The Reluctant Mr. Darwin

by David Quammen

  Elsewhere he simply called himself “muddled” on these big, irresolvable issues. He was bothered particularly by two contradictions he saw in or around orthodox Christian dogma: the tension between a law-governed universe and an intervening God, and the occurrence of evil in a world designed by an omnipotent deity who prefers good.

  Did physical laws encroach on divine prerogatives? For some thinkers they did, and not just in the biological realm. Even Newton’s law of gravitation, Darwin knew, had once been attacked by Leibniz as “subversive” of natural religion. Gravity was “an occult quality,” a godless fudge factor, invoked wrongly to explain the miraculous orbiting of planets—or so went Leibniz’s complaint. Had that criticism been accepted by reasonable people? No. Mostly they preferred Newton’s nice, grounding law. Then why accept the same complaint when applied to diversity and adaptation among living creatures? “I cannot believe that there is a bit more interference by the Creator in the construction of each species,” Darwin wrote, “than in the course of the planets.”

  The problem of evil, and of gratuitous suffering inflicted on innocents, troubled him at least as much. “I cannot see, as plainly as others do,” he wrote to Asa Gray, an American botanist friend at Harvard, “evidence of design & beneficence on all sides of us. There seems to me too much misery in the world.” Why would a benevolent God design ichneumon wasps, for instance, with the habit of laying eggs inside living caterpillars, so that the wasp larvae hatch and devour their hosts from inside out? Why would such a God design cats that torture mice for amusement? Why would a child be born with brain damage, facing a life of idiocy? he asked. Several months later, again to Gray, he pressed further: “An innocent & good man stands under [a] tree & is killed by [a] flash of lightning. Do you believe (& I really shd like to hear) that God designedly killed this man? Many or most persons do believe this; I can’t & don’t.” He wasn’t arguing only about a hypothetical man and a hypothetical flash of lightning. He was drawing on personal experience: the problem of evil as revealed in watching a ten-year-old daughter die of some wasting illness. Any god who controlled events on Earth closely enough to preordain such an occurrence—or to permit it, if divine permission was necessary—wasn’t one that Darwin could take seriously.

  A week after Annie’s death, while the images were fresh, he wrote a short private memoir recording a few of her charms, habits, and traits. Her pirouettes along the Sandwalk. Her prissy neatness. Her affection toward the younger children. Her talent for music. Her enthusiasm for dictionaries and maps. He and Emma had lost the joy of their household, Darwin wrote, and the solace of their old age. Surely the little girl must have known how much she was loved. “Blessings on her,” he ended, vaguely, this time omitting the name of God.

  A Duck for Mr. Darwin

  1848–1857

  19

  Darwin was busy at his barnacles, back in April of 1848, when a young man named Alfred Russel Wallace left Liverpool aboard a ship bound for Brazil. The two weren’t personally acquainted, not at that time, and Wallace (like the rest of the world) was ignorant of Darwin’s secretive work on transmutation. But he wasn’t oblivious to the subject. Wallace knew just enough natural history to be dissatisfied with the old explanations of species diversity, its distribution and origins. He wanted something more than natural theology. Now he was headed to the tropics in search of adventure, rare birds, gorgeous butterflies, giant beetles, and a chance to contribute new facts—maybe even insights—toward what he called “the theory of the progressive development of animals and plants.”

  Wallace’s main source of information about that theory, the book that had inflamed his enthusiasm, was Vestiges of the Natural History of Creation, by then in its seventh edition. Unlike those critical readers who dismissed Vestiges as junk, Wallace had found it a provocative starting point. At the book’s core he saw an ingenious hypothesis. This calls for further research, he concluded. This calls for me to jump on a boat to the Amazon. He was twenty-five years old, bright and ambitious, impetuous and impressionable, scientifically untrained. Events would show that he was also persistent, observant, and tough.

  Besides being fourteen years younger, Alfred Wallace differed from Charles Darwin in a whole list of ways: no family wealth, no university education, no mentoring by Anglican naturalists, no social connections to the British Navy, no opportunity to travel the world as a relatively pampered guest aboard one of Her Majesty’s ships. Wallace was the eighth child of nine born to middle-class parents who lacked middle-class income. His father, trained as a lawyer, had a knack for bad investments and a disinclination to practice law, so the family was downwardly mobile. Alfred left school at age fourteen, when the money for his childhood ran out, and apprenticed as a surveyor. For much of the next decade he surveyed railroad routes and property boundaries across the landscape of England and Wales, living out of inns, boarding houses, sometimes a rented cottage, while catching what education he could at mechanics’ institutes (self-improvement facilities for laborers) and public libraries. He had always loved to read. For a young surveyor, too curious and driven to piss away his evenings in pubs, the institutes and libraries opened vistas. He read Alexander von Humboldt’s great narrative of travels in South America (which had also inspired Darwin), William Prescott’s History of the Conquest of Peru, Lyell’s Principles of Geology, William Swainson’s A Treatise on the Geography and Classification of Animals (which described MacLeay’s quinarian systematics), and John Lindley’s Elements of Botany. He read Darwin’s Journal twice and found it thrilling, second only to Humboldt’s as a science-flavored travel narrative. He read W. H. Edwards’s rollicking new book, A Voyage up the River Amazon. He read Malthus.

  Meanwhile he developed a passion for life outdoors, hiking transects across the Welsh mountains, and began making himself into a naturalist. His early efforts focused on botany, until a new friend turned his head toward beetles. The friend was Henry Walter Bates, an apprentice in the hosiery business but restless for getaway and keen on natural history, like Wallace. They met in Leicester during a year Wallace spent there, on a temporary escape from surveying, as a schoolteacher. When he saw Bates’s collection of beetles—shiny like jewels, amazingly diverse, and almost all found near Leicester—Wallace was hooked. He got himself a collecting bottle, some pins, and a beetle box, and laid out precious shillings for a Manual of British Coleoptera. Bates helped him learn where to find beetles and how to identify them. When the teaching job ended and Wallace went back to Wales, he and Bates stayed in touch, sharing thoughts about scientific books and trading specimens of rare British beetles. Have you read Vestiges? he asked Bates in one letter. Have you read Lawrence’s Lectures on comparative anatomy? William Lawrence had been one of the radical materialists teaching anatomy in London, a subversive influence even before Robert Grant arrived. Wallace found his book “very philosophical,” meaning solid in logic and scientific method. Its discussion of variant races among the human species, he told Bates, bore directly on what interested Wallace so much: the theory of progressive development. He was already doubtful, as revealed in this letter to Bates, that the distinction between species and varieties was so clear and absolute as most people assumed.

  Around that time, probably while Bates was in Wales for a beetling visit, they conceived the idea of a more daring excursion. They’d go to the Amazon together, paying their expenses by shipping back natural history specimens for sale to dilettantish collectors in England. This wasn’t as impractical as it sounds; in that era, some gentleman dabblers kept cabinets of small biological trophies for display, just as others might show off their French paintings, their Chinese ceramics, or their items of native art. Wallace and Bates lined up a London sales agent, one Samuel Stevens, who knew the retail trade in beetles and butterflies. They equipped themselves with guns, nets, and other field gear, and finagled a few letters of introduction. Wallace got vaccinated. Bates was with him when the boat anchored at Pará, the Brazilian port near the mouth of th
e Amazon, on May 28, 1848.

  Neither of them could have said just where this scientific lark was headed or how long it would last. At one point Wallace told Samuel Stevens that he hoped to be back in England by Christmas of 1850. Instead he roamed the Amazon basin for four years. Bates stayed for eleven.

  After some months of collecting side by side, and mostly near the Amazon’s mouth, they separated in order to follow different instincts and to minimize competition. Wallace headed upriver. He worked to learn Portuguese and the Indian trade language. He shot birds, skinned them, and defended the skins against jungle rot and voracious ants. He collected gaudy butterflies and glittery beetles. He caught fish and pickled them in spirits. He carefully packed these various specimens into crates for shipment to England, adding other items (a small stuffed caiman, a pair of Indian calabashes) to fill out a crate. From his collected specimens, and from the landscape scenes around him, he made notes and sketches. He drew maps. He was curious about everything, human cultures and tropical vegetation as well as collectable animals. He recorded some anthropological observations and made a small study of the diversity and practical uses of palm trees. Eventually he ascended to the Rio Negro, a vast blackwater tributary of the main Amazon, and explored its upper reaches by canoe for most of two years.

  From a branch of the upper Negro he set off on an overland hike to the Serra do Cobati, a stony massif rising out of the forest, in search of a creature known as o galo-da-serra, the cock-of-the-rock. This bird, blazing vermilion except for its wing feathers and tail, with a disk-shaped crest obscuring the front of its face, was a spectacular oddity well worth the ten-mile slog. Two species are recognized nowadays. The one Wallace saw, the Guianan cock-of-the-rock (Rupicola rupicola), lives only around eroded mountain outcrops in the jungles of eastern Colombia, Venezuela, and northern Brazil, where the females build mud nests in crevices amid the steep rock. Both sexes feed on fruit. The males compete for females by assembling in display areas, known as leks, and taking turns showing off their physical splendor. Wallace spotted one in a dim thicket, “shining out like a mass of brilliant flame.” He raised his gun; the bird spooked and flew off; but after a little more tracking he got a second chance, and killed it. With help from his crew of Indian hunters, he eventually took twelve cocks-of-the-rock. Their lekking behavior, bringing them together in vulnerable crowds, may explain how he bagged so many.

  Those dozen birds, packed into a small box for shipment home, embody a critical aspect of Wallace’s collecting career, both in the Amazon and later: redundant sampling. That is, he wanted quantity, not just diversity. Because he was paying his way on a piecework basis, and because Rupicola rupicola was extraordinarily decorative, he killed as many individuals of the species as he could. Darwin, a rich man’s son collecting only for himself, might have taken just one or two. Wallace had hoped for fifty cocks-of-the-rock, but was glad to settle for twelve.

  When he laid them all side by side, did he notice intraspecific variation? Did he find that not every individual was quite so luminously red as the others? Did he see that some were rather more orangish? Did he detect differences in the diameter of the facial crest, or in the width of the thin yellow band across the tail? Did he recognize from such differences that multiple sampling of a single species isn’t actually redundant, but in fact yields information about variability? We don’t know. He didn’t say. But we can wonder. The abundance of naturally occurring variation within species was a crucial clue to the transmutation mystery, unnoticed by most naturalists of the day. Darwin needed eight years with barnacles, following five years of travel and ten years of study, to awaken him about variation in the wild. Wallace saw it sooner because, besides being an alert observer, he was a commercial collector, hungry and broke.

  Not that his insight about variation, or all his data, came easily. Wallace paid high human costs for everything he gleaned from the Amazon. Beyond his sheer labor, there were hardships—loneliness, the danger of drowning or being murdered or snake-bitten, pestilential mosquitoes and sandflies, delays and frustrations in hiring helpers or finding supplies, cash shortages when his letters of credit from Stevens didn’t arrive, days of subsisting on manioc flour and coffee, the incessant struggle to keep order among his collections and his thoughts, all within the relentless, gnawing entropy of a tropical forest. He spent two weeks with his arm in a sling, unable to work, because of an infected hand wound. His younger brother, Herbert, came out to learn the collecting trade at Alfred’s side but retreated back to Pará when it didn’t suit him, and then died there of yellow fever. Wallace himself was laid up by unidentified fevers more than once. He penetrated far into the headwaters of the Rio Uaupés, in what is now eastern Colombia, hoping to nab a rumored white form of a spectacular black bird, the umbrella chatterer, and was forced to conclude that the white version probably didn’t exist. Early in 1852, satisfied or exhausted, he started down from the Rio Negro headwaters in an overloaded canoe.

  He was bringing six crates of his specimens that hadn’t yet been shipped, plus all of his journals and notes and drawings, plus a menagerie that he hoped he might wrangle back to England alive: five monkeys, two macaws, twenty parrots and parakeets, and some other birds. He reached Pará around the end of June, completing a loop he’d begun four years earlier, and visited Herbert’s grave. On July 12 he boarded a ship, the brig Helen, bound for England.

  The Helen was an ill-fated tub. After three weeks at sea, still in mid-Atlantic, she suddenly caught fire. A combustible hazard in the hold, casks of balsam, had spontaneously bubbled into flame, taking the captain by surprise. Wallace stumbled down into his smoky cabin and grabbed what he could, tossing papers into a tin box. From all his Amazon treasures he saved just a small bundle of drawings and some notes. He was forced to abandon the specimen crates, which included his private collection of insects and birds, as well as most of his written records. He climbed into a leaky lifeboat with other castaways and watched the Helen burn, then sink, dragging his charred diaries and roasted parrots to the bottom. Four years of work dropped away like a cinder in a bucket.

  After ten days in the open lifeboat, patching its leaks with bits of cork, living on biscuit and raw pork and carrots, Wallace and his companions were rescued by another English ship, which turned out to be almost as blighted as the Helen. This old, slow boat, the Jordeson, nearly sank twice in high seas before they reached home. With two crews aboard, there wasn’t enough to eat. The hold was overloaded with Cuban hardwood. Not far from England they were hit by a gale that split one sail and nearly defeated the bilge pumps. Almost three months after leaving Brazil, Wallace limped ashore at Deal, in southeastern England. His ankles were swollen, his legs were weak. He celebrated, along with the Helen and Jordeson captains, over a dinner of beefsteak and plum tart. They were glad to be alive and then, presumably, glad to go separate ways.

  Wallace went to London. A less intrepid man, or a less stubborn one, would have written it all off as the misadventure of a lifetime and wanted no more. Not Wallace. Four days later he admitted to a friend that, though he had sworn never to sail another ocean, “good resolutions soon fade.” He was already plotting his next expedition. He hadn’t found a solution to the big mystery, the one about progressive development of animals and plants. He was more than ever convinced that such progression occurs, and that it could be explained by some physical process or law. He wanted a new arena for collecting and observing. Maybe he’d go to the Andes. Or to the Philippines. He had seen a great river. Now he might look at mountains or islands.

  20

  Despite all his bad luck, his near-death experiences and dispiriting losses, Wallace’s four-year excursion in the Amazon produced some important rewards. It was his second apprenticeship; instead of teaching him the surveyor’s craft, this one let him develop the skills and strengths of a tropical explorer, an expert collector and preserver of specimens, a sharp observer of animal diversity and other biological patterns. It began the process of alerti
ng him to the significance of varieties within species. It further excited his thinking about progressive development. And it made him a biogeographer.

  Biogeography, as I’ve mentioned, is the study of animal and plant distribution around the planet. It addresses two simple questions: Which kinds of creatures live where, and why do they live there but not elsewhere? Its significance for any theory of biological origins—an evolutionary theory, say, or a creationist theory—is that biogeography represents a complicated body of empirical facts that the theory must explain. Why do the Galápagos Islands harbor three endemic species of mockingbird, all closely related but no two of them native to any one island? Why do polar bears live in the Arctic, penguins in the Antarctic, and not vice versa? Why do tree kangaroos (arboreal marsupials of the genus Dendrolagus) inhabit tropical forests in northeastern Australia, and also in nearby New Guinea, but not tropical forests in South America or Africa? Why do hummingbirds and toucans occur only on one side of the Atlantic Ocean (in the Americas), while sunbirds and hornbills occur only on the other side (in Africa and farther eastward) of that ocean? A possible answer is that God specially created each species, plunking it into one ecosystem or another as suited His own opaque whim. This explanation is not wholly satisfying to the intellect, though it seems adequate to some people of faith. Another answer is that all creatures have evolved from common ancestors; that they have diverged slowly into distinct lineages and species, dispersing to new habitat as opportunity has allowed, although their dispersal has often been restricted by physical barriers such as mountains or seas; and that the current geographical distribution of species reflects the history of such divergence, restriction, and dispersal. That’s the answer favored by Darwin after he had seen the Galápagos and the plains of South America. Wallace came to it by way of the Amazon.