On Tue, 10 Jun 2003 17:33:47 +0000 (UTC), Michael Ragland
 
wrote:
>Larry Moran wrote 
>>Michael Ragland wrote,

[snip]

>>> I've been trying to learn a little about speciation and its an
>>> incredibly complex subject. Allopatry, sympatry, and parapatry are
>>> specific types of speciation under the umbrella term
"genetic drift". 
> 
>> Speciation is a broad term representing the formation of new species
>> from pre-existing species. There are several different ways that new
>> species can form. Some of the mechanisms of speciation involve random
>> genetic drift and some involve natural selection. It strikes me as
>> somewhat confusing to lump different types of speciation under the
>> "umbrella term genetic drift." 
> 
> Aren't allopatry, sympatry, and parapatry specific forms of genetic
> drift?

No.

[snip]

> My statement, "My point is even if mutations are
"neutral" as a result
> of random genetic drift they spring from genetic variation due to
> natural selection in progress" was to say natural selection produces
> positive mutations and filters deleterious mutations. 

Natural selection tends to lead to fixation of beneficail alleles and it
tends to eliminate delterious ones. Is this what you meant to say?

I still don't see how this relates to random genetic drift.

>I subscribe to the neutral theory of evolution by random genetic drift. 

"Neutral Theory" refers to the idea that many alleles are effectively 
invisible to natural selection. Such alleles may, or may not, become fixed
in a population by the mechanism known as random genetic drift. The mechanism
of random genetic drift also plays a role in the fixation or elimination
of beneficial anddeleterious alleles where it acts in concert with,or in
oppositionto, natural selection. This is why it's a mistake to equate 
"Neutral Theory" with "random genetic drift."

>I understand most genetic variation is in the non-coding region of our DNA. 
>I'm very disturbed by all of this as it regards our evolution. 

Why does this "disturb" you?

>Natural selection is not the main force in our evolution. That, however, 
>does not mean it hasn't played a driving role in evolution. 

Of course ... depending on how much emphasis you place on "driving."

>Most genetic variation is in the non-coding region and is not a result of 
>natural selection but in the coding region I would argue natural selection 
>plays a much more important role than random genetic drift. 

Well, I guess this depends on what you mean by "important." If you're 
referring to frequency then I'm afraid you're going to continue to be 
"disturbed" because most changes in the coding regions of genes result 
from fixation of neutral alleles by random genetic drift.

>For example, only a fool would suggest the trait of aggression is to be 
>found in the non-coding region. This was a positive trait selected by natural 
>selection. 

Some of us fools are skeptical about the existence of an "agression" gene
and skeptical about whether it would be selected if it existed.

>Random genetic drift is not adaptive evolution.

That is correct, by definition.

>It is aimless evolution. There is no guarantee the population will be any 
>more fit than the original one. 

That is correct. In fact, it's possible to fix deleterious alleles by
drift so a population could become less fit. Does that disturb you?

> If we're in agreement random genetic drift is not adaptive evolution, that 
> it is aimless, and there is no guarantee a population will be any more fit 
> than the original one...I think this raises some interesting concerns and 
> questions. 

Okay, I guess this is new information to you. Let's hear your questions.

> If we know natural selection is not the main force in evolution then how 
> can we proceed as a species to attempt to make our evolution adaptive? 

I don't know ... and I don't care.

> Given most genetic variation is in the non-coding region and much less so 
> in the coding region this does not mean the coding region isn't important in 
> evolution. 
> In terms of adaptive evolution it is more important than the non-coding 
> region. 

Yes, this is probably correct.

> I'm operating from the assumption we're currently not an adaptive species 
> in our evolution. 

I think I understand your perspective. You prefer to bring all discussions
of evolution around to your favorite topic, namely human evolution. So, why
do you operate from that assumption? Do you make the same assumption for
all modern species or only for Homo sapiens?

> Considering how long natural selection takes in effecting changes in our 
> coding region should biologists attempt to reach a consensus Darwinian 
> evolution can't be relied on to affect positive adaptive changes through 
> natural selection? 

No, of course not. Why would you ask such a silly question?

> I'm not getting off the topic Mr. Moran. I explained how natural selection 
> produces positive mutations and filters deleterious mutations in genetic 
> variation. You're point seems to be human populations don't have much 
> genetic variation to begin with which is naturally selected since most 
> genetic variation is neutral in non-coding regions. Fine. 

Firstly, please don't say things like, "natural selection produces positive 
mutations." I think I understand what you mean but it would be better to use 
correct terminology to avoid confusion.

Secondly, I did not mean to imply that human populations don't have a lot
of beneficial/deleterious alleles that are under selection. I simply pointed
out that these are a minority compared to all alleles.

> Nevertheless, there has to be some genetic variation which has occurred in 
> the coding region and has been naturally selected. Otherwise, we would be 
> slithering in ocean mud.  

Yes, and this same reasoning applies to every other living organism as well.
Nobody is denying adaptation. I'm just trying to convince you that there's
much more to evolution.



Larry Moran
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