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Galileo and the Leaning Tower of Pisa ✸ 95 5 Darwin’s Missing Frogs any old books claim that when Charles Darwin visited the Galápagos Islands, he was inspired to think about evolution by seeing variations in finches’ beaks. Most people believed that species were as unchangeable as the chemical elements. Just as no metallurgist could ever make gold, fish or lizards could never become birds. As the story goes, Darwin changed all that when he theorized the “Transmutation of Species.”Allegedly,he found that each species of finch belonged to a particular island and had developed distinct feeding habits that matched their evolving beaks, for cracking small or big seeds or for M Figure 5.1. Illustration of finches from the Galápagos, from Darwin’s book of 1845. 95 eating insects. That’s what many people still think, and so, one of the most widely reproduced pictures in history is that of Darwin’s finches. However, in sterling historical studies, Frank J. Sulloway of Harvard University showed that, really, Darwin was hardly influenced by finches and scarcely observed their feeding habits.1 He did not correlate their diets and beaks; in fact, Darwin collected too few specimens to determine whether any finch species was unique to each island. He did not even keep track of where he picked up every specimen. Really, no finch species was unique to any one island. Unfortunately, some teachers and writers remain unaware of Sulloway’s historical findings.2 The popular myth that the Galápagos finches crucially inspired Darwin to think about evolution arose because in the second edition of his Voyage of the Beagle he added one sentence about finches: “Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.”3 But that brief comment was foreign to Darwin’s travel books and thousands of research notes; there is no evidence that it represented his thoughts during his voyage in 1835.4 When he added that comment, in 1845, he had already believed in evolution for eight years. Yet the finches acquired fame partly because editions of his Voyage include an illustration of finches that, together with the quoted sentence, created the illusion that Darwin construed the finches as compelling evidence for evolution. Actually, Darwin’s observations of finches were so scant that his thoughts on them were inconclusive guesswork—so much that he did not refer to the Galápagos finches in his Notebooks on Transmutation or use them as evidence for evolution in his Origin of Species of 1859. Still the legend spread, partly through the book Darwin’s Finches by David Lack, published in 1947. In the Galápagos Islands, Lack extensively collected and analyzed data on the finches that showed that evolutionary processes could account for such species and varieties as well as their beaks, habits, and geographical locations. But along the way, Lack seemed to attribute some of those scientific findings to Darwin himself.5 Textbooks decorated by pictures of finches echoed such claims. Lack’s brilliant insight, that the finches’ beaks could be understood as evolu96 ✸ Darwin’s Missing Frogs tionary adaptations, was substantiated by Robert Bowman in 1961.6 Thus the insight that is routinely attributed to Darwin in the 1830s was only established scientifically more than a century later.7 Why did the legend spread? Why did the story about the finches propagate so widely? Sulloway argued that perhaps the story about the finches spread because it matched the format of traditional hero myths: a man departs from home on a bold adventure, encounters and overcomes hardships, and returns with a deep truth. Another reason is that the picture of four species of finches often seemed attractive as the only illustration in Darwin’s books that could be construed as a portrayal of evolution, and the story of discovery evolved as a fitting complement. Nowadays, science textbooks continue to highlight the imagery of finches, and authors finesse the story by noting that Darwin saw the finches but that only later did they turn out to be great examples of evolution . Other writers speculate about factors that“may have been” of decisive importance. For example, Stephen Jay Gould argued that perhaps five years of arguing against his ship’s authoritarian captain led Darwin to turn toward materialism and evolution:“Who knows what ‘silent alchemy ’ might...


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