The Reluctant Mr. Darwin (5 page)

In shorthand scrawl, he had his big idea. Years later he would articulate the details and call it “natural selection.”

6

The wedges metaphor went into his notebook on September 28. And then an odd thing occurred, by way of visible aftermath to this momentous epiphany: nothing. Darwin held his cards close and kept a poker face to the world.

In private he continued the notebook ruminations, finishing “D” with a burst of comments on the “differences” (that is, variations) among offspring in consequence of sexual reproduction, and starting the next in his transmutation series, notebook “E,” with some increasingly confident references to “my theory.” His theory explained how those small differences can accumulate into adaptations particular to differing circumstances. His theory, he realized, would be quite a horse pill for other people to swallow. Trying to keep his thoughts compartmented, Darwin also began another notebook, labeled “N,” which was devoted to “metaphysical enquiries” provoked by the scientific ideas he was considering. Does a dog have a conscience? Does a bee have a sense of communal responsibility? Is the human conscience just another form of inherited instinct, an adaptation for social behavior? Is the human mind just a function of the human body? Does the idea of God arise naturally in human minds from that instinctive conscience? Months earlier he had posed almost the same question about God and conscience—whether “love of the deity” might result simply from brain structure—and then had scolded himself delightedly: “oh you Materialist!” Now his materialism was getting deeper, firmer, less embarrassed. Still, he didn't feel ready to go public. There were already enough materialistic evolutionary radicals, he knew, amid the current political squabbling about Chartism, democratized medical education, changes to the Poor Law, and they weren't his kind of people.

It was the dizziest season of Darwin's life. He stopped writing letters to his friends and family. He kept busy at his
Beagle
-related tasks, guiding a volume of the
Zoology
into print and adding a preface to his own expedition
Journal
. He performed his duties as secretary of the Geological Society. His health was going bad, in some still unexplained way, and he needed rest. He trusted his most serious thoughts only to the notebooks. “Having proved mens & brutes bodies on one type,” he wrote, it would be “almost superfluous to consider minds,” adding, “yet I will not shirk difficulty.” In early November, two themes dominated his notations: the importance of sex and the search for laws. Sexual reproduction (as distinct from vegetative reproduction or budding, whereby an individual microbe or plant reproduces itself exactly) entails the paradox of inherited variation—that is, slight differences between parents and offspring, as a result of the mixing of elements from two parents. Fundamental laws (as distinct from divine whim) govern the occurrence of variation and the transmutation of species. He wanted to illuminate those “laws of life.” In the midst of this heightened sense of danger, excitement, and solitude, he did something uncharacteristically impulsive: He hopped on a train for Staffordshire, turned up at the home of his uncle Josiah Wedgwood, and asked his cousin Emma to marry him. It was a reckless leap toward safety.

His proposal surprised her. Emma was a sweet-spirited and pious thirty-year-old, on the brink of what in those days was considered spinsterhood. She and a hunchbacked elder sister were the last Wedgwood girls left in the house. She had known Charles nearly all her life, as the boy-cousin closest to her in age (though she was slightly older), and the families were cross-linked by multiple marriage connections. Charles's mother, who died when he was eight, had been the sister of Uncle Josiah, and just a year before this sudden offer to Emma, Charles's sister Caroline had married the eldest Wedgwood son, another Josiah. Even Charles's Wedgwood grandmother, his mother's mother, had been a Wedgwood by birth who married her cousin, another Wedgwood. First-cousin marriage was common in those days and those circles, though that's not to say people weren't aware that too much inbreeding could bring problems; otherwise they'd have been marrying their sisters and brothers. On the positive side, unions between cousins helped keep family fortunes together. So the pairing of Charles and Emma was an obvious one, in some ways. Would-be matchmakers in the Wedgwood family had probably pondered it more consciously than the principals ever had. Still, as these two cousins aged, it hadn't looked likely to happen. Charles had paid Emma some attention during his visit in July, though not with enough ardor to suggest that those few conversations were supposed to constitute courting. Now here he was out of nowhere—having done his private calculus of upsides and downsides and concluded he should marry
someone
—putting himself forward, humbly but abruptly, as her suitor.

The surprise went two ways. When she accepted him on the spot, he was startled. Then they both let the idea sink in. There was no whoop-de-doo echoing through the house that day. Emma felt “bewildered” rather than giddy, and Charles had a headache. Everyone else, both fathers included, clucked their conventional noises of approval. Charley and Emma, of course, how perfect.

It wasn't perfect. One imperfection was the discrepancy between Emma's fervent, Bible-based Christianity and Charles's recent free fall into disbelief. Charles himself didn't yet know how far that fall would drop him or where he would land. But his father had warned him, probably just months earlier, that a man with theological doubts should conceal them from his wife. Nothing to be gained for anyone, according to the hardheaded doctor, in giving a woman cause to worry about the salvation of her husband's soul. Things might go along well until one of them got sick, and then she would suffer miserably at the thought of eternal separation, making him miserable, too. Charles promptly ignored his father's advice (which may have been the most prescient thing, if not the wisest, that Dr. Darwin ever said to him), telling Emma at least something of his heterodox thinking. Most likely he didn't raise the topics of transmutation, monkey ancestors, the idea of the deity as an inherited instinct, or the conundrum of male nipples, but whatever degree of apostasy he confessed was enough that she called it “a painful void between us.” Then she brightened up and thanked him for his candor, having reassured herself that “honest & conscientious doubts cannot be a sin.”

Doubts? That was putting it politely. By this time he had a whole new framework of scientific and metaphysical convictions, not just doubts. But if she was willing to twine their fingers together across the void and ignore it, so was he. Nowhere on his clerkish lists of marital benefits had he posited that a wife should be a philosophical soul mate and a full intellectual peer. He told his friend Lyell, in a letter announcing the engagement, of his “most sincere love & hearty gratitude” toward Emma—gratitude for “accepting such a one” as him. This was probably a candid statement, more revealing than he wished: his love tepid but genuine, his gratefulness robust.

Back in London, he returned briefly to the “E” notebook before house-hunting and other domestic preparations swamped him. Near the end of November, with his usual bumpy punctuation, he wrote:

 

Three principles, will account for all

1. Grandchildren. like. grandfathers
   
2. Tendency to small change…especially with physical change
   
3. Great fertility in proportion to support of parents
   

Bare and elliptical, it was his first full outline of the three causal conditions for natural selection: (1) hereditary continuity across multiple generations; (2) incremental variations among offspring; and (3) the Malthusian factor of inherent population growth rate, producing so many unsupportable individuals. Put them together and you had an explanation of how species transmutation occurs.

So much for the notebook. In his personal diary, he wrote: “Wasted entirely the last week of November.” Was he complaining, apologizing, or bragging jocularly about a newfound sense of lightness? In early December, Emma came to town and stayed two weeks with her brother and sister-in-law, during which she and Charles threw themselves into the merry fuss of setting up a household. Then she went back to Staffordshire. To the end of the year, he occupied himself with further house-hunting, a bit of reading, and being laid up intermittently by his mystery illness. Having decided the marriage question, he was now impatient for the wedding to occur. His letters to Emma were cheery. In one, at the end of a long day, he described himself complacently as “stupid & comfortable.”

On January 29, 1839, they were married in a small church near the Wedgwood mansion. Charles's brother didn't come up from London for the event, and Emma's mother stayed home sick. Dr. Darwin and Uncle Josiah had arranged bounteous financial settlements, formalized in a document at the county records office: £10,000 from Dr. Darwin's deep pocket, £5,000 from the Wedgwood side, to be invested on behalf of the newlyweds at 4 percent annually. That meant Charles wouldn't need a job and they'd have servants in the house. They were young gentlefolk from affluent, provident families. The marriage ceremony was performed by Reverend Allen Wedgwood, a cousin to everybody. There was no reception, but not because the Wedgwoods couldn't afford a party. There was no honeymoon, but not because the couple didn't want to be alone.

Charles and Emma left Staffordshire that day. By way of matrimonial celebration, they shared sandwiches and a bottle of water on the train down to London. It was their chosen style. A quiet pair, disinclined toward ebullient display. And he had to get back to work.

1842–1844

7

T
hink of it as a bird's egg, taking form slowly inside him. Ovulation had occurred. Fertilization had occurred. Now came growth, from the microscopic scale of a single ovum to…well, to whatever size it would reach before laying. Don't think of a hen's egg or a goose's, or even the hefty egg of an avian lummox like the ostrich. Since the ovum was natural selection and the bird was Charles Darwin, think of it as the egg of a kiwi.

The kiwis are long-beaked, globular, flightless birds, strange creatures with hairlike feathers who run around at night eating insects and worms. There are several species and subspecies, all embraced by the genus
Apteryx
, all endemic (that is, native there and nowhere else) to New Zealand. They belong to the ratite group, meaning that ostriches, rheas, emus, and cassowaries are their closest living relatives. The elephant birds of Madagascar and the moas of New Zealand, two sets of extinct giants, were part of that group, too. If these birds are all related and all flightless, you might ask, how did they arrive in such remote and disconnected places as South America (rheas), Australia (emus and cassowaries), New Guinea (more cassowaries), Madagascar, and New Zealand? The answer seems to be that they walked. The ratite lineage dates back to an era before the ancient southern supercontinent, now known as Gondwanaland, separated into its continental and island fragments. Traveling on foot, the ancestral ratites dispersed all across Gondwanaland and then, sometime later, the land fragments drifted apart. The giant birds rode away like penguins on an iceberg.

Compared with other ratites, the kiwis are small—no bigger than an overfed chicken. Taxonomists have disagreed about just how many species to recognize, under just what scientific names, but currently the consensus seems settled on four: the North Island brown kiwi (
Apteryx mantelli
); the tokoeka (
Apteryx australis
); the great spotted kiwi (
Apteryx haastii
); and the little spotted kiwi (
Apteryx owenii
). The last was named for Richard Owen, who in 1838 presented a multi-part paper titled “On the Anatomy of the Apteryx” to the Zoological Society in London. Darwin, having heard at least some of Owen's paper, referred to it in his notebook “D.” The most remarkable thing about the apteryx, Darwin thought, was its small respiratory system, suggesting that in the wild this must be a shy, patient, creepy little bird, with little inclination to exert itself much and therefore little need to breathe heavily. Owen had only a single specimen to examine, a male, and he was an anatomist, not a physiologist or a field naturalist; so he missed some kiwi traits just as peculiar as the reduced lung capacity. An extraordinarily acute sense of smell. A low body temperature, unusually cool for a bird. An odd mix of furtive and aggressive behavior. Darwin missed them, too, along with the single most notable fact about kiwi biology: These little birds lay humongous eggs.

A female brown kiwi weighs less than five pounds. Her egg weighs almost a pound—constituting, that is, about 20 percent of her total weight. Among some kiwis, the egg-to-body weight ratio reportedly reaches 25 percent. A female ostrich, by contrast, lays an egg weighing less than 2 percent as much as herself. Certain other avian species—hummingbirds, for instance—lay more ambitious single-egg packages than ostriches, but few if any match kiwis. Relative to her body size, on a standard with other birds, the brown kiwi's egg is about six times as big as it should be. It contains also a disproportionate allotment of yolk, on which the chick will survive just after hatching. This egg takes twenty-four days to develop and, once it has, fills the female like a darning egg fills a sock. Having gorged herself for three weeks to support the growth of such a large embryo, during the last two days she stops eating. There's no room in her abdomen for another cricket. “Sometimes the egg-bearing female will soak her belly in puddles of cold water,” according to one source, “to relieve the inflammation and to rest the weight.” She is painfully replete with motherhood.

An X-ray photo of a gravid female kiwi, taken fifteen hours before laying, shows this: a skull, with its long beak; a graceful S-shaped neck; an arched backbone; a pair of hunched-up femurs; and at the center of it all, a huge smooth ovoid—her egg—like the moon during a full solar eclipse. She herself is now just a corona. It seems impossible. How can she carry this thing? How can she deliver? Will it reward her efforts and discomforts, or rip her apart?

The size of the kiwi's egg raises interesting evolutionary questions. For starters: Why is it so big? What are the adaptive advantages for kiwi females (and for males, who do much of the incubating) of such heavy investment in a single chick? How has the kiwi lineage changed over evolutionary time? Did the egg evolve toward largeness? Or did the bird itself evolve toward smallness—a shrinking ratite, descended from moa-sized ancestors—while the egg stayed as it was? If the bird shrank and the egg didn't, why not? Those questions could take us into a discussion of allometry (the study of growth rates and size disparities within organisms) and kiwi evolution, which might be amusing. But allometry isn't the point here.

The point is simply metaphor. Every time I see that X ray of the mama kiwi, I think: There's Darwin during the years of gestation.

8

By spring of 1842 he was a famous author, thanks to the surprising success of his
Journal
from the
Beagle
voyage (published in 1839), and a father of two, thanks to Emma. He had been elected a Fellow of the Royal Society, Britain's foremost scientific club. But he was still stuck in an ugly little row house in filthy, raucous London, and still slogging his way through the less glorious, more technical publishing chores that had followed from the five-year expedition. As for his transmutation theory, nothing. Nothing published, anyway. Nothing written except those disjointed notes and an occasional coy hint, in a letter to a friend, that he was working on the question of species and varieties. To his close colleague Lyell he had let drop his doubt that species have a divinely decreed beginning. In his
Journal
he had mentioned the Galápagos mockingbirds and finches, different species on different islands, but declined to speculate further on such a “curious subject.” He wanted to tell people about his theory, and he didn't. It wasn't ready. He wasn't ready. He had finished with his transmutation notebooks, three years earlier, and let them sit. Among his more overt reasons for inaction on the “curious subject” were that he had been too hectically busy and too often sick.

The mysterious vomiting, headaches, and other knockdown symptoms continued to afflict him intermittently. He had resigned from his secretaryship of the Geological Society, citing bad health, a legitimate excuse but also one that allowed him to immerse himself more fully in his own work. Intellectual hobnobbing was fine for those with the stomach; he found it literally nauseating. He was over the loneliness he'd felt aboard the
Beagle
, satiated with the sort of chirpy socializing his brother enjoyed, and had begun the process of retreating from London scientific circles into a reclusive life of research, writing, and invalidism. His marriage to Emma, entered in such a pragmatic and passionless spirit, had started developing toward what it would eventually be: an extraordinarily close mutual devotion and an asymmetric dependency, with her serving as his chief nurse and protectress. Even before the later children (eight more of them) arrived, those roles were enough to keep Emma busy—and, it seems, satisfied. She didn't need to function as her husband's intellectual sounding board, or as his transcriber, or his copyeditor, to feel fully engaged with his life.

Besides, there was still that “painful void” between his thinking and her beliefs, which neither of them cared to accentuate. They knew that their disagreements about God, scripture, creation, and afterlife were wide and irresolvable. Three years earlier, not long after their marriage, Emma had written Charles an earnest letter, describing her struggle to come to terms with his science-driven impiety. She was ambivalent, she admitted. She wanted to feel that “while you are acting conscientiously and sincerely wishing and trying to learn the truth, you cannot be wrong.” On the other hand, she couldn't always give herself that comfort. She worried that “the habit in scientific pursuits of believing nothing till it is proved” had blinded him to the importance of revelation. She wondered whether Charles hadn't been unduly influenced by his careless, doubting brother, Erasmus. She warned him gently of the danger to his immortal soul if, rejecting dogma, betting against orthodox views of spiritual reward and punishment, he was wrong. “Everything that concerns you concerns me,” Emma wrote, “and I should be most unhappy if I thought we did not belong to each other for ever.” He didn't want her to be perpetually unhappy, not in this life, let alone any other. So he preferred to let the matter drop—at least until he published his theory, whenever that might be.

But he never forgot her letter. He saved it among his private papers, in fact, and occasionally pulled it out to reread.

For the present, he needed to focus himself on immediate tasks and conserve strength. His volume on coral reefs would be published any month. He was offering an ingenious, well-supported explanation for how they are formed. Next he would do a book on volcanic islands. Both of those had been added to his original ambitious plan for the
Zoology of the Beagle
series. Eventually he would write three complete volumes of geological observations from the voyage, plus editing five volumes on the zoology. All this took time; years. Where did the days go? In his diary he tried to keep track. The coral reef book alone, Darwin figured, cost him twenty months of effort. That was spread across four years during which he had worked also on the
Zoology
, the Glen Roy paper, some other geological projects, and (marginally) transmutation, losing the rest of his workdays to illness. Being a husband, a father, and a householder also took time, notwithstanding the help supplied by a butler, a cook, a nurse for the children, and other servants, as well as Emma's own indulgence of his detached, contemplative habits. In May, he and Emma bustled their gang off to Staffordshire for a vacation at her family home. After a month there, he shuttled over to stay with his father and sisters in Shrewsbury, leaving Emma and the kids behind.

He had left his notebooks behind too, in London, but that didn't stop him thinking. The holiday from other work became a chance to put something on paper about transmutation. During those summer weeks of 1842, amid Emma's family and then his own, he found enough quiet hours to write a dense précis of his ideas and of the evidence and arguments he'd collected to support them. He worked in pencil. This “sketch,” as he called it, came to thirty-five pages. Unlike the notebooks it was carefully structured, moving from topic to topic in a way meant to build his case clearly and cogently; but like the notebook entries it was elliptical, with phrases and sentences suggesting much more (at least to him) than they actually said. It was an outline, an extensive one, of the book he intended to write.

He began with the topic of variation among domestic animals, noting the obvious point that individuals differ slightly from one another in size, weight, color, and other ways. Because some of those differences are heritable, human breeders have been able to perpetuate and even amplify desirable traits by carefully selecting which animals to pair. With enough selection over long stretches of time, breeders even produced new races—speedy horses versus dray horses and tallow cows versus beef cows, for instance. This was the setup for Darwin's crucial analogy.

From variation among domestics he moved to variation among wild creatures, and to what he called here “the natural means of selection.” Variation in the wild might not be as common or as extreme as variation among domestics (so he thought), but under certain circumstances it did occur. What caused it? He didn't know—and, for the present, that didn't matter. Some of those variations, like the ones among domestic animals, were heritable. Given the inherent rates of population increase and the enormous excess of insupportable offspring, to which Malthus had awakened him, wild creatures would be subjected to an automatic sort of culling, based on their capacities to compete for survival and for mating opportunities. By now he had hit upon not just his analogy, with domestic breeding, but his chosen term: “natural selection.” The net result over thousands of generations, he wrote mutedly, would be to “alter forms.”

He had described a physical mechanism (or at least, part of it) by which new species
could be
produced. But was there empirical evidence that they
had been
produced, one from another, through any such pageant of organic change? Yes, and in the second half of his draft he sketched that evidence, category by category: the fossil record, geographical distribution, systematic classification of species based on morphological resemblances, rudimentary organs (such as the wings of the apteryx), all of which tended to affirm the idea of transmutation and to belie special creation. Then he wrote a conclusion, highlighting as a sample case three species of Asian rhinoceros—those from Java, Sumatra, and India—and noting that a creationist would believe all three originated, with their “deceptive appearance” of close kinship, from separate acts of divine will. As for himself, Darwin wrote, he could just as well believe that the planets revolve in their orbits “not from one law of gravity but from distinct volition of Creator.” If all species are handmade by God, then a person might also assume that Mars and Jupiter fly around because He's playing them like yo-yos. That's unlikely. Maybe even blasphemous. Wasn't the deity, if any existed, too sublimely transcendent for what we'd now call micromanagement? Darwin was suggesting an idea even larger than natural selection: that the universe is governed by laws, not by divine whim, and that the transmutation of species by natural selection is merely one of those laws.