On Mon, 26 May 2003 17:28:27 +0000 (UTC), Brett Aubrey
 wrote:

>"r norman"  wrote...
>> On Sat, 24 May 2003 17:24:44 +0000 (UTC), Brett Aubrey
>>  wrote:
>> > wrote:
>> >> I contend that due to my model, no species 'evolves'
>> >> unless they are forced to adapt to harsh changes - thus
>> >> As environmental adaptation increases:
>> >>    directional and diversifying selection decreases
>> >>    AND stabilizing selection increases.
>> >>     (and vice versa)
>> >> So I contend that the brain development in hominids
>> >> was due to the harsh environmental weather at the time:
>> >> 
>> >By way of example, I might point to (my understanding of) the
>> >giraffe's neck, tongue, etc. to permit better access to fairly
>> >poorly exploited Acacia trees;    
>> Be careful of the examples you use for evolution!  There is evidence
>> that the giraffe's neck is NOT an adaptation for feeding high
>> above the ground, but rather is the result of sexual selection.  See
>>   R.E. Simmons and L. Scheepers,
>>   "Winning by a Neck: Sexual Selection in the
>>     Evolution of the Giraffe"
>>   American Naturalist 148:771-786 (1996)
>
>Thanks muchly for this, "r norman" - I'll certainly remember it in the
>future.  After perusing the Web for a while, I see this area is widely
>misunderstood as well as being somewhat controversial.  Your statement
>starts with "There is evidence that... " and many of the
sources I looked at
>varied significantly, so I still have one question:
>Is there any support for the high, unexploited tree "reason" among the
>professionals (biologists and such), or is sexual selection really the only
>main reason cited these days (i.e. there could be more than one underlying
>reason, at least in theory).
>
>TIA.  Regards, Brett.

I learned about the giraffe business from a new intro biology text,
"Biological Science" by Scott Freeman, Prentice-Hall, 2002.  From
there, it is easy to retrace the original journal publication of the
Siimmons and Scheepers' original work.

My on-line access to the journal American Naturalist, returns an image
of the text in a form that cannot be "cut and pasted" so here I will
copy some of the text (it is copyright, but this is "fair use" for
scholarly purposes!). I am omitting citations -- see the original.

"Unlike almost every other branch of evolutionary biology, the
evolution of the girafe's ... extraordinary height has attracted only
one serious hypothesis...Long necks allowed giraffe to outreach
presumed competitors, particularly during dry-season bottlenects when
leaves become scarce... So appealing is this hypothesis that students
of giraffe behavior and evolutionary biologists accept it
implicitly... Our aim in  this article is both to evaluate the feeding
competition idea and to suggest a novel alternative hypothesis. We do
so by testing the interspecific feeding competition hypothesis with
existing reseaarch .. and subsequently suggesting and supporting an
alternative explanation based on sexual selection."

I really have no idea where this alternative hypothesis stands.
However, it is entirely possible that the feeding hypothesis is so
"obviously true" that it became an accepted "just-so
story" without
good, hard evidence for it.  On the other hand, the work of Simmons
and Scheepers may also be (have been?) refuted by other animal
behavioralists.  So I played it safe and said, merely, that "there is
some evidence" to indicate the feeding hypothesis is false.

Actually, I just did a quick Google search on "Simmons Scheepers
giraffe".  Virtually all the sites I found are using the paper as
valid work except for the Creationist site that uses it to argue that
evolution is clearly false since evolutionists can't even agree about
the giraffe! Most people use it in their teaching as a good example
that, in science, you should never get too sure of yourself, even (or
especially) when your hypothesis is so clearly and obviously true that
there is no reason to question it!







"

>
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