Several questions on evolution, and mutation (rate)

Don Cates cates at cc.umanitoba.ca
Mon Sep 9 01:55:30 EST 1996


dyanega at denr1.igis.uiuc.edu (Doug Yanega) wrote:

>I'll respond to Ram and Don Cates both here...

[snip answer to Ram]

>In article <50vle9$cu9 at canopus.cc.umanitoba.ca>, cates at cc.umanitoba.ca
>(Don Cates) wrote:

>> (Ram Samudrala)
>> >>> Well, it's one use of the word.  I'd call the entire process, of a new
>> >>> trait arising from zero to non-zero frequency (via mutation,
>> >>> crossovers, magic, whatever) as evolution of that trait.  I'd call the
>> >>> spread of it through the population natural selection (if that was the
>> >>> mechanism of the spread). 
>> 
>> (Doug Yanega)
>> >>I have several texts on evolutionary genetics, not ONE does not call the
>> >>latter process evolution. Natural selection is a *subset* of the possible
>> >>modes of evolution.
>> 
>> [snip]
>> 
>> Let's see if I understand what you mean.  I will give some examples and
>> my understanding of what your interpretation woiuld be.  Then I will
>> explain why I think you would be wrong. 

Misunderstanding. Ram is the poster to whom I am replying, not you. So
any occurrances to "you" or "your" are references to him.

[snip a bit]

>>If I am wrong about your
>> interpretation I am sorry but it is an honest (possibly  flawed) reading
>> of your post.
>> 
>> There is some change in function of a gene. You call this evolution. 
                                              [for "you" read Ram]

>Strike one. As I say above, there are NO definitions of evolution which
>relate to function. If there is a change in an allele, then it is
>evolution

Yes, yes, I agree. Will the umpire reconsider his call?
The only place where I have a quibble with you is what I consider a bit
of an over-zealousness in its application. Since, as you state, only
populations evolve, how can you be sure that a change in an allele in an
individual is evolution if you don't have perfect knowledge of its
frequency in the population. In practical terms, though I am admittedly
not widely read in the subject, I cannot recall a single incidence of an
individual mutation being refered to as evolution. Surely one needs
stronger evidence than local novelty to be sure of evolution.

>> What if the change was not beneficial, but neutral? Would you say that
>> evolution took place? For me, it's only evolution if the change gets
>> passed on to a new generation.

>Close, but not quite. If there is a neutral mutation and a new allele
>results, then evolution occurred. If this is not passed on to the next
>generation, then the frequency has gone back down to zero, and evolution
>has resulted in the loss of that allele. 

[snip 'evolution is change; gain, loss, whatever][yes, I agree]

Though I agree in principle (particularly for single-cell organisms), in
practical terms, how do you *know* that an individual incident of a
locally "new" allele really is new in the population as a whole and is
not just an example of a small but relatively stable in frequency
background incidence.
I have a problem (I don't believe I'm ideosyncratic here) with your
definition as stated when applied to multi-cellular organisms. Me for
instance.
In which of the following scenarios do you believe constitute evolution?

I step outside and sustain a UV induced skin cell mutation. (1)
The mutant cell dies. (1)
I produce mutant sperm. (1)
I have a wet dream. (1)
My mutant sperm fertilizes an egg. (2)
(there exists a mutant fertilized egg [any method of mutation])
	The egg fails to divide. (2)
	The resulting blastoma fails to implant. (2)
	The fetus sponaneously aborts.(2)
	The fetus is stillborn early.(3)
	The neonate dies within a week. (3)
	Any death before reproduction. (3)
	One  mutant offspring. (3)
	Several mutant offspring. (3,4)
	Several generations (expanding numbers) of mutants. (4)

The numbers represent my opinion.
	(1) - no
	(2) - unlikely to have enough information, probably no
	(3) - unlikely to have enough information, possibly
	(4) - almost certainly, blending to certainly depending on numbers and
knowledge.

[snip more of what I sincerely believe is a response based on a
misunderstanding of my position. (at *least* partly my fault).


The best thing about mistakes is the joy they bring others.




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