The Heretic in Darwin’s Court: The Life of Alfred Russel Wallace

WHEN WALLACE DISEMBARKED with his “chattels” in Singapore in April 1854, he found himself in an exotic world. Singapore was like few other cities on earth and certainly like no other city he had ever seen. The harbor was crowded with massive war and merchant vessels from Europe, dwarfing the hundreds of colorful praus and junks of the Malays and Chinese moored nearby. Throngs of people pushed past him on the street, including the Portuguese of Malacca, East Indians of various sects, native Malays, Javanese and other peoples from the outer islands, the occasional Englishman, and the ubiquitous Chinese. The town was an anthropologist’s paradise.

Wallace had not come to Singapore alone. As he vowed when he was languishing in the Amazon in the grip of malaria, he brought with him an assistant and companion, a young apprentice collector named Charles Allen, the son of a London carpenter who had done some work for Fanny and Thomas Sims. After locating equipment and supplies sent ahead a few months earlier, the first task of the single-minded thirty-one-year-old naturalist and his inexperienced adolescent apprentice was to find a place to live. Accommodations in Singapore were not inexpensive; Wallace and Charles had no choice but to spend the first week in a costly hotel.

From the perspective of a naturalist, the town of Singapore had little to offer. Over the preceding half century, the expanding population had denuded the once thick-forested island. It was not much better beyond the city limits, where no insect or animal worth collecting was to be found along the barren, dusty roads leading to plantations of nutmeg and Oreca palm. Eventually, Wallace and Charles rented a room in a French Catholic mission, nestled among foothills eight miles from town. Atop of these hills was intact forest, which Chinese woodcutters were assiduously clearing, but the wood, sawdust, and decaying leaves they left behind proved to be ideal habitats for insects and their larvae. In a matter of days, Wallace made a remarkable collection.¹

Wallace quickly settled into a routine. At half past five, he would awaken, bathe, and have coffee, and then arrange and put away the insects collected the day before, setting them out in a safe place to dry. While he was doing this, Charles mended nets, filled pincushions, and packed up the supplies for the day’s outing. At eight, they would have breakfast and within an hour leave for the jungle. By the time they reached the top of the mission’s hill, they were drenched in sweat. For four or five hours, they would wander amid the felled trees and tangled vines gathering up insects—mainly beetles, some of which Wallace judged “very rare and beautiful”—and then return to bathe, change clothes, and kill and pin insects until dinnertime at four o’clock. After another hour or so of work, which included meticulously recording what he had captured in “registries”—two separate notebooks, one for insects, the other for birds and mammals—Wallace would relax with a cup of coffee, read, and then go to bed, though occasionally his collections were so numerous that he would continue killing and pinning well into the night.

By the end of May, he had shipped to Samuel Stevens 700 species of beetles, among which were 130 highly esteemed species of longicorns, prized for their attractive colors and antennae, which were long, thin, and playful, like a Dalí mustache—totaling approximately 1,000 specimens. Perhaps inspired by Henry Bates’s example, he began to document his experiences by sending regular reports to the various journals and societies, beginning with a letter dated May 9, 1854, printed in the Zoologist. For the next five years, the English zoological world was kept abreast of both men’s exploits, the one on the South American continent, and the other halfway around the globe in some of the remotest places on earth.

Sixteen years old and looking a few years younger, Charles would remain in Wallace’s service for only a year and a half. Wallace was a perfectionist, with a clear vision of his objectives, and he placed extraordinary demands on himself and others in order to achieve them. He was a tough taskmaster who hoped to elevate Charles to his own impossibly high standards. Wallace notes in a letter to Fanny that what struck him most about Charles in their first few weeks together was his untidiness: Charles had arrived in Singapore with his clothes somehow in tatters, looking like a homeless urchin shanghaied off the streets of London. At first, Wallace indulged the boy’s foibles and held out hope for improvement, allowing Charles to kill and pin flies, bugs, and wasps but not trusting him with the more delicate and valuable beetles. But by the following summer, when they were in Borneo, Wallace would be at his wit’s end. He had reported his travails to his mother, sister, and Stevens, all of whom were scouring London for a better prospect. In response to his sister’s report that they had found a suitable replacement, Wallace let out a torrent of frustration:

Singapore was poor in birds and mammals, and Wallace had no intention of limiting his collections to insects. In July, he and Charles left for Malacca, sixty miles north of Singapore, on the coast of the Malay Peninsula facing Sumatra. Malacca was an old city that had changed rulers many times over the preceding 300 years. In 1511 it was seized by the Portuguese; 130 years later, it was taken by the Dutch; 150 years after that, the Dutch entrusted it to the British for protection against an imminent invasion by Napoleon’s forces. Although England returned most of the East Indies to Holland, it negotiated hard to retain Singapore and Malacca, and the Dutch yielded reluctantly. In the case of Singapore, they made an enormous mistake—almost as great as their trade of Manhattan for one of the Spice Islands. Within thirty years, Singapore grew from a small fishing village to the largest free port in the Far East. England further expanded its foothold on the Malay Peninsula through a treaty with Siam; eventually, British Malaya would become Singapore and Malaysia, and Dutch Malaya would become Indonesia.

Wallace and Charles traveled for nine weeks in and around Malacca, but Wallace spent two of those weeks in bed recovering from a return bout of malaria. After a government doctor had “killed” his malady with liberal doses of quinine, Wallace walked to a government bungalow fifteen miles in the interior, accompanied by Charles, six Malay porters, and a local guide, a “young gentleman of Malacca” who had a “taste” for natural history and a familiarity with the Malays and their language. They brought enough provisions to last for a month, since food was difficult to obtain in the interior. A few weeks later, after making a good collection of birds and insects and observing the people, who were devout Muslims, he set out on his first true adventure to Mount Ophir, fifty miles east of town in the heart of the peninsula. With his native crew and English assistant, he passed through forested country that grew wilder and hillier by the day. Knee deep in mud, they were annoyed by leeches, which lay in wait on the leaves of plants, standing erect and moving their heads right and left in search of some mammal to attach themselves to. These Wallace and his men avoided; but others they did not see attached by the half dozen to their exposed skin and turned their clothes into a bloody mess. In the evening, while bathing, he found several on his body sucking their fill. One latched onto his neck a fraction of an inch from the jugular vein. How he extracted it he does not say, but like a true scientist he overcame his revulsion and described several of these undesirable companions as “beautifully marked with stripes of bright yellow.”³

Along the way, Wallace took measurements of the altitude for a topographic map of the region, and for a week he roamed the forests, filling his boxes with specimens that were eventually shipped to England. He hiked to the summit of Mount Ophir, ascending precariously by grabbing roots and creepers and refreshing himself with the water he found in unopened pitcher plants, a kind of “insect soup too strongly flavoured with formic acid.”⁴ Now and then, between the rolling clouds below, he had magnificent panoramic views.

In a letter to his mother written in July, Wallace had mentioned Cambodia as a possible destination, but when he returned to Singapore from Malacca in September, he contacted the “White Rajah,” Sir James Brooke, governor of Sarawak, who persuaded him to go to Sarawak instead. Sarawak was a sliver of territory on the northern coast of Borneo, the interior of which was terra incognita to exploring naturalists. Brooke offered Wallace every assistance for exploring the land under his rule. He invited him to join a small group of English residents and practice Malay, which he had to master if he was to expand his operations beyond the Malay Peninsula into the vast, unknown archipelago itself.

Brooke had lived in the Malay Archipelago for fifteen years. An aristocrat by birth, he led an aimless life as a youth and never completed his formal education. He enlisted in the British army in 1819 at the age of sixteen, but his military career was cut short six years later, when he was severely wounded in Assam during the Anglo-Burmese War. He returned to England, and in five years, when he was fully recovered, he rejoined the army. After arriving in Madras, he changed his mind about army life and boarded a navy vessel to the Far East. For the next year, he traveled in Malacca, Singapore, and China, an excursion that fired his imagination. Back in England, he convinced his father to buy a schooner so that he and some friends could embark on a “wild adventure” somewhere as traders. They sailed for China, their schooner laden with merchandise, but the poorly planned scheme was a fiasco and they were forced to sell their ship and cargo at a loss. In 1835 Brooke’s father died, leaving him a considerable sum of money. He bought another vessel and sailed around the Mediterranean, becoming expert in commanding a ship and more artful as a trader. By 1838 he was ready for a longer voyage. Once again, he found himself drawn to the Far East, and this time he chose as his principal destination the Malay Archipelago, most of whose islands were unexplored except for those parts the Dutch occupied. These islands were reputed to be richer in mineral wealth than the Americas and unrivaled in natural beauty; moreover, current political conditions offered the British a chance to gain a stronger foothold in Southeast Asia. Brooke shared the vision of Stamford Raffles, the founder of modern Singapore, of establishing a chain of commercial outposts from India to Australia that would dominate trade in the region. Both Holland and the Malay states were weak, and the northern coast of Borneo, with no significant settlements and a location close to China and Singapore, seemed the ideal place to seek one’s fortune. In August 1839, Brooke landed in northern Borneo at Kuching, Sarawak’s nominal capital, a small town of fifteen hundred inhabitants. The rest of the country was even more sparsely populated. In the interior were the pagan Dyaks, who did not cultivate enough to sustain themselves and depended on trade for survival; the scattered Islamic Malays, who lived off the proceeds of their small gardens and from fishing; and two or three hundred Chinese, who prospected for gold or mined antimony. Two years later, Brooke was awarded control of Sarawak by the sultan of Brunei in gratitude for his assistance in subduing insurgents who threatened the royal court.

Brooke established a benign, paternalistic dictatorship, convinced that “no Asiatic is fitted to govern a country” without enlightened European guidance. Hoping to avoid the usual corrupting influence of Western civilization on its colonized subjects, he drew up a series of regulations and rules of conduct that he had printed in Singapore in the Malay language. Murder, robbery, “and other heinous crimes,” he wrote, were to be punished according to harsh Bruneian law. All men—Malays, Chinese, Dyaks, and Europeans—were free to trade and enjoy their profits. He imposed a tax on every citizen, “more nominal than onerous,” guaranteeing protection for those who “act rightly” but vowing not to tolerate those who disturbed the public peace or committed crimes. With only a small staff consisting of four European and eight native assistants, in less than a year he brought peace to his little state, and soon an influx of Chinese merchants and traders brought prosperity. Brooke was pleased with his novel experiment in enlightened government, informing the British public that it “ensures the independence of native princes, and will advance the inhabitants further in the scale of civilisation by means of this very independence.”⁵

By all accounts, he was a dashing and charismatic figure. His private secretary and biographer, Spenser St. John, describes him as “handsome, elegant in look as well as in manner, fond of the lighter accomplishments of music and poetry and full of ability, and with his friends, brilliant in talk.” He was uncommonly brave and fearless. But when Wallace met him in 1854, he was a changed man, at least physically. A year earlier, he had been stricken with smallpox. His recovery was long and slow, and the disease left him fatigued and permanently disfigured.

Wallace sailed from Singapore on October 16 and arrived in Kuching on November 1. He would remain in Borneo until January 1856, a crucial period in his eight-year sojourn in the Far East, during which he formulated the details of his evolutionary theory. For a part of that time, he was a guest of the rajah, who acted as mentor, colleague, friend, and sounding board. Although Brooke served as the inspiration for Rudyard Kipling’s The Man Who Would Be King, a tale of greed and imperial arrogance, he was a more complex figure, vilified by some yet admired by many. Wallace was among his most loyal admirers and named a new species of butterfly he discovered in Sarawak after him: Ornithoptera brookiana. With a curved band of brilliant metallic green spots across its velvety black wings from tip to tip, it is among the most elegant species of birdwings, so called because of their enormous wingspan—some females of the species O. victoria can reach ten inches—and graceful flight.

Wallace’s visit to Sarawak came during a peaceful interlude in Brooke’s life. Only a few years earlier, he had vanquished a community of pirates who terrorized the northern coast of Borneo, but the manner in which he had achieved this success inflamed passions in Parliament and triggered an investigation. The English treasury had been tapped to provide money for every pirate head captured in battle, and Brooke’s little army of headhunters delivered more than five hundred heads; whether all of them had belonged to pirates was another question. The investigating commission had just left Singapore at the time of Wallace’s arrival; whatever the outcome of their findings, Brooke was enjoying a quiet life for the first time in more than a decade.

Brooke had built his residence on a knoll overlooking the Sarawak River. According to St. John, it was originally a four-room, lofty house surrounded by broad verandas, with a library in front, a “splendid” dining room in the middle, and two bedrooms in back. By the time of Wallace’s visit, Brooke had added a wing for his private use, leaving the other rooms for his staff and visitors. Fruit trees surrounded the house, and fragrant jasmine bordered the lawn and paths. He paid particular attention to his garden, especially the roses, which were his favorite flower. Partly hidden by dense foliage were pigeon houses, kitchens, and servants’ quarters. Rooms were comfortably furnished with matted floors, easy chairs, pictures, and books—all arranged, one visitor observed, “with more taste than bachelors usually display.” The walls of the large central room were adorned with every type of firearm. Over the years, Brooke had filled the library with all the classics, books by the best historians and essayists, travel narratives, theological works, and various maps, encyclopedias, and other reference books. “I well remember a sneaking parson from Singapore who came on a visit, examining the library, “St. John writes, “and when he found works of Priestley and Channing alongside those of Horsely and Pye Smith, going away and privately denouncing the Rajah as an infidel and an atheist, or, worse still, a Unitarian.” In this room, Brooke would spend part of his day reading or playing chess.⁶ At 11:00 A.M., he went to the Kuching courthouse to rule on pending cases, then returned home at 2:00 P.M. What Spenser St. John called “the great feeding-time” began at sunset. Brooke took his seat at the head of the table, and his staff and guests were seated according to their rank. After dinner, they all retired to the salon to smoke cigars and talk. At this time, the Chinese dropped in. They crept up to touch their rajah’s hand, and then retired to a corner of the room and squatted in silence for a couple of hours to listen to the proceedings before creeping silently out again. The conversation usually centered on religious or philosophical topics and would last until 11:00 P.M., at which point the rajah would send his guests off to bed.

Wallace enjoyed these lively nightly discussions. St. John had fond recollections of Wallace and the debates he stimulated. “If he could not convince us that our ugly neighbours, the orang-outangs, were our ancestors,” St. John recalls, “he pleased, delighted and instructed us by his clever and inexhaustible flow of talk—really good talk. The Rajah was pleased to have so clever a man with him, as it excited his mind, and brought out his brilliant ideas.” The next day, everyone would catch one another in Brooke’s extensive library, checking for authorities to bolster their arguments in the evening’s discussions. Among the many books and journals in the library was a copy of Vestiges of the Natural History of Creation, which Brooke had read in 1850 and was fond of discussing. With Wallace present, the content of the book aroused heated debate.⁷

Wallace and Charles spent their first four months exploring the various parts of the Sarawak River, from its mouth to the picturesque limestone mountains that it wound through inland. In March 1855, they ventured into Borneo, arriving at a coal mine managed by an Englishman, who put them up temporarily. Wallace was so pleased with the site that he had a small house with two rooms and a veranda built for himself and remained there for the next nine months.

In the untouched virgin forest of Borneo, insects were widely scattered, but the felled trees and large clearings near coal mines attracted a wide array of insects. Wallace had arrived just as the rains were diminishing; the sun shone every day, and butterflies and wasps ventured into open, sunny places. In less than two weeks, he had collected twice the number of beetles he had amassed in the preceding four months, on average taking in twenty-four new species a day. By the end of his nine months, he had collected two thousand distinct species in one square mile, aided by local Dyaks and Chinese workmen, who were paid a penny for each insect they brought him.

On March 12, 1855, Wallace began a special journal—separate from his travel diary and the insect, mammal, and bird registries he kept—to track his collections. In it, he made intermittent entries until sometime in 1859. Less polished than his travel journal, it contains a mixture of observations, anecdotes, extracts from scientific texts, and musings. He intended to use the notes in this new journal for a book called “On the Law of Organic Change,” and it is the only surviving document that gives a clue to the ideas on speciation that were brewing in his mind during his first five years in the Malay Archipelago.⁸

One of Wallace’s chief reasons for coming to Borneo was to observe the orangutan in its natural habitat and obtain good specimens of the different varieties and species of both sexes thought to exist. So impressed was he by this great anthropoid ape that he recorded five separate accounts of his observations.⁹ After a thorough examination of sixteen specimens (nine males and seven females), all but one of which he shot himself, he published a treatise on the orangutan in the Annals and Magazine of Natural History—a series of three articles intended to dispel previous misconceptions and inaccuracies. The Dyaks had told him that there were at least three types of orangutan. The first and most abundant the Dyaks called mias chappan; it was large, and the face expanded laterally into fatty protuberances or ridges over the temporal muscles—mistermed “callosities,” Wallace said. He believed that the mias chappan corresponded to the orangutan classified by taxonomists as Simia satyrus. The second and smaller type the Dyaks called mias kassu, corresponding to S. morio and described by the anatomist and paleontologist Richard Owen. As for the third species, Wallace could never get the Dyaks to define the differences with precision. Brooke—also something of a specialist in the orangutan, having presented his observations in a letter addressed to the Zoological Society on March 25, 1841 (and published in the Annals in 1842)—agreed initially with the general Dyak belief in the existence of three species. Edward Blyth, curator of the Museum of the Royal Asiatic Society of Bengal in Calcutta, imagined yet a fourth species, based on a few skeletons that he had received from Sarawak, distinguished from the other three by its shorter and more robust limbs and slightly projecting jaw. (In a letter to Darwin dated August 5, 1855, he names this species Pongo owenii.) But all these conclusions, Wallace said, had been made from a small number of specimens. By comparing the skulls of several specimens, he showed that there was only one species—with “great individual variation in form and proportion of scull [sic] and skeleton [as] decided as those existing between the most strongly marked forms of the Caucasian and African crania in the human species.”¹⁰ He believed that the error of the Dyaks had originated from an incorrect determination of sex: they thought that large, ridged skulls belonged to females as well as males, and that small, smooth skulls with short canines belonged to males as well as females. After returning to Sarawak in December, he presented his skins and skeletons to Brooke, who changed his mind after hearing Wallace’s argument and studying the facial anatomy. (Today taxonomists agree with Wallace, recognizing only one species—reclassified as P. pygmaeus—along with two subspecies: P. pygmaeus abelii of Sumatra and P. pygmaeus pygmaeus of Borneo.)

The articles that Wallace composed for the Annals are progressively daring. Emboldened by his subversion of previous authoritative accounts and with growing confidence in the validity of evolution, he was audacious. The springboard for his most radical speculation was, of all things, orangutan dentition. The purpose of the orangutan’s huge canine teeth, Wallace pointed out, was usually ascribed to defense against larger carnivorous animals, whereas he had observed that the orangutan never used its teeth in defending itself but instead relied on the brute strength of its arms. Nor were the canines necessary for acquiring or tearing food, since the orangutan’s diet consisted of fruits and soft vegetable matter: “Do you mean to assert, then, some of my readers will indignantly ask, that this animal, or any animal, is provided with organs and appendages which serve no material or physical purpose?” Without offering any further explanation, he added, echoing Sir Charles Lyell, “Naturalists are too apt to imagine, when they cannot discover, a use for everything in nature.” But he saved his most provocative comment for the end of the article. Why, he asked, would an animal of such a “high type”—one that so closely approximated a human being in physical structure, though with marked external differences—be confined to so limited a district in the world? If almost all other animals had been represented in previous ages by “allied yet distinct” forms, so must the orangutan, perhaps an indication of the former existence of allied species even more gigantic and more or less human in form: “Every class and every order has furnished some examples, from which we may conclude, that all isolations in nature are apparent only, and that whether we discover their remains or no, every animal now existing has had its representatives in past geological epochs.”¹¹

The immense variability within the same species, the remarkable similarity in structure and behavior to humans, and the presence of apparently useless characteristics were all due to some other law not yet discovered by the community of scientists. Even humankind, he implied, was represented by allied forms in the past. Evolution—or transmutation—was stamped all over his article. This allusion to ideas set forth in Robert Chambers’s Vestiges, with its revolutionary implications, and the jab at his fellow naturalists were both arrogant and heretical. Yet no naturalist who had ever contemplated such phenomena could deny that Wallace was raising necessary questions.

The Zoologist published parts of these three articles, omitting the offensive theoretical sections and preserving the more innocuous commentary.¹² Wallace also contributed anonymously an article entitled “A New Kind of Baby” to the November 22, 1856, issue of Chambers’s Journal. For three months, he had raised an infant orangutan that he had rescued from a swamp. Its uncanny resemblance to a human infant was a source of both amusement and serious reflection. The baby “must be a descendant of some very primitive people,” he boldly stated, suggesting to his audience that orangutans and human beings were derived from the same ancestral stock.

Wallace was in a mischievous mood. Some months before writing these four extraordinary articles, he had composed the even more extraordinary essay “On the Law Which Has Regulated the Introduction of New Species,” which was published in the September 1855 issue of the Annals and Magazine of Natural History. It was written at the end of the wet season in February 1855, when he was staying in a little house on the mouth of the Sarawak River at the foot of a mountain. The incessant rains had kept him indoors much of the time, and he had little else to do but “ponder over the problem which was rarely absent from my thoughts.”¹³ His head was filled with a vast amount of information, culled from his reading of William Swainson, Humboldt, Darwin, and the British Museum catalogues of insects and reptiles, which he knew by heart. At his side were Charles-Lucien Bonaparte’s annotated Conspectus Generum Avium and Lyell’s Principles of Geology. The nine months he had spent in the eastern tropics, the four years in the Amazon, and his readings, conversations, and attendance at scientific meetings had all provided him with a vivid impression of the diversity of life on the planet. He was unsatisfied with the manner in which naturalists had utilized these facts. Wallace’s essential premise—his Sarawak Law—was that “every species has come into existence coincident both in space and time with a preexisting closely-allied species.” As he explained it fifty years later in his autobiography, “[This] clearly pointed to some kind of evolution. It suggested the when and where of its occurrence, and that it could only be through natural generation, as was also suggested in the Vestiges; but the how was still a secret.”¹⁴

The immediate stimulus for writing “On the Law Which Has Regulated the Introduction of New Species” was an article by Edward Forbes, a noted biogeographer, marine biologist, and professor of botany at King’s College in London, published in the Proceedings of the Royal Institution of London in October 1854. Wallace may have seen this article in Brooke’s library, or he may have received a copy from Stevens in January or February. The article, “On the Manifestation of Polarity in the Distribution of Organized Beings in Time,” struck him as ludicrous. “I was annoyed to see such an ideal absurdity put forth when such a simple hypothesis will explain all the facts,” he later observed to Bates.¹⁵ Forbes was a disciple of William Sharp Macleay and his quinarian theory. His abstruse concept of “polarity” was a law or an attribute “of the divinely originating scheme of creation.”¹⁶ He attributed the radical differences between the fauna of the distant past and the fauna of recent times—with scanty numbers of species in the intermediate epochs—to two separate creations, and he saw a balance, a divine harmony, in the fossil record, which in his diagram resembled a dumbbell. With considerably less passion than Forbes’s article evoked, Wallace wrote, “It is only in consequence of some views having been lately promulgated, in a wrong direction, that [I] now venture to present [my] ideas to the public, with only such obvious illustrations of the arguments and results as occur to [me] in a place far removed from all means of reference and exact information.”¹⁷

He opened his article by advocating Lyell’s uniformitarian premise that changes to the earth’s surface had occurred over an immense but unknown period of time and operated continuously. As the earth’s topography slowly changed, so had the “whole series” of organic life. “[The] present condition of the organic world,” he wrote, “is clearly derived by a natural process of gradual extinction and creation of species from that of the latest geological periods. We may therefore safely infer a like gradation and natural sequence from one geological epoch to another.” Wallace’s introduction concluded with an allusion to the influence of the Vestiges on his thinking. He felt that he had gathered enough facts over a decade to provide structural support for an otherwise “wildly” untenable hypothesis: that some form of evolution (a word he did not use in his essay) was responsible for the past and present distribution of plants and animals. His reasoning was simple and elegant. Organizing his observations into several propositions that any naturalist would have to admit were true since they were based on known phenomena, he led his readers by inductive reasoning to his inevitable law.

The broadest categories of organisms (classes and orders), Wallace said, were spread over the entire earth, while families and genera were more limited in range. Similarly, genera of widely disseminated families and species of widely disseminated genera were also more limited. In regions rich in species, the most closely allied species either shared habitats or occupied adjoining habitats. (For example, birds as a class exist on every continent, while the Trochlidae, the hummingbird family, inhabit only the Americas. Throughout the Americas, the various genera and species of Trochlidae occupy overlapping or contiguous territories.)

Wallace also noted that in geologic formations could be found evidence of extinct species related to extant ones. Whether in geologic time or geographic space, a continuity of organisms suggested modifications of some unidentified ancestral forms, with gradual radiation of the new forms from their origins into different and distant zoological regions. Furthermore, no species had ever come into existence twice, a fact consistent with some theory other than the reigning dogma. If each species had been specially created, he concluded, no logical reason should prevent its repeat appearances over the course of the earth’s history.

Wallace believed that his law explained four phenomena: the relationships of families, genera, and species to one another; the geographic distribution of plants and animals; the temporal distribution of plants and animals (that is, the present and past “arrangements” of life on earth); and the existence of rudimentary organs. Wallace borrowed from Vestiges and transformed into a brilliant metaphor the crude diagram of a vertical line with its diagonal branches demonstrating the manner in which orders, families, genera, and species had arisen, as implied by embryologic development. He suggested that two or three distinct species may have been derived from a common “antitype [sic],” or ancestral form, and each of them may have served as an “antitype” for other closely allied species: “If we consider that we have only fragments of this vast system, the stem and main branches being represented by extinct species of which we have no knowledge, while a vast mass of limbs and boughs and minute twigs and scattered leaves is what we have to place in order, and determine the true position originally occupied with regard to the others, the whole difficulty of the true Natural System of classification becomes apparent to us.”

With this metaphor, Wallace cast aside more than two thousand years of thinking. He had advanced beyond the author of Vestiges by rejecting the concept of a great chain of being. Theories like Macleay’s and Forbes’s, which arranged species or groups in circles, not only were illogical but were not confirmed by the actual relationships of organic beings in nature. His arboreal metaphor illustrated two principles of nature: organisms were related by common descent, and they became modified and diverged into separate species.

In light of his theory, Wallace introduced the subject of the geographic distribution of organisms, citing Darwin’s investigations in the Galápagos Islands. To the best of his knowledge, no one had yet explained the phenomenon of the Galápagos, which contained “little groups of plants and animals peculiar to themselves, but most nearly allied to those of South America.” These ancient islands, he said, originally had been colonized by castaways from the nearby mainland, carried to the islands by the action of winds and currents. Over an unknown period of time, the original inhabitants became extinct and were replaced by closely allied or modified “prototypes.” But the Galápagos were only the most famous illustration of a more widespread biological phenomenon. By examining specimens from every region of the earth and fossils that had been recovered from geologic formations, one could demonstrate the temporal and spatial relationships of present-day animal and plant species to closely allied extant or extinct species. Intermittent geologic changes must have modified environmental conditions, he reasoned, leading to the extinction of some species and the survival and success of others. Arguing against catastrophic events on a global scale, he suggested that such extinctions were gradual events, played out over long periods of time. “To discover how the extinct species have from time to time been replaced by new ones down to the very latest geological period,” Wallace wrote, “is the most difficult, and at the same time the most interesting problem in the natural history of the earth.”

Although his theory appeared to support the notion of a progressive development from lower to higher forms of life, retrogression, Wallace said, was not inconsistent with this theory. According to his metaphor, the outermost twigs of a branch might be lost, while others, closer to the trunk and therefore less complex, might develop into different species. Hence it was possible for an existing species to be more “primitive” than its predecessors. Forbes’s paucity of species in the intermediate epochs was an illusion, he argued, caused by the imperfect fossil record. During periods of “geological repose,” species proliferated; during periods of geologic activity, extinctions occurred. Extinctions sometimes exceeded creations, and vice versa, but there was continuity throughout the biological record. His theory did not depend on the completeness of the fossil record, but was “founded upon isolated groups of facts, recogniz[ed] their isolation, and endeavour[ed] to deduce from them the intervening portions.”

In the final section of his article, Wallace stated that his theory offered an explanation for rudimentary organs, anomalies that baffled naturalists. The striking similarity between, for example, the jointed finger bones of the paddle of the manatee and the more developed hands and feet of other mammals raised an important question. “If each species has been created independently, and without any necessary relations with preexisting species,” Wallace asked, “what do these rudiments, these apparent imperfections mean?”

Wallace sent “On the Law Which Has Regulated the Introduction of New Species” to Stevens, who presented it to the editors of the Annals. In the September 1855 issue, they placed it in an unassuming position between “On the Genus Assimia” by John Edward Gray, director of the zoological section of the British Museum, and “On Some New Species of Hemipedina from the Oolites” by a naturalist named Thomas Wright. Nothing happened. Edward Forbes, one person who might have responded, had died unexpectedly on November 18, 1854, one month after the publication of his article, which Wallace would not have known when he wrote his essay. The apparent lack of response doubtless precipitated Wallace’s provocative commentary in the orangutan articles. Hoping to generate a scientific dialogue, he was becoming increasingly aggressive.

But Wallace was partly to blame for his colleagues’ silence. By omitting the word “transmutation” from his essay, a word that made the hair stand up on the back of the necks of most English naturalists, he failed to pull in his readers, or at least those who did not grasp the paper’s implications at first glance. His omission introduced an unintentional ambiguity in an otherwise clear exposition. It may have cost him greater recognition.

Wallace wrote to Brooke from the field to express his disappointment and enclosed a copy of the article with his letter. Brooke remained unconverted to Wallace’s ideas, but he was indignant about the state of English science. “My great surprise is … at the bigotry and intolerance with which views or facts apparently adverse to received systems and doctrines are received,” he wrote. “You say your little pamphlet is to feel the pulse of scientific men in regard to this hypothesis! What a reign of intolerance to need such caution! It is this which makes me despair of advance. What harm can [it] do us? What good can it not do us? And yet the inquiry is as beset with bristles as a porcupine’s back.”¹⁸

Eventually Stevens sent word of the effects of his article. What naturalists wanted him to do, Stevens relayed, was to “collect more facts,” not theorize.¹⁹ But Wallace’s Sarawak paper was not ignored by everyone. Lyell had read it, and he was struck to such a degree that he felt compelled to begin his own species notebook.

Since its publication beginning in 1830, Lyell had been making additions and corrections to his Principles of Geology to keep pace with the paleontological record, which was expanding at an unprecedented rate. The fourth edition, which Wallace owned, would soon be out of date, and Lyell struggled to maintain his primacy in a field that all acknowledged he had almost single-handedly elevated to a true science.²⁰ The new fossil discoveries seemed to support the doctrine of progressive development, and, in the view of some geologists and naturalists. this progressive development pointed to a divinely inspired plan, with humanity as the capstone of creation. But Lyell felt that the evidence also could be used to support Jean Baptiste Lamarck’s heinous idea about “transmutation,” or common descent, and the appalling conclusion that human beings and orangutans were related.²¹ Lyell remained adamantly opposed to Lamarck. Species were stable entities, he insisted, not “plastic,” and somehow appeared steadily throughout the course of geologic history. After their creation by an invisible guiding force, they lived out their natural species life history, became extinct, and were replaced by others newly created. On November 26, 1855, shortly after having read Wallace’s article in the Annals, Lyell began a journal to index books and articles on the species question. Wallace’s use of the uniformitarian principle to argue persuasively against Lyell’s firmly held beliefs was unsettling, and Lyell’s first entry included extracts and notes from Wallace’s paper. Two days later, he also recorded his private thoughts about Wallace’s theory in a second journal. Cracks were forming in the edifice of his grand scheme about the history of the earth.²²

Another individual who read “On the Law Which Has Regulated the Introduction of New Species” was Charles Darwin. “Nothing very new,” he wrote in the margins. “Uses my simile of tree. It seems all creation with him. … It is all creation, but why does … his law hold good; he puts the facts in striking point of view. Argues against our supposed geological perfect knowledge. Explains Rudimentary organs on same idea (I sh[oul]d state that put generation for creation and I quite agree).”²³ Around this time, in December 1855, Darwin was in the midst of an intensive and exhaustive study of variation in domesticated species and had drawn up a memorandum, addressed to a score of naturalists around the world, requesting specimens of any domestic breed of poultry, pigeons, rabbits, cats, and dogs bred for many generations in remote parts of the globe. One of the men he contacted was “R Wallace,” and he read Wallace’s paper shortly before or shortly afterward.²⁴ Darwin would have known something about Wallace’s explorations and discoveries from commentaries in the Zoologist and other journals or through the grapevine in the scientific community—one of the men he corresponded with was Brooke—but whether Darwin knew anything at the time about Wallace’s work in South America is unclear.

The request from Darwin flattered the younger naturalist, and Wallace was eager to comply. He obliged with specimens of not only the domesticated duck—a peculiar breed with a long, flat body and erect, penguinlike gait—but also the jungle cock, which had been domesticated on the island of Lombok, where Wallace would go that spring; it probably was one of the original species, he explained, from which the domestic breeds of poultry were derived.²⁵ Darwin was delighted, for he was amassing enough material to test his great theory; his only complaint was that the acquisition of all these specimens from naturalists around the world was costing him a small fortune.²⁶

In mid-April 1856, Lyell traveled to Darwin’s house to discuss Lamarck’s theory of “transmutation.” After three days of study, relaxation, and conversation, Darwin explained to Lyell for the first time his theory of natural selection as the evolutionary mechanism. With Wallace’s article still fresh in his memory, Lyell unexpectedly urged Darwin to publish at once, sensing that Wallace and Darwin were on the same trail. Claiming that he had not yet gathered enough facts, Darwin told Lyell that he was not ready.

“I wish you would publish some small fragment of your data, pigeons if you please & so out with the theory & let it take date & be cited & understood,” Lyell wrote a few weeks after his visit, reiterating his concern about Wallace.²⁷ Darwin thanked him for his sympathy but remained opposed to publishing simply for the sake of priority. “To give a fair sketch would be absolutely impossible, for every proposition requires such an array of facts,” he replied with some distress. “I do not know what to think. … I certainly should be vexed if any one were to publish my doctrines before me.”²⁸

A few days after Lyell’s return to London, Darwin met with Joseph Hooker, Thomas Huxley, and another naturalist to discuss different aspects of the species question. Darwin was sending out a trial balloon, as Wallace had done with the publication of his paper. Apparently, the trio was not prepared to embrace the whole “Lamarckian” doctrine. But Lyell’s advice disturbed Darwin. He wrote to Hooker to ask his opinion on the matter, stating that he feared abuse from the journal editor or scientific council members for a mere sketch of his views. He did not wish to suffer the fate of the author of Vestiges. “It [would be] dreadfully unphilosophical to give a résumé, without exact references, of an unpublished work,” Darwin wrote.²⁹ Hooker agreed with Darwin that his ideas were too preliminary to publish, but Darwin could not shake off Lyell’s letter. Rejecting the idea of a short, unannotated sketch or outline, he decided to write a more extensive work, which would organize eighteen years of data into a compelling argument to support the theory of evolution. Another five months passed before he wrote the first chapter of his proposed book, which he entitled “Natural Selection.”

Few men reacted appropriately to Wallace’s Annals paper, which required too radical a break with traditional thinking. Even Darwin did not fully appreciate its originality, and he was slow to grasp that Wallace was the serious threat Lyell believed him to be. Many years later, Huxley reflected on Wallace’s essay:

In the meantime, Wallace had spent a week in early December 1855 at Brooke’s private mountain retreat, twenty miles upriver from Kuching and perched on a summit that was reached by clambering over a rocky slope and up a rudimentary staircase made of notched tree trunks. Brooke’s redoubt was surrounded by a tangled mass of luxuriant vegetation. In the cool, fresh air hung the stench of durians, a fruit that was ambrosia to the Malay palate but repugnant to the uninitiated Westerner.³¹ Here the two men relaxed, bathing in a nearby spring under an overhanging rock and enjoying the mangosteens and lansats—“two of the most delicious of the subacid tropical fruits,” in Wallace’s opinion—brought to them in heaping basketfuls by the local Dyaks, who worshiped Brooke as some sort of deity. Brooke gave Wallace permission to use this cottage for a few weeks after Christmas, but not before Wallace returned with him to celebrate the holidays at his palace in Kuching. Every Christmas, all the Europeans in Sarawak were invited to enjoy the hospitality of the rajah, who, as St. John noted, “possessed in a pre-eminent degree the art of making every one around him comfortable and happy.” When Wallace returned to the mountain cottage after Christmas, he took with him Charles and a Malay boy named Ali, intended as Charles’s replacement. Only fourteen years old, Ali surpassed Charles in every way, and for the next seven years he would be Wallace’s trusted companion, servant, and assistant.

Brooke’s refuge was ideal for collecting moths. In his eight years of travel in the Far East, Wallace would never find a spot as entomologically productive. At night he sat out on the veranda, reading beside a lamp placed on a table—his pins, forceps, net, and collecting boxes at hand—and waited to see how many moths were drawn to the solitary light. The best times, he discovered, were the rainiest, but only when the moon was completely shrouded by clouds. On four occasions, he captured more than 100 moths, most of them separate species. Some settled on the wall or the table; others flew up to the rafters as he chased them all over the veranda. In the next four weeks, he collected 1,386 specimens. He owed his success to the house itself, with its low, sloping roof and white walls, which both attracted moths and prevented their easy escape, prompting him to recommend—not entirely in jest—that entomologists traveling in the Malay Archipelago take along a white canvas veranda-shaped tent.³²

Leaving Sarawak at the end of January or early February 1856, Wallace was determined to investigate the lesser-known islands of the eastern archipelago: Celebes, the Moluccas, Timor, and New Guinea. His two years in Singapore and Sarawak had been a necessary training ground for excursions farther afield. Having obtained a good sense of the flora, fauna, and geography of Borneo and the Malay Peninsula, he was prepared to fulfill his true mission. Wallace wrote to his London friends:

The port of entry to this region was Macassar, the modern city of Ujung Pandang, on the southern tip of Celebes. His boat from Kuching, however, arrived in Singapore on the very day that a vessel was leaving for Macassar, and he was now stranded for months in Singapore. For the next few weeks, he arranged his specimens for shipment back to England; they included two casks with five orangutan hides in spirits, a box containing sixteen orangutan skulls and two skeletons, six boxes holding fifteen hundred moths and five thousand other insects, a box of dried ferns, and a large case of bird and mammal skins, shells, and reptiles. For the orangutan hides alone, he expected to earn at least £250, and Stevens had found an enthusiastic insect collector, William Wilson Saunders, who became his entomological patron and ensured him a steady source of income.

Wallace summed up his collecting experiences in Borneo in an article for the Zoologist. He had acquired few novel birds and mammals except for the orangutans, but he had gathered enough “presumptive evidence” to hypothesize that there had been a land connection linking Sumatra, Borneo, and the Malay Peninsula in the not too distant geologic past. For an ornithologist seeking new species, Borneo thus was not the best collecting ground. He also addressed the complaints of some of his armchair naturalist colleagues, who were disappointed with his insect collections, “almost as if I made as well as collected them.” Where were all the big beautiful insects they were accustomed to seeing from the tropics? Why was he wasting their time with small, dull specimens? He reminded his readers of the true rewards of the dedicated naturalist. Despite illness and privation, despite the craving for intellectual and “congenial” society, he was more than compensated by the pleasures of looking forward to a time when the specimens he had amassed would furnish him with the “inexhaustible food for study and reflection” and remind him of the strange and beautiful scenes in which they were obtained.³⁴ To Stevens, Wallace privately berated one of his critics; “[His] remarks are very amusing, but he is no entomologist to despise small insects. He errs as most people do in believing that the tropical insects are generally large and beautiful. … Before I left London the constant cry was ‘Do not neglect the small things.’ ‘The small things are what we want because they have never been collected in the tropics.’”³⁵

The complaints from home exacerbated his frustration at being trapped in Singapore. But he was not too bored or frustrated to compose another essay, “Attempts at a Natural Arrangement of Birds,” in which he applied the principle of common descent, or his Sarawak Law, to bird classification.³⁶ Although he had not yet discovered the mechanism driving evolution, he already viewed the world through Darwinian eyes two years before Darwin announced an identical theory and long before other naturalists had abandoned creationism. Some of the branches on the metaphorical tree had been lost or had not yet been recovered, but absence of proof was not proof of absence. Where other authorities saw unbridgeable gaps between species, Wallace saw potential connections.

Wallace set sail from Singapore in late May 1856 on a vessel bound for Bali and Lombok, islands off Java that he would not have visited had he found a more direct passage to Macassar. From his perspective as an exploring naturalist, Bali and Lombok were inconvenient detours from his primary destination. Java itself had been thoroughly worked over by the English naturalist Thomas Horsfield, as well as by the Dutch earlier in the century; like other naturalists, Wallace regarded Bali and Lombok as zoological extensions of their larger neighbor. But his accidental voyage was to lead to one of the most important discoveries of his scientific career.

Before his departure, he wrote to Bates, summarizing two years of observations. Between Santarém and Pará and Santarém and Barra, he said, there were more differences in the species of all classes than among Malacca, Java, Sumatra, and Borneo combined. In comparison with the Amazon, the Malay Archipelago suffered from an “excessive poverty” of diurnal lepidoptera. Only in species of the genus Papilio were the two countries approximately equal. But in other orders, like the coleoptera, he believed that the archipelago surpassed what Bates had collected around Ega on the Amazon. His own collecting had suffered from six months of voyages and illness and six months of excessive rain; otherwise, he might have been more productive. He then listed for Bates what he had obtained thus far. In the space of two years, he had amassed approximately thirty thousand specimens, of which some six thousand were distinct species. The birds of the islands he had so far explored were well known and not worth collecting, but he had settled the question of the number of orangutan species. He liked the people and customs of the Malay Archipelago less than those of Brazil. Provisions and labor were expensive, traveling was tedious and expensive, and the high wages of servants prevented him from living in the “free-and-easy-style” of Amazonia.³⁷

In mid-June, Wallace arrived on the lush island of Bali, which astonished and delighted him. Never had he seen so beautiful and well cultivated a region outside Europe. As he rode on horseback into the interior, he marveled at the terraced rice paddies and the complex but efficient system of irrigation, which ensured a perpetual harvest of rice and other staples. Much to his regret, he had budgeted too little time to add anything significant to his collections, but he was pleased to have caught a glimpse of the only existing remnant of the great Hindu civilization in the Far East. On June 16, he crossed the fifteen-mile strait to the island of Lombok, a two-day cruise with spectacular views of the mist-enshrouded volcanoes of both islands. After anchoring a quarter of a mile offshore, he boarded a small boat to the black volcanic sand beach. For the next several days, he wandered around Ampanam, Lombok’s main town, shooting birds. Among his first specimens was a bird related to an Australian species. Although this was a novel and surprising acquisition, the scarcity of birds disappointed him, so he arranged to visit another district where they were said to be more plentiful. With a small quantity of luggage, he was rowed to his destination, a one-day journey from Ampanam.

There the surrounding landscape pleased Wallace: volcanic cinder cones, which had eroded into smooth hills over the long period of geologic time that Lyell had posited; enclosed valleys; and open plains. The slopes were covered with dense, scrubby bamboos, prickly trees, and shrubs; in the intervening basins were groves of majestic palm trees teeming with birds, the most conspicuous of which were flocks of screaming white cockatoos. On his treks through the region, he came across enormous mounds that no one could explain, but he soon discovered that they had been constructed by the orange-footed scrubfowl (Megapodius reinwardt), a bird the size of a hen, with large feet and long, curved claws that it employed to rake together all kinds of rubbish—dead leaves, sticks, stones, rotten wood—and heap it into mounds six feet high and twelve feet wide, in the middle of which its brick-red eggs were buried. Wallace told the local people that birds made the mounds, but they refused to believe him. More difficult to explain to himself was the discovery of this Megapodius, an “Australian” genus, on an island so close to Java, which ought to be a zoological extension of Asia.³⁸

The most beautiful bird he encountered was a species of Pitta, or ground thrush. It was elusive, hiding in dense thickets and requiring great patience for capture. Wallace’s practice was to walk cautiously along the narrow pathways near its habitat. When he detected a ground thrush, he stood motionless, imitating the bird’s whistle and waiting for a half hour or more until it came within shooting range. In addition to the ground thrush, there were green doves, little crimson and black flower-peckers, large black cuckoos, metallic king crows, golden orioles, and fine jungle cocks. The last he obtained for “Mr Darwin.”³⁹

But he paid a price for this diversion. He missed his connection to Celebes; he would have to wait for two and a half months for the next boat. The delay, though aggravating and a blow to his finances, gave him time to reflect on a remarkable and unexpected discovery. Lombok was inhabited by species allied to the fauna of Australia, while Bali contained species allied to the fauna of Asia. The short, deep strait between these two islands was a faunal divide, partitioning Asia from Australia. He had stumbled on what appeared to be the exact division between two distinct zoogeographic regions. “The islands of Baly and Lombock,” he observed in a letter to Stevens, “though of nearly the same size, of the same soil aspect, elevation and climate and within sight of each other, yet differ considerably in their productions, and in fact belong to two quite distinct Zoological provinces, of which they form the extreme limits.”⁴⁰

Wallace was impressed not only by the absence on Lombok of the most common birds found in the great “Indian” islands of Borneo, Java, and Bali but also by the absence of important groups of mammals, such as monkeys, large cats, and rodents. He was also impressed by the presence there of cockatoos and birds of the family Megapodiidae, which did not exist on Bali. “South America and Africa, separated by the Atlantic, do not differ as widely as Asia and Australia,” he would write in a paper two years later. “[In] a few hours we may experience an amount of zoological difference which only weeks or even months of travel will give us in any other part of the world!”⁴¹ Wallace’s discovery contradicted everything he had ever read about the kinds of fauna that should occupy neighboring islands that otherwise appeared nearly identical. That a mere fifteen-mile gap could be a chasm between two fundamentally different faunal groups was astonishing, and it bolstered his conviction that a mechanism other than a divine plan explained the phenomenon of animal distribution.

At the end of August, he boarded a little schooner and finally left for Macassar, which proved a disappointment. After four months there, he had little to show for his efforts. By December, when dark clouds appeared on the horizon portending the onset of the rainy season, he longed for better hunting grounds. He therefore jumped at the chance to go to the Aru Islands, an opportunity that had turned up unexpectedly.

Macassar was the only Dutch port that traded regularly with Aru. A thousand miles to the east, near the coast of New Guinea, the Aru Islands were one of the great objects of Wallace’s journey to the Malay Archipelago. Because of the monsoons, native vessels made the voyage only once a year, leaving Macassar in December or January and returning in July or August. He would travel by native prau, owned and commanded by a Eurasian captain, half Dutch and half Malay, who offered to take him there and bring him back six months later. The captain assured him that two types of bird of paradise were abundant in the Aru Islands—the large yellow great bird of paradise (Paradisea apoda) and the smaller red king bird of paradise (P. regia)—both of which he thought could easily be shot or bought from the natives. Thus encouraged, Wallace agreed to the passage, whose cost the captain left up to him. He dashed off a letter to Stevens: “What I shall get there it is impossible to say. Being a group of small islands, the immense diversity and richness of the productions of New Guinea will of course be wanting; yet I think I may expect some approach to the strange and beautiful natural productions of that unexplored country. Very few naturalists have visited Arru [sic]. … I suppose not twenty specimens of its birds and insects are positively known.”⁴² But it was birds of paradise that Wallace coveted most. No European naturalist had ever seen a specimen in its native habitat. Ornamental feathers from these magnificent birds were the rage in Europe, adorning women’s hats and adding a dash of exoticism to their wardrobe, and the native New Guineans were glad to oblige them. Trade in the feathers escalated during the nineteenth century, and the supply seemed endless until the threat of extinction brought people to their senses—but that was no one’s concern in 1856. The first skins of one species had begun to arrive in Europe from New Guinea (Papua) in the eighteenth century. Native birdcatchers, interested more in spectacular ornamental feathers than in scientific accuracy, amputated the feet and sometimes the wings for convenience before trading with merchants. Paradisea apoda, as Linnaeus christened the bird, thus gave rise to the myth of a footless bird, perpetually on the wing. Papuan ornithology remained a mystery until the 1770s, when a French traveler named Pierre Sonnerat returned home from the Moluccas and the Philippines with several unusual specimens. Others followed Sonnerat, most significantly René-Primevère Lesson, a resident naturalist aboard the vessel Coquille, which set sail from France in 1822 on a voyage of scientific exploration and discovery. Lesson brought back to Paris skins from more than a dozen species of bird of paradise, all obtained from the natives and therefore not accurately localized. Today the family Paradisaeidae is known to contain twenty genera, subdivided further into forty distinct species, and geographically limited to New Guinea, the Moluccas, and northern Australia. They are among the most beautiful and bizarre birds on earth, the orchids of the world’s avifauna.

The trip to Aru was Wallace’s riskiest journey to date. In all his travels, he never had ventured beyond the confines of European power. He felt as he had when, after leaving school at the age of thirteen, he was packed off to “that scene of all that is strange and new and wonderful to young imaginations—London!” Aru, separated into three distinct parts by narrow channels and surrounded by numerous islets—on a map greater Aru resembles a cracked egg—was inhabited by “lawless traders and ferocious savages.” He did not share this observation with his mother and sister, who were beseeching him to return home in every letter they posted to him. On December 10, he wrote euphemistically that he was “going out of reach of letters for six months.” He was well and in good spirits, dining in luxury on rich cow’s milk, good bread, and magnificent mangoes. The mangoes were his reason for leaving, he added lightly, as he feared he would overindulge.⁴³

After a smooth and enjoyable voyage, he arrived at Aru in early January 1857. On March 10, he sent a letter to the Entomological Society summing up his six weeks on the islet of Wamma in the town of Dobbo, a village jerry-built on a spit of land wide enough for three rows of houses. He shared with his colleagues an interesting observation that he had made about the zoogeography of the region: no two islands were exactly alike despite their proximity and similarity of habitat. For example, the Ke Islands (another island cluster, which he had passed before reaching Aru) and Wamma, only sixty miles apart, differed markedly in insect species.⁴⁴ Wallace did not elaborate on the implications of that difference in this letter, but in his species notebook he had noted the resemblance of the Malay Archipelago to the Galápagos Islands. “Here we must suppose special creations in each island of peculiar species,” he observed, “though the islands are all exactly similar in structure, soil and climate and some of them within sight of each other. It may be said it is a mystery which we cannot explain, but do we not thus make unnecessary mysteries and difficulties by supposing special creations contrary to the present course of nature?”⁴⁵ Those of his entomological friends who might have been made uncomfortable by his theorizing were doubtless pleased with the news that nine-tenths of his specimens were new to English collections.

Shortly after his arrival in Dobbo, Wallace inquired about birds of paradise. To find them, he would have to travel deeper into the interior of Aru, reachable only by boat; but he was delayed for weeks because of pirates, who had just attacked a prau and stripped its men of everything on board, including their clothes. The pirates had escaped into the labyrinth of Aru’s channels and islands, where they could continue to harass the local population without fear of capture. Not a soul would take him anywhere for any price, but in mid-March, when the danger of piracy abated, he finally secured a boat and a willing crew. Setting sail early one morning, he and his crew skirted the western coast of Wokan, the largest and northernmost of the three main Aru Islands, and entered the mouth of a small river. They made their way through a mangrove swamp until late afternoon, when they disembarked at a small village. Here, for the price of a chopping knife, he rented a five-foot sliver of space in a shed “of the most miserable description” that was already occupied by a dozen people. He ordered his crew to sleep in the prau to guard his provisions and gear. On the day of his arrival, he found some men who assured him that they could obtain specimens of birds of paradise, but after they set off into the humid forest he never heard from them again. On the second day, however, Ali unexpectedly returned to the hut with a perfect king bird of paradise. As Wallace examined the exquisite creature, which was not much larger than a thrush, admiring its gorgeous colors and extraordinary tail ornamented with two wirelike feathers hanging downward and spiraling into two glittering buttons, he could barely contain himself. “Thus one of the great objects of my coming so far was accomplished!” he later wrote. “My admiration and delight over this exquisite winged form quite amused my Aru hosts, who saw nothing more … than we do in the robin or chaffinch.”⁴⁶ What excited Wallace more was the knowledge that he was sending back a specimen that far surpassed in quality anything ever seen before in Europe:

This early success was not quickly matched. It rained incessantly. Wallace felt the need to penetrate farther into the Aru jungles, but he could not persuade any of the locals to guide him, pirates being the usual excuse. Eventually, he cajoled one native to captain his prau, and he and his crew set off at the end of March, sailing upriver until they reached Wanumbai, a village consisting of two houses, one of which he occupied after hard bargaining, the landlord yielding for the price of ten yards of cotton cloth. As in the Amazon, Wallace was the object of great curiosity. During his stay, there was an endless parade of onlookers. “I found the tables turned upon me,” he noted with amusement, “& I was become even as the Zulus or Aztecs which I had been one of the gazers at in London. I was to the Arru [sic] Islanders a new & strange variety of man, & had the pleasure of affording them in my own person an instructive lesson in comparative Ethnology.”⁴⁸

From his base in Wanumbai, he trekked into the jungle along paths of black mud that made his walks miserable. He was rewarded with a good collection of birds and beautiful butterflies. He obtained a specimen of the strange marsupial Cuscus maculatus, which had a woolly coat like a lamb’s, a long and powerful prehensile tail, and stumpy legs with long-clawed feet that resembled hands.

Wallace’s delight with the people and satisfaction with his collections were counterbalanced by various physical torments. Insect bites caused the most misery, and he jokingly wrote that insects were taking revenge for his persecution of them. Sand flies attacked him at night, and during his daily walks through banana plantations and black mud, mosquitoes assaulted his legs. In the moist tropical heat, these bites soon became ulcerated, which made walking impossible and confined him to his house for a week; there the incessant chatter of his hosts further tortured him. In the early-morning hours, just before sunrise, he lay pensively in bed, listening to the raucous calls of the birds of paradise as they searched for food; the cries resounded through the forest, changing direction rapidly and repeatedly. At the crack of dawn came the screeches of lories and parakeets and the screams of cockatoos. He was a pathetic sight, crawling down to the river to wash, his agony reaching its highest pitch as he helplessly watched a magnificent Papilio ulysses or another beautiful butterfly waft by. There was nothing to do but be patient and attend to one or another necessary task, like skinning or cleaning specimens. The bites, the stings, the pain, the constant irritation of insect pests of the tropics—all these he could bear without complaint. “But to be kept prisoner by them in such an unknown country as Arru [sic],” he lamented, “where rare and beautiful creatures are to found in every forest ramble, a country reached by such a long and tedious voyage and which may never be visited again, is a punishment too severe for a Naturalist to pass by in silence.”⁴⁹

Wallace was consoled by Ali’s enterprise. He brought him one bird of paradise after another, capturing excellent specimens of both the king and the great species and enabling Wallace to send a biblical note of triumph back home: “Rejoice with me, for I have found what I sought. … I have a few specimens absolutely perfect. … I believe I am the only Englishman who has ever shot and skinned (and ate) birds of Paradise, and the first European who has done so alive, and at his own risk and expense; and I deserve to reap the reward, if any reward is ever to be reaped by the exploring collector.”⁵⁰

Wallace’s ultimate goal was the vast and mysterious island of New Guinea, where he would seek the other thirteen or so known species of birds of paradise. New Guinea was one of the most dangerous places on earth for a white man; headhunters and cannibalistic tribes murdered anyone who trespassed on their territory. He had learned from his contacts in Dobbo which places were safe and which were not. Their accounts of the abundance of birds excited him so much that he could think of nothing else. His planned route would take him to the island of Ternate; from there, he could reach the westernmost arm of New Guinea, where a naturalist could work in relative safety, the inhabitants having been tamed by missionaries.

While recuperating from his skin infections in Wanumbai, Wallace wrote a treatise on the great bird of paradise for the Annals, intending to correct the many erroneous statements published by Lesson and other naturalists. He had discovered that its range was limited to one part of Aru and the southernmost peninsula of New Guinea, while an allied species inhabited the northern peninsula of New Guinea and one or two nearby islands. It was interesting, he said, that although the Ke Islands were closer to New Guinea than were the Aru Islands, no species of bird of paradise was found at Ke. He reemphasized the critical importance of pinning down as precisely as possible the range of a species, relying on one’s own observations or those that were verifiable. Lesson, the previous authority on the bird of paradise, was led to inaccuracies by failing to state where and how his specimens had been obtained. Knowing nothing about the birds’ habits, he was also unable to describe the most spectacular feature of their behavior: the courtship display of the males, during which vertical plumes behind the wings were spread in a magnificent fan as they performed a ritualized dance on the branches of trees.⁵¹

The bird of paradise was not the only avian family that stimulated Wallace to reflect on zoogeography. Once he had established himself in the central forests of Aru, new species “burst upon him,” forcefully revealing Aru’s intimate zoological connection with New Guinea. Although separated by at least 150 miles, Aru and New Guinea had many birds in common. The only other islands in the world known to possess species identical with those of the proximal mainland were Great Britain and Sicily. Ceylon and Tasmania had species—even genera—unique to them, though they were closer to India and Australia, respectively, than Aru was to New Guinea. From a zoological perspective, Aru seemed to be an outlying part of New Guinea, from which it had been separated during a recent geologic epoch. Wallace’s conclusion was further supported by the geologic evidence: soundings of the surrounding seas demonstrated the relative shallowness of the ocean bed between Aru and New Guinea, while the depth westward was “fathomless.” The most crucial evidence, however, was the presence of three broad channels traversing the three portions of greater Aru, which could be explained only if they had been true rivers with their source in the mountains of New Guinea and had been reduced to their present condition by the subsidence of the intervening land.⁵²

Wallace remained in Wanumbai for another six weeks. At night little marsupial rats ran about and nibbled at everything. Four or five types of ants attacked anything not isolated by water-filled moats, one variety even swimming across them. Huge spiders lurked in baskets and hid in the folds of his mosquito net. Centipedes and millipedes nestled under his pillow and ventured out to crawl on his head. Scorpions sought refuge under every board. “We need hardly to mention bugs and fleas & to tell the truth,” he confided to one of his journals, “I would not exchange all the others in my list for these last if as abundant as they often are at home. They are a constant & unceasing source of actual torment & disgust;—spiders centipedes & scorpions are large ugly and dangerous, but you may live among them a long time & get no hurt but fright.”⁵³

On May 6, with his bird box nearly overflowing and his legs still a mess, Wallace made the fifteen-hour trip back to Dobbo, arriving at dusk. He occupied the only place available, the courthouse of the Dutch commissioners, which was nothing more than a shed at the end of the village. Since his departure in March, traders had arrived in great numbers and more houses had been thrown up along the crowded little spit of land. Fleets of boats were lined up on shore to be repaired and repainted for the homeward voyage. An Australian menagerie picked through the refuse. Parrots, lories, and fruit doves cooed and chattered in cages hung from every doorway. An occasional small kangaroo wandered around the houses. During the day, there was at least one cockfight, with a circle of spectators cheering and betting as the birds tore each other to pieces. At night, there was singing and music. On Fridays, Dobbo’s Muslims prayed at the town’s mosque, the most distant from Mecca of any in the world.

By the end of June, threatening clouds had gathered on the horizon. The shops were hastily boarded up, and the traders prepared for departure; in a week, Dobbo would be a ghost town. The captain of Wallace’s prau arrived, as promised, and on July 2 they departed for Macassar along with fifteen other praus, forming a grand regatta. With fair weather and a strong, steady wind at their backs, they arrived nine days later. Awaiting him were seven months’ worth of letters, which he spent the night opening and reading. One was from Bates, congratulating him on the neglected article in the September 1855 Annals:

There was also a letter dated May 1, 1857, from Darwin on the subject of Wallace’s article; he was equally positive, though more reserved:

If Darwin’s revelation about the duration and magnitude of his work on the species problem was meant to intimidate Wallace, it did the opposite, acting like a spur.⁵⁷ Further emboldened, Wallace produced several original papers in a prolific outburst: “On the Natural History of the Aru Islands” for the Annals, “Note on the Theory of Permanent and Geographical Varieties” and “On the Entomology of the Aru Islands” for the Zoologist, and “On the Habits and Transformations of a Species of Ornithoptera, Allied to O. Priamus, Inhabiting the Aru Islands, near New Guinea,” for the Transactions of the Entomological Society. All were written in Macassar, when he had the leisure to examine and contemplate his specimens before shipping them off to England. For a month, he was occupied with analyzing, notating, and preparing a collection of nine thousand specimens comprising sixteen hundred species, more than three-quarters of them distinct species of insects. His labors exhausted him more than usual. In no other part of the tropics was so much care required to protect his collections. Ants posed a formidable threat to both his birds and his insects; two of these pestiferous species were minute and impossible to eradicate. Poor Ali received a severe scolding on two occasions for uncharacteristic carelessness in having allowed the edge of a palm mat and a slender bit of rattan to touch Wallace’s shelves, which were suspended from the ceiling. “One would think the ants must every night explore and wander everywhere,” Wallace complained, “for they never fail to discover even a hanging thread by which to ascend.” Ants established colonies in bird skins, devouring the eyelids and the bases of the beaks and thus ruining days of work and the efforts of weeks of exploration. Spiders, larvae, and mites were other pests that seemed immune to arsenic, camphor, and any other poison he could think of. Added to these were roaches and rats, which could get at anything not tightly sealed in a box.⁵⁸

But Wallace’s meticulousness paid off. The quality of his specimens impressed his colleagues, who pronounced his collections a very important addition to the knowledge of New Guinea fauna and the distribution of organisms in the Eastern Hemisphere. At the February 23, 1858, meeting of the Zoological Society, John Gould, England’s leading ornithologist, presented “a highly interesting series of birds collected by Mr. A. R. Wallace in the Aru Islands. Among them were two species of birds of paradise. … Hitherto these magnificent birds have only been sent to this country in mutilated condition, their skins having been prepared and dried by the Papuans, frequently without their wings, and almost always without their legs. Mr. Wallace’s skins, however, are perfect, and in the highest possible condition.” Wallace had also sent 121 species of birds, “showing great perseverance and energy on [his] part.”⁵⁹ One mammal, the ratlike marsupial—which was one of Wallace’s tormentors and subsequently was captured, skinned, and preserved—Gray of the British Museum honored with his name: Myoictis wallacii.⁶⁰ The Entomological Society was also pleased. At the March 1, 1858, meeting, Stevens exhibited

By now, Wallace was working hard on the species problem, trying to assemble the facts he had amassed into some greater schema. He was on the verge of a great discovery—of that he was convinced—a belief confirmed by the letters from Darwin and Bates. In his essay “On the Natural History of the Aru Islands,” published in the December 1857 supplement of the Annals, he trod on dangerous ground, targeting Lyell, whose version of the theory of special creation he picked apart. How, for example, could the geographic distribution of Vertebrata be accounted for? Why were the same species not found in the same climates all over the world? How did this theory explain the striking entomological, ornithological, and mammalian differences between New Guinea and Borneo, both virtually identical in climate and geography—differences not only at the species level but spanning the zoological spectrum of genera, families, and whole orders? Conversely, how could the remarkable zoological congruence between Australia and New Guinea—the former a desert, the latter a tropical rain forest—be explained? “[We] can hardly imagine that the great variety of monkeys, of squirrels, of Insectivora, and of Felidae, were created in Borneo because the country was adapted to them, and not one single species given to another country exactly similar, and at no great distance.” Wallace concluded that “some other law has regulated the distribution of existing species than the physical countries in which they are found, or we should not see countries the most opposite in character with similar productions, while others almost exactly alike as respects climate and general aspect, yet differ totally in their forms of organic life.”⁶² That law was his Sarawak Law, which he applied to the geographic distribution of species in the Malay Archipelago.

At one time, Wallace hypothesized, New Guinea and Australia were joined, and during this period the climate and physical features of each resembled those of the other. A separation occurred, leading to a change in climate and the extinction of certain groups of fauna. New species were then somehow “gradually introduced” into each, closely allied to the preexisting species, many of which were common to the two places. As time passed, these allied species became peculiar to their particular region, with few identical but many very similar, which explained the relative congruence between the fauna of Australia and that of New Guinea. The law of close affinity would not permit the appearance of groups not closely related to the original inhabitants. For example, a tiger would not suddenly materialize in New Guinea or a kangaroo in Borneo. At a later geologic period, the island complex of Aru separated from New Guinea. “Its separation must have occurred at a very recent period,” he concluded, “the number of species common to the two showing that scarcely any extinctions have since taken place, and probably as few introductions of new species.”

Wallace asked his readers to imagine the following scenario. Suppose that the Aru Islands were to remain undisturbed for a period “perhaps equal to about one division of the Tertiary epoch.” It is reasonable to believe that the change of vertebrate species over such a long time would be complete and that an entirely new “race” of vertebrates—all closely allied to those now existing—somehow would be introduced. Simultaneously, a new fauna gradually would have appeared in New Guinea. This future Aru and New Guinea would then resemble present-day New Guinea and Australia, with their faunal similarities and differences. Let the same uniformitarian process then continue for another geologic period. In one country, some species would have become extinct and not replaced with allied species, while in the other a series of modified but closely allied species somehow would have been introduced. Thus the faunas would come to differ not only at the species level but also at the genus level. If one imagined further geologic changes—say, the elevation of Aru into a mountainous country and its expansion by alluvial plains, and the flattening of New Guinea with a corresponding reduction of its surface area, leading to the extinction of many species—new species might then be more rapidly introduced into the modified and enlarged territory of Aru. Some genera and families that had gone extinct in New Guinea but still were present in Aru could proliferate there, echoing a phenomenon seen in Madagascar, where the families and some of the genera belonged to existing African groups, whereas others were peculiar at the species, genus, and even family level, though retaining a general resemblance to African forms. Wallace recorded in his species notebook: “It is quite unnecessary to suppose that new species have ever been created ‘perfectly dissimilar in forms, habits and organisation’ from those which have preceded them; neither do ‘centres of creation’ [here he quotes Lyell], which have been advocated by some, appear either necessary or accordant with facts, unless we suppose a ‘centre’ in every island and in every district which possesses a peculiar species.”⁶³

Wallace addressed one final question about the word “species” itself: What is the difference between a “species” and a “variety”? He presented the conundrum in his article “Note on the Theory of Permanent and Geographical Varieties”—it would be published in the Zoologist in January 1858—which sought to bring the evolutionists and creationists head to head. “As this subject is now attracting much attention among naturalists and particularly among entomologists,” Wallace wrote, almost certainly with Darwin in mind, “I venture to offer the following observations, which, without advocating either side of the question, are intended to point out a difficulty, or rather a dilemma, its advocates do not appear to have perceived.”

When did variation end and speciation begin, Wallace wondered. The generally adopted opinion was that species were independent creations that varied only within certain limits during their whole existence, while “permanent” varieties were not independent creations but produced by ordinary generation from species. The term “permanent variety” was an oxymoron: according to the old system of belief, boundaries were not supposed to be blurred. But in a state of nature, boundaries sometimes did blur. He admonished naturalists to stop straddling the fence: either reject special creation altogether and agree that species differed from varieties only by degree, as a result of common descent, or call any group with “permanent characters, however slight,” a species.⁶⁴

Shortly after completing “Note on the Theory of Permanent and Geographical Varieties,” Wallace sent a paper to the Entomological Society in order to inflame even further the controversy over the origin of species. In this paper, “On the Habits and Transformations of a Species of Ornithoptera,” he demonstrated that not only was it sometimes difficult to distinguish two species from each other but even genera might be difficult to differentiate. His specimen of a species of Ornithoptera was a case in point: the adult form so closely resembled an allied species that it might be considered a variety, yet its caterpillar almost exactly resembled that of a third species, from which it could be distinguished only by subtle changes in the color and size of certain appendages. Furthermore, the caterpillars and pupae of the genus Ornithoptera itself almost exactly resembled those of the genus Papilio!⁶⁵