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?

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? 



Larry Moran
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