Re: Peppered Moths again

Kevin O'Brien (
Wed, 31 Mar 1999 18:58:31 -0700

>>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

Except that there is no mechanism by which induction can occur. Without
such a mechanism, any evidence in "favor" of induction is meaningless.

Kevin L. O'Brien