Several questions on evolution, and mutation (rate)

Ram Samudrala ram at mbisgi.umd.edu
Wed Sep 4 21:08:13 EST 1996

James Foster (foster at cs.uidaho.edu) wrote:

>Well, "evolution" does mean "change".  But to biologists it really
>means "a change in the distribution of characters ocross

Well, I'm a biologist in a sense, and I just disagree with that
definition of evolution.  In fact, this is the first time I've come
across it, even though I've discussed this topic with various

>Selection cannot operate at all on a single individual divorced from
>any consideration of it's progeny.

Yes, of course.

>I'd say the thing you describe is just good old fashioned change in
>an individual...aka mutation.

How do you differentiate between mutations that give rise to a new
function, and mutations that do not?  

>: To clarify, suppose there was a single bacterium that was susceptible
>: to an antibiotic.  That baterium underwent a mutation in one of its
>: genes, and consequently one of its proteins, and that one protein
>: bound to the antibiotic and rendered it ineffective.  I would call
>: this "evolution" (of a new function, i.e., antibiotic resistance).
>: The fact that the bacterium could survive in an environment with this
>: antibiotic due to this evolution, and thus reproduce, passing this
>: gene on to its "offspring" across generations, while other bacteria
>: that didn't have this gene died, is what I'd call natural selection
>: (of that antibiotic resistance function).

>Without passing it on, that's just "mutation"...ie., "change".

It could pass it on.  What I'm saying is that at some point, for new
function to evolve, it must have happened in one organism (it could
happen simultaneously also), and subsenquently been selected to spread
to various generations.  The evolution of function is an interesting
topic in and of itself, which not many people think about (though I do
know of published attempts to attempt to create function, it has not
been successful).  This is what I've commonly heard (among
biologists/biophysicists) referred to as evolution.

How's that mutation different from a mutation that simply changes a
base pair, or an amino acid, without changing the function of the

>There are many others of course.  "The Coming Plague" talks about a
>particularly frightening case of observed new funcationality.  Or you
>could speak to anyone who develops new strains of crops or cattle.

I am not sure how you could observe new function evolve (I'm not
talking about observing functions being selected for, which I have
observed many times myself).  So are you saying these people knew for
sure that the genes with the mutations that had these functions didn't
already exist in ALL the animals in their cattle, and that they
weren't just selected for?  

What I'm saying is that to observe new function evolve, you would have
to make sure that the gene or genes that code for the function did NOT
exist in the population before.   Otherwise, how would you separate
out natural selection and what I call evolution?


me at ram.org  ||  http://www.ram.org  ||  http://www.twisted-helices.com/th
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