The Rise and Fall of Darwin's First Theory of Transmutation

Home , Continental drift, Pachydermata, South American jaguar, Transmutation of species

GEORGE GRINNELL

Department of History, McMaster University Hamilton, Ontario

In the four "Transmutations Notebooks," which Darwin filled for two years while living in London after returning to England from the Beagle voyage, are a host of thoughts, observations, quotations from books he was reading and from conversations with friends, such that it is difficult to know exactly which of the ideas expressed in the notebooks belong to Darwin as part of "my theory," and which are simply passing thoughts to be considered and then rejected, but a statistical study of the frequency with which Darwin uses certain words indicates that during the course of the two years there were three theories of transmutation which he considered to be "mine" and that the host of other ideas which he expressed contemporaneously were either sub- sidiary to these or of only passing interest (with one major exception). 1 The question is, were these three theories complementary or were they mutually exclusive? If they were complementary, then the implication is clearly in favor of the importance of the empirical data in shaping Darwin's thought, but if they were mutually exclusive, the implication is that Darwin approached the data with a prior world view which he attempted to superimpose on the data by means of various hypothetical models and mechanisms. This paper begins with an account of Darwin's dispute with Robert Fitzroy, captain of the Beagle, over the nature and origin of the Gal~pagos finches. It describes how the dispute is settled by John Gould, ornithologist of the Zoological Society of London, when he takes Fitzroy's side by declaring the finches to be real species. A brief description of Gould's career is given in order to clarify Darwin's relationship to him. Next is shown how Darwin reconciles his interpretation of the origin of the Gal~ipagos finches with Gould's classification of them by supposing that all species are mutable. This starts him off on the long quest for the secret of the origin of species. After watching

1. G.J. GrinneU, "The Darwin Case: A Computer Analysis is Scientific Creativity," unpub, diss, University of California, Berkeley, 1969.

him construct a hypothetical model of the origin of the Gal~pagos species, we see him extrapolate this model to the general case by invent- ing island archipelagoes, land bridges, and continental movements, only to have the anomalies of geographic distribution inundate him and eventually force him to abandon the theory, or, at least, part of it. The significance of this study of Darwin's first theory of evolution is its revelation of Darwin's commitment to a philosophy of nature which enabled him to rearrange data creatively through an act of will, rather than inductively through research.

On page 105 of the Origin of Species, Darwin wrote: "Hence an oceanic island at first sight seems to have been highly favourable for the production of new species, but we may thus greatly deceive ourselves. ''2 It was a deception which it took Darwin several years to penetrate; and it was not without great agony that he finally did so, for his first theory of evolution had proposed such a notion based on the Gal~pagos Islands case and it was precious to him. Its failure appears to have led him close to a nervous breakdown. Yet it is the mark of the great scientists that they can see their favorite theories destroyed by stub- born facts, and yet go on to create new ones. Two years after returning from the voyage on the Beagle, Darwin had opened a journal to record his life's work, in which is found an entry, written later, for July 1837, describing the origin of his first theory of evolution: "In July opened first notebook of 'Transmutation of Species' -Had been greatly struck from about month of previous March on character of S. American fossils- and species on Gal~pagos Archipelago. These facts origin (especially later) of all my views," he writes, a This statement is confirmed by the notebook to which he refers. In it .we find Darwin describing how species originate on islands owing to their isolation: "According to this view," he wrote, "animals on separate islands ought to become different if kept long enough apart. ''4 During their visit to the Gal~pagos Archipelago in the autumn of

2. Charles Darwin, On the Origin of Species: A Facsimile of the First Edition, ed. Ernst Mayr (Cambridge, Harvard University Press, Mass.: 1964), p. 105. 3. "Darwin's Journal," ed. Sir Gavin de Beer, Bulletin of the British Museum (Natural History) Historical Series, 2, no. 1. (1959), entry for July 1837. 4. I, 7. Darwin's four "Transmutation Notebooks," edited by 'Sir Gavin de Beer, have been published in the Bulletin of the British Museum (Natural History)

260 The Rise and Fall of Darwin's First Theory of Transmutation

1835, Charles Darwin and Robert Fitzroy, the young captain of the Beagle, had fallen into one of their numerous disputes, this time over the origin of a group of brownish-black birds resembling finches. Darwin surmised that their ancestors had been blown out from the mainland, and that successive generations had adapted-themselves to their new environment by their own resources. Having done so, they should, he believed, be considered only varieties rather than new species, and hence were not worth collecting carefully. Fitzroy, on the other hand, believed them to be new, hitherto undiscovered, species and had a special collection made for himself. Fitzroy had noted that the shape of the beaks varied from group to group such that each was created for the type of island on which it had been placed. "This appears to be one of those admirable provisions of Infinite Wisdom by which each created thing is adapted to the place of which it was in- tended," he wrote in his account of the voyage, and concluded there- from that these species were created by God. s Thus the dispute between Darwin and Fitzroy arose. Its revolutionary significance did not become apparent to Darwin until after these finches had been turned over to the ornithologist of the Royal Zoolo- gical Society, John Gould (1804-1881), who declared Fitzroy correct in supposing them real species, and, in so doing, threw Darwin into an intellectual turmoil. Gould's paper had been read on January 10, 1837, at a meeting of the Zoological Society, in which he named the finches, Geospiza, and declared them an endemic genus, consisting of eight

Historical Series, vo. 2, nos. 2 through 5. No. 6 of this series contains "Addenda and Corrigenda." Vo. 3, no. 6 (1967), contains the recovered pages excise by Darwin. The designation I, 7, refers to "Darwin's First Notebook on Trans- mutation of Species," p. 7 of his pagination; fall citations to the "Transmutation Notebooks" will be given in this form. I do not use British Museum pagination except when referring to one of their footnotes. Unfortunately, the excised pages were not recovered until after I had run the expurgated edition through the computer, but after studying carefully these recovered pages, I believe that they would not!seriously alter the computer's results except to reinforce conclusions already drawn from tlae data. 5. Robert Fitzroy, Narrative of the Sureveying Voyages of his Majesty's Ships Adventure and Beagle (London, 1839), II, 503. For a full description and beatiful illustrations of these birds see "Birds" by John Gould in The Zoology of the Voyage of H.M.S. Beagle, under the Command of Robert Fitzroy, R.N. (London, 1841), part 3, pp. 98-103, plates 36-39. For a more modern description and for references to subsequent literature see: David Lack, Darwin's Finches (New York: Harper Torchbook, 1961).

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species and three subgenera, Omarhynchys, Cactornis, and Certhidea, which, in turn, consisted of five additional species. 6 A few months later, in March 1837, Darwin was going over his ornithological notes with Gould in order to learn the names of the various specimens he had collected, 7 for he was in the process of writing up his diary of the trip for publication. His own collection of the Gal~pagos species being incomplete, they were studying Fitzroy's samples, s Apparently his old argument with Fitzroy of a year and a half earlier came back to him, and he began wondering whether Gould had really been right in classifying the Gal~ipagos specimens as distinct species. In rewriting his ornithological notes, he suggests once again that the finches of the Gahipagos are only varieties: "When I see these Islands in sight of each other and possessed of but a scanty stock of animals, tenanted by these birds but slightly different in structure and filling the same place in Nature, I must suspect they are only varieties, ''9 he declares in defiance of Gould's classification, for this trivial detail of taxonomy was of overwhelming importance because of what it implied. It implied that God, the creator of species, but not of varieties, so governed nature as to personally oversee the origin of even so minute a detail as the beak of the Galhpagos finches. Darwin could believe in some abstract first.principle God, but not in the paternalistic, interfer- ing GOd implied by Fitzroy's and Gould's clasification of Geospiza, Something had to give. At first, Darwin fought Gould's classification, but Gould was England's leading ornithologist while Darwin was an admitted amateur with no training in the subject at all. Although only thirty-three (five years older than Darwin), Gould had already distinguished himself through the pubhcation of numerous technical papers and three important books about birds: A Century of Himalayan Birds (1832), a five-volume series entitled Birds of Europe (1832-1837), and a Synopsis

6. Proc. ZooL Soe.Lond., January 10, 1837, p. 4. 7. Charles Darwin, ed. The Zoology of the Voyage of H.M.S. Beagle... (London, 1839-43). See "Advertisement." 8. Ibid., p. 99. "Unfortunately I did not suspect this fact until it was too late to distinguish the specimens from the different islands of the group; but from the collection made for Captain Fitzroy, I have been able in some small measure to rectify this ommission," Darwin wrote. The actual date when Darwin tried to "rectify this ommission" is unknown. 9. Ornithological Notebooks; I have accepted note 25, chap. 5 of Gertrude Himmelfarb's Darwin and the Darwinian Revolution (New York: Doubleday, 1959).

262 The Rise and Fall of Darwin's First Theory of Transmutation of the Birds of Australia and the Adjacent Islands (1837-1838). (He later went on to publish 41 books and more than 300 scientific papers about birds.) Darwin, on the other hand, did not even know the names of most of the species he had himself collected, and, in fact, had to go to Gould to learn them. Gould supplied him not only with names, but also with a vast number of important facts about birds. In the first two notebooks, Darwin refers to Gould more frequently than to any other scientist. Some typical references are as follows: "In Mr. Gould's Australian work some most curious cases of close, but certainly distinct species between Australia and van Diemen's land," Darwin records after studying Gould's Synopsis of the Birds of Australia and the Adjacent Islands. Here was a significant parallel to the Gal~pagos case. lo Similarly Gould was Darwin's source of information for the relationship between English and Continental species: "Gould on Motacilla, Loudon's Mag., September or October 1837, species peculiar to continent and Eng- land, ''11 he notes tersely. And again: "Get a good many examples of animals and plants very close (take European birds Mr. Gould's case of willow wren and other varying in wild state to show that we do not know what amount of difference prevents breeding," he instructs himself, citing Gould's The Birds of Europe as the source of information. 12 Darwin stood to Gould as student to teacher. He was thus psychologi- cally unable to oppose Gould's classification of Geospiza for long; in March 1837, Darwin changed his tack and instead of questioning Gould's classification, began to question the origin of species, which was the only other alternative. Thus we have, immediately following the passage in the Ornithological Notebooks in which he questions Gould's classification, a repudiation of that doubt and a new idea replacing it that species are not stable: "... if there is the slightest foundation for these remarks, the Zoology of Archipelagoes will be well worth examining; for such facts would undermine the stability of species." 13 Two months later Darwin had finished rewriting his Journal of

10. I, 49. 11. I, 138. 12. I, 241. 13. Nora Barlow, ed., Charles Darwin and the Voyage of the Beagle (London, 1945, p. 246; for further discussion of this passage see Nora Barlow, ed., "Darwin's Ornithological Notes," Bulletin of the British Museum (Natural History) Historical Series, 2, no. 7, ( 1963), note 1.

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Researches for publication and was ready to turn his full attention to the species problem. In July 1837, he opened the First notebook on transmutation with the Gal~pagos Islands phenomena acting as a model for evolution, and here the story of the origin of the Origin of Species really begins. First Darwin tried to show that it was theoretically possible for the Gal~pagos species to have originated by natural cases; then he attempted to project this model onto all species. At first he had success. Thinking up means by which seeds might be transported to the Galfipagos Islands was not difficult. Lyell had already shown the way. He had imagined them blown out to the Islands during storms, carried by ocean currents, or transported in the stomachs of birds: "we know many seeds might be transported, some blown - floating trees - thrushes (Turdus Guyanensus? and Buntings) (Emberiza Brasiliensis? ) and coots (Publica Chloropus) might bring in stomachs etc. etc. (Mem. & Discover what kind of seed these plants)," Darwin writes about halfway through the first notebook. 14 He is in the process of learning the scientific names for birds, hence he interrupts his train of thought in order to try out his newly acquired scientific vocabulary. While seeds were easy to transport, Darwin had difficulty with the small Gal~pagos mouse, and the Gal~pagos tortoise and lizards proved even more troublesome. Early in the first notebook, he asks: "owls transport mice alive? ''Is About halfway through the first notebook, he asks again, "Galhpagos mouse, brought by canoe? ''16 By the beginning of the second notebook, opened half a year later, he had still not solved the problem: "Gal~pagos mouse not the same, section with house mice. It is wonderful how it could have been transported! ,17 In the third notebook, he finally comes to grip with the problem once and for all and decides that the mouse was transported by man. "Argue the case of probability, - the Gal~pagos mouse probably transported like the New Zealand one.- it should be observed with what facility mice attach themselves to man. ''la If he was able to solve the Gal~pagos mouse problem, it was a small one compared to those he faced trying to account for the geographic

14. I, 192. 15. I, 82. 16. I, 220. 17. II, 29. 18. III, 65.

264 The Rise and Fall of Darwin's First Theory of Transmutation

origins of the Gal@agos tortoises and lizards. The nearest relative to the tortoise lived as far from the Gal@agos Islands as it is possible to imagine, on an island in the Indian Ocean. To transport one to the Gal~pagos involved a trip of 14,000 miles across the Pacific and Indian Oceans. Relatives of the Gahipagos lizards were even more difficult to locate. The closest kin probably lived in South America or Mexico, although the differences of some species were too striking for Darwin's uniformitarian principles to accept a direct line of descent. The Gal@agos species began to look even to Darwin's eye more like special creations than like transmutations. Darwin, however, considered the possibility that the effects of salt water on the lizards' eggs might have caused transmutations while they were in transit, thus explaining the anomalies, and he devised experiments to test this hypothesis. "Ex- perimentize on land shells in salt water and lizards ditto. - ask Eyton to procure me some. ''19 At this time Darwin did not carry out this experiment. He had another alternative which was preferable, namely, to postulate a continent of the Pacific which had once provided the Gal~pagos and South Sea Islands with their flora and fauna and which had then conveniently sunk beneath the surface of the ocean carrying with it all record of its existence and the ancestral forms of the Gal~ipagos tortoise and lizard. "When continent of Pacific existed, might have been monsoons," Darwin speculates. "When they ceased, importation ceased and changes commenced, -or immediate land existed- or they [the lizards and tortoises] may represent some large country long separated. ''2° In the pursuit of his theory, that species were formed on islands owing to isolation, Darwin combed accounts of travels to distant islands to see what animals and plants had been discovered and what relationship these species had to continental types. But while, on the one hand, he eagerly sought new facts to support his theory, he apparently began to dread the discovery of some new large quadruped on islands - transportation facilities for which it would be impossible to provide even hypothetically. On discovering that New Zealand was devoid of large quadrupeds, he almost sighed with relief: "New Zealand, compare to van Diemen's land, glorious fact of absence of quadrupeds"; but at the same time he learned of the opossum and agouti of the West Indies, the gigantic tapir of the East Indies, and the elephant of the island of Ceylon, all of which presented insurmountable difficulties of trans-

19. I, 248. 20. I, 11.

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portation. 21 Upon reading W. Swainson's A Treatise on the Geography and Classification of Animals (London, 1835), he learned that rhinoceroses lived on the islands of.Sumatra and Java. Transporting a pair of mice by native canoes was trivial compared to the problem of ferrying a pair of rhinoceroses to the East Indies from Singapore. Increasingly he was unable to account for the geographic distribution of the larger animals. As a result, he placed less emphasis on transportation and began instead to speculate on the possibility of the elevation and subsidence of land bridges. "Species formed by subsidence," Darwin writes, "Java and Sumatra. Rhinoceros, Elevate and join keep distinct, two species made. Elevation and subsidence continually forming species. ''22 The idea of elevation and subsidence of land masses was pressed into service with mounting vigor until Darwin had the entire earth in motion. "The motion of the earth must be excessive up and down," he admitted. 23 "Elephants in Ceylon -East India Archipelago- West Indies - Opossum and Agouti same as on continent - 3 Paradoxusi in common to Van Diemen's land and Australia. England and Europe, Ireland -common animals. Ireland longer separate. Hare of two countries different. Ireland and Isle of Man possessed elk, not England. Did Ireland possess Mastodons?" The paradoxes of distribution in- undated him, but his idea of elevation and subsidence was so much more successful than the idea of transportation out to isolated islands (from which the idea had originated) that it began to replace it in the notebooks; "Mauritius -what a difficulty when elevated, subsidence near is only hope," he suggests. ~ Darwin now articulated ideas about the relationship of crustal movement to speciation and the words "sub- side" and "elevate" appear with increasing frequency. With an almost total absence of data to support his theory, he sustained it through an act of will.

21. I, 219. What made the absence of quadrupeds in New Zealand "glorious" is not altogether clear. It was either "glorious" because it saved Darwin the labor of dreaming up transportation facilities for them, or, equally possible, it may have been "glorious" because it indicated God had been inconsistent in creating quadrupeds on some islands and not on others. The text suggests the latter interpretation is more probable, but fearing controversy, I have adopted the former interpretation, which is also consistent with the text. At any rate, the image here, as elsewhere, is of a scientist with a very def'mite point of view gathering facts to support it. 22. I, 82. 23. I, 80. 24. I, 219.

266 The Rise and Fall of Darwin's First Theory of Transmutation

While Darwin was able to account for the similarity of flora and fauna of the East Indies by supposing that the land had once been elevated to provide a land bridge and then had subsided, and whereas he was able to explain the similarity between the flora and fauna of Mauritius and Madagascar by elevating and subsiding a land mass between them, and while he was able to acount for the peculiar lizards of the Gal~pagos Islands by imagining a land bridge between those islands and a hypothetical continent in the Pacific, he had more difficulty explaining the zoological relationship of South America and Africa, in particular, the close relationship of the wingless rhea of Sout America - which Darwin had pursued across the plains of Patagonia in company with the wild gauchos, 2s to the ostrich of Africa. The. sapajou monkeys of South America, although possessing a structure peculiar to them in the anatomy of their tails, were nonetheless similar to their African counterparts in general type. The slow-moving edentates, the sloths, armadillos, and anteaters, also possessed relatives in Africa, although like the rhea and the monkey, not in NorthAmerica. Then the jaguar of South America seemed to resemble more the leopard of Africa and Asia than it did the North American mountain lion. Clearly, another land bridge across the Atlantic Ocean was called for. Instead of creating one, however, Darwin worked out another idea, even more ingenious, that of continental drift. In order to gather data on the problem of geographic distribution, Darwin had studied William Kirby's recently published Bridgewater Treatise. Kirby attributed the general similarities of type found between the animals of different continents to the fact that they had all been created by one God and hence had a common design. Differences between members of the same type he had attributed to God's divine providence, pointing out how much duller natural history would be if life was homogenous everywhere the naturalist traveled. 26 Although he did not share Kirby's teleological point of view, Darwin was indebted to him for demonstrating the relationship between Asiatic species and those of western North America. 27 The similarity in type

25. Darwin uses the expression "cuidado" in his notebooks as his imagination gallops like a gaucho over the plains of Natural History; see I, 44: "Heaven knows whether this agrees with nature, cuidado! " 26. I, 141-147. William Kirby, On the Powers, Wisdom and Goodness of God, as Manifested in the Creation of Animals and in Their History, Habits and In- stincts (London, 1835), I, 57. 27. Ibid., p. 390 n. 14.

267 GEORGE GRINNELL between animals of different continents Darwin attributed to descent from a common ancestor, rather than to God's having created them on the same "plan," as Kirby had done, while the divergence in peculiar characteristics Darwin ascribed to the physical "influences" on the environment, chiefly climate. However, this theory, like his theory about islands, called for modes of transportation. If the Asiatic bear resembled the North American bear as Kirby asserted, then, according to Darwin's theory, they must have had a common ancestor, which meant that there must have once been a land connection between Asia and America as well as between America and Africa. Using the same principle he had used for the East Indian species, Darwin imagined a land bridge across the Aleutians, connecting Siberia to Alaska. He employed this bridge to account for the several similarities and specific differences between the bears and foxes of the two continents, "I should expect that Bears and Foxes are same in North America and Asia; but many species closely allied, but different, because country separated since time of extinct quadrupeds; - same argument applies to England - Mere. Shrew mice. ''28 The success with which Darwin met in accounting for the similarities between the bears and foxes of Asia and America inspired him to press the Aleutian land bridge into further use, particularly to account for the similarity between the Asiatic horse and the extinct American horse, and between numerous pachyderms (elephants, rhinoceroses, and pigs), living in Europe and Asia and the extinct remains of these animals found in America. All went well until he attempted to connect the species of Africa with those of South America. First, there was the problem of the connection of the African zebra with the fossil American horse; next, it was that of the Cape anteater with the South American variety; and finally, that of the South American jaguar with the African and Asiatic leopard. "Seeing how horse and elephant reached South America, - explain how zebras reached South Africa," he suggests to himself. 29 While bears, foxes, horses, and the various pachyderms were found in both the northern and southern hemispheres, and thus presumably could have originated from some centrally located common ancestor

28. I, 65. The reference to "shrew mice" is taken from T. Bell, then at work on the Beagle's reptiles. He had recently made a study of them along with Water- house, who was working over the Beagle's mammals, hence Darwin's knowledge of them. 29. I, 62.

268 The Rise and Fall of Darwin's First Theory of Transmutation and have migrated out in rays, the edentates (armadillos, sloths, and anteaters) were found only in the southern hemisphere. Darwin was obliged to explain why, if the South African species had migrated via the Aleutian land route, they had left no relatives anywhere along the way. He attempted to transport the scaly Cape of Good Hope anteater north through Africa, across Arabia, Persia, and India, over the Himalayas, across the Gobi Desert, Outer Mongolia, and Siberia, over the Aleutian land bridge, then south again through North America and Central America, and into the jungles of Brazil, whence it became transmuted into a hairy anteater. It was a long trip for a slow-moving animal. The Reverend William Kirby, in his Bridgewater Treatise, had employed a similar route to explain the dispersion of the animals from Noah's ark after it had landed in the Himalayas. (He was up to date: The older fundamentalists had believed that the ark had landed in the Caucasus, but with the advance of science, more particularly the advance of Englishmen into India, the Himalayas were discovered to be higher than the Caucasian Range. As the ark was supposed to have landed on the highest mountain, the place of landing was transferred from Mount Ararat in Armenia to Dhawalagiri in Nepal). a° At any rate, Kirby had accounted for the dispersal of the animals to their appointed sections of the globe by pointing out that God had provided them with instincts for this very purpose. But Darwin steadfastly refused to use God-endowed instincts to explain the geographical distrubution of the edentates; and as a result, he was deeply troubled about why they had left no relatives along their migration routes. "It is very great puzzle," he wrote, "why marsupials and edentata should only have left off- springs in or near South Hemisphere. ''31 The more animals he attempted to transport over the Aleutian land bridge, the more difficulties he encountered. Even monkeys gave him troubles. Despite the fact that monkeys are widespread not only in Africa and South America but also throughout Southeast Asia and the East Indies, making the connection between the South American species and those of Africa by means of the Asiatic-American land bridge was a problem. His French ally, Geoffroy Saint-Hilaire, whom Darwin was not at all eager to contradict, had expressed the opinion that monkeys were not wanderers. "St. Hilaire thinks monkey produce by climate, not a wanderer," Darwin records in his notebook, an

30. Kirby, On the Powers, I, 45. 31. I., 106.

269 GEORGE GRINNELL

opinion which made monkeys unlikely candidates for a long arctic migration, a2 In order to alleviate the difficulty of transporting southern species over such a long northern route, Darwin shortened the distance in the most sensible way available to him - by moving the continents closer together into the middle of the Pacific Ocean. "Speculate on land being grouped towards centre near Equator at former periods and then split- ting off" he suggested to himself in his first notebook, aa The idea, like so may of Darwin's other ideas, quickly gathered momentum before rolling to its final destruction. A few pages, he wrote: "I really think a very strong case might be made out of world before zoological divisions";a4 and a little later: "Now if we suppose the world more perfectly continental, we might have wanderers...,,as Darwin's early theory of continental drift is quite extraordinary not only in that it antedates the modern theory by nearly a century, but also in that it united Asia, Africa, Australia, and America in the middle of the Pacific Ocean, rather than in the Atlantic, which is more fashion- able these days. Darwin's choice of the Pacific, and hence of uniting America with Asia rather than with Europe, probably can be traced back to the influence of fundamentalists like the Reverend William Kirby and Captain R. Fitzroy. The fundamentalists, supposing that Noah's Ark had landed either in Armenia or the Himalayas, had taken those points as the focus of dispersal of the animals around the globe. From central Asia, the shortest land route to America was via Siberia. When Darwin needed to shorten the route by moving continents, his thoughts were oriented toward the Asiatic-American connection, rather than to the South America-Africa possibility. This grouping put the east coast of South America as far as possible from the west coast of Africa, with India being at the center of the imaginary protocontinent, which in turn caused Darwin to predict that the flora and fauna of the east coast of South America would be the furthest removed from those of the west coast of Africa, and those of India intermediate between the two: "West coast of Africa and east of America ought to present great contrast in Forms, India, intermediate, see how that is," he writes, a6 It wasn't very good, but a not too careful scrutiny of the literature

32. I, 135. 33. I, 72. 34. I, 95. 35. I, 134. 36. I, 223.

270 The Rise and Fall of Darwin's First Theory of Transmutation apparently affirmed this relationship; a few pages later he writes: "American and African forms mingle in India and East Indian islands. ''aT This was later to lead to some problems, but during the writing of the first notebook, Darwin was either sufficiently optimistic to believe that he would be able to solve them, or sufficiently ignorant of the details of the flora and fauna of South America and Africa not to let them bother him. At any rate he was very pleased with the continental drift theory, which enabled him to solve so many of the puzzles of zoological distribution which had been plaguing him; and he reveled, for a brief time, in his triumph: "If I had not discovered channel of communication by which Edentata might have roamed to Europe and Pachydermata from Europe to America," he wrote, "how strange would presence of Jaguar have been in South America. ''as Inspired by his success, he decided to list the benefits which would accrue to science from his theory:

We get first a horizontal history of Earth within recent times, and many curious points of speculation, for having ascertained means of transport, we should then know whether former lands intervened. Second by character of any two ancient fauna, we may form same idea of connection of those two countries. Hence, India, Mexico, and Europe - one great sea. (Coral reefs and shallow water at Mel- ville Island)... It explains the blending of two genera. - It explains typical structure... It leads you to believe the world older than geologists think, it agrees with excessive inequalities of numbers of species in divisions - look at articulata! ! ! ? It leads to knowledge what kind of structure may pass into each other .... My theorywouldgive zest to recent and fossil Comparative Anatomy; it would lead to study of instincts, heredity and mind heredity, whole metaphysics, a9 But there were still some details to be worked out - details which were ultimately to destroy this first theory. Although it is possible for one fact to destroy a theory, there was no single fact which destroyed Darwin's first theory; rather a whole series of anomalies accumulated which brought it down: the contradictory

37. I, 242. 38. I, 223. 39. I, 224-228.

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facts about inbreeding, about geographical distribution, and especially about the relationships of some species to the "tree of life." Whereas the Gal~pagos birds had shown a certain amount of variation, possibly owing to crossbreeding between finches,4° the reptiles, Darwin now had to acknowledge, appeared to be unregnerate remnants of the Oolitic period. Isolation, instead of producing variation, as he had first supposed, appeared to prevent it. The collapse of the first theory did not come about all at once. Darwin began to lose interest in it in the second notebook but as late as 1844 he still appears to have subscribed to it in part, and even in the Origin of Species, he clung to aspects of it. 41 Yet in the first notebook, Darwin had become aware of the anomalies which were to lead to the theory's ultimate repudiation; in particular, he had learned some facts about the echidna of Australia, which, try as he would, could not be reconciled at all with it. He had attempted to move Australia over to North America to help provide a common ancestor for the echidna and the porcupine. Asia, India, and Africa had followed Australia across the Indian Ocean to unite the echidna and the porcupine to the scaly ant-eating pangolin of South Africa, but the unique reproductive system of the echidna had made the prospects of a common ancestor between porcupine, echidna, and pangolin an unlikely prospect in spite of the new continental arrangement. Increasingly Darwin had to recon- cile himself to the fact that isolation did not lead to a progressive transmutation of species; quite the opposite. The isolated marsupials of Australia, the isolated lizards and tortoises of the Galfipagos, the fresh- water ganoid fishes, the strange flora and fauna of Madeira, these were not examples of new species being created by isolation, but rather of old species being preserved by isolation. "Hence an oceanic island at first sight seems to have been highly favourable for the production of new species," Darwin was driven to remark in the Origin of Species, "but we may thus greatly deceive ourselves." He later went on to abandon this first theory of evolution in favor of a second, that of habits causing a change in structure. By the third notebook, he had abandoned that theory as well as in favor of the domestic breeding model, the one that was ultimately to be the most successful. Summary: In this paper we have seen how Darwin, using the

40. David Lack, Darwin's Finches, pp. 99, 100, denies the role of hybridization in the speciation of Geospiza. 41. Origin of Species, pp. 103-109; see also Ernst Mayr's introduction.

272 The Rise and Fall of Darwin's First Theory of Transmutation

Gal~pagos Islands phenomena as a model, attempted to generalize the particular case of the origin of Geospiza to the origin of all species. Tending to assume that isolated inbreeding would bring about variation, 42 he invented hypothetical means by which all species might have been isolated at one point in their past. This involved the creation of land bridged which had allowed animals and plants to migrate to archipelagoes, where presumably they became isolated when the land bridge subsided. Later, the altered species were united with their continental ancestors when a new land bridge was thrown up. The land bridge theory proved inadequate to explain the relationship between South American and South African species. Darwin then entertained notions of continental movements which had once united these and other continents and had subsequently separated them. Yet there existed anomalies which could not be explained simply by these means. The biggest anomaly was perhaps that of the antiquated condition of the marsupials of Australia. Here were species which had been isolated, but which had failed to change. They bore a far closer resemblance to the fossils of the Stonesfield slate than to any living form. A closer look at the Gahipagos lizards and tortoises also seemed to indicate that these too were relics of a bygone era, rather than highly transmuted species. By the end of the first notebook, Darwin's theory had undergone both considerable articulation and modification. Although he expressed great confidence in it toward the end of the notebook, he showed signs of being aware that it was inadequate to the task he had set for it, and he began to branch out into other directions, particularly into the realm of domestic breeding. Conclusions: Darwin began his work from a highly abstract and speculative base. His later careful research into minute details followed rather then preceded his theoretical activities. When he worked out his first theory he was ignorant of most branches of natural history with the exception of geology and geographic distribution subjects which he had learned while on the Beagle voyage. His original purpose in opening these notebooks was to try out various models of "transmutation." The extent to which he was willing to push one model, and after its collapse, to entertain new models suggests that he was philosophically inclined to transmutation theories for reasons that transcended the empirical data with which he originally worked.

42. I, 1.

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