Larry Moran wrote:
> On Sun, 23 May 2004 18:07:23 +0000 (UTC), A
> non.  wrote:
> 
>>Larry Moran wrote:
>>
>>>On Sat, 22 May 2004 02:26:53 +0000 (UTC), 
>>>Anon.  wrote:
>>>
>>>>Larry Moran wrote:
>>>
> 
> [snip]
> 
> 
>>>>>In terms of total amount of evolutionary change, random genetic
>>>>>drift is the main mechanism of evolution, by far. Almost all
>>>>>evolutionary biologists know this.
>>>>
>>>>Doesn't that depend on how you measure evolutionary change?
>>>
>>>  
>>>I suppose. One could presumably eliminate or ignore some kinds of
>>>evolutionary change in order to make natural selection seem more
>>>important.
>>>
>>>
>>>>At the sequence level, I would agree (well, until someone shows
>>>>me some evidence to the contrary).
>>>
>>>Okay. So, if we take into account ALL evolutionary change then you
>>>agree that random genetic drift is the most important mechanism?
>>>
>>
>>I think I can still use my same question: Doesn't that depend on how 
>>you measure evolutionary change?  It's not clear to me that we have 
>>to measure it at the sequence level.  
> 
> 
> I didn't say you *have* to measure it at the sequence level. I just
> said that when you take into account ALL evolutionary change, including
> change at the sequence level, then drift is the main mechanism.
> 
To measure "all evolutionary change" you have to measure both phenotypic 
and genotypic change.  How do you put these onto the same scale?  You 
have to weight them somehow, and it's not clear to me that there is a 
unique way of doing this - it will depend on your ideas about the 
relative importance of the genotypic and phenotypic levels in evolution. 
    You can, I think, get either selection, or drift, (or contingency?) 
as being the most important mechanism, depending on how you weight them.

Bob

-- 
Bob O'Hara

Dept. of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5)
FIN-00014 University of Helsinki
Finland
Telephone: +358-9-191 23743
Mobile: +358 50 599 0540
Fax:  +358-9-191 22 779
WWW:  http://www.RNI.Helsinki.FI/~boh/
Journal of Negative Results - EEB: http://www.jnr-eeb.org
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