Re: Hamilton's Nonsense
From: Perplexed in Peoria (jimmenegay_at_sbcglobal.net)
Date: 12/29/04
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Date: Wed, 29 Dec 2004 02:45:15 +0000 (UTC)
"Tim Tyler" <tim@tt1lock.org> wrote in message news:cqs2lm$31ht$1@darwin.ediacara.org...
> Jim McGinn <jimmcginn@yahoo.com> wrote or quoted:
> > Perplexed in Peoria wrote:
> > > "Jim McGinn" <jimmcginn@yahoo.com> wrote
>
> > > > Does IBD actually measure relatedness
> > > > or is it, as I indicate, a vague abstraction that
> > > > is only peripherally indicative of relatedness?
> > > > [snip]
> > >
> > > This question seems to be at the heart of your misunderstanding,
> > > so I will try to address it.
> > >
> > > Short answer:
> > > What "really" matters is how frequently the recipient of altruism
> > > carries the gene for altruism, as compared to non-recipients.
> >
> > There is no one gene for altruism. As with any and all
> > traits/behaviors there are many genes that determine their phenotype.
> > All members of any population will share over 99% of an such genes.
> > Consequently this notion that there is one gene for altruism is an
> > idiotic notion that has nothing to do with biological reality.
>
> Before jumping to the conclusion that "Perplexed in Peoria" is spouting
> idiocy, you might want to re-examine the possibility that you didn't
> properly understand what he meant.
>
> The accusation that "no one gene codes for any particular trait" is one I
> frequently encounter. However - AFAICS - it is almost never justified.
> In fact it is usually pretty patronising.
In fact, "Perplexed in Peoria" quite clearly IS an idiot, as
evidenced by the fact that he keeps trying to communicate with
McGinn. A wise man would tell McGinn to read a textbook and then
would keep his mouth shut thereafter.
One of the advantages of a textbook is that shorthand language such
as "gene for ..." is either avoided or justified. And the language
can be justified - it just takes some effort - effort that is not
usually taken in sbe.
Naively (I like that word, "naive"!), there are three problems with
"gene for ..." language.
1. "Gene" is ambiguous. Properly, one should talk of alleles or loci.
2. Epistasis. There may be many "genes" contributing to a trait.
Hence, as McGinn indicates, there are many "genes for altruism".
3. Pleiotropy. Any "gene" contributes to many traits. Hence, no
gene is exclusively "for" altruism.
Nevertheless, in order to get to the situation that McGinn describes,
in which "all members of any population will share over 99% of any
such genes", those genes had to increase in frequency at some point.
Each and every one of those genes had to increase in frequency. So
let us focus on just one of those genes and inquire why it increased
in frequency. That gene is arguably "a gene for altruism", and after
we have selected it as the focal gene, we can call it "the gene for
altruism".
In principle, thinking of this sort - ignoring epistasis and pleiotropy -
can be traced back to Fisher. The arguments justifying this kind
of thinking are completely spelled out in the textbooks. Those of
us who have read the textbooks sometimes forget that not everybody
has had our advantages.
Of course, you can avoid all of the arguments regarding the justification
of genetic models by taking the high road of a direct proof of
Hamilton's rule at the quantitative trait level - starting perhaps
from the Price equation. Unfortunately, though, this doesn't answer
McGinn's questions regarding the relationship between IBD and
"relatedness".
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