Re: Kin Selection contradiction?

From: Jim Menegay (jimmenegay_at_sbcglobal.net)
Date: 06/15/04 

Date: Tue, 15 Jun 2004 18:31:06 +0000 (UTC)

Tim Tyler <tim@tt1lock.org> wrote in message news:<cakk2v$dod$1@darwin.ediacara.org>...
> Name And Address Supplied <name_and_address_supplied@hotmail.com> wrote or quoted:
> > Tim Tyler <tim@tt1lock.org> wrote in message news:<cag108$259q$1@darwin.ediacara.org>...
>
> > > Normally most members of the population are not close relatives - and
> > > there's no powerful selective force making non-relatves evolve identical
> > > genes as one another[*], and segregation distorters normally have a low
> > > frequency in the population - and often only affect one chromosome.
> > >
> > > [*] I.e. in practice, identical genes means that the genes are identical
> > > by descent - them being identical by chance or selection would both be
> > > fantastically unlikely occurrences.
> >
> > Can I jump in and say that, if I have understand what you mean by
> > "identical by chance", then I would definitely not agree with the
> > above statement for all cases in which the allele in question is not
> > vanishingly rare in the population.
>
> If an allele is common in a population, then basically, it must have
> got that way by inheritance from a common ancestor - i.e. the reason it is
> shared is due to shared descent.
>
> The other possibilities for such circumstances arising are so unlikely
> as to be hardly worth considering.

Tim. There is a subtlety here that you are missing, and I believe
that it may be what NAS is disturbed about.

I agree that a fixed or common allele arose (in the sense of formal
cause) from a single mutation which happened once in some remote
common ancestor of the current population. However, there is more
to be explained here than just the formal cause. After all, the
current population shares many remote common ancestors - what is
the explanation of why that one allele instance became common, whereas
the other allele instances of the remote past have mostly become
extinct? Clearly it happened due to either selection or drift
(in the sense of efficient cause) - and those are the two things
that you said were "fantastically unlikely occurrences".

I doubt that you are confused about this, but I think that you
were carelessly unclear, at the very least.

It is also important to note that formal cause IBD, as described
above, is not the kind of IBD we need for Hamilton's rule! You
MAY have been confused about this point, many people apparently
are.

Relevant Pages

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