the field. Even as taxonomy—the classification of plant and animal species—flourished, inquiries into the origin of living beings were relegated to the forbidden sidelines. Natural history devolved into the study of nature without history.
It was this static view of nature that Darwin found troubling. A natural historian should be able to describe the state of the natural world in terms of causes and effects, Darwin reasoned—just as a physicist might describe the motion of a ball in the air. The essence of Darwin’s disruptive genius was his ability to think about nature not as fact—but as process, as progression, as history. It was a quality that he shared with Mendel. Both clergymen, both gardeners, both obsessive observers of the natural world, Darwin and Mendel made their crucial leaps by asking variants of the same question: How does “nature” come into being? Mendel’s question was microscopic: How does a single organism transmit information to its offspring over a single generation? Darwin’s question was macroscopic: How do organisms transmute information about their features over a thousand generations? In time, both visions would converge, giving rise to the most important synthesis in modern biology, and the most powerful understanding of human heredity.
In August 1831, two months after his graduation from Cambridge, Darwin received a letter from his mentor, John Henslow. An exploratory “survey” of South America had been commissioned, and the expedition required the service of a “gentleman scientist” who could assist in collecting specimens. Although more gentleman than scientist (having never published a major scientific paper), Darwin thought himself a natural fit. He was to travel on the Beagle—not as a “finished Naturalist,” but as a scientist-in-training “amply qualified for collecting, observing and noting any thing worthy to be noted in Natural History.”
The Beagle lifted anchor on December 27, 1831, with seventy-three sailors on board, clearing a gale and tacking southward toward Tenerife. By early January, Darwin was heading toward Cape Verde. The ship was smaller than he had expected, and the wind more treacherous. The sea churned constantly beneath him. He was lonely, nauseated, and dehydrated, surviving on a diet of dry raisins and bread. That month, he began writing notes in his journal. Slung on a hammock bed above the salt-starched survey maps, he pored over the few books that he had brought with him on the voyage—Milton’s Paradise Lost (which seemed all too apposite to his condition), and Charles Lyell’s Principles of Geology, published between 1830 and 1833.
Lyell’s work in particular left an impression on him. Lyell had argued (radically, for his time) that complex geological formations, such as boulders and mountains, had been created over vast stretches of time, not by the hand of God but by slow natural processes such as erosion, sedimentation, and deposition. Rather than a colossal biblical Flood, Lyell argued, there had been millions of floods; God had shaped the earth not through singular cataclysms but through a million paper cuts. For Darwin, Lyell’s central idea—of the slow heave of natural forces shaping and reshaping the earth, sculpting nature—would prove to be a potent intellectual spur. In February 1832, still “squeamish and uncomfortable,” Darwin crossed over to the southern hemisphere. The winds changed direction, and the currents altered their flow, and a new world floated out to meet him.
Darwin, as his mentors had predicted, proved to be an excellent collector and observer of specimens. As the Beagle hopscotched its way down the eastern coast of South America, passing through Montevideo, Bahía Blanca, and Port Desire, he rifled through the bays, rain forests, and cliffs, hauling aboard a vast assortment of skeletons, plants, pelts, rocks, and shells—“cargoes of apparent rubbish,” the captain complained. The land yielded not just a cargo of living specimens, but ancient fossils as well; laying them out on long lines along the deck, it was as if Darwin had created his own museum of comparative anatomy. In September 1832, exploring the gray cliffs and low-lying clay bays near Punta Alta, he discovered an astonishing natural cemetery, with fossilized bones of enormous extinct mammals splayed out before him. He pried out the jaw of one fossil from the rock, like a mad dentist, then returned the next week to extract a huge skull from the quartz. The skull belonged to a megatherium, a mammoth version of a sloth.
That month, Darwin found more bones strewn among the pebbles and rocks. In November, he paid eighteen pence to a Uruguayan farmer for a piece of a colossal skull of yet another extinct mammal—the rhino-like