In a message dated 5/17/01 10:24:50 AM, jhofmann@Exchange.FULLERTON.EDU
writes:
<< It is simply not true that textbook authors have not taken steps to improve
student understanding of the moth data. On my website below, please look at
entry 8.3e for Kenneth Miller's comments which he supplies for his students
in conjunction with Chapter 14 of his textbook. Entry 8.3d is a
comprehensive review of Wells' book. >>
Jim,
Your course material is impressive. I have archived it for future reference.
Granted, Miller evidently made modifications. But one change of heart does
not make for a reform of a total textbook industry.
I have examined entry 8.3e, the conclusion of which I have reproduced below,
with my comments. Ken Miller wrote:
"The population of dark moths rose and fell in parallel to industrial
pollution, and the percentage of dark moths in the population was clearly
highest in regions of the countryside that were most polluted. As Majerus,
the principal scientific critic of Kettlewell's work wrote, "My view of the
rise and fall of the melanic form of the peppered moth is that differential
bird predation in more or less polluted regions, together with migration, are
primarily responsible, almost to the exclusion of other factors (p. 155)."
Comment: It is necessary to be clear on what is being presented. The rise
and fall of dark moths in parallel to industrial pollution is simply an
observation, not an explanation. In statistical terms it would be called a
correlation. The magnitude of the correlation is not calculated, perhaps
data needed to perform the calculation may not be attainable. It is simply
called "rise and fall." But even if the correlation were perfect it needs to
be recognized that a correlation does not demonstrate a cause and effect
relationship.
Next, Majerus gives us his "view" namely that bird predation is the causal
factor. He is properly cautious, yet it is very clear which way he is
leaning.
Miller continues:
"So what is going on here?
"Well, the best way to put it is that what we are seeing is the scientific
process at its best. Majerus and other ecologists have carefully examined
the details of Kettlewell's work and found them lacking. As Majerus
explains, to be absolutely certain of exactly how natural selection produced
the rise and fall [i.e., correlation, DH] of the carbonaris form, we need
better experiments to show that birds (in a natural environment) really do
respond to camouflage (and not other factors like behavior), and that
migration rates of moths from the surrounding countryside are not so great
that they overwhelm the influence of selection in local regions by birds.
Until these studies are done, the peppered moth story will be incomplete.
Not wrong, but incomplete."
Comment: So far so good.
Miller concludes:
"What we do know is that the rise and fall of dark-colored moths, a
phenomenon knows as 'industrial melanism' remains a striking and persuasive
example of natural selection in action. What we have to be cautious about is
attributing 100% of the work of natural selection in this case to the
camouflage of the moths and their direct visibility to birds."
Comment: It is this kind of mixed message that I, and probably others who
question the adequacy of the data to support the theory of natural selection,
find so objectionable 1) Majerus expresses his "view" that predation is the
causal factor, 2) Miller expresses caution: "Not wrong, but incomplete."
3) Miller then expresses certainty. He says that "we _do know_ is that the
rise and fall of dark-colored moths, a phenomenon knows as 'industrial
melanism' remains a striking and persuasive example of natural selection in
action." 4) Then he urges caution.
Further, #3) is an unwarranted expression of certainty. It is not warranted
by the data. It is at best a hypothesis that still needs to be demonstrated.
The jury is still out on this decision.
Yet, there's something here for everybody. Do you doubt that natural
selection has been shown to be the primary causal factor? We do too. We are
cautious about that claim. Do you believe that natural selection has been
shown to be the primary causal factor? So do we. We "do know."
Moreover, there is no consideration given to other possible interpretations,
e. g., that industrial melanism is merely a case of reversible adaptation, a
local back-and-forth phenomenon, that is going nowhere, and is thus
irrelevant to the major question of whether natural selection is the causal
factor in the descent with modification from one or a few common ancestors.
It is a long stretch for skeptics like me to see any significance in the
conclusion from these studies of industrial, with their flimsy data support,
for the larger question of whether natural selection produced the effects it
is purported to have produced over the entire history of the organic world.
There is an even more radical hypothesis that could also be considered.
Cannot the data be reasonably interpreted as nature's end game, an effort to
forestall extinction of a species? After all, if the moths didn't change
their color the species would become extinct. If that be the case, what is
the significance of industrial melanism for the larger question given above?
Does averting extinction sound like a move toward descent with modification?
In sum, one of my major objections to natural selection as an explanation for
changes observed is that it stops exploration for other possible
explanations. When Miller explains industrial melanism by natural selection,
the matter is closed. I consider that poor science.
Thanks for your consideration,
Bob
Bob
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