The Flamingo’s Smile

by Stephen Jay Gould

  A second statement, taken in conjunction with a misreading of the Ornithological Notes, might also be considered as evidence that Darwin became an evolutionist at sea in 1836. He wrote in his pocket journal: “In July opened first notebook on ‘Transmutation of Species’—Had been greatly struck from about Month of previous March on character of S. American fossils—and species on Galápagos Archipelago. These facts origin (especially latter) of all my views.” We know that he started the first Transmutation notebook in July 1837, and we might therefore interpret the “previous March” as 1836, about the time that he penned the Ornithological Notes at sea. But the previous March might as well be 1837 when, as we shall soon see, he was in London learning from specialists at the Zoological Society about the true character of his Galápagos collections—a set of phenomena that he had failed to observe during his own visit.

  What, then, did Darwin see on the Galápagos, and what did he miss? Three groups of animals have come down through history as the most famous evolutionary laboratories of the Galápagos: mockingbirds, tortoises, and finches. Only for the mockingbirds did Darwin make the key observation that underlies the evolutionary tale developed later (although, as we have seen, Darwin first explicitly rejected the evolutionary reading for a different interpretation). In short, he noticed that varying forms (later recognized as true species, although Darwin originally labeled them varieties) inhabited the different islands he visited. He landed first at Chatham Island, then at Charles, and he realized that he could distinguish the Charles Island mockingbird from the form he had previously collected at Chatham. Thus, he collected more mockingbirds wherever he landed and he carefully kept the separate island collections well labeled and distinct. He could not distinguish the Albemarle mockingbird, on the third island he visited, from the Chatham form, but the James Island bird represented a third, distinct variety (by his original interpretation).

  Galápagos tortoises are all of one species, but most islands feature their own recognizable subspecies. These span an impressive range of form, from smooth, dome-shaped carapaces to the peculiar saddlebacks, with a pronounced hump in the carapace just above the head. Darwin missed this story completely. He never even noted the saddlebacks. Moreover, his basic concept of these tortoises virtually guaranteed that he would not be able to make the key observation.

  Nicholas Lawson, the vice-governor, told Darwin that “the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought” (although distinctions abound, this statement is overly optimistic and modern experts cannot always distinguish each island). But Darwin, by his own admission, made little of this information, writing in the 1845 edition of the Beagle Voyage:

  I did not for some time pay sufficient attention to this statement, and I had already partially mingled together the collections from two of the islands. I never dreamed that islands, about fifty or sixty miles apart, and most of them in sight of each other, formed of precisely the same rocks, placed under quite similar climate, rising to a nearly equal height, would have been differently tenanted.

  As the result of a common error in classification, Darwin was ill-disposed to consider the differences between islands as evolutionarily (or even taxonomically) meaningful. Darwin accepted the general view that Galápagos tortoises were not taxonomically distinct but belonged to the species Testudo indicus, the giant land tortoise of the Aldabra Islands in the Indian Ocean. They had only recently been brought, so the false story continued, to the Galápagos by buccaneers. Hence, differences among islands, if they existed at all, could only be immediate and superficial—inspired by harsh climates at the time of introduction. Moreover, Darwin never saw live saddleback tortoises. He only observed living tortoises on James and Chatham islands, and both contain nearly indistinguishable versions of the dome-shaped carapace.

  Still, Darwin cannot be entirely excused from a charge of some carelessness in observation. He did have an opportunity to observe the saddleback form but either failed to do so or recorded no impression. The Charles Island race was extinct when Darwin landed, but old carapaces were abundant at the settlement, where they served as flowerpots. Moreover, Darwin showed singularly little interest in preserving specimens for comparison among islands, a sure sign that he did not regard Lawson’s statement as significant (much to his later regret). Captain Fitzroy took thirty large Chatham tortoises on board to beef up the Beagle’s supply of fresh meat during the long Pacific crossing. Sulloway remarks:

  But Darwin and the other crew members gradually ate their way through the evidence that eventually, in the form of hearsay, was to revolutionize the biological sciences. Regrettably, not one of the thirty Chatham Island carapaces reached England, having all been thrown overboard with the other inedible remains.

  Darwin’s reaction to the Galápagos finches included even more error and misunderstanding. First, he showed no appreciation for the importance of differences between islands. In fact, he didn’t even bother to record or label the islands that had housed his specimens. Only three of his thirty-one finches are identified by island in the Ornithological Notes, all members of a highly distinctive species that Darwin remembered seeing only on James Island. He later wrote with regret in the Voyage of the Beagle: “Unfortunately most of the specimens of the finch tribe were mingled together.” Second, he failed completely to collect any finches on one of the islands he visited—Albemarle. True, he was there for only part of a day, but his own diary records an abundance of easily collectable finches at a spring near Bank’s Cove: “To our disappointment the little pits in the Sandstone contained scarcely a gallon of water and that not good. It was however sufficient to draw together all the little birds in the country; Doves and Finches swarmed around its margin.”

  Third, except for cactus and warbler finches, Darwin failed to observe any distinction in diet among the species and believed erroneously that they all ate the same kinds of food. Thus, he could not have reconstructed our modern story, even if he had been inclined to evolutionary views.

  Fourth, Darwin’s entire style of collection on the Galápagos strongly reflected his creationist presuppositions. Evolutionists see variation as fundamental, as the raw material of evolutionary change. Species can only be well defined by collecting many specimens and defining the spectrum of their variation. Creationists believe that each species is endowed with a fixed essence. Variation is a mere nuisance, a confusing array of environmentally induced departures from an ideal form. Creationists tend to gather a limited number of specimens from each species and to concentrate on procuring individuals closest to the essential form. Darwin collected very few specimens, generally only a male and female of each species. In all, he procured but thirty-one finches from the Galápagos. By contrast, a 1905–1906 California Academy of Sciences expedition, dispatched to study evolution explicitly, brought back more than 8,000 specimens.

  Fifth, and most importantly, the finches tell no evolutionary tale unless you recognize that, despite their outward differences in form and behavior, all form a tightly knit genealogical group. But Darwin, while on the Galápagos, was fooled by the stunning diversity and failed to recognize Darwin’s finches as a taxonomic entity. He referred the cactus finch to a family of birds that includes orioles and meadowlarks, and he misclassified the warbler finch as either a wren or warbler. Those that he recognized as finches, he divided into two distantly related groups within the family. Sulloway remarks: “As for Darwin’s supposed insight into evolution by adaptive radiation while he was still in the Galápagos, the more the various species of finch exhibited this remarkable phenomenon, the more Darwin mistook them at the time for the forms they were mimicking.”

  The theoretical source of Darwin’s error lies in a fairly arcane principle of the creationist style of taxonomy that he followed. If animals are created according to a rational and general plan in the Deity’s mind, then certain “key” characters might be clues to taxonomic structure at different levels. For e
xample, variation in such “superficial” characters as size and shape might define different species, while variation in such “fundamental” traits as the form of essential organs might record the more important differences between genera and families. Ideally, a hierarchy of key characters should define taxonomic levels. Darwin tried to follow such a system in his preliminary Beagle classifications. Species within a bird genus should differ in plumage, while genera should be separated by such characters as the form of the beak. Darwin’s finches are all similar in plumage, but differ greatly in styles of feeding and, consequently, in the shapes of their beaks. By Darwin’s creationist hierarchy of key characters, they belonged to different genera or families.

  The key character hierarchy makes no sense in an evolutionary context. Characters that define genera in one situation might vary widely among species within another group. Bills may define feeding types, and feeding types may usually distinguish genera on continents. But if only one kind of small bird manages to reach an oceanic archipelago and then diversifies, in the absence of competitors, into a wide range of niches and feeding types, then the traditional criterion for genera—form of the bill—will now differ among closely related species. In the blooming and buzzing confusion of evolution, as opposed to the order of a creator’s mind, responses to local preset environments, not rules of change, determine what parts of the body will be modified in any particular case. Behavior and plumage in one place; feeding and shape of the beak in another. There is no such thing as an invariably “specific” or “generic” character.

  In summary, then, Darwin entered and left the Galápagos as a creationist, and his style of collection throughout the visit reflected his theoretical stance. Several months later, compiling his notes at sea during the long hours of a Pacific crossing, he briefly flirted with evolution while thinking about tortoises and mockingbirds, not finches. But he rejected this heresy and docked in England, October 2, 1836, as a creationist harboring nascent doubts.

  This retelling of the finch story is particularly satisfying because the new version squares so much better than the old legend with Darwin’s use of the Galápagos finches throughout his later writing. He never mentioned them in any of the four Transmutation Notebooks, which he kept from 1837 to 1839 and which serve as a foundation for his later work. They receive only passing notice in the first (1839) edition of the Voyage of the Beagle. To be sure, the second edition (1845) does contain this prophetic statement, written after Darwin had learned that the finches form a closely knit genealogical group.

  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.

  But if the finches made such a belated impression, the impact didn’t seem to last. Darwin’s finches are not mentioned at all in the Origin of Species (1859); the ornithological star of that great book is the domesticated pigeon. Sulloway concludes, rightly I think:

  Contrary to the legend, Darwin’s finches do not appear to have inspired his earliest theoretical views on evolution, even after he finally became an evolutionist in 1837; rather it was his evolutionary views that allowed him, retrospectively, to understand the complex case of the finches.

  Darwin returned to England in 1836 as an ambitious young man, anxious to make his mark in science; his later, courtly modesty as an old man should not be allowed to mask this youthful vigor. He knew that the key to his reputation lay in the valuable specimens he had collected on the Beagle, and therefore he made determined and successful efforts to farm them out to the best specialists and to procure funds for publication of the results. In March 1837 he moved to London, largely to be near the various experts studying his specimens. He began a series of meetings with these men, finally learned the true character of his material, and emerged within a month or two as an evolutionist.

  He wrote, in the famous entry in his pocket journal cited earlier, that the character of South American fossils and species of the Galápagos had been the primary catalysts of his evolutionary conversion. Richard Owen, Britain’s most eminent vertebrate paleontologist, had agreed to study the fossils and informed Darwin that they represented different, usually larger versions of distinctive animals that still inhabit South America. Darwin recognized that the best interpretation of this “law of succession” cast the ancient forms as evolutionary ancestors of altered modern animals.

  The famous ornithologist John Gould (no relation) had taken charge of the Beagle’s birds. Darwin met with him toward the middle of March and learned that the three forms of mockingbirds were separate species, not mere and superficial varieties of a single, created type. Darwin had already proclaimed that such a conclusion (which he had previously rejected) “would undermine the stability of species.” Moreover, Gould informed him that twenty-five of his twenty-six Galápagos land birds were new species, but clearly allied to related forms on the South American mainland. Darwin integrated this spatial information with the temporal data that Owen had supplied, and he tilted further toward evolution. The distinct Galápagos birds must be evolutionary descendants of mainland colonists from South America. Darwin was now fully primed for an evolutionary reading of the finches, and Gould’s correction of Darwin’s errors furnished this piece of the puzzle as well (although Gould himself did not adopt evolutionary views).

  Although a creationist in taxonomy, Gould recognized right away that bills could not be used as a key character to separate genera of Galápagos finches. He understood that these birds were not, as Darwin had thought, a heterogeneous assemblage of divergent finches with an unrelated warbler and oriole thrown in, but a peculiar group of thirteen closely related species, which he placed in a single genus with three subgenera. “The bill appears to form only a secondary character,” Gould proclaimed. Darwin finally had the basis of an evolutionary story.

  Darwin was exhilarated as he converted to evolution and prepared to reread his entire voyage in this new light. But he was also acutely embarrassed because he now realized that his failure to separate finches by islands, no particular problem in a creationist context, had been a serious and lamentable lapse. He couldn’t do much with his own collection, beyond probing a faulty and fading memory; but fortunately, three of his shipmates had also collected finches—and since they (ironically) had not collected with an actively creationist theory in mind (with its implied irrelevancy for precise geographic data), they had recorded the islands of collection. As a further irony, one of these collections had been made by Captain Fitzroy himself, later Darwin’s implacable foe and the man who stalked around the British Association meeting where Huxley demolished Wilberforce, holding a Bible above his head and exclaiming, “the Book, the Book.” (Fitzroy’s collection included twenty-one finches, all labeled by island. Darwin also had access to the smaller collections of his servant Syms Covington and of Harry Fuller, who had spent a week collecting with him on James Island.)

  Darwin therefore tried to reconstruct the localities of his own specimens by comparing them with the accurately labeled collections of his shipmates and, unfortunately as it turned out, by assuming that the finch story would resemble the pattern of the mockingbirds—with each species confined to a definite island. But since most of the finch species inhabit several islands, this procedure produced a large number of errors. Sulloway reports that substantial doubt still exists about the accuracy of geographic information for eight of fifteen among Darwin’s “type” (or name bearing) specimens of finches. No wonder he was never able to make a clear and coherent story of Darwin’s finches. No wonder, perhaps, that they never even appeared in the Origin of Species.

  Why, in conclusion, is this correction of the finch legend of any great importance? Are the two stories really all that different? Darwin, in either case, was greatly influenced by evidence from the Galápagos. In the first, and false, version he understands it all by himself while on the visit. In the
second, modified account he requires a nudge (and some substantial corrections) from his friends when he returns to London.

  I find a world of difference between the tales for what they imply about the nature of creativity. The first (false) version upholds the romantic and empirical view that genius attains its status from an ability to see nature through eyes unclouded by the prejudices of surrounding culture and philosophical presupposition. The vision of such pure and unsullied brilliance has nurtured most legends in the history of science and purveys seriously false views about the process of scientific thought. Human beings cannot escape their presuppositions and see “purely” Darwin functioned as an active creationist all through the Beagle voyage. Creativity is not an escape from culture but a unique use of its opportunities combined with a clever end run around its constraints. Scientific accomplishment is also a communal activity, not a hermit’s achievement. Where would Darwin have been in 1837 without Gould, Owen, and the active scientific life of London and Cambridge?