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Darwin, Charles Robert (1809-1882), was a British scientist, who laid the foundation of modern evolutionary theory with his concept of the development of all forms of life through the slow-working process of natural selection. His work has been of major influence on the life and earth sciences and on modern thought in general.
Born in Shrewsbury, Shropshire, on February 12, 1809, Darwin was the fifth child of a wealthy and sophisticated family. His maternal grandfather was the successful china and pottery entrepreneur Josiah Wedgwood; his paternal grandfather was the well-known 18th-century doctor, poet, and savant Erasmus Darwin. His father was a successful provincial physician with a dominant personality; his mother died when Charles was only eight, after which time he was looked after by his elder sisters. Known as a rather ordinary student, Darwin left Shrewsbury School in 1825 and went to the University of Edinburgh to study medicine. Finding himself squeamish at the sight of human blood and suffering, Darwin left Edinburgh and went to the University of Cambridge, in preparation for a life as a Church of England clergyman, which he thought would best allow him to pursue his increasing interest in natural history. At Cambridge he came under the influence of two figures: Adam Sedgwick, a geologist, and John Stevens Henslow, a botanist. Henslow not only helped build Darwin's self-confidence but also taught his student to be a meticulous and painstaking observer of natural phenomena and collector of specimens. After graduating from Cambridge in 1831, the 22-year-old Darwin was taken aboard the English survey ship HMS Beagle, largely on Henslow's recommendation, as an unpaid naturalist on a scientific expedition round the world. This voyage, which began on December 27, 1831, determined Darwin's whole future career.
Voyage of the Beagle
The Beagle, under the command of Captain Robert Fitzroy, a strict disciplinarian of aristocratic stock and fundamentalist religious beliefs, was originally scheduled to spend a year or two primarily charting the coastal waters of South America. In the event, it was gone for five years and circumnavigated the globe. Almost four of those years were spent on the east and west coasts of South America, and Darwin was able to leave the ship for two extended periods on the mainland. In September 1835 the Beagle headed west for Australia, returning to England via the Cape of Good Hope. Darwin's job as naturalist gave him the opportunity to observe a variety of geological formations in different continents and islands along the way, as well as a vast array of fossils and living organisms. In his geological observations, Darwin was most impressed by the effect that natural forces have on shaping the Earth's surface.
At the time, most geologists adhered to the so-called catastrophe theory that the Earth had experienced a succession of creations of animal and plant life, and that each creation had been destroyed by a sudden catastrophe, such as an upheaval or convulsion of the Earth's surface. According to one prominent version of this theory, the most recent catastrophe was the Flood of Noah, as recorded in the Bible. It wiped away all land animals except those taken into the ark (plants and fishes presented a problem); the rest were visible only as fossils. According to the catastrophists, species of plants and animals were individually created and immutable, that is, unchangeable for all time.
The catastrophist viewpoint (but not the immutability of species) was challenged by the British geologist Sir Charles Lyell in his three-volume work Principles of Geology (1830-1833). Lyell maintained that the Earth's surface is undergoing constant change, the result of natural forces operating uniformly since the Creation (which he argued was millions of years ago).
Darwin was given the first volume of Lyell's work just before he left England, and the subsequent volumes were sent to him in South America. Lyell's uniformitarian principles provided him with exactly the framework he needed for his own geological observations. Lyell argued that active geological change was still going on apace, and Darwin was especially impressed with an earthquake he experienced while in Chile that actually raised the coastline by several feet. Beyond that, however, he realized that some of his own observations on the local relationships between fossils and living plants and animals cast doubt on Lyell's vague views on the special creation of new species. Darwin noted that some fossils of supposedly extinct species in a particular geographical area closely resembled living species of the same region. In the Galápagos Islands, 1,000 km off the coast of Ecuador, he also observed that each island supported its own form of tortoise, mocking bird, and finch; the various forms were closely related but differed in structure and eating habits from island to island. These observations raised the question, for Darwin, of possible links between distinct but similar species.
Theories of Natural Selection
When Darwin returned to England in 1836, he was a mature scientist. His letters and packages of specimens sent to Sedgwick, Henslow, and others during his voyage had established his reputation at home. He immediately threw himself into the work of preparing his share of an extensive report of the scientific discoveries made during the Beagle voyage, and editing his own travel diary for publication. Darwin's Journal of Researches (1839) achieved popular as well as scientific acclaim, and it was followed in 1844 and 1846 by further volumes on volcanic islands and on the geology of South America.
None of this published work by Darwin challenged the assumption that biological species are immutable. However, in July 1837 Darwin opened a private notebook entitled "Transmutation of Species", in which he recorded observations and speculations bearing on the question (which he subsequently called "that mystery of mysteries"). His thinking on how organisms evolve was brought into sharp focus in September 1838, when he read An Essay on the Principle of Population (originally published in 1798) by the British economist Thomas Robert Malthus. Malthus observed that all biological species, including human beings, possess a far greater reproductive capacity than can actually be realised. For human beings, there was always a potential disparity between the means of subsistence and the number of mouths to feed. Human population growth was thus limited by dire checks, such as famine, disease, and war.
Darwin immediately saw the relevance of Malthus's work for his own thinking: if all the offspring of a plant or animal cannot survive to reproductive maturity, there must be biological reasons why those that survive do so. This constant press, which he called natural selection, was the motor of biological change over time. In 1838, 1842, and 1844 he produced increasingly elaborate private versions of his evolutionary theory; the latter is virtually a précis of the famous book that he eventually published in 1859.
In the meantime, Darwin had married, in 1839, his first cousin, Emma Wedgwood, and they soon afterwards left London for a small estate, Down House, in Downe, Kent. His father had left him independently wealthy. At Down, he and his wife had ten children, three of whom died in infancy. By then, too, Darwin was beginning to suffer from an illness that was to plague him intermittently for the rest of his life. It produced shaking, nausea, dry retching, and great prostration. It left him, by his own testimony, unable to work for days and weeks on end, although his output of scientific books and correspondence continued to be prodigious. The source of his illness will probably never be completely unravelled, although it possibly had a large psychosomatic component. It also relieved him of many social, professional, and domestic obligations, thus enabling him to concentrate on what mattered most to him: his work.
In 1856, after eight years of sustained work on fossil and living barnacles (published in two large volumes), Darwin at last began work on a volume that he intended to call Natural Selection. It was interrupted in 1858, when Alfred Russel Wallace, a young naturalist then working in Malaysia, sent Darwin his own brief sketch of evolution through natural selection. Lyell, who had been privy to Darwin's own evolutionary thinking, arranged for a joint presentation of Wallace's sketch and a brief essay by Darwin at a meeting of the Linnean Society in London. Darwin was then stimulated to write On the Origin of Species by Means of Natural Selection. It sold out on the first day of publication in November 1859 and remains one of the greatest scientific treatises ever written. It went through five further editions in Darwin's lifetime.
Darwin's was by no means the first treatise to argue for the change of biological species over time. His grandfather, Erasmus Darwin, had developed his own evolutionary ideas in a series of medical writings and poems. The French naturalist Jean-Baptiste Lamarck, in his Philosophie Zoologique (1809), expounded a comprehensive evolutionary synthesis, based on the commonly held notion that characteristics acquired in an organism's lifetime could be passed on to the offspring. He famously argued that the giraffe's long neck was the result of generations of stretching to reach leaves higher in the trees. This form of inheritance was described as "Lamarckian". In 1844 the Scottish publisher Robert Chambers anonymously published his own evolutionary synthesis, entitled Vestiges of the Natural History of Creation. Darwin knew all these works, and in later editions of the Origin provided a historical introduction. Their influence on him was general rather than particular, however, as revealed by the differences in his theory.
Darwin's theory of evolution by natural selection is essentially that, because of the population pressure as described by Malthus, the young born to any species compete intensely for survival. Those young that survive to reproduce tend to embody favourable natural variations (however slight the advantage may be) - the process of natural selection - and these variations are passed on by heredity. Darwin recognized that his understanding of the mechanisms of heredity was limited, but he insisted that as long as inherited variation does occur, his theory would work. Therefore, some members of each generation will be able to adapt themselves to changing environmental conditions (changes in food supply, predators, or climate, for example), and this gradual and continuous process of adaptation is the source of the evolution of species. Within Darwin's vast conceptual scheme, extinct and present-day species of plants and animals were represented as a kind of "tree of life", in which closely related modern organisms are descended from common ancestors. Moreover, he provided additional support for the older concept that the Earth itself is not static but evolving.
In a deliberate attempt to make his ideas more acceptable, Darwin did not discuss human evolution in the Origin, confining himself to a single sentence: "Light will be thrown on the origin of man and his history". Nevertheless, his private notebooks make it clear that he recognized from the beginning that human beings were also part of the evolutionary process. He elaborated his views on human evolution in two later works, but the popular idea that he argued that human beings are descended from apes is false: within his scheme, human beings and other primates, such as modern apes and monkeys, are all descended from common, more primitive ancestors.
Reactions to the Theory
Darwin was extremely anxious about how his theory would be received, but, a shy man, he declined to debate his work publicly. Thomas Henry Huxley ("Darwin's Bulldog") became his most ardent spokesman. Reaction to the Origin was immediate. Some biologists argued that, since there was no laboratory proof of Darwin's theories, it must remain a hypothesis. Others criticized Darwin's concept of variation, pointing out that he could explain neither the origin of variations nor how they were passed between generations. This particular scientific objection was not answered until the birth of modern genetics in the early 20th century. Still others believed that natural selection was not sufficiently powerful to produce the changes Darwin attributed to it. In fact, Darwin's work convinced many scientists of the fact of biological evolution, but his theories were doubted by many until the early 20th century. The most publicized attacks on Darwin's ideas, however, came not from scientists but from religious opponents (or scientists acting out of religious belief). The thought that living things had evolved by natural processes denied the special creation of humankind and seemed to place humanity on a plane with the animals; both of these ideas were serious challenges to orthodox theological opinion.
Huxley himself (who coined the word "agnostic" to describe his own religious opinions) was never afraid of a tussle with the theologians, most famously in 1860 with Samuel Wilberforce, Bishop of Oxford. The idea of man descended from apes was already prominent by then, and Wilberforce patronizingly asked Huxley "Was it through his grandfather or his grandmother that he claimed his descent from a monkey?" Huxley replied that he would rather be related to an ape than to a man of intelligence who used his eloquence to obscure the "real point at issue". Darwin himself was cagey about expressing himself publicly on religious matters, partly from timidity, partly to avoid causing pain to his devout wife Emma. We know from his letters and private notebooks that he gradually lost his own faith and can be said to have vacillated between atheism and agnosticism.
Darwin kept revising successive editions of the Origin, to account for various scientific criticisms that were raised. In addition, he produced a series of monographs that elaborated different aspects of matters discussed in the Origin. The Variation of Animals and Plants Under Domestication (1868) expanded the analogy between "artificial" and natural selection, pointing out that animal and plant breeders could produce significant new variations simply by selectively breeding offspring. "How much more powerful than man," he insisted, "is Nature herself." The Descent of Man (1871) tackled the emotive issue of human evolution (which he had avoided in the Origin), and also developed a theory of sexual selection as another mechanism of organic change, complementing natural selection. The Expression of the Emotions in Man and Animals (1872) was essentially an essay in comparative psychology, drawing on Darwin's close observations of the early development of his own children.
Darwin was also a gifted botanist who used his own gardens at Down to great effect. In the last two decades of his life he wrote five botanical books, describing a wide range of observational and experimental work. It included the role of insects on cross-fertilisation; the adaptations of climbing plants such as ivy; the intriguing sensitive plants that respond to touch and are sometimes insectivorous (such as the Venus flytrap); and the important function of the humble earthworm in breaking down leaves and turning earth into fertile soil.
By the time he died on April 19, 1882, Darwin was a world-famous scientist. He had been given many with honours and awards, such as fellowship of the Royal Society, and honorary membership in many scientific academies. Despite the controversial nature of many of his ideas, the scientific establishment recognised his worth and he was buried in Westminster Abbey.
Although Darwin was not the first evolutionist, modern evolutionary biology begins with him. He was the first to marshal enough scientific evidence to convince his fellow scientists that biological species can change over time by natural means. However, the principal mechanism he proposed - natural selection - was not properly appreciated until the 20th century, when the work of biologists such as John Burdon Haldane, Sewell Wright, and Julian Huxley (T. H. Huxley's grandson) combined Mendelian genetics and population dynamics to produce what was called Neo-Darwinism. This synthesis remains the basis of much contemporary research in evolutionary biology.
During Darwin's lifetime, his vision of struggle as a brute fact of biological life was more widely accepted. The English social theorist Herbert Spencer coined the phrase "survival of the fittest" as an alternative to Darwin's less-loaded "natural selection", and social Darwinism (more accurately called "social Spencerianism") became the basis of much social and economic thought. In particular, evolutionary ideas were used to explain many social phenomena and to justify the dominant capitalistic and imperialist ideology of the age. As evolution and development became fundamental features of the modern world-view, few areas of human life and endeavour escaped an evolutionary analysis, although in many cases it has been misunderstood or misappplied.
Now try the exercises: Exercise a, Exercise b, Exercise c.
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