The Reluctant Mr. Darwin (14 page)

It was back at the center of his desk. He'd had sixteen years to think about the transmutation of species, to refine his idea of natural selection, to mine the biological literature for relevant facts, to ponder his own data on variation and adaptation in the wild, to hone the arguments he had outlined in 1842 and drafted in 1844. Meantime he had also fathered nine children, buried two of them, and sent his oldest son off to boarding school. He had published eight books (not counting the edited volumes of
Beagle
zoology), seven of them technical and one a popular travel narrative. He had made himself an expert on the classification of a difficult group of animals, and his expertise had been certified by a major award. No one had a right, he had once worried, “to examine the question of species who hasn't minutely described many,” and now he had earned that right. So was it time to
publish
his theory? No, not yet. He still wasn't ready.

Instead he launched a further program of empirical research to fill some of the gaps in his trove of evidence. He became an experimentalist, cluttering his house and grounds with simple but astute science projects that often smelled bad but supplied useful data. He worked his network of far-flung contacts for answers to obscure questions. He started keeping pigeons. Throughout the next two years he concerned himself largely with the anatomy and development of domestic animals, plant hybridization, plant fertilization, patterns of species diversity reflected in plant classification, and the capacity of plants for transoceanic travel.

How long, Darwin wondered, can a cabbage seed be soaked in salt water and still germinate? How long for a radish seed? A carrot seed? A kidney bean? A pea? He was curious about what he called “accidental means” of plant species dispersal, which might entail a seed, a pod, or a seed-bearing stem floating passively across a wide stretch of sea. So he tested the salt-resistant viability of a whole list of vegetables and other plants: rhubarb, asparagus, celery, cress, capsicum, furze, barley, and more. He mixed up a salt solution resembling sea water, poured it into bottles, dropped in seeds as though they had fallen on the ocean, and left them to ride the brine, or to sink and marinate, for measured stretches of days. From this set of experiments he learned several things. He learned that asparagus could float for twenty-three days if it were green and succulent, or as much as eighty-five days if dried first, and that the seeds would remain viable. He learned that cabbage and radish seeds became putrid and stinky “in a quite extraordinary degree,” but that the radishes would still germinate after forty-two days of soaking, while the cabbages wouldn't. He found that cress seeds put out “a wonderful quantity of mucus,” but that they too would sprout after forty-two days' immersion. Given the average rate of ocean currents, Darwin calculated, forty-two days was long enough for a floating seed or a pod to travel 1,300 miles. Most of the other species he tested were able to produce at least some germinations after twenty-eight days. The conclusion that Darwin drew from these experiments involved biogeography: Plants were certainly capable of crossing oceans. It didn't take an ancient land bridge that had sunk beneath the sea (as some of his colleagues imagined), and it didn't take an act of God, to explain how vegetation might appear on a new volcanic island.

Floating seeds weren't the only means for a plant to colonize across water. There were winged seeds, and tiny seeds with parachute rigging like those of a dandelion, which could travel on the wind. Another possibility was transport by a bird—a living bird, or even a dead one. Seeds might stick to the muddy legs of a heron or an egret and be rinsed off in a new location. His young son Francis, now eight years old, made a boy's gory-minded suggestion about dead birds—such as those that fall victim to a hawk, or to lightning, or maybe to apoplexy—and Darwin pounced on it. He floated a dead pigeon in salt water for thirty days. Seeds from the pigeon's crop germinated nicely.

Another bird-related experiment went to the question whether small animals, such as snails, might hitchhike from one place to another. Darwin cut off a pair of duck's feet and suspended them in an aquarium full of freshwater snails. If a duck was asleep on the water's surface, dangle-footed and oblivious, how many snails might climb aboard? Would they cling tightly when the duck flew away? Darwin waved his duck feet through the air. How long would the snails stay alive out of water? He let the snails languish overnight. His results suggested that freshwater snails could catch and survive a ride of six hundred miles.

He wondered too about lizard eggs. Would they float on seawater? For how long? Having floated for a month or so, would they still hatch? He offered to pay schoolboys a shilling for every half-dozen lizard eggs they could find; snake eggs welcome, too. He'd float them in his cellar. It was all relevant, just as the seed-brining experiments were relevant, because transmutation implied the necessity of natural dispersal. If there was no special creation, there was no special delivery. Biogeography, from a transmutationist perspective, reflected the fact that species had arisen one from another, adapted, and traveled. Darwin needed to prove, among other things, how well plants and animals could get around.

He also wanted measurements of different varieties of domestic animal, especially fetuses and juveniles, in order to see how their differentiation in form during growth and development might echo evolutionary divergence from common ancestors. He asked friends to keep his morbid interests in mind when any of their pets or livestock died. In one letter, to W. D. Fox, he begged for a week-old chicken and a nestling pigeon, from which he meant to make skeletons. He mentioned passingly to Fox that he'd already begun comparing wild and tame ducks. When he got live birds, he killed them with chloroform or ether, boiled the carcasses to soften them, and then stripped off the flesh, a smelly process that often made him vomit—and not just him, with his delicate stomach, but also Parlsow, the all-purpose butler. So he outsourced that phase of the work. About mammals, he reported cheerily: “I have puppies of Bull-dogs & Greyhound in salt.” And he had commissioned someone to make careful measurements of young colts, both racehorses and cart horses. Whenever possible he wanted data from standard-aged juvenile forms, so that comparisons were valid; for birds, he tried to get them seven days after hatching. But juveniles of some species and some breeds weren't always easy to find. Did anyone know, he asked, how to lay hands on a seven-day-old wild duck?

He solved the availability problem for pigeons by setting up his own breeding operation in a backyard aviary. He was interested in the fancy breeds, the pouters and fantails and tumblers and English carriers and others, whose extravagant shapes and behaviors reflected hundreds of years' selective breeding by proud, obsessive pigeon fanciers. “The fancy,” as it was called, wasn't an expensive avocation and some of those fanciers were workingmen, who coddled and bred their birds in London rooftop coops and talked the subtleties of coloring, beak shape, carunculated eyes, and feathery decor in their local pubs. Having begun with the cold detachment of an experimentalist, Darwin found himself charmed by the pigeons and amused by this subculture surrounding them. He studied breeders' manuals, corresponded with experts, read
Poultry Chronicle
, went on pigeon-shopping excursions in London, even joined two of the city's pigeon-fancier clubs. At the height of his own fancy, he had sixteen different breeds. “I am getting on splendidly with my pigeons,” he told his son William, the one at boarding school. He'd just added some trumpeters, nuns, and turbits, plus a small pair of German pouters, given to him by a brewer pal in London. In the summer, Darwin confided to Willy, he looked forward to flying his tumblers. So much for the cold heart and the sharp knife of science.

Late in 1855 he drafted a form letter, a generalized request he intended sending to overseas contacts and acquaintances. It was phrased like a classified ad under the
WANTED
heading. “Skins,” it began: “Any domestic breed or race, of Poultry, Pigeons, Rabbits, Cats, & even dogs, if not too large, which has been bred for many generations in any little visited region, would be of great value.” He was asking a sizable favor: Please ship me specimens. In addition to the skin with its feathers or fur, he wanted a humerus and a femur and as much as possible of the cranium, preferably all still connected by sinew. The part about “many generations” in a “little visited region” was important for his studies of how individuals within a given population vary. Darwin now recognized that this crucial phenomenon, variation, occurs constantly in wild species as well as in domestic stock—but what
causes
it? Huge question. He didn't know. One possibility, he thought, was differences in external circumstance. So he hoped to see how domestic breeds might vary when raised in exotic locales such as Persia, Jamaica, or Tunisia. He would happily reimburse the costs of skinning and shipping.

He made a list of the men to whom this request went. It included such figures as Rajah James Brooke (in Sarawak), Sir John C. Bowring (governor of Hong Kong), Sir Robert Schomburgk (an explorer of Guiana, and then British consul in Santo Domingo), the botanist G. H. K. Thwaites (in Ceylon), E. L. Layard (a museum curator in Capetown), and Edward Blyth (another curator, in Calcutta). Blyth would become one of Darwin's most helpful and prolix respondents. Halfway down the list appeared an inconspicuous name, “R. Wallace,” unaccompanied by any geographical notation. Darwin evidently had a mailing address of some sort for Alfred Russel Wallace—possibly the one in Sarawak, Wallace's temporary base—but at this point he couldn't have guessed exactly where, within the vast Malay Archipelago, Mr. Wallace might actually be. And they barely knew each other. Darwin was just tossing a penny into a well.

23

Wallace's paper from Sarawak, about the “law” regulating the “introduction” of new species, was published in September 1855. It created no sensation, but it did generate some murmurs. Wallace's agent, Samuel Stevens, told Wallace about several London naturalists who had groused that he should stop theorizing and stick to collecting facts. Charles Lyell, on the other hand, found the paper intriguing. Out in Calcutta, Edward Blyth got his copy of the
Annals and Magazine of Natural History
and reacted similarly. In one of his long letters to Darwin, near the end of the year, Blyth asked: “What think you of Wallace's paper in the
Ann. M. N. H.?
” His own answer: “Good! Upon the whole!” Darwin's opinion was different. He read the paper around that time and made some notes for his own memory, as he routinely did with his eclectic research reading. That was Darwin's way, methodical and thorough; he chewed through huge amounts of material, swallowed the good bits, spit out the rotten stuff and the husks. Wallace's paper tasted like husk.

It discussed geographical distribution, Darwin recorded, but offered “nothing very new.” It used the simile of a branching tree (“my simile,” in Darwin's jealous view) to represent affinities and diversity in nature. It mentioned rudimentary organs, though to what point? And the Galápagos comment—about how those peculiar creatures and curious patterns had never received “even a conjectural explanation”—didn't pass unnoticed. Darwin may even have winced, knowing it was true. He
hadn't
risked any explanation in the
Journal
, but…give a man time. Well, all right, he'd
had
time. Still, not enough. And what did Mr. Wallace know of the complex considerations? Rather than arguing the point in his mind, or rising to this small provocation as a challenge, Darwin dismissed Wallace's whole effort. He saw no real explanatory value to the “law” of juxtapositions and he heard nothing in the vague language except a rehash of old-fashioned natural theology. Now if Wallace had scratched the word “creation” and spoken instead about “generation” of new species, Darwin told himself, he could agree with the paper. So far as it went. But Wallace hadn't used any such word. “It seems all creation with him,” Darwin judged, and went back to his pigeons.

He sent off his letters to Thwaites, Layard, and those others on the list, including “R. Wallace.” I would be most grateful, he told them, for any skins of chickens, pigeons, rabbits, or ducks.

24

After a year in Sarawak, Alfred Wallace shifted onward in the Malay Archipelago to find new hunting grounds, beyond the range of previous British travelers and collectors. He caught a Chinese-owned schooner that stopped briefly at Bali and then deposited him on Lombok, a small island just thirty miles further east. Wallace stayed on Lombok for two months, shooting birds and observing the local culture while waiting for another boat that would take him to Macassar, a port on the bigger island of Celebes. Lombok is where he first encountered the sulfur-crested cockatoo, a gorgeous but noisy bird not found on Bali or any of the other islands westward. He also noticed the rainbow bee-eater, another pretty species common in Australia. Wallace would eventually realize from these signals and others that, just in bouncing from Bali to Lombok, across a narrow but deep strait, he had moved from one biogeographical zone into another. He was now in the realm of Australian fauna. That seemed odd. Why should there be such well-demarcated zones?

From Lombok, he sent off a crate of specimens, to Stevens in London by way of Singapore, containing more than three hundred bird skins. Most of those, including as many cockatoos as he'd been able to kill, were intended for sale. The crate also contained something so ordinary that, coming from a commercial collector of biological exotica, it must have seemed peculiar: a local variant of the barnyard duck. Wallace's note to the agent explained: “The domestic duck var. is for Mr. Darwin.” Please forward.

It's hard to say whether that duck ever reached Darwin. If so, he was presumably grateful but not surprised. He had come to expect a high degree of generous cooperation from the people (especially those below him in social status) he called on for research assistance. Around the same time, Wallace wrote to him directly. Sent from Celebes, traveling the slow mail routes of the day, this letter took six months to reach Down House. Like Darwin's first note to Wallace, it hasn't been preserved in the huge archive of Darwin correspondence; its existence and contents can only be inferred from the reply it evoked. “By your letter, & even still more by your paper in Annals,” Darwin wrote Wallace on May 1, 1857, “I can plainly see that we have thought much alike.” Choosing his phrases with some delicacy, he added that “to a certain extent” they had reached “similar conclusions.” Furthermore, Darwin said, he endorsed “almost every word” of Wallace's paper and considered it rare for two theorists to agree so closely. Given Darwin's cold dismissal of the “law” paper in his reading notes—“nothing very new”—this was spreading the butter a bit thickly.