When Charles Darwin was a boy, he used to ramble around the woods of his father’s Shropshire estate in England in search of beetles. Years later he remembered how one day, after tearing some bark off a tree, he saw “two rare beetles and seized one in each hand; then I saw a third and new kind, which I could not bear to lose, so that I popped the one which I held in my right hand into my mouth. Alas it ejected some intensely acrid fluid, which burnt my tongue so that I was forced to spit the beetle out, which was lost, as well as the third one.”
The story says a lot about Darwin—about his dogged persistence, his obsessive interests, his self-mocking humility. Born into a prosperous and somewhat eccentric family, he spent the bulk of his boyhood hunting birds, riding horses, and generally avoiding commitment toward a vocation. Such behavior provoked his father, the stern and corpulent physician Robert Darwin, to warn his second son that he was destined to be “a disgrace to yourself and all your family.” Only in hindsight can we detect in the youth a glimmer of the person Darwin would eventually become: someone who adored nature and who possessed an intellect that gravitated toward questions of process, of why and how. Like some persistent leaf-eating insect, his mind bored through conceptual problems, patiently chewing over facts and evidence until a larger explanation at last presented itself.
Still, collecting beetles was not exactly a career path. With his father’s encouragement, the young man went to Edinburgh, where he studied medicine and where the lectures bored him stiff and the cadavers made him ill. Again at his father’s suggestion, he traveled to Cambridge to study for the ministry, hoping to become one of those rustic vicars who hastily wrote his sermons so that he might devote his time to collecting mollusks or aphids or butterflies or beetles. Around this time Darwin was visited by an enormous stroke of luck. He was invited to serve as the captain’s companion aboard HMS Beagle, a ten-gun brig-sloop commissioned to chart the eastern coast of South America on a journey of imperial exploration and mapmaking. The expedition lasted five years and spanned the globe. Darwin, who was seasick much of the time and who would suffer from the effects of the journey for the rest of his life, nevertheless made a transformation every bit as stunning as those of the Brazilian caterpillars he gathered. He became a genius.
There are hints of this transformation in his first major book, the Journal of Researches into the Geology and Natural History of the Countries visited during the Voyage of H.M.S. Beagle round the World, under the Command of Capt. FitzRoy, R.N., a work now better known as The Voyage of the Beagle. A gripping travelogue, the Voyage made its shy and reclusive author a transatlantic celebrity. Darwin observed earthquakes and volcanoes. He hiked the Andes, crossed the pampas with a band of gauchos, visited the fur-clad peoples of Tierra del Fuego, and gloried in the glaciers and the stars in the southern hemisphere. He also discovered the fossils of massive prehistoric animals, gathered geological samples from across the continent, shot and preserved thousands of brilliantly colored birds, and collected a rich cache of botanical and zoological samples for Her Majesty’s museums. Never afraid to make a fool of himself while in pursuit of knowledge, he chronicled his misadventures riding the Galápagos tortoises and capturing giant lizards by their tails. And he conveyed it all in a charming, wonder-struck style.
Almost instinctively he fit his observations into larger patterns of significance. In December 1833 the Beagle traveled south from Patagonia. “While sailing in these latitudes on one very dark night,” he recounted, “the sea presented a wonderful and most beautiful spectacle. . . . The vessel drove before her bows two billows of liquid phosphorous, and in her wake she was followed by a milky train.” Most writers would have ended the account of bioluminescent creatures here, but Darwin continued to ponder the phenomenon. He noted how the phosphorescence diminished as the Beagle traveled farther south. “This circumstance probably has a close connexion with the scarcity of organic beings in that part of the ocean,” he reasoned. Still he wasn’t finished. Scooping some of the phosphorescent particles from the ocean, he observed that they “were so minute as easily to pass through fine gauze.” He placed the glowing substance in a water glass, restlessly mulled the evidence. Was there a connection between the type of creatures and the colors of their phosphorescence? Was the light produced by these dead organisms part of a complicated process by which “the ocean becomes purified”? Unable to answer these questions conclusively, he finally dried the net he had used to gather the luminous matter and twelve hours later found that, when he took it up again and dipped it into the ocean, “the whole surface sparkled as brightly as when first taken out of the water.”
So much of this extended passage is characteristic of Darwin: the examination of phenomena from a variety of angles, the compulsive working over of evidence until he has understood it as deeply as possible. It is typical of him that he begins at ground level—as if the tiniest, most insignificant occurrence in the physical world might enable him to unlock nature’s greatest secrets. He took the same approach with the people he encountered on his voyage. In one of the book’s most infamous passages, the privileged young Englishman grappled with the implications of the naked, filthy Fuegeans he encountered at the southernmost tip of South America. “I could not have believed how wide the difference between savage and civilized man,” he confessed. “It is greater than between a wild and domesticated animal, in as much as in man there is a greater power of improvement.” This statement, which has been understood as an insensitive and imperialistic pronouncement, quickly yields to a host of other impressions, including Darwin’s admiration for the Fuegeans’ ability to mimic the English language with uncanny fidelity—something no “civilized” person could accomplish half so quickly or so well.
If there is a plot nested within the Voyage’s pages, it is of a narrator awakening to the rich particularity of the world. That awakening led to his most extraordinary insight, famous in the annals of science, which occurred soon after his return to England, in 1836. Darwin was cataloging a number of birds he had shot in the Galápagos Islands, an isolated collection of volcanic rocks some six hundred miles off the west coast of South America, when he noticed a dozen or so finches he had collected from the various islands. Each bird was small and delicate; the biggest weighed only 38 grams. Each was dun-colored. At first glance, the birds looked identical. But upon closer inspection Darwin noticed differences in their beaks; some were larger, some sharper, some as blunt as hammers. Every island in the Galápagos apparently had a slightly different version of the finch. In an intuitive leap, Darwin seized on the conclusion that each of these different birds had adapted over time to the conditions of its particular island, producing wholly new species in the process. “Mine is a bold theory,” he wrote with typical understatement in his notebook.
His name is of course forever associated with the idea of evolution (a word he seldom used, preferring instead the more accurate descent through modification). But the notion that a dog might derive from a wolf or that multiple species of finches might share a common ancestor—that they had evolved from a common source—was not particularly new, even in 1836. Decades earlier Darwin’s radical and notoriously lusty grandfather, Erasmus, had postulated evolutionary development in a sprawling, whimsical, and occasionally bawdy poem entitled “The Temple of Nature, or The Origins of Society.” Proposing to write an epic that would describe how organic forms “rose from elemental strife,” the senior Darwin pictured the development of species as a protean, mounting process, an upward climb along “a thousand jasper steps with circling sweep / . . . winding steep.”
Other eighteenth- and nineteenth-century scientists had also theorized about what was more typically referred to as “transmutation.” Especially prominent was Jean-Baptiste Lamarck, a French botanist who began arguing for evolution in 1799 and codified those ideas in his 1809 Philosophie Zoologique. For Lamarck, the history of all living things was progressive and vertical: an upward series of transitions from simple one-celled organisms, like the amoeba or algae, to increasingly complex creatures. The most basic creatures had arisen spontaneously, but over time they had grown more intricate and specialized, developing into shrubs and trees, birds and alligators and elephants. The process that enabled organisms to change and improve was something Lamarck called the “inheritance of acquired characteristics.” His most famous illustration was the giraffe. Because adult giraffes stretched their necks to browse the highest leaves of a tree, he argued, their offspring were born with longer necks. This process eventually led to the oddly shaped creatures we now recognize. Humans had arrived through a similar development, Lamarck believed, becoming the most complex and ideal species, their very existence indicating that the world was progressing from imperfection to perfection.
These ideas would be developed in greater detail in the best-selling Vestiges of the Natural History of Creation, published in England a decade and a half before the Origin and read by nearly every major intellectual on both sides of the Atlantic. Henry David Thoreau devoured the Vestiges soon after its publication. So did Bronson Alcott and the transcendentalist Ralph Waldo Emerson. Many read the book with a mixture of fascination and repulsion. The anonymous author of Vestiges presented a general theory of creation that started with nebular “Fire-mists” and continued with the appearance of successive life-forms. Most scandalously, he claimed that humans, while occupying the pinnacle of the animal kingdom and serving as “the true and unmistakable head of animated nature upon this earth,” had evolved from primates. Chimpanzees and orangutans were self-evidently related to us, the author of Vestiges claimed, for “in our teeth, hands, and other features grounded on by naturalists as characteristic, we do not differ more from the simidae than the bats do from the lemurs.”
The theories of Lamarck and the author of Vestiges were prompted by recent scientific discoveries that described the world as both immeasurably older than once believed and in a state of constant change. Only a generation or so earlier, geologists had begun rewriting the story of the Earth, overturning biblical accounts of creation in the Garden of Eden with descriptions of an unimaginably ancient planet. The Scottish physician James Hutton provided a glimpse into Earth’s “deep time” in his 1788 Theory of the Earth; or an Investigation of the Laws Observable in the Composition, Dissolution, and Restoration of Land upon the Globe. His ideas were subsequently refined by one of Darwin’s closest friends, the geologist Charles Lyell, whose three-volume Principles of Geology (1830–33) revealed a planet that was always changing. Both geologists believed that the Earth’s surface constantly remade itself; huge landmasses rose during earthquakes and volcanic eruptions, only to be reduced by wind and water erosion. Continents formed and disappeared. The idea that the Earth might be millions or even billions of years old suddenly explained a host of previously mysterious phenomena. When William Buckland, an Anglican clergyman in Yorkshire, discovered the first dinosaur fossil in 1824, he initially thought he had excavated the bones of a sea monster preserved during the Flood of Noah. As Hutton’s and Lyell’s theories gained acceptance, however, he revised his opinion, conceding that the bones belonged to a creature far older than could be accounted for by the biblical narrative.
Darwin came of intellectual age amid these discoveries. His was the first generation of naturalists capable of surveying a landscape and imagining strange, vanished worlds filled with fantastic creatures, gaseous swamps, ferns the size of elm trees—all of which had vanished eons ago and were preserved in fossils. Veins of basalt or jagged granite suggested the upheavals of volcanoes or the grinding displacements of glaciers. Layers of sediment, mixed with the remains of tiny marine creatures, revealed the action of mud and water over impossibly long stretches of time. Suddenly the geological past had become as dramatic and compelling as a novel by Sir Walter Scott or a poem by Byron.
What distinguished Darwin’s theory from its precursors wasn’t his emphasis on deep time, however. It was the process he called “natural selection.” This activity involved the slight, random variations observable within any species. Imagine a litter of fox pups. (The example is Darwin’s.) Subtle differences will invariably exist between individuals. One pup may have longer hind legs, another a slightly thicker coat. Now imagine that these creatures prey on rabbits and the occasional hare. (Hares are faster than rabbits and, because of their coloring, blend into their surroundings slightly better.) If the rabbit population shrinks for any reason—if they are ravaged by disease, for instance—foxes with longer legs or with better eyesight will tend to succeed at chasing hares. And these foxes will survive and produce more young than their less favored siblings. Gradually, as the slower foxes die out, the population will change into one better adapted to catching hares. Given sufficient amounts of time, this population might differentiate from rabbit-catching foxes in other regions. A new variation would come into existence—perhaps even a new species.
What made Darwin’s insight so radical was its reliance upon a natural mechanism to explain the development of species. An intelligent Creator was not required for natural selection to operate. Darwin’s vision was of a dynamic, self-generating process of material change. That process was entirely arbitrary, governed by physical laws and chance—and not leading ineluctably, as Lamarck would have it, toward progress and perfection. The world in which natural selection functioned was a world in which change was the only constant. Natural selection was a brilliant concept, but like many brilliant concepts it assaulted long-cherished ideas and beliefs. It threatened the notion that human beings were a separate and extraordinary species, differing from every other animal on the planet. Taken to its logical conclusion, it demolished the idea that people had been created in God’s image.
• • •
Asa Gray met Charles Darwin for the first time in 1839, when he sailed across the Atlantic to inspect Europe’s great institutions of science. A London friend, the botanist Joseph Dalton Hooker, escorted Gray to the College of Surgeons, just off Lincoln’s Inn Fields, where the two visited the Hunterian Museum, a massive collection of anatomical specimens that included the eight-foot skeleton of Charles Byrne, the so-called “Irish Giant” who had been exhibited as a freak in London back in the 1780s. Here, in one of the crowded exhibition rooms, Gray was introduced to the renowned anatomist Richard Owen, who in turn presented him to a serious beetle-browed young man described as “the naturalist who accompanied Captain King [sic] in the Beagle.”
Both men promptly forgot each other. Gray moved on to Paris, then to Italy, where among other things he amused himself by comparing the marble sculpture of the Apollo Belvedere with Byron’s description of it in Childe Harold’s Pilgrimage. Darwin was preoccupied with yet another discovery. Several months earlier he had picked up Thomas Malthus’s An Essay on the Principle of Population, a grim, adamantine work of political economy first published in 1798. Malthus’s book contained a simple premise: “The power of population is indefinitely greater than the power in the earth to produce subsistence for man.” Human reproduction outstripped agricultural food production. When this happened, a bleak struggle to exist resulted. Darwin’s innovation was to extend Malthus’s vision beyond political economy and into the realm of all living things. In nature, he believed, every single species competed with every adjacent species in a struggle to acquire the resources necessary for survival. A superficial glance at a grove of trees yielded a peaceful landscape: oaks, elms, plane trees scattered across a hillside. But in truth this tranquil scene seethed with competition and death. Tear off a fragment of tree bark, and you might discover beetles and centipedes and slugs, all engaged in the fierce business of staying alive long enough to produce a successive generation. Even the trees were engaged in a kind of competition. Each oak or pine over ten feet tall had survived against incredible odds, enduring frost and drought and the incessant depredations of squirrels and birds and browsing deer. Each tree had gained a perilous toehold amid the dense rootlets of grass, growing despite the shade cast by mature trees, winning out over hundreds of thousands of other seedlings and now annually producing tens of thousands of winged seeds or acorns in order to repeat the process all over again. Landscapes weren’t peaceful at all, Darwin realized. They were rife with conflict and tragedy.
This observation led to another: ceaseless competition was the engine driving change and development. It had propelled the Galápagos finches along their divergent paths of transmutation, ensuring that individuals best suited to the environment would thrive and reproduce. Like a farmer sifting beans for planting, Death sifted out individuals poorly suited for survival. Malthusian theory was a crucial step in Darwin’s mature concept of natural selection.
He said nothing of this to Gray in 1839. Nor did he mention it twelve years later, when the two naturalists met once again. This time they lunched with Joseph Hooker at the Royal Botanic Gardens at Kew, the celebrated herbarium created by Hooker’s father, Sir William. In the interim Gray had married a Boston woman, Jane Loring, who accompanied him on this trip and recorded her impression that Darwin was a “lively, agreeable person.” The English naturalist soon had occasion to recall their convivial meeting in a letter to his new American friend: “I hope that you will remember that I had the pleasure of being introduced to you at Kew,” he wrote. Then he asked a favor. “As I am no Botanist, it will seem so absurd to you my asking botanical questions, that I may premise that I have for several years been collecting facts on ‘Variation’, & when I find that any general remark seems to hold good amongst animals, I try to test it in Plants.” He then begged permission to ask Gray whether alpine plants from North America could be found in other parts of the world.
Gray, it turned out, was interested in precisely this question. In response to Darwin’s query, he compiled “Statistics of the Flora of the Northern United States,” which compared hundreds of plants east of the Appalachians with allied species in Europe and Japan. Darwin read the work with delight. “I have been eminently glad to see your conclusion . . . it is in strict conformity with the results I have worked out in several ways. It is of great importance to my notions.” A few weeks later he hinted at his work. “Nineteen years (!) ago, it occurred to me that whilst otherwise employed on Nat. Hist., I might perhaps do good if I noted any sorts of facts bearing on the question of the origin of species; & this I have since been doing.” In his next letter he enclosed an abstract that detailed the operations of something he called “natural selection,” which he intended to make “the title of my Book.”
This was in 1855. There would be no book, however, until the summer of 1858, when Darwin received a package that was weather-beaten and addressed in a hand he did not recognize. The small bundle had been carried across the South China Sea, passing palm-fringed atolls and green archipelagos, traveling through the monsoons of the Indian Ocean, circling the tip of South Africa, then had been carried north along the Atlantic, where it at last reached Darwin’s ivy-clad home in Kent after some five months. It contained a twenty-page essay entitled “On the Tendency of Varieties to Depart Indefinitely from the Original Type,” written by a tall, bespectacled explorer named Alfred Russel Wallace, who had mailed it on impulse from his remote outpost in the mountainous environs of the Malay Archipelago.
Wallace was fourteen years younger than Darwin. Poor and ambitious, his personality would forever be seasoned with a dash of resentment toward a class system that had prevented him from attending university. Born in a chill and sunless Welsh village, he had quickly cast himself off like some airborne seed, floating out into the world, collecting exotic plant and animal specimens he then sold to museums and private collectors throughout Europe. By age thirty-five, he had spent more than a third of his life in South America (mainly along the Amazon) and in the South Pacific, writing about his adventures in a series of uneven but nevertheless quite readable travelogues. Early in 1858, while collecting birds of paradise in the Malay Peninsula, Wallace was stricken by tropical fever. As Wallace sweat and shivered, wrapped in a blanket and unable to sleep, the mechanism by which plants and animals became new species suddenly became clear to him. As with Darwin, the key was Malthus; Wallace had read the political economist in his early twenties, and in his current fever it “occurred to me that [Malthusian pressures] or their equivalents are continually acting in the case of animals also.” His feverish mind swarmed with visions of “enormous and constant destruction,” and it occurred to him “to ask the question, why do some die and some live? And the answer was clearly, on the whole the best fitted live.”
Darwin was devastated. By a nearly identical thought process, an obscure Welsh explorer had arrived at exactly the same conclusion he had developed two decades earlier. “I never saw a more striking coincidence,” Darwin exclaimed soon after receiving the package. “If Wallace had my manuscript sketch . . . he could not have made a better short abstract.” It took some time for this development to sink in, but when it did, Darwin despaired. “All my originality, whatever it may amount to, [is] smashed,” he wrote his friend Charles Lyell. But Lyell, who was one of the first geologists to believe the world was older than three hundred million years, took a longer view. He wrote back asking whether Darwin had ever mentioned natural selection to an impartial acquaintance, someone with no vested interest in the originality of the idea, who might vouch for the priority of Darwin’s claim, who might even possess written evidence of his theory.
Only then did Darwin recall the letter he had sent to his American friend at Harvard.