Re: Peppered Moths again
Wed, 31 Mar 1999 11:30:51 -0600 (CST)

Jonathan Wells doesn't read this list, so he's not here to defend
himself. For the record:

1. Jonathan's research into the peppered moth experiments began
several months before the Coyne review or the Telegraph article, and
in fact was conducted entirely independent of both. He began examining
the Kettlewell experiments in the context of a book he is writing
with UC-Berkeley biology professor Richard Strohmann. Jonathan
read deeply in the primary literature and personally contacted
many of the principals in the field. He more than qualified to have
an opinion on the matter.

2. Problems with the Kettlewell experiments and their interpretation
are well-known, and the critical literature extends far beyond Michael
Majerus. See, for instance, the latest volume of _Evolutionary
Biology_, Theodore Sargent et al., "The 'Classical' Explanation of
Industrial Melanism: Assessing the Evidence," _Evolutionary Biology_
30 (1998): 299-322. From the summary:

We have reviewed the evidence that appears to support
what we have described as the "classical" hypothesis
regarding industrial melanism, i.e., that melanism has
increased in industrial areas because of a cryptic
advantage that melanics enjoy on the darkened substrates
that industrialization creates.

This hypothesis seems eminently reasonable and has
become a standard textbook example of evolution in
action. However, the process envisioned is based on a
number of assumptions, many of which we feel are not
convincingly supported. Thus, for example, we fail to
find the close association of melanism with industrialization
that the "classical" intepretation predicts. Increased
rural melanism, coincident with industrial melanism,
seems to have been quite prevalent, especially in
North America.

We have examined three types of experiments that are
often cited to support the selective-advantage/crypsis
interpretation of melanisms and find inadequacies in
all of these areas. Background choice experiments,
for example, have often suffered from inappropriate
design, including the repeated use of individual subjects
and lack of clarity regarding the implications of positive
results. Predation studies in the field are beset with
problems that arise in large measure from our lack of
knowledge regarding the natural resting habits of the
species involved. And, without observations of
naturally resting moths, there can be no observations
of natural acts of predation on them. Thus, we have
no real knowledge of either the predators involved
or their impact with respect to survivorship and
fitness in even the best-studied species exhibiting
industrial melanism. These problems have also raised
concerns with respect to interpreting the mark-release-
recapture experiments that are often cited as convincing
evidence for the "classical" view. Are the moths
that are released actually resting as the species
normally does? Are the numbers being released
affecting normal densities? Are predators being
attracted, because of either inappropriate behaviors
or high densities, that would otherwise ignore the
moths? (p. 317)

Interestingly, out of 100+ references, this paper cites Majerus only
once, and it's not the recent book, but a 1982 paper. Sargent et al.
conclude, "Of course, the 'classical' explanation may be true, in
whole or in part. We contend, however, that there is little persuasive
evidence, in the form of rigorous and replicated observations and
experiments, to support this explanation at the present time" (p. 318).

Paul Nelson
Senior Fellow
The Discovery Institute