while disagreeing with other aspects.]  Individuals are not
> even close to merely the additive effects of genes.  They are emergent
> phenomena that result from many non-linear interactions among genes
> and between a developing individual and its external environment.  One
> of Dawkins' many hidden premises is that gene effects are additive,
> although I am sure that he would not admit or probably recognize that
> he makes this assumption.

Yes but one of the effects of stabilizing selection is that it tends to 
favor genes with "only" additive effects - they are compatible with a 
wide variety of other genes (especially in large populations) but confer 
specific benefits. (The analogy is to the desirability of medicines with 
no side effects - and yes I am aware that in practice these are few and 
far between) And actually Dawkins recognizes that genes have significant 
interactions with other genes - but this has not convinced him that he is 
wrong about the proper unit of selection.

 Gene copies do replicate with high fidelity,
> but their effects on individual phenotypes generally change from one
> individual to the next.  To the extent that the phenotypes of sexual
> individuals are heritable, genetics is only one of several mechanisms
> of heredity, albeit an important one.  When Dawkins writes about
> memes, he promotes the correct idea that high fidelity replication is
> not an important requirement for selection, and implicitly suggests
> that all mechanisms of inheritance that influence organismal 
> phenotypes can play roles in selection at the individual level.  These 
> mechanisms include maternal effects, training/learning, and control
> over environments during development (including the conditions of
> internal development during say pregnancy).  These factors, along with
> genetics, reflect varying degrees of effect in terms of individual
> phenotype heritability and variation in individual fitnesses; and none
> of them can logically be separated from the others as THE replicator
> on which individual selection relies.  Indeed, Darwin and Wallace did
> quite a good job of conceiving of how natural selection works without
> any knowledge of genes, because the process did not rely on the
> existence of underlying genes.  As Darwin said, it really only relied
> on heritability of fitness differences at the individual level.  The
> genes are merely a critical mechanism, along with a set of other
> mechanisms that can rise in importance in particular instances.
> 
> Because it is still rather inconceivable to me how natural selection
> can operate when the reproducing agents exist at a scale of
> organization different from that where fitness is manifested (others
> might prefer to word "evaluated" here), I hope that you (or anyone)
> can explain it to me.  I am not aware of any logical explanation being
> provided by Dawkins, and IMHO there is no such logic.

I fail to understand this last paragraph. Clearly reproducing agents, 
whatever their scale, are not the same as fitness agents. As you note 
above genotypes are influenced by environmental effects, but not all of 
these are heritable. Since the disconnect exists in any case, why does 
the scale matter? Evolution is constrained by the realities of DNA 
structure and function, even if that reality is not accurately depicted 
by the concept of "gene". So natural selection does operate with 
reproducing agents being different from selected agents, conceivability 
notwithstanding.

Yours,

Bill Morse
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