Peppered Moths - in black and white (part 1 of 2)

Kevin O'Brien (
Tue, 30 Mar 1999 09:06:16 -0700

Lately, in my debates with David Tyler over this issue, I have accepted the
creationist evaluation of the peppered moth scenario without much objection
(what I objected to was the further claim that the peppered moth was no
longer a legitimate example of either evolution or natural selection).

Now, however, it appears that I was wrong: I should not have accepted the
creationist evaluation at face value, but should have followed both my
instincts and my experience and realized that as usual creationists were
blowing this entire subject out of proportion.

What follows is a two-part look at how Michael Majerus actually treats the
peppered moth scenario in his book _Melanism: Evolution in Action_, which
was posted to another list that I am a member of. As you will soon see,
Jerry Coyne's book review in _Science _ and the interview with Majerus and
Coyne in the _The Telegraph_ do not accurately represent Majerus's own

The bottom line is this: not only is the peppered moth scenario not dead,
it isn't even sick; it is still considered to be an example of "evolution in
action" even though the scenario is not as simple as it is frequently
portrayed to be.

Peppered Moths - in black and white (part 1 of 2)

A while back creationists on the lists I subscribe to, and elsewhere in the
"real" world and cyberspace, began crowing over the death of the peppered
moth as "an example of evolution." The references cited are a book review
by Jerry Coyne in _Science _ of Michael Majerus's _Melanism: evolution in
action_, and a later article from interviews with Majerus and Coyne in the
on-line version of _The Telegraph_. These documents have been quite
literally flaunted to show that evolutionists have been the willingly blind
victims of everything from poor research to outright fraud, and that this
famous example of natural selection has been abandoned by "knowledgeable
scientists". I have already seen the peppered moth story compared to the
Piltdown forgery.

I have not included copies of the articles named above. Both have been
posted by creationists here or copied from their posts. If desired, I can
repost both articles. All other references I have used (or seen) are listed
at the end.

The partying by creationists over this "victory" has been matched by various
levels of intimidation of many evolutionists who don't know enough about the
matter to respond, or those at the wailing wall bemoaning our lack of rigor
in ferreting out poor research.

I have intended to comment on the discussions and claims regarding this
subject for some time. For those of you who don't know me, my formal
background is in entomology, specifically in the study of Lepidoptera
(butterflies and moths). I did a great amount of field research on moths
for about ten years. Although I know the pepper moth story in general
terms, I didn't consider myself expert enough on the subject to take on the
inevitable authority-thrusting of the review and article just noted. I was,
however, suspicious of the spectacular claims made by cyberspace
creationists, and well known creationists such as Philip Johnson (at a
recent ID conference) and, just this past week, John Morris (April Acts and

I finally became fed up with this newest creationist claim, and the fact
that no one seemed to refer to the actual book upon which Coyne's review was
based, but simply to the review itself. To evaluate the situation I located
the seemingly notorious book by Majerus at UC Riverside, (it is not
out-of-print as states, mine is on order now). I read the
Introduction, and the chapters on "The Pepper Moth Story" and "The Pepper
Moth Story Dissected" - the latter two are the basis of Coyne's review. I
also searched Biosis for 1993-1999 for "melanism" and copied all the
articles that appeared to relate to the peppered moth.

I opened Majerus's book anticipating a bashing for Kettlewell, who did the
classic studies on the peppered moth, as well as problems with subsequent
research that I knew existed. From twenty years of reading anti-evolution
literature, as well as other advocacy of non-mainstream science views, I
think I can pretty often see the attack coming in the form of qualifying
with "supposed evidence", etc. and confrontational discussions throughout
the text. I expected this from Majerus.

The Introduction to the book explains how Majerus became interested in the
pepper moth and melanism in general (his main research now is on melanism in
lady bird beetles). Throughout the chapter "The Pepper Moth Story", Majerus
gives not the slightest hint of the bomb I was waiting for. His discussion
of Kettlewell's experiments, and those of others, are so fairly and
complimentarily done that I was amazed at the thought that he was about to
destroy it all. I therefore felt I had encountered a Saturday afternoon
serial of the old days, realizing that most readers would have no idea of
the cliff-hanger ending to the initial chapter. How was Majerus going to
unhinge the discussion in "The Pepper Moth Story Dissected"? And why did he
lead his readers on so cruelly without a hint that they were being given
trash data? I read to the end of the second chapter like it was a
whodoneit. Did the butler do it? Was it Miss Scarlet in the library with
the candlestick? WHEN was Majerus going to tell all? And then I came to
the last page·

If you're waiting for the punch line, here it is. There is essentially no
resemblance between Majerus's book and Coyne's review of it. If you pick
through the book, you might be able to argue for Coyne's accuracy - but only
at the expense of completely ignoring the majority of the text and all of
Majerus's intent. If I hadn't known differently, I would have thought the
review was of some other book. I would recommend here a comparison with the
other review I found of Majerus's book by Lawrence Cook, another researcher
on peppered moths (Cook, 1998). Cook seems oblivious to the doom of the
peppered moth example of natural selection.

Coyne describes the "standard textbook litany", then in the next paragraph
describes Majerus's "absorbing two-chapter critique." I suggest that any
interested reader compare Coyne's "standard textbook litany" to the entirety
of Majerus's discussion in both chapters, particularly the latter's final
summary on the subject. I myself cannot find his striking contrast.

I will comment on Coyne's entire paragraph describing Majerus's "critique,"
divided into four points. Remember, Coyne is claiming that Majerus supports
these views

Coyne: "Criticisms of this story have circulated in samizdat for several
years, but Majerus summarizes them for the first time in print in an
absorbing two-chapter critique (coincidentally, a similar analysis [Sargent
et al., Evol. Biol. 30, 299-322; 1998] has just appeared)." [all comments in

I found eight articles on pepper moths and one other review of Majerus's
book in a simple search over the last few years (all but one are since
1993). Majerus's book clearly summarizes data representing seven of the
eight articles. The last one stands out as the only argument that the
peppered moth story is seriously, if not fatally, flawed - coincidentally
the only one that Coyne cites (above). The cited paper offers an
alternative to cryptic coloration as due to mutation-selection. Under
"Genetics and Induction", the authors defend the idea that melanism may be
caused by induction from exposure to environmental pollutants, and that this
induced change can be inherited without later exposure. This is, to say the
least, an interesting notion. There are a lot of "might be" and "could be"
in the summary, but no mention of their alternative. Coyne's book review
looks much more like a summary of the Sargent et al paper than of Majerus's

Coyne: "Majerus notes that the most serious problem is that B. betularia
probably does not rest on tree trunks -- exactly two moths have been seen in
such a position in more than 40 years of intensive search. The natural
resting spots are, in fact, a mystery."

Readers can consult Majerus's discussion on p. 121ff. Peppered moth adults
have rarely been collected from resting sites - Majerus refers to these data
as "pitifully scarce" and "negligible." Coyne's "exactly two moths" comes
from Majerus's reference to a single article on Sir Cyril Clark's extended
trapping study, and these are the only two specimens the original quote
refers to as having been found at all. You would think Coyne could just as
well have drawn the opposite conclusion. As trivia, the original says 25
years (Clarke's study), not 40; if Coyne means all research (this seems
implied), he ignores the rest of the discussion and all other possible
literature. More importantly, Majerus's next paragraph cites his own
personal records from resting-site collections, "the largest data set," of
47 specimens in 32 years. These data, and trap-associated resting data, are
summarized in two tables (Table 6.1 and 6.2). He lists 6 specimens each
from "exposed trunk" and "unexposed trunk" (12.8% each) for the first
(natural) set. (I warn readers not to take the trap-associated data in the
book too seriously; moths may remain in unnatural sites around light traps
after sunup.) Coyne's term "exactly two moths" therefore gives a wrong
impression as to what the original says, and his number ignores Majerus's
own data tables. Finally, Coyne's reference to a "mystery" of where
peppered moths rest appears to contradict Majerus, who refers to his and
others experiments on branch-related resting sites - apparently the most
common location. Experiments with moths attached to these locations support
the cryptic advantage of earlier studies from trunks. Majerus quotes
Kettlewell himself as stating that the normal resting position was probably
higher in the trees than in his studies, and the reasons for Kettlewell's
procedures are explained and qualified.

Coyne: "This alone invalidates Kettlewell's release-recapture experiments,
as moths were released by placing them directly onto tree trunks, where they
are highly visible to bird predators. (Kettlewell also released his moths
during the day, while they normally choose resting places at night.)"

This appears to be Coyne's own conclusion. Many of Kettlewell's experiments
were done on the exposed trunk because it was the only location that could
be studied at a distance, without disturbing potential predators. Majerus
makes very clear that initial opposition to Kettlewell's claims concerning
bird predation relied on both entomologists and ornithologists denying that
birds prey on adult resting moths. Kettlewell (with animal behaviorist Niko
Tinbergen) filmed birds preying selectively on the moths both in polluted
and unpolluted areas. This could only be done on exposed trunks, and the
comparison still appears valid to me (and others). In his discussion of
these experiments, Majerus refers to the experiments as "inspired" (p. 109)
since Kettlewell covered all foreseeable forms of criticism (but apparently
not Coyne's). As I noted above, Majerus makes clear that Kettlewell
understood there were limits to his approach. I would note here that
Kettlewell worked with live moths, whereas many subsequent researchers have
used dead moths glued into place. I guarantee you that live moths are
infinitely more difficult to work with in the field than dead ones, although
the birds presumably can't tell the difference until they attack.

Coyne: "The story is further eroded by noting that the resurgence of typica
occurred well before lichens recolonized the polluted trees, and that a
parallel increase and decrease of the melanic form also occurred in
industrial areas of the United States, where there was no change in the
abundance of the lichens that supposedly play such an important role."

There are critics of industrial melanism who treat local claims as universal
laws. These appear to me to be strawman arguments, unless they are
supported by someone specifically. The lichen argument takes observations
about peppered moths in England, and makes it a requirement anywhere
industrial melanism is seen. The argument is for crypsis, a resemblance to
the background. This need not involve lichens, just a change in background
coloration. Majerus states on this very subject, and referring to the same
paper cited by Sargent et al (again, "coincidentally?" repeated by Coyne):

"However, given the assessments of lichens were anecdotal, rather than
systematic, and that the woodland canopies may not have been monitored, this
comment should be viewed tentatively. The more so, because other authors
have recorded increases in lichens following anti-pollution legislation. But
the importance of this case [parallel decrease in melanic peppered moths in
the U. S.] is not in the minutiae." (p. 154)

The comments above are from ONE paragraph of Coyne's "book review." Other
comments differ from Majerus's throughout the article. Coyne states:

"Majerus concludes, reasonably, that all we can deduce from this story is
that it is a case of rapid evolution, probably involving pollution and bird
predation. I would, however, replace 'probably' with 'perhaps'."

There is absolutely no indication of "probably" in Majerus's book. He, and
all other authors of the articles I found, excepting Sargent et al, are most
definite in their opinions regarding pollution as a factor. Majerus is
quite clear on both these points, and I take the following from his final

"My view of the rise and fall of the melanic 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

"My view of the story, is, I know, not held by all other entomologists or
evolutionary biologists. However, in reviewing well over 100 papers written
about this case, and having collected peppered moths in the wild for over 30
years, I am unconvinced that there must be other important selective factors
involved in the evolution of melanism in the peppered moth in Britain. My
view may well be proved to be incorrect. However, if it is to be refuted,
research into the case must continue and be amplified. Recently (New York
Times, 12 November 1996), the eminent evolutionary biologist Dr Douglas I.
Futuyma said of the peppered moth story: 'We don't know the whole story yet,
but it should be possible to find out what it is'."

I have tried to give a simple assessment of this situation, without writing
a book myself. If anyone wishes to take me to task over some detail, I
suggest you first read Majerus's book. Whatever arguments might be made
over quantity of evidence (infinite regress comes to mind), Coyne's
conclusions do not come from Majerus's. There are certainly things we don't
know completely (as Majerus points out), but critics like Sargent et al, and
seemingly Coyne, rely on arguments many of which can never be resolved by
real-world research.

My experience with creationists is that this is a one-time lesson at best.
The next "magic bullet" will appear to replace this one - assuming
creationist readers even accept what I have written. Also, a warning. This
is the third subject I have investigated brought up by creationists in the
last few months based on _Science_ or _Nature_ articles that I have found to
be based on really poor scholarship. I fear there is a rash of authors
trying to make a name by bashing icons.

By the way, I recommend Majerus's book as an excellent reference on the
subject. Just be ready to drop $105 for the hardback, $45 for the


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environment", Advances in Ecological Research, 11:373-404.

Clarke, C. A., F. M. M. Clarke and B. Grant. 1993. "Biston betularia
(Geometridae), the peppered moth, in Wirral, England: An experiment in
assembling", Journal of the Lepidopterists' Society, 47:17-21.

Cook, L. 1998. "Book Reviews: Melanism: evolution in action", Genetical
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Coyne, J. 1998. "Not black and white" [review of Majerus, 1998], Nature,

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