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”
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.
Lamarck and Geoffroy had been friends at the museum for decades, but Geoffroy came to accept evolution through his own research, comparing the anatomy of different animals. The conventional wisdom of the day held that animals were similar to each other only when they functioned in similar ways. But Geoffroy was struck by exceptions to this supposed rule. Ostriches have the same bones as flying birds, even though they don’t fly. And Geoffroy showed that what looked like unique hallmarks that set off a species from other animals often were not so singular after all. A rhino’s horn might seem to make it unique, for example, but it is really just a clump of dense hair.
As Geoffroy struggled to uncover the hidden connections between animals, he found much inspiration in the work of German biologists. They saw science as a transcendentalist quest to discover the hidden unity of life. The poet (and scientist) Goethe argued that the various parts of a plant—from its petals to its thorns—were all variations on one fundamental form: the leaf. For these German biologists, the complexity of life hid certain timeless models, which they called archetypes. Geoffroy set out to find the archetype of all vertebrates.
Every bone in every vertebrate’s skeleton, Geoffroy suggested, was a variation on an archetypal vertebra. He then pushed his scheme even further, claiming that invertebrates were based on the same transcendental plan. A lobster and a duck, by his reasoning, were variations on the same theme. Lobsters are arthropods, a group that also includes insects, shrimp, and horseshoe crabs. Arthropods bear some faint resemblances to vertebrates: their bodies are symmetrical along their long axis; they have heads equipped with eyes and a mouth. But the differences are vast. Arthropods build their skeleton—a hard shell—on the outside of their bodies, whereas vertebrates put theirs on the inside. Vertebrates have a spinal cord running along their back and a digestive tract running down the front of their bodies. In a lobster, or any other arthropod, the arrangement is reversed: the gut runs down the back and the nervous system runs along the belly.
This might seem to make the arthropods and vertebrates incomparable, but not to Geoffroy. He claimed that arthropods lived inside a single vertebra. And it was a simple matter to transform belly to back, and thus turn a lobster into a duck. Arthropods had the same design as vertebrates, but it was simply turned upside down. “There is, philosophically speaking, only a single animal,” Geoffroy declared.
By the 1830s, Geoffroy had taken his theory a step further. These transformations weren’t simply geometrical abstractions, he declared; animals had in fact changed shape over time. Geoffroy was not reviving Lamarck; he didn’t accept Lamarck’s hypothesis that a trait acquired during an animal’s life could be passed down to its offspring. Geoffroy suggested instead that a change in an animal’s environment might disturb the way it developed from an egg. Freaks would be born, and would become a new species.