Anyone Seen Evolution?

Tim Ikeda timi at mendel.berkeley.edu
Tue Nov 19 04:04:50 EST 1996


Jeff,
I suggest moving this discussion to the newsgroup, talk.origins,
which was specifically developed to debate issues of creation vs.
evolution.  Bionet.molbio.evolution is part of the bionet
hierarchy which was created for scientists in biological research.

In article <Pine.SUN.3.91.961118165752.6882A-100000 at joel>, Jeff Bush
<jbush at afit.af.mil> wrote:
> On Sun, 17 Nov 1996, Greg Adcock wrote:
[...]
>> Resistance... of hatever sort you like... insects to insecticides,
> 
> Sounds like natural selection, can you expound on that. How do
> I know there weren't a small percent of insects that were resistant
> to the insecticide to begin with.

That would be incredibly difficult to demonstrate in most cases
because it would require a complete survey of _all_ members of
the population.  Better to work with predefined populations
where the variations can be determined.

With regard to bacteria, the Lederbergs conclusively demonstrated
that phage and drug resistance can arise _spontaneously_.  See
"Replica plating and indirect selection of bacterial mutants",
(J. Bacteriol. [1952] 63:399-406) by Joshua and Esther M.
Lederberg.  This is a classic experiment described in many
microbiology textbooks.  I also have to mention that Luria &
Delbruck demonstrated pretty much the same thing in their
fluctuation experiments.  Unfortunately, that reference is
away from my desk at the moment, but perhaps someone else could
post it.

> My question was pointing at *observing* a  benifitial mutation
> in the genetic code.

Yes, "beneficial" mutations (ie. those that enable an organism
to do better in a particular environment) have been observed.
Jeff Adcock mentions that he has generated them in lab.  I have
too, often accidentally.  This shouldn't come as a surprise.
Similar demonstrations are routinely performed as part of
undergraduate microbiology lab courses.

Regards, Tim Ikeda (timi at mendel.berkeley.edu)



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