Academic journal article Transactions of the American Philosophical Society

Chapter 11: Papilio Dardanus: The Natural Animal from the Experimentalist's Point of View

Academic journal article Transactions of the American Philosophical Society

Chapter 11: Papilio Dardanus: The Natural Animal from the Experimentalist's Point of View

Article excerpt

INTRODUCTION

In 1930, German geneticist Richard Goldschmidt joined four of the most prominent English biologists at a dinner party at London's Athenaeum Club: J. S. Huxley, J. B. S. Haldane, R A. Fisher, and E. B. Ford. Fifteen years later, in a paper regarding mimicry, genetics, and evolution, Goldschmidt imagined what may have happened if the conversation had turned to mimicry so many years before:

If the conversation and discussion had turned to the topic of mimicry I should probably have stated my views similarly to the contents of the following paper. Had this been the case, it would certainly have been a lively, if not heated discussion, but nevertheless one among friends. In such a spirit the foUowing critical discussion is presented. (Goldschmidt, 1945)

Goldschmidt's paper provoked a vigorous attack from E. B. Ford, who suggested that the debate between micromutation and macromutation might be laid to rest through a detailed genetic analysis of a Little known African swallowtail: Papilio dardanus.

P. dardanus was converted to a laboratory animal for a brief period. Its value depended upon its natural variability. It was the focus of a specific study to address a specific aspect of evolutionary biology, namely the evolution of defensive mimicry.1 Scientists hoped that P. dardanus would help them determine the nature of genetic change: macromutation versus micromutation. Using Papilio dardanus as a lens, in this chapter I examine the scientific discourse regarding evolutionary gradualism (continuous evolution via micromutation) versus saltationism (discontinuous evolution via macromutation). The central characters of my story are familiar; indeed, several of the major figures in the forging of the evolutionary synthesis play key roles. Also familiar is the topic of debate, namely, evolutionary gradualism versus saltationism. Less familiar (and little known in the history and philosophy of science) is the butterfly Papilio dardanus. In reconstructing the path of P. dardanus from natural entity to exemplary organism in the laboratory, I argue that certain organisms are so closely linked to the questions they answer that their utility drops once such questions have been answered. "Exemplar" is an apt term for P. dardanus in the story that follows.

Recently historians of the life sciences have recognized that we can learn from the organisms that scientists study (just as we can learn from studies of scientists themselves, their institutions, social contexts, and cultural contexts). As study objects, organisms define questions while simultaneously answering them (see Clarke 8c Fujimura, 1992; Kohler, 1994; Lederman & Burian, 1993; Provine, 1971; Rader, 1998, 2004; Travis, 2006). For the scientist, the organism becomes a tool that he or she uses to learn about the nature of life. The scientist asks, "What can this organism tell me about life? Evolution? Genetics?" As a historian, I see the organism in a very different light. For me, the organism is a lens through which to view the development of scientific ideas. The central question to my mind has to be, "What is the impact of the actual choices of biological material on the content of biological knowledge?" Yet, this question raises the consideration of its inverse: "How has biological knowledge affected the biological material examined by scientists?" As knowledge and the material develop, the answers and the questions can change.

Before launching into the arguments surrounding Papilio dardanus, it will be useful to situate this debate in its broader context of the history of evolution and genetics.2 This term-laden and concept-laden conflict centered on the rate of variation in evolution. Darwin himself struggled with this problem.3 The issue was whether variation in nature occurred gradually in small discrete steps or whether variation happened suddenly in large leaps. Darwin beUeved that the latter type of variation (which he called "sports") was too uncommon to be the mechanism of change on which natural selection operated. …

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