On Tue, 25 May 2004 23:48:33 +0000 (UTC), 
Anon.  wrote:
> Larry Moran wrote:
>> On Sun, 23 May 2004 18:07:23 +0000 (UTC), A
>> non.  wrote:

[snip]

>>>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.

Why not give it a try? We already have an effective and quantitatvie way of 
measuring evolution by looking at changes in DNA sequence. If you want to 
find a more effective measure then let's see what you come up with. So
far, all I've seen is some warm fuzzy feeling that "phenotypic change"
should get a higher score in order to restore the supremacy of natural
selection as a mechanism of evolution. Can you turn that subjective
feeling into a scientific definition that we can examine?

Let's take the evolution of humans and chimps as an example. We already
know that they differ by about 2% in DNA sequence. How would you evaluate
the "phenotypic changes" along each lineage in order to arrive at some
quantitative measure of the amount of evolution in each species from
the time of the last common ancestor? How much of that is due to natural
selection?




Larry Moran
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