He did extensive fieldwork, first in the Amazon River basin and then in the Malay Archipelago, where he identified the Wallace Line dividing the fauna of Australia from that of Asia. He is best known for independently proposing a theory of natural selection which prompted Charles Darwin to publish on his own theory. Wallace was also one of the leading evolutionary thinkers of the 19th century who made a number of other contributions to the development of evolutionary theory, including the concept of warning colouration in animals, and the Wallace effect, a hypothesis on how natural selection could contribute to speciation by encouraging the development of barriers against hybridization. He was also considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography".
Wallace was strongly attracted to unconventional ideas. His advocacy of Spiritualism and his belief in a non-material origin for the higher mental faculties of humans strained his relationship with the scientific establishment, especially with other early proponents of evolution. In addition to his scientific work he was a social activist who was critical of what he considered to be an unjust social and economic system in 19th-century Britain. His interest in biogeography resulted in his being one of the first prominent scientists to raise concerns over the environmental impact of human activity.
Wallace was born in the village of Llanbadoc, near Usk, Monmouthshire, Wales. He was the eighth of nine children of Thomas Vere Wallace and Mary Anne Greenell. His mother was from a respectable middle-class English family from Hertford. Thomas Wallace was of Scottish ancestry. His family, like many Scottish Wallaces, claimed a connection to William Wallace, the leader of a 13th-century rising against England. Thomas Wallace received a law degree, but never actually practiced law. He inherited some income-generating property, but bad investments and failed business ventures resulted in a steady deterioration of the family's financial position.
When Wallace was five years old, his family moved to Hertford, north of London. There he attended Hertford Grammar School until financial difficulties forced his family to withdraw him in 1836. Wallace then moved to London to live and work with his older brother John, a 19-year-old apprentice builder. (In 1979, a plaque was placed at 44 St. Peter's Road in Croydon commemorating the fact that he lived there at one point during this period.) This was a stopgap measure until William, his oldest brother, was ready to take him on as an apprentice surveyor. While there, he attended lectures and read books at the London Mechanics' Institute, where he was exposed to the radical political ideas of social reformers like Robert Owen and Thomas Paine. He left London in 1837 to live with William and work as his apprentice for six years. At the end of 1839, they moved to Kington near the Welsh border before eventually settling at Neath in Glamorgan. Between 1840 and 1843, Wallace did surveying work in the countryside of the west of England and Wales. By the end of 1843, William's business had declined due to difficult economic conditions. Wallace left in January, aged 20. One result of Wallace's early travels has been a modern controversy about Wallace's nationality. Since Wallace was born in Monmouthshire, Wales, some sources have considered him to be Welsh. However some historians have questioned this because neither of his parents were Welsh, his family only briefly lived in Monmouthshire, the Welsh people Wallace knew in his childhood considered him to be English, and because Wallace himself seems to have consistently referred to himself as English rather than Welsh. One Wallace scholar has stated that because of these facts the most reasonable interpretation was that Wallace was an Englishman born in Wales.
After a brief period of unemployment, he was hired as a master at the Collegiate School in Leicester to teach drawing, mapmaking, and surveying. Wallace spent a lot of time at the Leicester library where he read An Essay on the Principle of Population by Thomas Malthus and where one evening he met the entomologist Henry Bates. Bates was only 19 years old, but had already published a paper on beetles in the journal Zoologist. He befriended Wallace and started him collecting insects. William died in March 1845, and Wallace left his teaching position to assume control of his brother's firm in Neath, but he and his brother John were unable to make the business work. After a couple of months, Wallace found work as a civil engineer for a nearby firm that was working on a survey for a proposed railway in the Vale of Neath. Wallace's work on the survey involved spending a lot of time outdoors in the countryside, allowing him to indulge his new passion for collecting insects. Wallace was able to persuade his brother John to join him in starting another architecture and civil engineering firm, which carried out a number of projects, including the design of a building for the Mechanics' Institute of Neath. William Jevons, the founder of that institute, was impressed by Wallace and persuaded him to give lectures there on science and engineering. In the autumn of 1846, he, aged 23, and John were able to purchase a cottage near Neath, where they lived with their mother and sister Fanny (his father had died in 1843). During this period, he read avidly, exchanging letters with Bates about the anonymous evolutionary treatise Vestiges of the Natural History of Creation, Charles Darwin's Journal and Remarks, and Charles Lyell's Principles of Geology.
Inspired by the chronicles of earlier travelling naturalists, including Alexander von Humboldt, Charles Darwin, and William Henry Edwards, Wallace decided that he too wanted to travel abroad as a naturalist. In 1848, Wallace and Henry Bates left for Brazil aboard the Mischief. Their intention was to collect insects and other animal specimens in the Amazon Rainforest and sell them to collectors back in the United Kingdom. They also hoped to gather evidence of the transmutation of species. Wallace and Bates spent most of their first year collecting near Belém do Pará, then explored inland separately, occasionally meeting to discuss their findings. In 1849, they were briefly joined by another young explorer, botanist Richard Spruce, along with Wallace's younger brother Herbert. Herbert left soon thereafter (dying two years later from yellow fever), but Spruce, like Bates, would spend over ten years collecting in South America.
Wallace continued charting the Rio Negro for four years, collecting specimens and making notes on the peoples and languages he encountered as well as the geography, flora, and fauna. On 12 July 1852, Wallace embarked for the UK on the brig Helen. After twenty-eight days at sea, balsam in the ship's cargo caught fire and the crew was forced to abandon ship. Wallace's entire collection was lost, and he could only save part of his diary and a few sketches. Wallace and the crew spent ten days in an open boat before being picked up by the brig Jordeson.
After his return to the UK, Wallace spent eighteen months in London living on the insurance payment for his lost collection and selling the surviving remnants. During this period, despite having lost almost all of the notes from his South American expedition, he wrote six academic papers (which included "On the Monkeys of the Amazon") and two books; Palm Trees of the Amazon and Their Uses and Travels on the Amazon. He also made connections with a number of other British naturalists — most significantly, Darwin.
From 1854 to 1862, age 31 to 39, Wallace travelled through the Malay Archipelago or East Indies (now Malaysia and Indonesia), to collect specimens for sale and to study nature. His observations of the marked zoological differences across a narrow strait in the archipelago led to his proposing the zoogeographical boundary now known as the Wallace line. Wallace collected more than 125,000 specimens in the Malay Archipelago (more than 80,000 beetles alone). More than a thousand of them represented species new to science. One of his better-known species descriptions during this trip is that of the gliding tree frog Rhacophorus nigropalmatus, known as Wallace's flying frog. While he was exploring the archipelago, he refined his thoughts about evolution and had his famous insight on natural selection.
Accounts of his studies and adventures there were eventually published in 1869 as The Malay Archipelago. The Malay Archipelago became one of the most popular journals of scientific exploration of the 19th century, kept continuously in print by its original publisher (Macmillan) into the second decade of the 20th century. It was praised by scientists such as Darwin (to whom the book was dedicated), and Charles Lyell, and by non-scientists such as the novelist Joseph Conrad, who called it his "favorite bedside companion" and used it as source of information for several of his novels, especially Lord Jim.
After a year of courtship, Wallace became engaged in 1864 to a young woman whom, in his autobiography, he would only identify as Miss L. However, to Wallace's great dismay, she broke off the engagement. In 1866, Wallace married Annie Mitten. Wallace had been introduced to Mitten through Richard Spruce, who had befriended Wallace in Brazil and who was also a good friend of Annie Mitten's father, William Mitten, an expert in mosses. In 1872, Wallace had a house built of concrete on land he leased in Grays in Essex, where he lived until 1876. The Wallaces had three children: Herbert (1867–1874) who died in childhood, Violet (1869–1945), and William (1871–1951).
Wallace continued his scientific work in parallel with his social commentary. In 1880, he published Island Life as a sequel to The Geographic Distribution of Animals. In November 1886, Wallace began a ten month trip to the United States to give a series of popular lectures. Most of the lectures were on Darwinism (evolution and natural selection), but he also gave speeches on biogeography, spiritualism, and socio-economic reform. During the trip, he was reunited with his brother John who had emigrated to California years before. He also spent a week in Colorado, with the American botanist Alice Eastwood as his guide, exploring the flora of the Rocky Mountains and gathering evidence that would lead him to a theory on how glaciation might explain certain commonalities between the mountain flora of Europe, Asia and North America, which he published in 1891 in the paper "English and American Flowers". He met many other prominent American naturalists and viewed their collections. His 1889 book Darwinism used information he collected on his American trip, and information he had compiled for the lectures.
He was also profoundly influenced by Robert Chambers' work Vestiges of the Natural History of Creation, a highly-controversial work of popular science published anonymously in 1844 that advocated an evolutionary origin for the solar system, the earth, and living things. Wallace wrote to Henry Bates in 1845:
I have a rather more favourable opinion of the ‘Vestiges’ than you appear to have. I do not consider it a hasty generalization, but rather as an ingenious hypothesis strongly supported by some striking facts and analogies, but which remains to be proven by more facts and the additional light which more research may throw upon the problem. It furnishes a subject for every student of nature to attend to; every fact he observes will make either for or against it, and it thus serves both as an incitement to the collection of facts, and an object to which they can be applied when collected.
Wallace deliberately planned some of his field work to test the hypothesis that under an evolutionary scenario closely related species should inhabit neighbouring territories. During his work in the Amazon basin, he came to realize that geographical barriers — such as the Amazon and its major tributaries — often separated the ranges of closely-allied species, and he included these observations in his 1853 paper "On the Monkeys of the Amazon". Near the end of the paper he asks the question "Are very closely allied species ever separated by a wide interval of country?"
In February 1855, while working in the state of Sarawak on the island of Borneo, Wallace wrote "On the Law Which has Regulated the Introduction of Species", a paper which was published in the Annals and Magazine of Natural History in September 1855. In this paper, he gathered and enumerated general observations regarding the geographic and geologic distribution of species (biogeography). His conclusion that "Every species has come into existence coincident both in space and time with a closely allied species" has come to be known as the "Sarawak Law". Wallace thus answered the question he had posed in his earlier paper on the monkeys of the Amazon river basin. Although it contained no mention of any possible mechanisms for evolution, this paper foreshadowed the momentous paper he would write three years later.
The paper shook Charles Lyell's belief that species were immutable. Although his friend Charles Darwin had written to him in 1842 expressing support for transmutation, Lyell had continued to be strongly opposed to the idea. Around the start of 1856, he told Darwin about Wallace's paper, as did Edward Blyth who thought it "Good! Upon the whole!… Wallace has, I think put the matter well; and according to his theory the various domestic races of animals have been fairly developed into species." Despite this hint, Darwin mistook Wallace's conclusion for the progressive creationism of the time and wrote that it was "nothing very new… Uses my simile of tree [but] it seems all creation with him." Lyell was more impressed, and opened a notebook on species, in which he grappled with the consequences, particularly for human ancestry. Darwin had already shown his theory to their mutual friend Joseph Hooker and now, for the first time, he spelt out the full details of natural selection to Lyell. Although Lyell could not agree, he urged Darwin to publish to establish priority. Darwin demurred at first, then began writing up a species sketch of his continuing work in May 1856.
By February 1858, Wallace had been convinced by his biogeographical research in the Malay Archipelago of the reality of evolution. As he later wrote in his autobiography:
The problem then was not only how and why do species change, but how and why do they change into new and well defined species, distinguished from each other in so many ways; why and how they become so exactly adapted to distinct modes of life; and why do all the intermediate grades die out (as geology shows they have died out) and leave only clearly defined and well marked species, genera, and higher groups of animals?
According to his autobiography, it was while he was in bed with a fever that Wallace thought about Thomas Malthus's idea of positive checks on human population growth and came up with the idea of natural selection. Wallace said in his autobiography that he was on the island of Ternate at the time; but historians have questioned this, saying that on the basis of the collection registries he wrote at the time, he was more likely to have been on the island of Gilolo. Wallace describes it as follows:
It then occurred to me that these causes or their equivalents are continually acting in the case of animals also; and as animals usually breed much more quickly than does mankind, the destruction every year from these causes must be enormous in order to keep down the numbers of each species, since evidently they do not increase regularly from year to year, as otherwise the world would long ago have been crowded with those that breed most quickly. Vaguely thinking over the enormous and constant destruction which this implied, it occurred to me to ask the question, why do some die and some live? And the answer was clearly, on the whole the best fitted live… and considering the amount of individual variation that my experience as a collector had shown me to exist, then it followed that all the changes necessary for the adaptation of the species to the changing conditions would be brought about… In this way every part of an animals organization could be modified exactly as required, and in the very process of this modification the unmodified would die out, and thus the definite characters and the clear isolation of each new species would be explained.
Wallace had once briefly met Darwin, and was one of the correspondents whose observations Darwin used to support his own theories. Although Wallace's first letters to Darwin have been lost, he carefully kept the letters he received. In the first letter, dated 1 May 1857, Darwin commented that Wallace's letter of 10 October which he'd recently received as well as Wallace's paper "On the Law that has regulated the Introduction of New Species" of 1855 showed that they were both thinking alike and to some extent reaching similar conclusions, and said that he was preparing his own work for publication in about two years time. The second letter, dated 22 December 1857, said how glad he was that Wallace was theorising about distribution, adding that "without speculation there is no good and original observation" while commenting that "I believe I go much further than you". Wallace trusted Darwin's opinion on the matter and sent him his February 1858 essay, "On the Tendency of Varieties to Depart Indefinitely From the Original Type", with the request that Darwin would review it and pass it on to Charles Lyell if he thought it worthwhile. On 18 June 1858, Darwin received the manuscript from Wallace. While Wallace's essay did not employ Darwin's term "natural selection", it did outline the mechanics of an evolutionary divergence of species from similar ones due to environmental pressures. In this sense, it was very similar to the theory that Darwin had worked on for twenty years, but had yet to publish. Darwin sent the manuscript to Charles Lyell with a letter saying "he could not have made a better short abstract! Even his terms now stand as heads of my chapters… he does not say he wishes me to publish, but I shall, of course, at once write and offer to send to any journal. Distraught about the illness of his baby son, Darwin put the problem to Charles Lyell and Joseph Hooker, who decided to publish the essay in a joint presentation together with unpublished writings which highlighted Darwin's priority. Wallace's essay was presented to the Linnean Society of London on 1 July 1858, along with excerpts from an essay which Darwin had disclosed privately to Hooker in 1847 and a letter Darwin had written to Asa Gray in 1857.
Wallace accepted the arrangement after the fact, happy that he had been included at all. Darwin's social and scientific status was far greater than Wallace's, and it was unlikely that, without Darwin, Wallace's views on evolution would have been taken seriously. Lyell and Hooker's arrangement relegated Wallace to the position of co-discoverer, and he was not the social equal of Darwin or the other prominent British natural scientists. However, the joint reading of their papers on natural selection associated Wallace with the more famous Darwin. This, combined with Darwin's (as well as Hooker's and Lyell's) advocacy on his behalf, would give Wallace greater access to the highest levels of the scientific community. The reaction to the reading was muted, with the president of the Linnean remarking in May 1859 that the year had not been marked by any striking discoveries; but, with Darwin's publication of On the Origin of Species later in 1859, its significance became apparent. When Wallace returned to the UK, he met Darwin and the two remained friendly afterwards. Over the years, a few people have questioned this version of events. In the early 1980s, two books, one written by Arnold Brackman and another by John Langdon Brooks, even suggested that not only had there been a conspiracy to rob Wallace of his proper credit, but that Darwin had actually stolen a key idea from Wallace to finish his own theory. These claims have been examined in detail by a number of scholars who have concluded that they are not credible.
After the publication of Darwin’s On the Origin of Species, Wallace became one of its staunchest defenders. In one incident in 1863 that particularly pleased Darwin, Wallace published the short paper "Remarks on the Rev. S. Haughton's Paper on the Bee's Cell, And on the Origin of Species" in order to utterly demolish a paper by a professor of geology at the University of Dublin that had sharply criticized Darwin’s comments in the Origin on how hexagonal honey bee cells could have evolved through natural selection. Another notable defence of the Origin was "Creation by Law", a review Wallace wrote in 1867 for The Quarterly Journal of Science of the book The Reign of Law, which had been written by the Duke of Argyle as a refutation of natural selection. After an 1870 meeting of the British Association, Wallace wrote to Darwin complaining that there were "no opponents left who know anything of natural history, so that there are none of the good discussions we used to have.
Others have noted that another difference was that Wallace appeared to have envisioned natural selection as a kind of feedback mechanism keeping species and varieties adapted to their environment. They point to a largely-overlooked passage of Wallace's famous 1858 paper:
The action of this principle is exactly like that of the centrifugal governor of the steam engine, which checks and corrects any irregularities almost before they become evident; and in like manner no unbalanced deficiency in the animal kingdom can ever reach any conspicuous magnitude, because it would make itself felt at the very first step, by rendering existence difficult and extinction almost sure soon to follow.
The cybernetician and anthropologist Gregory Bateson would observe in the 1970s that, though writing it only as an example, Wallace had "probably said the most powerful thing that’d been said in the 19th Century". Bateson revisited the topic in his 1979 book Mind and Nature: A Necessary Unity, and other scholars have continued to explore the connection between natural selection and systems theory.
Shortly afterwards, Wallace became a spiritualist. At about the same time, he began to maintain that natural selection cannot account for mathematical, artistic, or musical genius, as well as metaphysical musings, and wit and humour. He eventually said that something in "the unseen universe of Spirit" had interceded at least three times in history. The first was the creation of life from inorganic matter. The second was the introduction of consciousness in the higher animals. And the third was the generation of the higher mental faculties in mankind. He also believed that the raison d'être of the universe was the development of the human spirit. These views greatly disturbed Darwin, who argued that spiritual appeals were not necessary and that sexual selection could easily explain apparently non-adaptive mental phenomena. While some historians have concluded that Wallace's belief that natural selection was insufficient to explain the development of consciousness and the human mind was directly caused by his adoption of spiritualism, other Wallace scholars have disagreed, and some maintain that Wallace never believed natural selection applied to those areas. Reaction to Wallace's ideas on this topic among leading naturalists at the time varied. Charles Lyell endorsed Wallace's views on human evolution rather than Darwin's. However, many, including Huxley, Hooker, and Darwin himself, were critical of Wallace. As one historian of science has pointed out, Wallace's views in this area were at odds with two major tenets of the emerging Darwinian philosophy, which were that evolution was not teleological and that it was not anthropocentric.
…I remain an utter disbeliever in almost all that you consider the most sacred truths. I will pass over as utterly contemptible the oft-repeated accusation that sceptics shut out evidence because they will not be governed by the morality of Christianity… I am thankful I can see much to admire in all religions. To the mass of mankind religion of some kind is a necessity. But whether there be a God and whatever be His nature; whether we have an immortal soul or not, or whatever may be our state after death, I can have no fear of having to suffer for the study of nature and the search for truth, or believe that those will be better off in a future state who have lived in the belief of doctrines inculcated from childhood, and which are to them rather a matter of blind faith than intelligent conviction.
Wallace was an enthusiast of phrenology. Early in his career, he experimented with hypnosis, then known as mesmerism. He used some of his students in Leicester as subjects, with considerable success. When he began his experiments with mesmerism, the topic was very controversial and early experimenters, such as John Elliotson, had been harshly criticized by the medical and scientific establishment. Wallace drew a connection between his experiences with mesmerism and his later investigations into spiritualism. In 1893, he wrote:
I thus learnt my first great lesson in the inquiry into these obscure fields of knowledge, never to accept the disbelief of great men or their accusations of imposture or of imbecility, as of any weight when opposed to the repeated observation of facts by other men, admittedly sane and honest. The whole history of science shows us that whenever the educated and scientific men of any age have denied the facts of other investigators on a priori grounds of absurdity or impossibility, the deniers have always been wrong.
Wallace began investigating spiritualism in the summer of 1865, possibly at the urging of his older sister Fanny Sims, who had been involved with it for some time. After reviewing the literature on the topic and attempting to test the phenomena he witnessed at séances, he came to accept that the belief was connected to a natural reality. For the rest of his life, he remained convinced that at least some séance phenomena were genuine, no matter how many accusations of fraud sceptics made or how much evidence of trickery was produced. Historians and biographers have disagreed about which factors most influenced his adoption of spiritualism. It has been suggested by one biographer that the emotional shock he had received a few months earlier, when his first fiancée broke their engagement, contributed to his receptiveness to spiritualism. Other scholars have preferred to emphasize instead Wallace's desire to find rational and scientific explanations for all phenomena, both material and non-material, of the natural world and of human society.
Spiritualism appealed to many educated Victorians who no longer found traditional religious doctrine, such as that of the Church of England, acceptable yet were unsatisfied with the completely-materialistic and mechanical view of the world that was increasingly emerging from 19th-century science. However, several scholars who have researched Wallace's views in depth have emphasized that, for him, spiritualism was a matter of science and philosophy rather than religious belief. Among other prominent 19th-century intellectuals involved with spiritualism were the social reformer Robert Owen, who was one of Wallace’s early idols, the physicists William Crookes and Lord Rayleigh, the mathematician Augustus De Morgan, and the Scottish publisher Robert Chambers.
Wallace's very public advocacy of spiritualism and his repeated defence of spiritualist mediums against allegations of fraud in the 1870s damaged his scientific reputation. It strained his relationships with previously-friendly scientists such as Henry Bates, Thomas Huxley, and even Darwin, who felt he was overly-credulous. Others, such as the physiologist William Benjamin Carpenter and zoologist E. Ray Lankester became openly and publicly hostile to Wallace over the issue. Wallace and other scientists who defended spiritualism, notably William Crookes, were subject to much criticism from the press, with The Lancet as the leading English medical journal of the time being particularly harsh. The controversy affected the public perception of Wallace’s work for the rest of his career. When, in 1879, Darwin first tried to rally support among naturalists to get a civil pension awarded to Wallace, Joseph Hooker responded:
Wallace has lost caste considerably, not only by his adhesion to Spiritualism, but by the fact of his having deliberately and against the whole voice of the committee of his section of the British Association, brought about a discussion of on Spiritualism at one of its sectional meetings. That he is said to have done so in an underhanded manner, and I well remember the indignation it gave rise to in the B.A. Council.
Hooker eventually relented and agreed to support the pension request.
In 1872, at the urging of many of his friends, including Darwin, Philip Sclater, and Alfred Newton, Wallace began research for a general review of the geographic distribution of animals. He was unable to make much progress initially, in part because classification systems for many types of animals were in flux at the time. He resumed the work in earnest in 1874 after the publication of a number of new works on classification. Extending the bird system developed by Sclater — which divided the earth into 6 separate geographic regions for describing species distribution — to cover mammals, reptiles and insects as well, Wallace created the basis for the zoogeographic regions still in use today. He discussed all of the factors then known to influence the current and past geographic distribution of animals within each geographical region. These included the effects of the appearance and disappearance of land bridges (such as the one currently connecting North America and South America) and the effects of periods of increased glaciation. He provided maps that displayed factors, such as elevation of mountains, depths of oceans, and the character of regional vegetation, that affected the distribution of animals. He also summarized all the known families and genera of the higher animals and listed their known geographic distributions. The text was organized so that it would be easy for a traveler to learn what animals could be found in a particular location. The resulting two-volume work, The Geographical Distribution of Animals, was published in 1876 and would serve as the definitive text on zoogeography for the next 80 years.
In 1880, Wallace published the book Island Life as a sequel to The Geographical Distribution of Animals. It surveyed the distribution of both animal and plant species on islands. Wallace classified islands into three different types. Oceanic islands, such as the Galapagos and Hawaiian Islands (then known as the Sandwich Islands) formed in mid-ocean and had never been part of any large continent. Such islands were characterized by a complete lack of terrestrial mammals and amphibians, and their inhabitants (with the exceptions of migratory birds and species introduced by human activity) were typically the result of accidental colonization and subsequent evolution. He divided continental islands into two separate classes depending on whether they had recently been part of a continent (like Britain) or much less recently (like Madagascar) and discussed how that difference affected the flora and fauna. He talked about how isolation affected evolution and how that could result in the preservation of classes of animals, such as the lemurs of Madagascar that were remnants of once widespread continental faunas. He extensively discussed how changes of climate, particularly periods of increased glaciation, may have affected the distribution of flora and fauna on some islands, and the first portion of the book discusses possible causes of these great ice ages. Island Life was considered a very important work at the time of its publication. It was discussed extensively in scientific circles both in published reviews and in private correspondence.
…yet the general aspect of the island is now so barren and forbidding that some persons find it difficult to believe that it was once all green and fertile. The cause of this change is, however, very easily explained. The rich soil formed by decomposed volcanic rock and vegetable deposits could only be retained on the steep slopes so long as it was protected by the vegetation to which it in great part owed its origin. When this was destroyed, the heavy tropical rains soon washed away the soil, and has left a vast expanse of bare rock or sterile clay. This irreparable destruction was caused, in the first place, by goats, which were introduced by the Portuguese in 1513, and increased so rapidly that in 1588 they existed in the thousands. These animals are the greatest of all foes to trees, because they eat off the young seedlings, and thus prevent the natural restoration of the forest. They were, however, aided by the reckless waste of man. The East India Company took possession of the island in 1651, and about the year 1700 it began to be seen that the forests were fast diminishing, and required some protection. Two of the native trees, redwood and ebony, were good for tanning, and, to save trouble, the bark was wastefully stripped from the trunks only, the remainder being left to rot; while in 1709 a large quantity of the rapidly disappearing ebony was used to burn lime for building fortifications!
A more comprehensive list of Wallace's publications that are available online, as well as a full bibliography of all of Wallace's writings, has been compiled by the historian Charles H. Smith at the The Alfred Russel Wallace Page