On Wed, 3 Mar 2004 16:51:12 +0000 (UTC), 
Jeffrey Turner  wrote:
> Larry Moran wrote:

[snip]

>> Hmmmm ... I see where you're coming from. You observe that all
modern species 
>> of elphants have bigger ears than their ancestors and their modern cousins 
>> such as manatees, dugongs, and hyraxes. This leads you to the
conclusion that 
>> large ears are an adaptation. However, if the ancestors of modern elephants
>> just happened to have large ears, and large ears were not a disadvantage, 
>> then the presence of large ears could just as easily be due to drift. The 
>> fact that modern species possess a certain characteristic feature is not
>> prima facie evidence of adaptation since drift and the founder effect would
>> achieve the same result.
> 
> True, but the advantage of large ears in a large mammal that can't
> really stay out of the tropical sun is obvious.  

Not obvious to me. There are all kinds of species that inhabit similar
environments but don't have big ears.

> Why would you think that big ears would be a random occurrence?  

It's a reasonable hypothesis. My main point is to simulate people into 
recognizing the possibility instead of blindly attributing everything 
to selection.

> Drift is probably a minor
> effect, while founders are interesting because of the advantage that
> made them a new species not because of their random minor traits.

I understand that you think of random genetic drift as a trivial process
in evolution. I'm hoping to get you to examine that assumption.

>> But that's not what I had in mind. I was referring to the fact that Asian
>> elephants have much smaller ears than African elephants. If ear size is 
>> under strong selection then one has to account for this fact. On the other
>> hand, if ear size is non-adaptive then the difference between Asian and
>> African elephants could be due entirely to chance.
> 
> Gee, why don't humans have large ears if they are just by chance?

Are you serious? Do you understand what chance is?

> Ever think that climate differences account for the smaller ears in
> Indian elephants?  

That's a characteristic response from an adaptionist. Whenever you're 
faced with new bits of information you make up a new just-so story to
support adaptation. Start thinking about other possibilities.

> There's no reason to believe that non-adaptive mutations lead to 
> speciation - and that's where all the marbles are.

I can see that you're not familiar with modern evolutionary theory 
of speciation. I suggest you read any of the standard textbooks on 
evolution. The section on allopatric speciation should be most 
informative.

[snip]

>>>Considering genetic diversity, itself, gives a species an advantage,
>>>you're going to have to explain why traits would develop for
>>>non-adaptive reasons.
>> 
>> 
>> Two points ...
>> 
>> 1. Genetic diversity cannot be an adaptation since this requires a form
>>    of group selection that has been thoroughly discredited. If a species
>>    accidently possesses more diversity then it will be the lucky survivor
>>    when the environment changes. This is more like evolution by chance
>>    that real adaptation.
> 
> Discredited?  We all know that in many species that have familial
> groups, say lions, the males leave or are expelled from the group to
> find mates elsewhere.  That type of behavior occurs across many
> species with the obvious effect of diversifying the genetics.  I seem
> to recall research that showed that pheromones may play a role in
> selecting a mate with different characteristics even in humans.

You can't select for future events. While it's true that diversity within
a species might pay off when the environment changes, it's not true 
that you can *select* for diversity on the off-chance that it will be
beneficial sometime in the future. That kind of group selection has 
been discredited. 

>> 2. All kinds of traits can arise by chance. Take the ability of some
>>    people to roll their tongues as a simple example. Why do I have
>>    to explain why traits would develop for non-adaptive reasons? Is
>>    it because of your (irrational) belief that everything MUST be
>>    an adaptation?
> 
> Not everything is an adaptation, but adaptation plays a much more
> important role than chance.

I understand that you think this. I'm hoping to get you to re-examine
that faith.

[snip]

> Adaptations ARE evolution.  Evolution doesn't care about junk DNA or
> mutations that are neutral from the perspective of natural selection.

Sorry, you don't get to redefine evolution to suit your personal 
prejudices.

>> 2. The most reasonable minimal definition of evolution is change in
>>    the frequency of heritable characteristics in a population over
>>    time. This definition includes fixation by random genetic drift of 
>>    almost neutral alleles. You seem to want to change that definition 
>>    to restrict it to changes in phenotype - where presumably you mean 
>>    only observable phenotypes. Furthermore, when you say that this is 
>>    "all that evolution can work" with you imply that evolution is 
>>    synonomous with natural selection. In other words, you would like to 
>>    change the definition of evolution so that the only
"real" evolution 
>>    is adaptation. This is consistent with the fact that you aren't
>>    interested in any other kind of evolution but here you go one step
>>    farther. Now you are suggesting that we re-define evolution so 
>>    that my interests become illegitimate. If you succeed (highly 
>>    unlikely) then what word will you use for all those heritable changes 
>>    that aren't adaptations? Will this be pseudoevolution?  :-)
> 
> Your interests aren't "illegitimate," they are other aspects of
> biology.  But genetic drift isn't important to evolution, junk DNA and
> other unexpressed genes aren't either.  Biology and genetics are areas
> that hold other intrinsic interest.  Why are you trying to shoehorn
> all of biology into the study of evolution?

I understand that you aren't interested in any kind of evolution that
doesn't involve adaptation. I don't share your narrow approach to
what's interesting in evolution.

>>>>and evolution by accident.
>>>
>>>Evolution by accident?  Can you explain?
>> 
>> Yes, I'm referring to evolution that takes place without natural selection
>> playing a significnat role. It includes things such as the random 
>> elimination of some species, and the survival of others, at the time of
>> mass extinctions. (The so-called "Field of Bullets"
senario of David Raup.)
> 
> Something usually causes mass extinctions.  A significant stressor.
> It may or may not be transitory.  But I suspect that, for the most
> part, we can find common characteristics among the surviving species
> that would explain why they survived.  I have my doubts that things
> are totally random.

That's a typical answer from an adaptionist. When faced with a question
about evolution (e.g., the results of mass extinctions) the first (only?)
response is an adaptionist just-so story. I'm hoping to convince you that
there are other possibilities worth considering. Do you have any idea 
what the "Field of Bullets" scenario is all about?

>> It includes lots of other things as well. When I use the phrase
"evolution
>> by accident" I mean it to be a direct contrast to
adaptionism. The phrase
>> is intended to provoke people into thinking outside their box. (It's
>> also a convenient way to emphasize the contrast between real evolution and 
>> intelligent design.)
> 
> Ah, curiosities for arguing with Luddites.  Can you actually convince
> them of anything?

I'm not having any luck here. You need to abandon your old-fashioned out-
dated view of evolution and move into the 21st century.

>>>>I'm not having 
>>>>much luck on sci.bio.evolution. This newsgroup is heavily dominated 
>>>>by people who reject the very concept of drift or who have
deliberately
>>>>chosen not to understand it. I find this very strange in a newsgroup 
>>>>that's supposed to be devoted to discussing evolution at a serious 
>>>>level.
>>>
>>>Maybe because "drift" doesn't seem to be very well defined.
>> 
>> Not true. It's as well-defined as natural selection. It may be a more
>> difficult concept to grasp and it may be unfamiliar to those who have
>> been brought up on a steady diet of adaptionist dogma, but that's a
>> different kettle of fish. You can't dismiss random genetic drift just
>> because you don't understand it.
> 
> I can dismiss it because it's not significant in evolution.  You
> haven't shown any method by which it would cause speciation.

You don't know much about evolution, do you?



Larry Moran
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