Text 55, 98 rader
Skriven 2004-09-15 06:09:00 av R Norman (1:278/230)
Ärende: Re: Genetic Drift and Mut
=================================


On Tue, 14 Sep 2004 21:11:44 +0000 (UTC), "John Edser"
<edser@tpg.com.au> wrote:

>
>
>Brett Aubrey <brett.aubrey@shaw.ca> wrote:
>
>> > RN:-
>> > snip<
>> > In a small population, it is quite possible (even very likely) that
>> > the abundance of a particular allele might change just be chance over
>> > generations.  For example, those individuals with big noses just
>> > happened to have more babies with big noses than expected.  It is sort
>> > of like flipping a coin twice. You expect one head, one tail, but
>> > sometimes you end up with two heads. That is the definition of genetic
>> > drift: a change in the genetic composition of the population (in the
>> > allele frequencies). 
>
>JE:-
>Of course, RN has _not_ eliminated Darwinian natural
>selection from the proposed drift process so that RN's
>conclusion that genetic drift is alone causative remains 
>incorrect. Clearly, if "those individuals with big noses just
>happened to have more babies with big noses than expected"
>and raised more big nosed offspring to fertile adulthood
>then any assumption that "just happened" was ONLY chance
>remains utterly incorrect.
>
>I have described an experiment that can eliminate all
>natural selection within an _expanding_ population 
>only allowing genetic drift as causative to allele
>freq. changes. All you have to do is artificially
>force all members of one population to raise the
>exactly the same number of fertile forms to adulthood
>where this number is larger than just a parental
>replacement value.  The prediction is: all natural 
>selection must be halted within this experiment while 
>Darwinian fitness equality can remain enforced. Thus only 
>genetic drift (which cannot be eliminated) is now left 
>to cause "evolution". This being the case, RN's
>proposition (which is the standard Neo Darwinian
>position) that genetic drift can, on its own, cause
>evolution can now be tested. My prediction is that
>drift acting without selection can only cause the
>dissolution of each selectee within that population.
>The population will deteriorate to such an
>extent that it will become impossible to enforce
>Darwinian fitness equality and Darwinian selection
>will force its way into that population to
>correct the dissolution caused by drift acting
>alone.
>
>The simple truth is, genetic drift as just a
>random process, cannot validly constitute 
>evolution without selection. However selection
>could cause evolution without genetic drift.
>This is easy to see as just a thought experiment. 
>Genetic drift is not evolution it is temporal
>variation.  When you allow just a random process to
>become  causative to evolution in its own right without 
>the aid of any non random process then evolution
>is reduced to just an "iron man" theory. This
>means it becomes irrefutable. In Popperian
>epistemology such a view cannot be tested
>and has no more or less to offer than creationism.
>In short, gene centric Neo Darwinism, in its
>wisdom, has, misusing the drift argument, reduced
>the status of evolutionary theory to non
>testable, i.e. puts it on a par with creationism. 
>No wonder schools are being requested to teach
>"creation science" all over the USA. "What
>is good for the goose is also good for the
>gander". I cannot imagine how much lower
>evolutionary theory could degrade itself..
>
>> BA:-
>> Thanks muchly.  This is now making sense.  Is there any quanification (or
>> guidelines) of what constitutes a "small population" with regards 
>> to genetic
>> drift?
>
>JE:-
>I would request Brett to think again.

John Edser does not care for genetic drift.  This is an old story, one
which I do not care to keep reworking.  Let's just put it simply:  I
disagree, as do most biologists (neoDarwinisans, in his terms).  Just
how much degradation that entails is a matter of opinion.  I can live
with it.
---
ū RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info@bbsworld.com

---
 * RIMEGate(tm)V10.2á˙* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 9/15/04 6:09:49 AM
 * Origin: MoonDog BBS, Brooklyn,NY, 718 692-2498, 1:278/230 (1:278/230)