David Wÿss Rudge

Does being wrong make Kettlewell wrong for science teaching

Biology textbooks, almost without exception, introduce students to evolutionary theory with reference to the phenomenon of industrial melanism, long regarded as the classic example of natural selection. Its status as an icon among biology teachers and the public stands in stark contrast to ongoing debates among scientists which reveal that this phenomenon is nowhere near as well understood as textbooks would have us believe. The ‘classic’ account of the phenomenon of industrial melanism, associated with the work of H B D Kettlewell and recounted in texts and the popular media, is reviewed. Several major discrepancies are identified that have led some to conclude that it should be removed from textbooks altogether. It is argued that these problems actually augment the value of discussing the phenomenon of industrial melanism, and Kettlewells work in particular, for the teaching of evolutionary biology. The ‘classic account’ has several advantages that make it particularly useful as an introduction to the concept of natural selection. Discussing some of the details so often omitted from texts can potentially enhance student understanding about the nature of science as a process.

Taking the Peppered Moth with a Grain of Salt

H. B. D. Kettlewells (1955, 1956) classic field experiments on industrial melanism in polluted and unpolluted settings using the peppered moth, Biston betularia, are routinely cited as establishing that the melanic (dark) form of the moth rose in frequency downwind of industrial centers because of the cryptic advantage dark coloration provides against visual predators in soot-darkened environments. This paper critiques three common myths surrounding these investigations: (1) that Kettlewell used a model that identified crypsis as the only selective force responsible for the spread of the melanic gene, (2) that Kettlewells field experiments alone established that selection for crypsis was the most important factor in the spread of melanic forms, and (3) that Kettlewells investigations in an unpolluted wood near Dorset constituted a control for his earlier Birmingham studies (contra Hagen 1993, 1996). This analysis further identifies two features that distinguish manipulative experiments in evolutionary biology from experiments in other contexts. First, experiments in evolutionary biology rest on a wealth of information provided by strictly observational ecological studies; in the absence of such information experiments in evolutionary biology make no sense. Second, there is a trade-off between how much control investigators have over the conditions being studied and how informative the results of the experiment will be with regard to natural populations.

Did Kettlewell commit fraud? Re-examining the evidence

H.B.D. Kettlewell is famous for several investigations conducted in the early 1950s on the phenomenon of industrial melanism, which are widely regarded as the classic demonstration of natural selection. In a recent (2002) book-length popularization of this episode in the history of the science, science writer Judith Hooper draws attention to what she interprets as discrepancies in the results reported by Kettlewell in his first scientific papers on the subject. On the basis of correspondence among Kettlewell and his associates, a survey of scientific publications that mention outstanding questions surrounding the phenomenon, as well as interviews with his son, surviving colleagues, and scientists who have worked on industrial melanism, Hooper all but explicitly concludes that Kettlewell committed fraud. The following essay critically examines her evidence in support of this allegation, including her discussion of his character, the alleged motives, and whether fraud was even committed. None of Hooper’s arguments is found to withstand careful scrutiny. The concluding section draws several conclusions about how history of science should be depicted to the public.

Kettlewell from an Error Statistician's Point of View

Bayesians and error statisticians have relied heavily upon examples from physics in developing their accounts of scientific inference. The present essay demonstrates it is possible to analyze H.B.D. Kettlewells classic study of natural selection from Deborah Mayos error statistical point of view (Mayo 1996). A comparison with a previous analysis of this episode from a Bayesian perspective (Rudge 1998) reveals that the error statistical account makes better sense of investigations such as Kettlewells because it clarifies how core elements in the design of experiments are used to minimize erroneous inferences rather than dwelling on whether the strategies used are reasonable.

The Role of Photographs and Films in Kettlewell's Popularizations of the Phenomenon of Industrial Melanism

H.B.D. Kettlewells investigations on the phenomenon of industrial melanism are generally referred to in textbooks and other popularizations of science as the classic demonstration of natural selection (Majerus 1989). A central question for historians of this episode is accounting for why public perceptions of the importance of Kettlewells work have diverged from those of researchers who actually work on the phenomenon. In a recent paper published in Biology and Philosophy, Joel Hagen draws attention to the role Kettlewell and his colleagues played in idealizing his investigations as an example of controlled experimentation in their several retrospective popular accounts. The present essay discusses the important role photographic and film depictions of differential bird predation played in Kettlewells popularizations. This analysis supports Hagens contentions that Kettlewell deftly and strategically used these visual representations to command assent to his interpretation of the phenomenon and shore up claims about the scientific legitimacy and importance of his work. It nevertheless disputes that these images were intended to portray Kettlewells experiments as an example of controlled experimentation. In a concluding section, the essay draws several morals from this analysis regarding the use of popularized articles and visual images to teach science.

The Beauty of Kettlewell's Classic Experimental Demonstration of Natural Selection

Abstract H. B. D. Kettlewells work on the phenomenon of industrial melanism is widely regarded as the classic demonstration of natural selection and one of the most beautiful experiments in evolutionary biology. The following essay discusses the mark–release–recapture experiments Kettlewell conducted in 1953 and 1955, with reference to Robert Creases analysis of what it means for an experiment to be considered beautiful (significance of results, overall conceptual simplicity, conclusiveness). In fact, much of the apparent beauty of these experiments is illusory: the phenomenon of industrial melanism and Kettlewells work on it are much more complicated than they are usually depicted in textbooks and the popular media. These complexities do not undermine the continued use of Kettlewells work in science teaching, but they do suggest that the very features that lead scientists to appreciate Kettlewells experiments as “beautiful” may be largely an artifact of how they have been portrayed.

Mendel and the Nature of Science

Abstract Students often have difficulty understanding inheritance patterns and issues associated with the nature of science as a process. To help address these issues, we developed a unit plan based on Gregor Mendels well-known research on inheritance patterns among pea plants. The unit introduces students to Mendels background and the questions he sought to address. Students then conduct their own investigation, using Virtual Genetics Lab II (VGLII) software to attempt to confirm Mendels results. In the course of completing their investigations, students learn about alternative inheritance patterns to Mendelian genetics. The unit was created in the context of a college introductory biology course but could be implemented in a high school course.

Using David Lack's Observations of Finch Beak Size to Teach Natural Selection & the Nature of Science

Abstract One of the key aspects of natural selection is competition, yet the concept of competition is not necessarily emphasized in explanations of natural selection. Because of this, we developed an activity for our class that focuses on competition and provides an example of the effects of competition on natural selection. This hands-on activity models the field study completed by David Lack on Darwins finches. By using this historical study, we also give students an example of the nature-of-science concept of multiple methods. Although this activity was created for a college introductory biology course, it is appropriate for high school. We also provide an additional objective for upper-level ecology and evolution courses.

Typhoid Mary: A Story-Based Approach to the Teaching of Epidemiological Concepts

Abstract Understanding Kochs postulates, including how they are used to study the spread of disease within a population, is central to the teaching of microbiology. These concepts are often presented and discussed with little or no historical background, and as a result students fail to appreciate how the field has developed from past to present. We designed a lesson based on the story of Typhoid Mary to engage students in the learning and application of Kochs postulates in the field of epidemiology and provide insight into the interplay between scientists and the public as illustrated by this episode. The lesson uses an interrupted story technique in which students watch a documentary about Typhoid Mary, with pauses to discuss the events and engage in a role-play to reenact Marys trial. The purpose is to improve student understanding of central concepts and to foster a deeper understanding of issues associated with the nature of science (NOS), such as how the process of science is influenced by culture and society (and vice versa). This lesson plan was created for a college-level microbiology course for non-majors, but can be easily modified for use in high school settings.

Using the Discovery of the Structure of DNA to Illustrate Cultural Aspects of Science

Abstract DNA is a central topic in biology courses because it is crucial to an understanding of modern genetics. Many instructors introduce the topic by means of a sanitized retelling of the history of the discovery of the structure of DNA by James Watson and Francis Crick. Historical research since 1968 has revealed that Rosalind Franklins contributions were more significant than they are usually depicted. In light of this, we developed a two-class lesson plan that draws attention to Rosalind Franklins role in the discovery and to the social and cultural aspects of science. The first class provides background information regarding what led scientists to recognize that DNA was the molecule of heredity. Students watch a documentary video that includes interviews with some of the surviving protagonists. Students (working in groups) are then asked to debate Franklins role to refine their awareness of how social and cultural factors affected both the process of science and how it has been recounted. The second class has students work in groups to build a structural model of DNA through hands-on activities. The essay concludes by drawing attention to how the two-day lesson plan, developed for a college-level biology course, can be adapted for use in other settings.