Guy Hoelzer  wrote:

> in article bc39e6$nqs$1{at}darwin.ediacara.org, John Wilkins at
> wilkins{at}wehi.edu.au wrote on 6/9/03 5:40 PM:
> 
> > Donald Forsdyke  wrote:
> > 
> >> "Michael Ragland"  wrote
in message
> >> news:bbt56n$1sor$1{at}darwin.ediacara.org...
> >>> 
> >>> Random Genetic Drift
> >>> Copyright © 1993-1997 by Laurence Moran
> >>> [Last Update: January 22, 1993]
> >>> 
> >>> [moderator's note: I hope Larry doesn't mind the inclusion of his
> >>> entire (and copyrighted) document; Mr. Ragland's comments are, as
> >>> usual, at the end of the whole thing. Any followups should be
> >>> edited for space, okay? - JAH]
> >>> 
> >>>  The two most important mechanisms of evolution are
natural selection
> >>> and genetic drift. Most people have a reasonable understanding of
> >>> natural selection but they don't realize that drift is
also important.
> >>> The anti- evolutionists, in particular, concentrate their attack on
> >>> natural selection not realizing that there is much more
to evolution.
> >>> Darwin didn't know about genetic drift, this is one of
the reasons why
> >>> modern evolutionary biologists are no longer
"Darwinists". (When
> >>> anti-evolutionists equate evolution with Darwinism you
know that they
> >>> have not done their homework!)
> >> 
> >> In Belgium, polymath Delboeuf wrote about what we would now
call genetic
> >> drift at least as early as 1877. Darwin died in 1882. How do
we know that
> >> Darwin did not know about genetic drift?
> >> See:http://post.queensu.ca/~forsdyke/gulick.htm
> >> 
> > Is there documentary evidence that he did? I do not know all his
> > letters, but I don't recall him or any of the Darwinians discussing
> > anything like it until, of all people, Weismann, said something about
> > it:
> > 
> > "... there are very variable species and very constant species, and it
> > is obvious that colonies which are founded by a very variable species
> > can hardly ever remain exactly identical with the ancestral species; and
> > that several of them will turn out differently, even granting that the
> > conditions of life be exactly the same, for no colony will contain all
> > the variants of the species in the same proportion, but at most only a
> > few of them, and the result of mingling these must ultimately result in
> > the development of a somewhat different form in each colonial area."
> > p286 in
> > 
> > Weismann, August. 1904. The evolution theory. Translated by J. A.
> > Thompson and M. R. Thompson. 2 vols. London: Edward Arnold.
> > 
> > which is so far as I can tell the founder effect via stochastic sampling
> > of the alleles of peripheral populations.
> 
> I am not familiar with the work of Delboeuf, but Weisman's comments were
> very insightful.  Nevertheless, there is no way that either of these
> gentlemen or Darwin could have really appreciated the notion of genetic
> drift in biological populations.  The very foundation of this idea rests on
> the premise of particulate inheritance.  In other words, Mendel's message
> had to be heard before the notion of genetic drift could be understood, and
> this did not happen until later.  Indeed, once particulate inheritance
> became the accepted view, the process of genetic drift was an unavoidable
> corollary.
> 
> Guy

Darwin himself toyed with a particulate inheritance in the Notebooks,
IIRC. However, I do not see how they cannot have comprehended *drift* in
evolution merely because they could not understand the nature of
*genetic drift*. I think Donald's argument is that Delboeuf wrote about
the evolutionary phenomenon we *now* call genetic drift, because it is
caused by stochastic sampling of alleles in populations. Darwin could
have appreciated drift as the stochastic sampling of hereditable
variation. Possibly the reason he did not is because of his difficulty
with swamping by blending inheritance - drift would not occur unless
this did not apply. Weismann was the first person to reject blending
inheritance, and so it is unsurprising that he was the first person to
appreciate *genetic* drift, even if he did not (and could not) call it
that.

Donald: I read briefly through the Delboeuf paper, but could not find
the section you described. Can you locate it for me here? I find the
long web page format distracting, and there is no option to download
just that portion as a standalone to print out.
-- 
John Wilkins
"And this is a damnable doctrine" - Charles Darwin, Autobiography
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