A Little Bird Collecting

With the coastal survey finished, the Beagle sailed north to Lima and then westward, leaving South America altogether. After the blasting winds of Tierra del Fuego and the hollow cold of the Andes, Darwin was looking forward to the tropics. The first stop would be at a peculiar cluster of islands called the Galápagos.

The Galápagos Islands have a reputation as the place where Darwin’s theory of evolution was born, but Darwin would not realize their significance until nearly two years after his visit. When he arrived at the Galápagos Islands, he was still thinking more about geology than biology, and he looked forward to visiting a place where he could see new land being created as Lyell had proposed.

Darwin first set foot on Chatham Island (now known as San Cristobál), a raw volcanic heap still untamed by plants and soil. Ugly iguanas and countless crabs greeted him. “The natural history of this archipelago is very remarkable,” Darwin later wrote. “It seems to be a little world within itself.” A world, he meant, unlike the greater one. Here there were enormous tortoises, with shells 7 feet in diameter, that fed on prickly pears and didn’t care if Darwin rode on their backs. Here lived not one but two hideous species of iguana–one that stayed on the islands and another that dove into the ocean to eat seaweed. The birds of the Galápagos were so tranquil that Darwin could walk up to them without their taking flight.

Darwin dutifully added the birds to his collection, making only a few notes about them. Some had big beaks, good for crushing large seeds, while others had beaks shaped like needle‑nose pliers, for grabbing seeds that were small and hard to reach. Judging from their beaks, Darwin guessed that some were wrens, others finches, warblers, and blackbirds. He did not, however, bother to note which islands the birds came from. He assumed that the birds were South American species that had colonized the islands at some point.

Only after Darwin had finished collecting his animals did he realize that he should have been more careful. Shortly before the Beagle left the islands, he met the director of the penal colony on Charles Island (Santa María), an Englishman named Nicholas Lawson. Lawson used tortoise shells for flower pots in his garden, and he had noticed that the tortoises of each island were so distinct from one another that he could tell where they came from by the shape of the flares and flanges on their shells. The tortoises on each island, in other words, were a unique variety, or perhaps even a unique species. The plants of the islands, Darwin learned, were likewise distinct.

Perhaps the birds were as well, but since he hadn’t marked where most of his birds had come from, Darwin couldn’t know. It would not be until he returned to England that Darwin would finally sort out his birds, and only then would he begin to work out the way in which life changes from one form to another.

Life Builds Itself

When the Beagle was finished at the Galápagos, it set sail across the glassy Pacific. It traveled quickly, reaching Tahiti in three weeks, New Zealand in another four, and Australia in only two. As it crossed the Indian Ocean, the Beagle’s objective was to map coral reefs. Coral reefs are living geography, produced by colonies of tiny polyps as they build external skeletons. The polyps can live only near the surface of the ocean because, as marine biologists would later discover, they depend on photosynthetic algae that live inside their tissues. As the Beagle passed reefs in the Indian Ocean, Darwin wondered how they formed such perfect circles, sometimes around islands and sometimes around nothing but water. And how was it that the reefs could always be found close to the surface of the water, which was exactly where they needed to be in order to get enough sunlight to grow?

In Principles of Geology Darwin had read Lyell’s hypothesis on corals: they formed only on the tops of submerged volcanic craters. For once, Darwin thought that Lyell was wrong. The crater hypothesis was ugly and awkward, since it would require that every reef sit precisely on a crater that just happened to be lurking close to the surface of the ocean. Darwin came up with another explanation.

If the Andes were rising, according to Lyell’s geology, Darwin reasoned that some other part of the planet must be sinking. That could well be happening in places such as the Indian Ocean. Corals might form in the shallow waters around new islands or along the coasts of mainlands, which then began to sink. As the land began to subside underwater, the corals would sink with them. But they might not be lost, Darwin reasoned, because new corals could grow on top of the reefs as the ground sank. While the old corals died in the darkness, the reef would survive. After a while the island itself might completely erode away, but the reef would have maintained itself near the water’s surface.

Every coral reef that the Beagle surveyed fit somewhere along this sequence. At Keeling Islands (Cocos Islands), the surveyors on the Beagle found that on the seaward edge of the reef there was a sharp drop to the ocean floor. When they scraped off corals from near the bottom, they found that they were dead. It was all as Darwin had predicted.

Darwin was no longer a mere disciple of Lyell, but a mature, independent thinker. He had used Lyell’s principles to formulate a better explanation for coral reefs than Lyell’s own, and he had worked out how he could test it. Darwin was learning how to study history–in this case, the history of life on Earth–scientifically. He could not replay thousands of years and watch coral reefs grow, but if history had unfolded the way he proposed, he could test his predictions. “We get at one glance an insight into the system by which the surface of the land has been broken up, in a manner somewhat similar but certainly far less perfect, to what a geologist would have done who had lived his 10,000 years, and kept a record of the passing changes,” he later wrote.

The planet might look changeless, but Darwin was learning to see it on a scale of millions of years. And from that perspective it was a quivering ball, rising and collapsing, its skin tearing itself apart. Darwin was also learning how life could change on the same scale as well. Given enough time, coral reefs could keep from drowning as the ocean floor fell out from under them. They could build giant fortresses, founded on the skeletons of their ancestors.

It took Darwin six months to travel from the coral atolls back to England, rounding the Cape of Good Hope and passing the Azores, and by then his reputation had preceded him. Henslow, his mentor at Cambridge, had culled some of Darwin’s letters and turned the extracts into a scientific paper and a pamphlet. His mammal fossils had made the voyage home safely, and some of them were admired by Britain’s leading anatomists. Even Darwin’s idol, Lyell, was impatiently waiting to meet him on his return.

Five years after leaving Plymouth, the Beagle sailed up the English Channel in a drenching rain. FitzRoy held his final service on October 2, 1836, and later that day, Darwin walked off the ship and headed for home. He would never leave Great Britain again; he would barely even leave his own house.

As Darwin set foot on English ground, he knew that he had changed profoundly. There was now no way he could tolerate life as a country parson. He had become a practicing naturalist, and he would spend the rest of his life as one. On top of that, he knew that he would be happy only if he could work as an independent scholar like Lyell, rather than at a university. But if Darwin was to live the life of Lyell, his father would have to give him money to establish himself. As ever, Darwin was nervous about what his father would think.

Darwin stepped off the coach at Shrewsbury late in the evening of October 4. He was eager to see his family again, but was too proper to disturb them in the middle of the night. He slept at an inn, and the next morning, just as his father and sisters were sitting down to breakfast, he walked into the Mount unannounced. His sisters cried out in joy. His father declared, “Why, the shape of his head is quite altered.” His dog acted as if Darwin had been gone only a day and was ready for their usual morning walk.

Darwin’s fears of his father’s anger turned out to be unfounded. While he had been away, his brother Erasmus had abandoned medicine and set himself up as an independent scholar in London. Erasmus had blazed the trail for his younger brother, and their father had not objected. When Robert read Charles’s pamphlet, he was filled with pride. He realized that as a naturalist, Charles would not waste his life shooting rabbits. He gave his son stocks and an allowance of 400 pounds a year, enough to establish himself on his own.

Charles Darwin would never again fear his father. But he had inherited Robert’s taste for respectability, and whenever possible he avoided unseemly confrontations. He had never been a rebel and would never want to become one. Yet within a few months of returning home, he would terrify himself by beginning a scientific revolution.

Two

“Like Confessing a Murder”

The Origin of Origin of Species

In London, Darwin discovered that his brother had turned out not to be a very dedicated naturalist. Erasmus was most comfortable at dinner parties and gentlemen’s clubs rather than in his laboratory. He introduced Charles into his social circles, and Charles blended in well. But unlike Erasmus, Charles also worked furiously. He wrote papers about geology, put together a book about his travels, and arranged for experts to study his specimens–fossils, plants, birds, flatworms.

Within a few months, Darwin’s work had paid off: he had a reputation as one of England’s most promising young geologists. But he also began harboring a secret. He would scribble in small, private notebooks, not about geology but biology. He had become obsessed with a disturbing possibility: perhaps his grandfather had been right after all.

Biology had come far during the five years Darwin had been away. New species were being discovered that challenged the old order, and under microscopes scientists were learning how eggs developed into animals. British naturalists were no longer content with Paley’s celebration of God’s design on a case‑by‑case basis. It didn’t allow them to answer the profound questions about life. If God had providently designed life, how exactly had He done so? What accounted for how similar some species were, and how dissimilar others? Had all species come into existence at the beginning of Earth, or had God created them as time went by?

For British naturalists, God was no longer a micromanager; instead, He had created laws of nature and had set them in motion. A God who needed to step in at every moment seemed less capable than a God who designed things correctly–and flexibly–at the start. Many British naturalists accepted that over the history of the planet life had changed. Simpler groups of plants and animals had gone extinct, replaced by more complex ones. But they saw it as a stately, divinely guided process, not an earthly evolution like the one that Lamarck had proposed in 1800. And a fresh shudder passed through their ranks in the 1830s as another zoologist at the National Museum in Paris championed a new theory of evolution: Etienne Geoffroy Saint‑Hilaire.