Re: Peppered Moths again
Wed, 31 Mar 1999 16:51:15 -0600 (CST)

Mark Kluge wrote, responding to Brian Harper:

>> Aren't you just re-inforcing Wells' point by insisting that the
>> explanation for the "increased reproductive success" involves a
>> Darwinian mechanism while admitting at the same time that such
>> mechanism is "perhaps unknown".
>Wells doesn't have a point. Here the Darwinian mechanism is
>tautological. What is (or was) observed is changing differential
>reproduction rates between familiar and carbonaria peppered
>moths. What causes such changes? The most general and skeptical
>answer is that something in their environment changes, resulting
>in, for some reason, known or unknown, increased ability of organisms
>exhibiting one of a heritable trait at the expense of organisms
>exhibiting another heritable trait. Such processes are called
>"selection", which is the Darwinian mechanism.
>That some selection process is involved is not disputed by anyone,
>nor can it be.

On the contrary:

It also seems plausible at the moment to suggest that melanism
may arise via some form of induction that is triggered by an
environmental change....The question of induction with respect
to melanism is sometimes related to the question of the
adaptive significance of melanism. If melanism can be induced,
some would argue, then its recent occurrence may not be
adaptive but rather a selectively neutral (or even maladaptive)
response to some predisposing "condition"....Whatever the case,
we emphasize the point that an induction process would be
compatible with either a neutralist or selectionist interpretation
of the industrial melanism phenomenon.

(see Theodore D. Sargent, Craig D. Millar, and David M. Lambert, "The
'Classical' Explanation of Industrial Melanism: Assessing the Evidence,"
_Evolutionary Biology_ 30 [1998]: 299-322; pp. 303-304) Obviously,
if melanism were environmentally induced, observed frequencies of
melanics vs. typicals could shift without any Darwinian selection

As with much else in this matter, the evidence for induction is
inconclusive (see also David Lambert et al., "On the classic case of
natural selection," _Rivista di Biologia - Biology Forum_ 79 [1986]:
11-49), but it is on the table among investigators as a genuine

Paul Nelson
Senior Fellow
The Discovery Institute