Guy Hoelzer  wrote in
news:c3dade$tfa$1{at}darwin.ediacara.org: 
 
> in article c34m6p$12js$1{at}darwin.ediacara.org, William Morse at
> wdmorse{at}twcny.rr.com wrote on 3/15/04 8:38 AM:
 
 
>> Given my previous attempt on this thread to differentiate phenomena
>> primarily attributable to selection from phenomena primarily
>> attributable to drift (all are in fact products of both), I would
>> request that you clarify what you mean by "all of these
phenomena".
 
> In the context of the discussion, I meant both minor distinctions
> between sibling species and "more complicated examples of evolution."
 
>> The English and Irish
>> finches may meet the requirements of a default assumption for drift,
>> but they may not, and drift only qualitifies as a default assumption
>> for a limited set of observed phenotypic differences.
 
> Hmmm.  Can you name one example of an "observed phenotypic difference"
> for which drift would not qualify as a "default" explanation?

Let's see:  the big ears of elephants, (which I have previously 
mentioned);the long noses, sticky tongues, and lack of teeth in the 
anteaters, pangolins, and spiny anteaters;the fact that both cetaceans and 
birds have good vocal abilities;the recently acquired resistance of 
Staphylococcus aureus to antibiotics; sickle cell anemia in humans; 
eusociality in ants, termites, and naked mole rats; development of hooves 
in perissodactyla and artiodactyla; homeothermy in birds, mammals, and 
beehives; large brain size in humans; morphology of the head in deer and 
kangaroos vs. leopards and hyenas;conspicuous colors in monarch 
butterflies, poison dart frogs, and coral snakes; the relative sizes of 
testicles and penises in humans, chimpanzees, and gorillas; the eye of 
vertebrates and cephalopods, transparency in tunicates and comb 
jellies;morphology of caecilians and earthworms; the relationship of 
skeletal mass vs. body mass in mammals from mice to elephants:aggregation 
in dictyostelium, myxococcus fulvus, and physarum viride - oh I forgot you 
only asked for one example :-)

Now you may object that most of the above are similarities, not differences 
and I stand guilty as charged. But the similarities are all between animals 
that are to greater or lesser degree unrelated. The flip side of this is 
that they are more different from more closely related species. And 
"drift" doesn't explain this, but "selection" does (see
my earlier follow 
for why the terms are in quotes). 

You can probably give an equally long litany of examples of "drift". This 
is exactly my point. You argued in another follow on this thread that 
neutral drift should always be the null hypothesis. I disagree strongly 
with that statement. Both drift and selection always occur, but their 
influence differs in different circumstances. I think we know enough about 
evolution to recognize when one or the other is _likely_ (note emphasis) to 
be dominant. So we do not need to posit one or the other as a universal 
default.

Yours,

Bill Morse
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