>On Mon, 16 Oct 2000 20:29:34 -0500, Susan Brassfield Cogan wrote:
>
>[...]
>
> >>SB>Wesley was talking about isolating natural selection from drift and my
> >>>understanding was that he was talking about populations over a large
> amount
> >>>of time.
>
> >SJ>>Why does Susan think that Wesley *needs* to see "natural selection" in
> >>"populations over a large amount of time"?
>
>SB>I'm sorry, since you (mis)quoted Wesley originally, I thought you had been
> >following his conversation.
>
>If Susan claims I "(mis)quoted Wesley originally", she should state: 1) what
>was the original context; and 2) why she thinks my quote was not in that
>original context..
>
> >>SB>You see natural selection every time you spray for roaches or
> >>>don't take all your antibiotics.
>
> >SJ>I would have no problem with this if it *was* natural `selection', i.e.
> >>differential survival and reproduction.
> >>
> >>But as a matter of interest how does Susan *see* "natural selection
> >>*every* time you": 1. "spray for roaches" or 2. "don't take all your
> >>antibiotics"?
>
>SB>You should get your doctor to explain the antibiotics to you. I'm
>surprised
> >he/she hasn't already. The doctor will warn you to take *all* the
> >antibiotics, in order to raise the chance that you will kill all of them
> >(cause a little extinction, if you will). If you only take some of them,
> >you kill off all the weak ones leaving only the strong ones. Then after a
> >while you have only the strong ones in your body and the antibiotics don't
> >have any effect on them. Perhaps you should read some the WHO stuff that's
> >been coming out lately on this subject.
>
>I am a former Hospital Administrator so I am well aware that bacteria
>become resistent to antibiotics. And I said "I would have no problem with
>this if it *was* natural `selection'"
>
>But that wasn't my question. Susan said she could "see natural selection
>every time you ... don't take all your antibiotics" and I asked "how does
>Susan *see* "natural selection *every* time you" .... "don't take all your
>antibiotics"?
Chris
Two points:
1. You still haven't shown why there is a significant difference between
natural selection (natural exclusion of some organisms/genotypes from
reproducing) and non-natural selection (non-natural exclusion of some
organisms/genotypes from reproducing). Other than certain statistics (and
not always even that), what is this mystical difference between the two? Do
you think that the remaining, non-excluded genotypes somehow "know" about
who or what killed off their comrades? Do you think that a bacterium that
survives an antibiotic injected by a human responds differently from one
whose fellow bacteria were killed off by the same antibiotic (such as
penicillin from some mold that the bacterium happened to come in contact
with)? As the man asked of the thermos bottle, regarding the fact that it
keeps hot liquids hot and cold liquids cold, "How do it know?" How does the
surviving bacterium know that that antibiotic was supplied by a drug
company instead of locally-growing mold?
And, supposing that it does "know," why would that fact make a difference?
When it reproduces, will this change the variations that are produced in
some systematic way? If your answer is yes, do you have any evidence that
this actually occurs, that bacteria can distinguish between the same
antibiotic from different sources and respond differently *genetically* in
response to this information about the source of it?
I very much doubt it.
2. Do you seriously think that we *designed* penicillin (and the rest) so
that some bacteria would survive because of naturally-occurring genetic
differences? Do you think this was *planned*? If so, why do you think so?
If no, then how can it *possibly* be relevant to the ID question whether we
humans are deliberately using antibioltics or they just happen to occur
naturally? Since we are clearly *not* designing bacteria, and since we
clearly *don't* have control over what genetic variations occur, the mere
fact that *we* provide a selective factor can hardly be relevant, if we are
not doing it to *cause* evolution, can it? After all, Nature does similar
things quite frequently. Why do you think the Finch's beak varies as it
does? It does it because the conditions nature imposes are uniformly
selective for birds with different beaks at different times. I don't put
much weight on Finch-beaks because I think they evolved a "library" of
beak-genes a very long time ago to enable them to adapt rapidly by turning
genes on and off. I suspect we might even find a mechanism that increases
the variation rate of the genes that do this turning on and off.
But, the point I'm making (and have made before) is that no one has shown
how such things as the building of resistance by bacteria to antibiotics is
*relevantly* different from the building of similar resistance by bacteria
or other organisms to naturally-occurring selective factors, particularly
since even the population-dynamics and exclusion-rates are sometimes the same.
> >SJ>In the case of 1. if a "roach" survives after Susan sprayed it with
> >>insecticide, how does Susan "see" that it did not survive because she
> >>did not spray it properly? Also how does Susan "see" that the "roach"
> >>does not die later without offspring?
> >>
> >>As for 2. how does Susan "see" bacteria, let alone that they have been
> >>naturally `selected' against the effects of the "antibiotics"?
>
>SB>I'm not sure what you are asking here. I don't need to "see" them to know
> >that the Suprax which worked on my infection last time isn't working now.
>
>How does Susan know it was "natural selection" that is the reason her
>antibiotic "which worked on" her "infection last time isn't working now"?
>
>How does she know it wasn't: 1) A different strain of bacteria; 2) random
>genetic drift; 3) lateral gene transfer; 4) or a bad batch of antibiotics?
>There
>is even some evidence that bacteria can 5) evoke a Lamarckian inheritance
>of aquired characteristic directly.
>
>SB>The people who developed Suprax in the first place "saw" the bacteria
>being
> >selected by it. That's why it's on the market now.
>
>I am not questioning that a drug company might be able to see natural
>`selection' working in a carefully controlled laboratory experiment.
>
>What I am questioning is how *Susan* sees it.
>
> >SJ>Finally, if Susan did manage to "see" the above, how does she know
> >>that what she sees is not natural `selection' but instead genetic "drift"?
>
>SB>Drift? drift is slow. Natural selection is fast.
>
>It more like the other way around. As I posted before, in one of my
>Biology labs last semester we simulated drift and natural selection, and it
>was *amazing* and completely counter-intuitive to all of us how fast and
>dominant over natural selection drift is in a small, isolated population,
>
>SB>It's my understanding
> >(someone more knowledgeable should jump in here) that drift only pertains
> >to genes that don't have immediate survival value--like red hair or the
> >ability to curl your tongue from side to side.
>
>No. They (or at least the tongue curl example) are caused by recessive
>alleles.
>
>Drift has nothing especially to do with those. Drift is just random
>stochastic
>(i.e. statistical) changes that happen in small populations. Like tossing two
>coins a small number of times. If H(eads) = a favourable allele and T(ails) =
>an unfavourable allele, there is a small but real chance that only the
>unfavourable T alleles will reproduce/survive and the H alleles would be
>eliminated from the population. For example in a small population on an
>island the animal with the selectively advantageous H allele gets killed by
>lightning.. In a large number of flips (= in a large population) this is very
>unlikely to happen
>
>Steve
>
>--------------------------------------------------------------------------
>"Biology is the study of complicated things that give the appearance of
>having been designed for a purpose." (Dawkins R., "The Blind
>Watchmaker," [1986], Penguin: London, 1991, reprint, p.1)
>Stephen E. Jones | Ph. +61 8 9448 7439 | http://www.iinet.net.au/~sejones
>--------------------------------------------------------------------------
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