William Morse  wrote in message
news:...
> "Anon."  wrote in news:bg3ev9$19l5$1
> {at}darwin.ediacara.org:
> 
> > Jim McGinn wrote:
> >> 
> >> Guy Hoelzer  wrote
> >> 
> >> 
> >> 
> >> > Finite samples of variable populations, such as all
> >> > real populations, tend to have different proportions
> >> > than the source population.
> >> 
> >> Agreed.  (Have I ever disputed this?)
> >> 
> >> > This is, of course, what we mean by the process of
> >> > genetic drift.
> >> 
> >> Now explain how this is, supposedly, distinct from
> >> the process of NS.  (Or are you arguing that since you
> >> mean it to be GD that, therefore, it's not NS?)
> >> 
> > With drift, the expectation of the frequency is equal to the current
> > frequency.  In less technical terms, this mens that if you had a large
> > (=infinite) number of identical populations, each one with an allele at
> > frequency p, then in later generations, they would all have different
> > frequencies of the allele (due to drift), but the mean of the
> > frequencies would be p.
> > 
> > If you have selection, then the mean of the frequencies would not be
> > equal to p.
> > 
> > Oh, and if we know enough about the properties of the populations, then
> > we can calculate the variance in the frequencies too.
> 
> Thanks for one of the cleanest explanations of drift I have yet seen. 
> It's funny how sometimes shifting a viewpoint (in this case from 
> organisms to statistics) can help clarify an idea.

It would be cleaner still if he invoked God as the 
cause.

> 
> 
> Yours,
> 
> Bill Morse
> 
> (I don't think it will help with Jim, who resolutely refuses to accept 
> the premise that things can happen by chance.)

I do accept that things can happen by chance.  But 
I reject the supposition that things can happen 
because of chance.

[moderator's note: I think this is the crux, Jim: what's the
difference between "happening by chance" and "happening because
of chance"? In words, I mean? - JAH]


Jim
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