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Peppered moth

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Contents

Other EvoWiki-related moth pages

Published examples of selection in wild populations -- Bernard Kettlewell -- Michael Majerus -- Judith Hooper -- Jonathan Wells -- Did Kettlewell commit fraud? -- Kettlewell's data -- Peppered moth timeline -- Science in the media

The Short Version

Typical Coloration of the Peppered Moth Biston betularia

(This section should give an overview of the peppered moth and debates about it in a few paragraphs)

The peppered moth, Biston betularia (L.), is one of some 2,500 moth species found in the United Kingdom. It became a famous example of evolution by means of natural selection. after the Industrial Revolution. The typica variety of the moth is white with black speckles and is a striking lichen mimic.

Starting in about 1850 entomologists began to notice a dark morph of this moth (termed carbonaria), and a range of intermediately shaded variants (termed insularia). Over the next 50 years, the dark variety gradually became the most prevalent in regions downwind from large industrial centers, where soot and other air pollutants from factories darkened the bark of trees and killed most lichens. The rapidity and striking nature of the change drew scientific attention; in 1896 Tutt proposed that carbonaria might be better camouflaged than typica on polluted surfaces, and that therefore natural selection, in the form of relatively higher bird predation on typica might account for the spread of carbonaria in polluted regions. In 1924 J.B.S. Haldane calculated that the selection coefficient required to produce such a change must have been ~0.3, a selection coefficient much higher than had been previously thought likely for natural evolution. [Q: too technical?]

Starting in 1953, Bernard Kettlewell conducted field experiments on the peppered moth, providing hard evidence that differential bird predation based on relative camouflage was the primary selective force contributing to the different fitnesses of the moth morphs in polluted and unpolluted environments. These experiments became the famous textbook examples of evolution by natural selection in action, and have in the main been supported by numerous subsequent studies. However, due to a strange combination of a few scientific dissidents, antievolutionist propaganda and poor media coverage, the notion has become widespread that Kettlewell and the differential predation hypothesis has somehow been disproved or discredited. [last sentence; rewrite]

The Long Version: Purpose

(The following sections should give a detailed review)

The purpose of this article is to present a thorough review of:

  1. H.B.D. Kettlewell and the paradigm he established. That paradigm, the "Bird Predation Theory" (BPT), explained industrial melanism in the peppered moth as due primarily to natural selection in the form of differential bird predation on differently-camouflaged backgrounds.
  2. Kettlewell's original experiments, their strengths and weaknesses, and the recent accusations/implications that these experiments were hopelessly flawed (alleged by Jonathan Wells in Icons of Evolution and by his creationist fans) or even fraudulent (a charge from journalist Judith Hooper's book Of Moths and Men).
  3. Textbook accounts of the science done by Kettlewell and later researchers in light of the above controversies. Do peppered moths still belong in textbooks?
  4. This page should provide readers with enough background on the science and scientists involved in the peppered moth case that they will be able to make well-informed assessments of the case for themselves.

Kettlewell's science, and the science that followed him, has gotten a very bad rap as of late, from creationists, from Hooper's book and other poor science journalism, and even from a few scientists who are poorly acquainted with the scientific literature on the peppered moth. The reader should make no decision about the Bird Predation Theory based on an alleged authority -- arguments like "Jerry Coyne said that the peppered moth example was dead or dying in a book review in Nature" have misled a great many people. Jerry Coyne is an evolutionary biologist but has never done field research on peppered moths, so his pronouncements are not definitive, especially since his conclusion is disputed by all of the active peppered moth researchers. The reader is encouraged to look up some of the key references presented here, and to evaluate the body of evidence as a whole when reaching conclusions about this or that aspect of Kettlewell, his Bird Predation Theory, and the arguments surrounding it.

To begin, some background must be presented. Far too many have expressed opinions on the Bird Predation Theory despite an obvious lack of knowledge of basic facts about moths and peppered moths.

Introduction

If one reads Judith Hooper's 2002 book Of Moths and Men, one might get the impression that the differential bird predation theory has been falsified, or at the very least the theory is unproven and upheld by little more than wishful thinking. Of Moths and Men claims not to be a creationist work, but continues the press tradition of hyperbole and obituary-writing for the differential bird predation theory.

This has been the tenor of commentary in the popular press, and even some of the scientific press, ever since the publication of peppered moth researcher Michael Majerus' 1998 book Melanism: Evolution in Action. Majerus (1998) reviewed the peppered moth case in detail and was interpreted by many as drastically undermining Kettlewell's Bird Predation Theory. Majerus' book happened to coincide with a critical review (Sargent et al., 1998) of the peppered moth case written by three long-time dissenters to Kettlewell's theory (Ted Sargent, and Millar and Lambert). A subsequent review of Melanism, in the top journal Nature, was written by evolutionary biologist Jerry Coyne (Coyne, 1998). Coyne was clearly heavily influenced by Sargent et al., and concluded that "we must discard Biston as a well-understood example of natural selection in action" and that his feeling about this "resembles the dismay attending my discovery, at the age of six, that it was my father and not Santa who brought the presents on Christmas Eve."

With this seemingly authoritative pronouncement, the science press on peppered moth research switched to "long-standing paradigm overthrown" mode and hasn't quit since. Robert Matthews' March 14, 1999 piece in the U.K.'s The Sunday Telegraph was a classic example of this kind of hyperbole. It was entitled "Scientists pick holes in Darwin moth theory", and it declared that the peppered moth example was "based on a series of scientific blunders", that Kettlewell's experiments were "worthless", and that they were "designed to come up with the 'right' answer". Creationists sniffed trouble and have since trumpeted the death of this classic textbook example of natural selection in literally hundreds of webpages and articles, most prominently in the form of Jonathan Wells' articles and (2000) book Icons of Evolution. Referring to textbook accounts, creationists cried "fraud" and "the peppered moth is a peppered myth".

In addition Hooper (2002) also makes the even more lurid claim, not previously advanced by even the creationists, that Bernard Kettlewell's original results might have been due to unconscious or conscious fraud.

Given this setting, how could things get any worse for Kettlewell and his peppered moths? A Nature review says the case is unproven, the press says that the paradigm is dead, creationists are declaring victory, and even a noncreationist journalist is alledging fraud. Surely this must be a scientific view widespread among the experts, correct?

Well, no. Here is what the aforementioned Michael Majerus, whose 1998 book Melanism sparked the blaze, wrote in his 2002 book Moths:

[E]very scientist I know who has worked on melanism in the Peppered moth in the field still regards differential predation of the morphs in different habitats as of prime importance in the case. The critics of work on this case and those who cast doubt on its validity are, without exception, persons who have, as far as I know, never bred the moth and never conducted an experiment on it. In most cases they have probably never seen a live Peppered moth in the wild. Perhaps those who have the most intimate knowledge of this moth are the scientists who have bred it, watched it and studied it, in both the laboratory and the wild. These include, among others, the late Sir Cyril Clarke, Professors Paul Brakefield, Laurence Cook, Bruce Grant, K. Mikkola, Drs Rory Howlett, Carys Jones, David Lees, John Muggleton and myself. I believe that, without exception, it is our view that the case of melanism in the Peppered moth still stands as one of the best examples of evolution, by natural selection, in action. (Majerus 2002, p. 252)

Majerus wrote this at the conclusion of yet another review of the peppered moth case, to which he devoted most of a chapter of his book Moths. It may surprise the reader to learn that this review was quite similar, and had the same conclusions, as Majerus' 1998 review in Melanism. And in fact, the other peppered moth researchers have expressed similar sentiments. Laurence Cook wrote a rebuttal to Coyne and Sargent et al. in the Biological Journal of the Linnean Society in 2000, Bruce Grant wrote a rebuttal in the journal Evolution in 1999, and Grant and Clarke collaborated on another review of the peppered moth case for the Encyclopedia of Life Sciences in 2000.

So here is the paradox: according to these scientists, the world experts on peppered moths and industrial melanism, Kettlewell (while acknowledged to be imperfect) is basically doing just fine, along with the differential bird predation theory. And there is the additional point that if Kettlewell was right after all, then fraud does not need to be invoked to explain his remarkable results. Despite this, the press and other inexpert commentators are giving the public a picture of a paradigm going down in flames.

For many readers, it may be enough to know that the peppered moth researchers are still supporting the differential bird predation theory, and that the scientific dissidents are (a) few in number and (b) armchair observers of peppered moth research. As a practical matter, all of us decide to trust the experts in numerous matters of science, technology, and medicine, every day, essentially relying on their authority. If one decides to rely on authority here, then the case is closed, and the peppered moth retains its prominent position in textbooks, with some small modifications.

If, however, one wishes to develop a reasonably well-informed opinion on the peppered moth case, then it will be important to:

Once this has been accomplished, one is in a good position to decide what the likelihood of the differential bird predation theory is, and also assess the probability of alternative hypotheses that have been suggested by various parties. Here it is also important to consider what future observations would increase or decrease confidence in the theory and the alternatives.

Background

An attempt will be made to review the essentials of the peppered moth case. This is a fairly massive task, so contributions on any aspect of the case are encouraged.

Common Names

The peppered moth is so called because the typica morph, with a primarily white body and wings covered with small black spots, looks like it has been sprinkled with pepper. One of the first recorded uses of this name occurs in the 1766 work of Moses Harris, The Aurelian or Natural History of English Insects; Namely, Moths and Butterflies<ref name="Harris">M. Harris (1766) The Aurelian or Natural History of British Insects; Namely, Moths and Butterflies, Newnes (Twickenham, UK)</ref>. An older name is the "salt and pepper moth". In the German language it is known as "Birkenspanner", in the Dutch language "Berkespanner"; and in the French language "Phal讥 du bouleau" all meaning "birch moth", the birch tree being one of its principle food sources. In the Japanese language it is known as "Oo-shimofuri-eda-shaku" meaning "frosted branch-measuring moth.

Taxonomy

Moths and butterflies together make up the order Lepidoptera. Lepidoptera are one of the subgroups within the class Insecta, which in turn are a subgroup of the phylum Arthropods. More references and links on the Lepidoptera can be found at the Tree of Life Lepidoptera page, the University of California Museum of Paleontology (UCMP) Introduction to the Lepidoptera page, and the very extensive Electronic Resources on Lepidoptera.

According to one webpage, there are about 140,000 species of Lepidoptera worldwide. In the U.K. alone over 2,000 species have been recorded (Majerus 2002). The vast majority of Lepidoptera (>90%) are moths, although most people pay much more attention to butterflies. According to Majerus (2002) there is not, in fact, a hard-and-fast distinction between butterflies and moths. Very generally speaking, moths fly at night, but butterflies by day; and butterflies tend to be brightly colored whereas moths are dull-colored. There are, however, brightly colored, day-flying moths. Many pictures of British moths can be found at UKMoths.

Peppered moths fall with in the family Geometridae, the geometer or geometric moths; one of the numerous families of Lepidoptera. The scientific name for the peppered moth is Biston betularia. "betularia" means of the birch tree, which is one of its major food plants.

Peppered moths have three subspecies, one on each continent. B. b. betularia in Europe, B. b. cognataria in North America and B. b. cognataria in Japan.

This [full classification] of the peppered moth has it as:

Lineage: cellular organisms; (superkingdom) Eukaryota; Fungi/Metazoa group; (kingdom)Metazoa; (superclass) Eumetazoa; (class) Bilateria; Coelomata; Protostomia; Panarthropoda; (phylum) Arthropoda; Mandibulata; Pancrustacea; (superclass) Hexapoda; (class) Insecta; Dicondylia; Pterygota; (subclass) Neoptera; (infraclass) Endopterygota; (superorder) Amphiesmenoptera; (order) Lepidoptera; (suborder) Glossata; (infraorder) Neolepidoptera; (parvorder) Heteroneura; Ditrysia; Obtectomera; (superfamily) Geometroidea; (family) Geometridae; Ennominae; (genus) Biston

Ecology

A brief introduction to the biology and ecology of butterflies and moths is the Order Lepidoptera page at the Animal Diversity Web.

The life-cycle of your standard moth (or butterfly) is basically this: an egg which has been laid hatches, resulting in a larva, also known as a caterpillar. The larval stage actually encompasses most of the lifetime of the organism; this is where most of the feeding and growing is done; indeed, in some species the adult, winged "moth" stage does no feeding at all.

In the case of the peppered moth, one of the first acts of the young larva is to make a silk thread; this will be caught by the wind and act as a "parachute" which disperses the larva as part of the aerial plankton, often a considerable distance (as we will see later, the various methods of migration of peppered moth individuals are crucial to understanding gene flow and the distribution of melanic forms in relation to polluted areas).

The larval food is generally some kind of plant matter (before synthetic fibers were common in clothing, a few moth species made pests of themselves by eating clothes). Peppered moth larvae appear to be generalist leaf-eaters, consuming a wide variety of species. As larvae grow older, they go through a number of molting stages, shedding their hardened outer cuticle and growing a new one. Each growth stage is known as an "instar".

The main goal of the caterpillar stage is to eat as much as possible and avoid being eaten. Caterpillars therefore exhibit a wide range of defenses including camouflage, poison and warning coloration, and defensive behaviors such as dropping off a branch but keeping a silk thread attached to the branch climb back up. In the peppered moth, camouflage is the primary means of larval defense. Very small larvae may be transparent and will therefore be the color of whatever is in their gut; at later stages, larvae will display some combination of environmentally and genetically controlled coloration. Majerus indicates that the larvae of many leaf-eating species, among them the peppered moth, are sensitive to the background on which they are living; he writes, "[i]n the main, larvae of these species reared just on green leaves were of a green colour, while those reared with brown twigs became brown." (Majerus 1998, p. 67) This is an example of the common kind of "induction", where the environment has an influence on a trait but the "acquired" trait of color is not known to be inherited -- the next generation can have a different color, again depending on the environment.

When the larva is fully grown, it will make a pupa (cocoon) out of silk. In this stage the larva reorganizes into a completely different adult stage. In some species, the pupal stage may be the form in which the moth spends the winter.

The final stage occurs when the adult breaks out of its cocoon. The adult will hang on the cocoon or nearby, and spend an hour or two pumping hemolymph (body fluid) into its wings to pump them up. The peppered moth will usually emerge in the afternoon. In the first night, the female peppered moth will engage in a relatively short dispersal flight; this dispersal urge decreases over several nights. In order to attract mates, the female releases a powerful pheromone. The male moths can smell this pheromone and will follow it, and remain active flyers until they find a mate. Marked males have been recaptured many kilometers from their release site.

In the peppered moth, a mated pair will remain linked for a day or more; this is probably how the male guarantees that other males do not mate the same female. (The reproductive intrigues of various insects is a fascinating topic that we cannot go into here; I recommend The Evolution of Mating Systems in Insects and Arachnids, edited by Choe & Crespi, for an introduction.) The female will then proceed to lay her eggs (preferably under a foliose lichen, barring that a crack, Liebert & Brakefield 1987), and both adults will die shortly thereafter. The adult stage of the peppered moth lasts a matter of a few days.

The phenomenon: industrial melanism

It is important to distinguish the phenomenon of industrial melanism from the hypotheses and theories which might explain the phenomenon in this or that species.

[insert description of industrial melanism generally and in peppered moths, e.g. from Kettlewell 1973]. No. Insert Majerus 1998 classification as it is superior to Kettlewell's. This displays full industrial melanism. Alternatives are partial industrial melanism.

The Bird Predation Theory

The use of the word "theory" for the explanation of industrial melanism in the peppered moth is quite deliberate. A scientific theory is defined as a well-confirmed hypothesis that explains a large body of facts and which has inspired a large body of research. Clearly the Bird Predation Theory is not as "big" a theory as General Relativity or Evolution by Natural Selection, but it is on a par with many smaller theories commonly discussed in science. The word "hypothesis" could have been used, but it is the argument of this webpage that Kettlewell's explanation is much better confirmed than just another hypothesis. Theories can of course still be tested, proven wrong, and replaced by a new working hypothesis which may eventually become a theory, so the choice of the word "theory" is not a barrier to a fair consideration of the topic.

The Bird Predation Theory (BPT) argues that natural selection, in the form of differential bird predation on different color morphs of the peppered moth, is the primary cause for the advance, and in modern times the decline, of the dark carbonaria form of the peppered moth Biston betularia in and around industrial areas.

The BPT is laid out explicitly in order to distinguish it from various subsidiary stories, hypotheses, and miscellaneous brick-a-brack. For example, the BPT is not exactly the same thing as "the traditional textbook stories", which often contain additional but peripheral elements ("peppered moths rest on tree trunks") which are often oversimplified but can be easily corrected without changing the validity of the BPT. If the BPT is well-supported, then the essence of the textbook accounts is correct, and the peppered moths deserve to remain in textbooks, whatever fine points need correcting. This distinction is important because authorities like Majerus have indeed been critical of short textbook accounts. Even though Majerus is a strong and explicit supporter of the BPT, his remarks have often been misinterpreted as critiques of the Bird Predation Theory instead of textbooks.

The BPT should also be distinguished from some subsidiary ideas which were sometimes tacked on to the BPT over the years by Kettlewell and others. Examples include: Kettlewell's hypothesis about the mechanism of background choice in the peppered moth (the "contrast-conflict hypothesis") and the evolution of background choice, and the evolution of dominance of the melanism trait via the accumulation of modifiers. Other nonessential hypotheses include heterosis and Kettlewell's "recurrent necessity" conception of melanism. These hypotheses are extraneous to the question of the truth of the BPT and should be assessed independently of it; however, both Sargent et al. (1998) and Hooper (2002) link the issues. For example, Sargent's only experimental work testing any of Kettlewell's ideas was Sargent's testing of Kettlewell's "contrast-conflict hypothesis" in the late 1960's (although not, strangely, with peppered moths). Kettlewell did not appreciate Sargent's critiques and this may go a ways towards explaining Sargent's bitterness towards the "peppered moth establishment" (as Hooper would put it) but the whole matter is peripheral to the question at hand.

Additionally, the BPT does not state that "natural selection by bird predation explains every aspect of the distribution of carbonaria morphs." This straw man is sometimes set up for knocking down by Hooper, for example when Hooper quotes a scientist saying that bird predation doesn't explain everything (need a p. #). Migration, for one thing, will have a huge impact on gene flow, and will in turn be impacted by abiotic factors such as the prevailing wind and even particular weather events month-to-month and season-to-season. Therefore, whenever a scientist is quoted as saying that bird predation is an incomplete explanation, one has to consider, among other things, if the scientist was referring to migration as an additional piece of the puzzle. Moths have wings and it does not weaken the BPT if they use them.

Additional factors which have been invoked in predictive computer models to explain the relative frequencies of the three varieties of peppered moth over the whole of England and Wales include frequency-dependent selection and "nonvisual selective pressure". Frequency-dependent selection is almost an obligatory inclusion: it stands to reason that, if a moth is in an environment where dark color is favored, then it will be at a bigger relative selective advantage if only 10% of the moths are dark, than if 95% of them are dark. Thus, frequency-dependent selection is like migration, a factor that must be considered but not an alternative to the BPT. "Nonvisual selective pressure", for example an innate difference in viability between moth morphs, could be a challenger to the BPT as described; however, the challenge for a nonvisual selection hypothesis is to explain the phenomenon of industrial melanism, which means that it has to account for both the increase in carbonaria with pollution, and the decrease following the implementation of clean-air laws. In conclusion, unless the hypothesized nonvisual selection somehow changes direction with pollution, it is like migration and frequency-dependent selection in that it is a factor to be considered during detailed modelling, but is complementary to, rather than an alternative of the BPT.

In concluding the section, the BPT is described explicitly so that the reader may keep clear the distinction between the key issue, the assessment of Kettlewell's BPT, and the various subsidiary issues, e.g. textbooks, extraneous hypotheses, and subsidiary factors important for modelling distributions but not crucial to evaluating the BPT. Scientists who have published in the literature criticisms of these latter topics should be rigorously distinguished from scientists criticizing the BPT.

Scientific research on the peppered moth

[This is a huge project and will hopefully be accomplished by multiple authors. For an up-to-date review see Majerus, 1998, Melanism: Evolution in Action]

Pre-Kettlewell

When the peppered moth was first described by Moses Harris in 1766, only the white typica morph was known to entomologists. In 1848, the darker carbonaria morph was discovered by an amateur butterfly collector<ref name="Edelson">Edelson, R.S. (1864) Amphydasis betulularia. Entomologist 2, p. 150</ref>. Many other collectors began to notice the darker form, especially around industrial centres. In the late 19th century, the Victorian lepidopterist James W. Tutt hypothesized that the increased prevalence of the darker form was due to an advantage in camouflage it would have against the dark bark of trees on which the white lichens had been removed by pollution. That the carbonaria form had an advantage was also considered by geneticist Edmund Brisco Ford, although Ford seemed to think that the gene for dark coloration had a second effect on some part of the physiology of the moth, making the darker forms hardier than their pale counterparts<ref name="Ford">Ford, E.B. (1940) "Problems of heredity in the lepidoptera." Biological Reviews 12, pp. 461–503</ref>.

Kettlewell

English physician and geneticist Bernard Kettlewell became a a Nuffield Research Fellow in the Department of Genetics of the Department of Zoology at Oxford University in 1952. Under the supervision of E.B. Ford, who was at the time the Director of the Genetics Laboratory and in 1963 became Professor of Ecological Genetics, Kettlewell conducted three surveys of morph frequencies: from 1952-1956, from 1957-1964 and from 1965-1970.

Kettlewell's actual experiments

In the summer of 1953, Kettlewell began his first series of experiments on the peppered moth. Kettlewell began to breed the moth on a large scale in preperation for his experiments. In addition, Kettlewell devised a scoring system to judge how conspicuous a resting moth would be. This involved walking backwards from a resting moth until it became indistinguishable from the bark of the tree on which with the moth rested. Kettlewell claimed he could tell the score of an insect, after practice, without pacing out the distance. He corroborated his scored with others, including a Dr. R. A. Hinde, and found his results "seldom diverged by more than plus or minus one unit<ref name="Kett1955">Kettlewell, H.B.D. (1955) Selection experiments on industrial melanism in the lepidoptera. Heredity 9, pp. 323–342</ref>.

Distance (yards) <2 5 10 10-20 20-30 >30
Score +3 +2 +1 -1 -2 -3

Kettlewell began by conducting scoring experiments in the field. He released 651 moths into a "circumscribed wood in the Birmingham district, where the melanic [carbonaria] form comprised about 90 per cent. of the population"<ref name="Kett1955">-</ref>. He released 171 typica, 416 carbonaria and 64 insularia moths at 33 release points, which were located at the trunks and boughs of birch and oak trees. He found that on the dark bark of Birhimingham oak trees (which lacked lichen), the typica moths had an average score of -2.11 whereas the carbonaria had an average score of +2.33 and insularia scored +0.857. On the birch trees, which featured areas of both dark and light patches, the typica, carbonaria and insularia scored averages of +2.53, -0.54 and +2.50 respectively.

Kettlewell then set about determining whether moths would be eaten by birds. He released peppered moths into the aviaries at the research station of Madingley in Cambridge, which housed insectivorous great tits (Parus major). To provide adequate resting sites, Kettlewell introduced 5 darkened poles and 15 light poles, which in addition to the 13 dark support poles of the aviary, provided roughly equal opportunity for resting sites. The results showed that the more conspicuous moths (light moth on dark background, or dark moth on light background) were preyed upon in preference to the less conspicuous moths<ref name="Kett1955">-</ref>. Kettlewell also repeated this experiment using other insects in addition to the moths, to prevent the birds from searching each pole individually for moths, and found similar results.

Post-Kettlewell

Evolution in reverse

q: what does this mean? A: it refers to the decreasing frequency of the carbonaria morph after the industrial pollution decreased. 'Evolution in reverse' is also the title of a research paper by Cyril Clarke, published in 1985 in the Biological Journal of the Linnean Society.

Summary table of experimental support for the BPT

Conclusion

The modern controversy

Precursors

Kettlewell's critics

Creationists

Sermonti, Lambert, Millar

[note; In Berry 1990 there is a reference to a paper by these two Kiwis which would show that Kettlewell's experiments were void. It was to appear in Biological Reviews, but was it peer-reviewed out for being, well, nonsense?]

Sargent, Majerus, and Coyne

The Press

Jonathan Wells

More of The Press, and Judith Hooper

Reviews of Hooper: Good, Bad, and Ugly

The peppered moth researchers respond

Summary

Criticisms

Moth resting positions

Where they actually rest

Who cares where they actually rest?

Release times

Moth breeds

Changing the experimental protocol

Lichens

Distribution patterns

Computer model anomalies

Summary

The BPT versus alternatives

Induction

Sargent's strange model

Thermal melanism

Drift

Morph-specific viability

Bats did it

Majerus has done experiment on this.

Larval predation (beetles did it)

The marginal but possible alternative: pollution resistance

Did Kettlewell commit fraud?

No previous allegations

Hooper's "evidence"

The numbers

What about the moon?

Conclusion

Conclusion

In recent years, the classic textbook example of natural selection, industrial melanism in the peppered moth Biston betularia, has gotten a lot of bad press. A minority opinion of a very few scientists -- bordering on the fringe in some cases -- has, through a bizarre series of amplification events by uncritical science journalists and antievolutionists, somehow suddenly become conventional wisdom for a large number of people.

As this new conventional wisdom has it, the traditional peppered moth thesis has been overthrown, or at least put so badly in question that it should be removed from textbooks for extensive repairs. Furthermore, the new conventional wisdom has it that the success of the traditional peppered moth thesis was due primarily to wishful thinking and the desire to support neodarwinian theory, rather than evidence and logical reasoning.

It has been the argument of this webpage that the new conventional wisdom has got it all wrong. Like the proverbial butterfly (or moth?) fluttering its wings in China, eventually causing a storm on the other side of the planet, the current storm surrounding the peppered moth case began with the fringe views of a very few scientists. An uncritical acceptance of these views by journalists and a few scientists, plus a rather large amount of outright misinterpretation of the mainstream scientific literature on the peppered moth, created the impression among many moderately-informed readers of secondary scientific literature that the traditional thesis was on the rocks. From there, antievolutionists caught wind of the story and trumpeted the death of the peppered moth example as widely as possible, most notoriously in Intelligent Design Creationist Jonathan Wells' book Icons of Evolution.

This process is now feeding back into itself, with the publication of a noncreationist book on the supposed overthrow of the traditional peppered moth thesis, written by science journalist Judith Hooper and entitled Of Moths and Men: Intrigue, Tragedy and the Peppered Moth. Hooper's assessment of the state of the scientific question regarding the peppered moth makes all of the mistakes made by Wells' Icons of Evolution, plus some new ones of her own invention. While Wells' mistaken claims have been dealt with in extensive detail elsewhere, Hooper's book will undoubtedly be taken as vindication by antievolutionists and as confirmation of the new conventional wisdom by those readers, the public and many scientists alike, who depend on the secondary literature for information about the state of the peppered moth case.

The purpose of this webpage has therefore been to review the entire case for and against the traditional peppered moth thesis, with reference to the primary literature, and with specific attention being paid to the arguments put forward by science journalist Judith Hooper in her book Of Moths and Men, and the arguments of her primary inspiration, scientist T. D. Sargent. These arguments do not hold up to critical scrutiny, and therefore the often-made claims about the death of the peppered moth example have been greatly exagerrated. Kettlewell's Bird Predation Theory remains well-supported and deserves inclusion in textbooks.

References

<references/>

  1. R.J. Berry, 1990. Industrial melanism and peppered moths (Biston betularia (L.)), Biol. J. Linn. Soc., 39, 301-322.
  2. R.S Edleston 1864. Untitled (first f. carbonaria melanic morph Biston betularia). Entomologist 2:150
  3. J.B.S. Haldane, 1924. A Mathematical Theory of Natural and Artificial Selection, Trans. Canmb. Phil. Soc., 23, 19-41.
  4. J.W. Tutt, 1896. British Moths. George Routledge: London

See Also

Guidelines

This page should provide an overview to peppered moths, Kettlewell, and the recent controversies. Linked pages should be created for resources and specific topics.

Anyone who wishes to add material to this or related pages is encouraged to do so.

==Appendix I: Resources (online or otherwise) on Biston betularia == Webpages giving more or less the 'textbook' version

(note that not all textbooks even use the peppered moth -- e.g., Campbell (1999) doesn't even mention it, although an earlier edition did, which perhaps leads me to think that they were as misled by Sargent et al. and Coyne as everyone else, although obviously I have no direct knowledge of the textbook writers' reasons for doing anything).

Short version

  1. The Effects of Natural Selection : The Response of the Peppered Moth Biston betularia to Industrial Pollution. A biology course lab assignment.
  2. Natural Selection. Lecture notes.
  3. The Evolution of Populations. Lecture notes.
  4. More notes.
  5. Genetics Exercises: Industrial Melanism. With picture.
  6. Natural Selection Observed. Short discussion & questions.
  7. Natural selection. Lecture notes.
  8. Evolution: Introduction & Overview. Course notes.
  9. More lecture notes
  10. A brief treatment of Industrial Melanism
  11. Introduction to Population and Evolutionary Genetics. Brief outline.

Non-course pages

  1. A brief anti-creationist (Morris) page invoking moths by W.R. Elsberry.
  2. The Peppered Moth Controversy by Ross L., Creation vs. Evolution II Team Member. A debate of some sort.
  3. Virtual Peppered Moths. Shockwave simulation. You be the bird. Doubtlessly simplified version of real life, bird UV vision not being simulated and all, but still pretty darn cool.

Longer treatments

  1. General Selection Model. Lots of math for a population genetics course.
  2. How Kettlewell found Darwin's missing evidence in the British Peppered Moth by Chris Young. A much more detailed account than in most textbooks; some good graphics and discussion of Kettlewell's results.
  3. Introductory Exercises with the Genetics Model
  4. How is Science Done? Case of the Peppered Moth. Introducing hypothesis-testing via Kettlewell.
  5. Evolution in Peppered Moths: An Update. Discusses Grant's (1996) article.
  6. Pages giving the conventional view but citing Wells or Coyne or expressing extra caution
  7. The Peppered Moth - An Update. On Ken Miller's homepage; an update for his textbook Biology. August, 1999. A wee bit more conservative on the moth story than is probably necessary.
  8. Natural Selection and Speciation. An introductory biology course page on natural selection.
  9. "Are Mutations Harmful?" by Richard Harter (1999). At talk.origins. Accessed online 10/11/2001. I posted a feedback asking that this be revised or extended to include the full complexity of the situation.
  10. Directional selection in peppered moths (Biston betularia) in England
  11. Industrial Melanism
  12. Industrial Melanism in an "Evolution and Adaptation" page.
  13. The Peppered Moth. Moth drawings.
  14. London's Peppered Moths: A Case Study of Natural Selection. By Laura Klappenbach at the Animals/Wildlife section of About.com. The focus on London is odd. Gives standard story but links to pages on recent controversy.

Resources giving the 'dissenting' scientific view on peppered moths

An older flurry, based again on few articles rather than the consensus of moth experts

  1. Jeremy Cherfas, "Exploding the myth of the melanic moth," New Scientist 112: 25 (1986/7).
  2. "Not black and white," by Jerry A. Coyne. Nature, volume 396, 35 - 36 (1998). Hosted at Peter Gegenheimer's "Kansas Evolution" page, unfortunately under the heading "Reviews of Pseudoscience Books by Jerry Coyne." Certainly no one thinks that Michael Majerus' book was pseudoscience.
  3. "Scientists pick holes in Darwin moth theory, " by Robert Matthews (1999), Science Correspondent. The Telegraph (telegraph.co.uk), Issue 1388. Sunday, March 14, 1999. Accessed online 10/11/2001.

By or about Jonathan Wells

  1. "Second Thoughts about Peppered Moths," by Jonathan Wells (1999). The Scientist, vol 13[11]:13, May. 24, 1999. In the 'Opinion' section. A toned-down version of Wells' arguments on the peppered moth; still, this was a bit of a coup as it leant additional credibility to Wells.
  2. "Second Thoughts about Peppered Moths: This classical story of evolution by natural selection needs revising," by Jonathan Wells (1999, last modified Oct. 7, 2001). At trueorigin.org. A less toned-down version.
  3. Significance of the Peppered Moth Argument, by Jonathan Wells (2000). Online at ARN. Responds to a letter and reemphasizes his arguments.
  4. Moth-eaten Darwinism, by Carla Yu (1999). April 5, 1999, in the [Alberta Report Alberta Report]. Wells pulls a fast one and gets mistaken for being a real scientist. Also contains the "How convoluted do you want to make it for a first-time learner?" quote from textbook author Bob Ritter (a good point, actually).

General Wells pages

  1. Jonathan Wells at ARN

Other members of the 'Intelligent Design' (ID) movement

  1. The Wedge: Breaking the Modernist Monopoly on Science. By Phillip E. Johnson. In Touchstone Magazine. Quote in the "Peppered Moth" box: "The textbook story is now thoroughly discredited." And cites Coyne.

The creationist take

"The peppered moth is just microevolution within a type"

which is true, if "type" means "species," which is what it originally did.

  1. Do Peppered Moths Prove Evolution? by John D. Morris (1994), of the Institute for Creation Research.
  2. "The Peppered Moth Shows Evolution In Action," by David N. Menton (1991). Missouri Association for Creation.
  3. Variation and seletion (within a kind, of course). From Jason's Creation Page. More moth pics [http://physics.colorado.edu/~lisle/create/moths.html here.]
  4. "Biology Class Discussion" in the Creation-Evolution Encylopedia. Typical "professor is an idiot"-type dialog.

The "peppered moth story is dead"

From organized group pages:

  1. What About the Peppered Moth? by John D. Morris (1999), president of the Institute for Creation Research.
  2. The Hoax of the Peppered Moth. A copy of "Goodbye, Peppered Moths: A classic evolutionary story comes unstuck" by Carl Wieland of Creation Magazine (June-August 1999).
  3. Let's mothball the peppered myth. A crude re-hashing by Margaret Helder of the Creation Science Association of Alberta.
  4. Biston betularia - Peppered Research on the Peppered Moth. By Wayne R. Spencer. More moderate. At the DFW Creation Net.
  5. A moth-eaten evolutionary story. By David J. Tyler (June 1999). Criticizes Steve Jones's writing in the Daily Telegraph. On the website of the Biblical Creation Society.
  6. The Peppered Moth: Evolution Comes Unglued. By Mark Varney of the Crystal Lake Church of Christ. Repeats "only two moths" myth. Powerpoint presentation.
  7. Famous Evolution Hoaxes and Exaggerations. By David Dewitt, Associate Director of Creation Studies at Liberty University. The peppered moths are right up there with Piltdown Man and Nebraska Man. In the National Liberty Journal online.

Individuals

  1. A particularly confused page. Format is currently screwy, but the 'thermal melanism' (for a nocturnal moth!) alternative explanation is proposed.
  2. Doctored Evolution Data: The Piltdown Peppered Moth by Emerson Thomas McMullen at his site at Georgia Southern University.

Kettlewell pages

  1. Kettlewell Archive Site. Everything you could want to know about Bernard Kettlewell.
  2. Henry Bernard Davis Kettlewell Bibliography
  3. A proposal for a book on Kettlewell and Peppered Moths by Dave Rudge.

Other experts

  1. Bruce S. Grant, Professor of Biology at College of William and Mary. Recent publications listed.
  2. Grant, Bruce S. 1999. Fine tuning the peppered moth paradigm. Evolution 53: 980-984. A must-read article.
  3. Grant, Bruce S. and Cyril A. Clarke. 2000. Industrial Melanism. Encyclopedia of Life Sciences. Macmillan Reference Ltd. May require personal or institutional subscription. Similar to Grant (1999).
  4. A Bayesian Analysis of Strategies in Evolutionary Biology, by David Wÿss Rudge (1998). Perspectives on Science 6.4 (1998) 341-360. A philosophy of science article that discusses Kettlewell's experiments to see how they fit with other examples of scientific observation and experiment. Puts particular emphasis (appropriately) on the use of experimental controls by Kettlewell.

Moth research in the media

  1. Moths become media stars. The University [of Michigan] Record, November 26, 1996. Picture of moth collections.
  2. Back and Forth, and Back Again: Biologist makes an unprecedented discovery about one of the most noted examples of evolution in nature. Article on Bruce Grant by Poul [Paul?] E. Olson at William and Mary.

Miscellaneous

  1. The evolution and maintenance of industrial melanism in the Lepidoptera. by Michael E. N. Majerus (1999). Bol. S.E.A., nº 26, 1999 : 637-649. For all you Spanish speakers out there. Some good graphics, though.
  2. E.S. George Reserve of the University of Michigan, where Grant did some of his work.
  3. The Great Peppered Moth Debate by Andrew J. Bradbury. A pro-Blyth site (Blyth described natural selection, adaptive radiation, the struggle for existence, etc. long before Darwin tackled these subjects. The site includes four of Blyth's key articles). This particular session discusses views on the significance of peppered moths both pro and con.
  4. Top Ten insects, by Dr. Dorothy Feir, a former president of the Entomological Society of America, giving her list of the Top 10 most fascinating insects (Biston is number 6).
  5. Moth sightings. I guess they've got moth watchers over in the UK.
  6. The Peppered Moth, a novel by Margaret Drabble, apparently about people and relationships and things and not really about moths.
  7. Gray Peppered Moths and Brilliant Minds. By Tom Hunt (1997). Somehow, peppered moths and learning disabilities are connected.

Random pictures

  1. Biston betularia cognataria: Pepper-and-salt Geometer Moth
  2. WILDLIFE MATTERS PHOTOGRAPHIC LIBRARY. Buy your bug photos here!
  3. Nachtfalter rund um Freiburg. Pictures of bugs, including Biston.

Lichens and air pollution research

  1. Lichen further research

Acknowledgments

-- Nic Tamzek (created page and provided seed material)

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