Larry Moran wrote:
> On Tue, 24 Feb 2004 20:57:28 +0000 (UTC), Anon. 
>  wrote:
> 
>>dkomo wrote:
>>
>>>Tim Tyler wrote:
>>
> 
> [snip]
> 
> 
>>>>Drift may have something to say about small populations on islands
>>>>around speciation events - but it's probably a bit player in most
>>>>other places - as far as the *features* of organisms go (as opposed
>>>>to the makeup of their genes).
>>>
>>>Really?  You mean the fact that people have brown, green, or blue
>>>eyes, are short or tall, fat or skinny, beautiful or ugly, have red,
>>>black or blonde hair, are prone to get different diseases in old age,
>>>have different reactions to medications, have different physical
>>>abilities like being able to run for long distances, sing very well,
>>>be really strong, and so on and so on -- these are all the result of
>>>adaptations and natural selection?
>>>
>>
>>Why not?  Their ancestors have experienced different environments, so 
>>hte selective pressures will be different.  Add into the mix variation 
>>in the environment (which can help maintain polymorphism), and 
>>disruptive selection, we have plenty of adaptive explanations for the 
>>diversity we see.
>>
>>Of course, drift may also be an explanation, but I believe that we can 
>>only separate out the contributions of the different causes empirically.
> 
> 
> Yes. Until we can actually test the hypotheses it's wise not to *assume*
> that all morphological features are adaptations, don't you think?
> 
As long as we can't exclude non-adaptive explanations, then we can't 
dismiss them.  But there may be occasions when making that assumption 
does lead to further enlightenment.  It seems to be a problem of 
scientific rhetoric.

Hmm.  I'm not sure whether I answered you or not.

> Tim seems to be making the default assumption that most morphological
> features are due to natural selection. Dawkins certainly makes that 
> assumption. Is this valid? 
> 
Well, it's valid.  Is it correct?  My feeling is that it is, but if 
someone show me evidence that it isn't, then I'll change my mind.

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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