Darwin, Charles Robert

(b. The Mount, Shrewsbury, England, 9 February 1809; d. Down House, Downe, Kent, England, 19 April 1882)

natural history, geology, evolution.

Darwin was the fifth child and second son of Robert Waring Darwin, a successful and respected physician practicing in Shrewsbury, and Susannah Wedgwood, daughter of the potter Josiah Wedgwood I. The Darwin family was characterized by the high intellectual quality of its members, prosperity, industriousness, professional ability, and wide cultural interests.

Darwin’s education was begun by his elder sisters after the premature death of his mother. In 1817 he was sent to a day school at Shrewsbury, where he was found to be slow at learning. In 1818 he was entered at Shrewsbury School under Dr. Samuel Butler (grandfather of the author of Erewhon). He afterwards complained he was taught nothing but classics, a little ancient history, and geography. “The school as a means of education to me was simply a blank.” This statement is perhaps unfair in that his grounding in the classics probably helped him afterwards to think so devastatingly straight. But his headmaster rebuked him publicly for wasting his time on chemical experiments, and his father upbraided him with the remark, “You care for nothing but shooting, dogs, and ratcatching, and you will be a disgrace to yourself and all your family.” He was removed from Shrewsbury School in 1825 and sent to Edinburgh University to study medicine.

Darwin stayed at Edinburgh until 1827, attending courses of lectures on materia medica, pharmacy, chemistry, and anatomy, which he found unbearably dull. But worst of all were his experiences attending operations, performed perforce without anesthetics. These repelled him to such an extent that he rushed out and vowed that medicine was no career for him. The chief advantages that he gained from his stay at Edinburgh were his friendship with Robert Grant, zoologist, who accepted Lamarck’s teachings on evolution; geological excursions with Robert Jameson; and expeditions onto the Firth of Forth to collect marine animals.

Confronted with the necessity of starting his son on a new line of endeavor, Darwin’s father sent him to Cambridge as a preparation for entering the Church of England as a clergyman. At that time, he accepted the Articles of Faith, and perfunctorily attended lectures, but his three years at Cambridge he thought “wasted as far as the academical studies were concerned, as completely as at Edinburgh and at school.” But he there made the acquaintance of Adam Sedgwick, who interested him in geology, and, most important of all, John Stevens Henslow, who fired him with a passionate interest in natural history and inspired him with a friendship that gave him confidence in himself, after his discouragement in his own family, at school, and at Edinburgh. Henslow acted as a second father to young Darwin during this critical, formative period in his life, which was climaxed by the voyage of the Beagle.

After taking a poor degree at Cambridge in 1831, Darwin was at home when he received an invitation, instigated by Henslow, to join the Admiralty survey ship H. M. S. Beagle, under the command of Robert FitzRoy, as unpaid naturalist on a voyage to survey the coasts of Patagonia, Tierra del Fuego, Chile, and Peru; to visit some Pacific islands; and to carry a chain of chronometrical stations around the world. Darwin wished to accept at once, but his father objected. Darwin’s uncle, Josiah Wedgwood II, thought the objection unreasonable and persuaded his brother-in-law to withdraw it. Darwin sailed on the Beagle on 27 December 1831.

The five years of the voyage were the most important event in Darwin’s intellectual life and in the history of biological science. Darwin sailed with no formal scientific training. He returned a hard-headed man of science, knowing the importance of evidence, almost convinced that species had not always been as they were since the creation but had undergone change. He also developed doubts of the value of the Scriptures as a trustworthy guide to the history of the earth and of man, with the result that he gradually became an agnostic. The experiences of his five years in the Beagle, how he dealt with them, and what they led to, built up into a process of epoch-making importance in the history of thought.

On 29 January 1839, Darwin married his first cousin, Emma Wedgwood, daughter of the Josiah Wedgwood who had saved his place in the Beagle. At first the young couple lived in London, but ill health began to attack Darwin shortly after his marriage. He found himself increasingly handicapped by great lassitude, nausea, and intestinal discomfort, which made it impossible for him to lead a normal life with social and academic contacts. The Darwins therefore moved to the country, fifteen miles from London, to Down House, in the village of Downe, in Kent. There Darwin had a garden, a small estate about which he could walk, spare rooms for the few friends who were occasionally invited to stay, a study where he could work, and peace and quiet.

His ill health gradually restricted him to a routine of four hours’ work a day, walks in the garden, visits to the greenhouses, occasional walks in the neighborhood or rides on a pony, interspersed with periods of rest on a sofa while reading a novel. Dinner was followed by listening to the piano and then early bed.

As his physicians could not discover any organic cause for Darwin’s ill health, the idea gained ground that he was a hypochondriac, and in recent years some psychiatrists have attempted to show that he was of a neurotic disposition, but the evidence is not wholly satisfactory. Following the suggestion of Saul Adler, a pathologist expert on South American infections, other commentators note that Darwin was heavily bitten in the Argentine by the Benchuca, the “black bug of the pampas,” Triatoma infestans, 70 percent of which are now reckoned to be vectors of Trypanosoma cruzi, the causative agent of Chagas’ disease. As this trypanosome was not discovered until 1909, Darwin’s doctors would have been unable to find an organic cause for his trouble; but the clinical picture found in sufferers from Chagas’ disease matches Darwin’s symptoms in detail. The parasite invades the muscle of the heart causing lassitude; it also invades the nerve cells of Auerbach’s plexus in the wall of the intestine, upsetting peristalsis; and it invades the auricular-ventricular bundle of the heart, interference with which may cause heart block. It has unpredictable periods of latency, after which it can be recovered from blood of patients infected many years before. Darwin suffered heart attacks and died from one. Whether in addition Darwin showed neurotic tendencies, accepting the overcare which his wife bestowed on him and taking advantage of his semi-invalidism to protect himself from the distractions of society and amusement, will never be known.

Darwin and his wife had ten children, of whom three died in infancy or childhood. The healths of the survivors (all of whom lived to ripe ages), and their launching in life, gave him anxiety. He once wrote that his chief worries were the discovery of gold in California and in Australia, “beggaring me by making my money on mortgage worthless”; the French coming by the Westerham and Sevenoaks roads, and, therefore, enclosing Down; and, third, “professions for my boys.” His fears were groundless. His investments were very profitable, Napoleon III did not invade England, and his sons made careers for themselves of which any father could be proud: Sir George Darwin, mathematician and astronomer; Sir Francis Darwin, botanist; Leonard Darwin, engineer and promoter of eugenics; and Sir Horace Darwin, scientific engineer and founder of the Cambridge Scientific Instrument Co. These men, their children and grandchildren, like their father and ancestors, provide material for Galton’s theory of the inheritability of intellectual eminence.

Darwin’s contributions to science fall into three main groups: geology, evolution and natural selection, and botany.

Darwin as Geologist. When Darwin sailed in the Beagle, the most commonly accepted theory in geology was that of catastrophism, which held that the forces which had produced change during the past history of the earth had been on a far greater scale than any which are active today. When geologists had concluded that stratified rocks had originated as beds of sediment laid down beneath the sea, they had then been obliged to explain how the sedimentary strata had been raised up from the sea bottom to form hills and mountains, and how they had been shifted from the horizontal position, in which they must originally have been deposited, to the inclined or even vertical positions in which they are now so often found. There were two possible explanations: (1) that the sea had formerly stood at a higher level and had in fact extended over the whole earth’s surface, or (2) that the strata had been upraised and disturbed. By 1831 most geologists had rejected the idea that the sea had formerly covered the whole earth, but when they tried to imagine forces capable of raising rock strata from the bottom of the sea to form hills or ranges of mountains, it seemed to them that such changes would necessarily involve tremendous convulsions of the earth’s surface. Furthermore, they saw a link between periods of convulsion and upheaval in the history of the earth and changes in animal life. They concluded, naturally, that a convulsion of the earth’s surface tended to destroy many species of animals and that when the convulsion had subsided new species were created to replace those that had been lost.

In the view of the catastrophists, there had been in the history of the earth a succession of creations of animal and plant life. Each creation had survived during a period of relative tranquillity of the earth’s surface, but had later been destroyed in a catastrophic disturbance and upheaval. The history of the earth therefore included periods of tranquillity interrupted by catastrophes, and each catastrophe was followed by a new creation. The catastrophic theory of geological history was reconciled to the account of creation in the Bible by supposing that the most recent catastrophe had been the flood of Noah. Many fossil animals were therefore characterized as antediluvian, or from before the flood. Geologists also supposed that the successive creations were of a progressively higher order which culminated finally in the creation of man.

Since the time of the flood the surface of the earth had been fixed, stable, and unchanging and the whole system of nature tranquil and orderly. The modern order of nature, catastrophists thought, was so very different from that which had existed throughout most of the history of the earth that little could be inferred of past events from present conditions.

The catastrophist viewpoint, firmly held by such English geologists as William Buckland, William Daniel Conybeare, and Adam Sedgwick, was challenged in 1830 by Charles Lyell in his Principles of Geology. Lyell had concluded that strata could be elevated from the bottom of the sea by the repeated action of earthquakes continued over long periods of time. In Italy and Sicily he had found recently elevated strata in the neighborhood of active volcanoes and in an area where severe earthquakes had occurred frequently throughout historic time. He showed to his own satisfaction that the strata had been elevated very gradually over an immense period of time, instead of by a single convulsion, and then went on to investigate how far the phenomena of geology might be explained by the various forces observable on the earth’s surface today. With great success he showed that the ordinary action of rain, running water, and the waves of the sea was sufficient to explain the wearing down of land and deposition of sediments, whereas the ordinary, long-continued action of volcanoes and earthquakes was sufficient to elevate continents and mountain ranges.

When Darwin sailed in the Beagle, he had with him the first volume of Lyell’s Principles of Geology (1830), which he had been advised to read but on no account to believe. That is, however, exactly what Darwin did, because he satisfied himself that Lyell’s views accorded with the facts: the first step in the making of a man of science possessed of critical judgment.

Santiago in the Cape Verde Islands provided Darwin’s first material for geological study. By applying Lyell’s principles, he quickly unraveled the history of the island. From the clear exposure of the rocks on the coast he saw that the oldest were crystalline and volcanic. Overlying them was a bed of limestone containing shells of marine organisms of Tertiary date, sixty feet above sea level and twenty feet thick. This bed, Darwin reasoned, had been deposited in a shallow sea and had since been raised to its present height; the island had undergone subsidence and then elevation. Above the limestone was more recent volcanic rock which had altered the uppermost limestone and baked it; evidence of metamorphism in situ.

St. Paul’s Rocks in mid-Atlantic enabled him to make acquaintance with an island which he correctly recognized as being of neither volcanic nor coralline origin; it is regarded today as an exposed portion of the mantle of the earth. But it was South America that presented itself as a model for his observational and interpretative skill. By comparing lavas of undoubted volcanic origin with igneous rocks of the Andes, he saw that they were closely related. He found that minerals in granites and in lavas were in all respects similar, and he showed a perfect graded series between crystalline granites and glasslike lavas. By observing the direction of strike and the angle of dip of strata, he found that the planes of foliation in schists and gneisses and the planes of cleavage in slates remained constant over areas stretching hundreds of miles, while their planes of inclination could vary greatly. Foliation planes and cleavage planes were parallel to the direction of the great axes along which elevation of the land had taken place. This was directly contrary to the then accepted views put forward by Sedgwick and by Lyell, and Darwin was able to prove that foliation and cleavage are not original phenomena dependent on the deposition of the strata, but had been subsequently superimposed on the beds by pressure, resulting in recrystallization in the case of foliation. He observed clay slate passing over into gneiss as it approached granite, which showed how homogeneous rocks could develop foliation by metamorphosis. Darwin’s demonstration of the origin of metamorphic rocks by deformation and of the distinction between cleavage and sedimentary bedding was a major contribution to geology.

The west coast of South America was an equally fruitful geological laboratory for Darwin. He was a witness to the earthquake that devastated Concepción and saw that it had resulted in an elevation of the land by several feet. He was further able to make out a connection between elevation of the land and neighboring volcanic activity because at the time when the land rose near Concepción a number of volcanoes in the Andes renewed their activity, and a new volcano beneath the sea erupted near Juan Fernandez. All these facts were shortly to be woven into an unexpected pattern.

By observing that the shells in beds raised to heights of as much as 1,300 feet belonged to species still living, and in proportions of species similar to those in the ocean, Darwin was able to prove, as Lyell had in Sicily, that such elevation was recent. In the Andes, at a height of 7,000 feet, he found a fossil forest of trees in situ (i. e., not drifted from elsewhere) because their trunks projected several feet perpendicularly from the stratum in which they were embedded, which was itself overlaid by thousands of feet of sedimentary deposits alternating with volcanic lavas. This showed that the trees had been buried thousands of feet beneath sea level as the deposits accumulated, and had since been raised to their present height. Here was proof of extensive subsidence as well as elevation.

Beds containing shells that had been raised up were far fewer and much less extensive than low-lying beds, and Darwin found that this was due to the erosion that constantly attacks land surfaces and destroys deposits. This fact had a bearing on estimations of the age of the earth, because while the time taken for a deposit to be formed can be roughly gauged, it is impossible to tell how long an interval of time has gone by while the beds were eroded. This means that the nonconformities between geological formations may represent much longer periods of time than the formation of the beds themselves, and that the age of the earth must be vastly greater than was then imagined.

From these findings, Darwin was led to consider what are the most favorable conditions for the accumulation of beds many thousands of feet thick containing fossils, such as are found elsewhere. He concluded that it could only have been when a slow subsidence continually lowered the bottom of a shallow sea, so that the depth of that sea below sea level remained fairly constant. These conditions further imply that such a sea was near to continental land, from which erosion brought down the material spread out in the deposits. Proof of this was obtained in observation of beds south of Valparaiso, 800 feet thick, containing shells of animals which when alive lived in shallow water, not more than 100 feet deep. The lowest beds of the deposit must have lain 700 feet higher than at present when the first shells became embedded, and as subsidence started the deposits continued and kept pace with the drop of 700 feet. Another bed showed evidence of the same process involving a subsidence and deposits of 6,000 feet. The various conditions required for such accumulations of fossils can only have been met occasionally and at particular localities in the history of the earth, from which it follows that the fossil record must be expected to be erratic and incomplete.

Another line of study to which Darwin was led by his expeditions in the Andes was the change in climate which regions must have undergone, both in geological time and during the life of man. This followed from observation of deserted houses, abandoned by Indians, up to the snowline in places now quite uninhabitable because of lack of water and fertility. This connection between geological phenomena and life was further developed in his studies of coral reefs.

While in South American waters, Darwin had never seen a coral reef, but he knew that atolls in their myriads all over the oceans are about at sea level, and that the coral polyps which build them can live only in waters less than 120 feet deep and at temperatures above 20°C. The theory of the origin of atolls, or lagoon islands, developed by Lyell, was that they were formed on the rims of submarine volcanic craters. Darwin quickly saw that such a hypothesis was untenable, and he put forward his own deductively. There must have been a foundation for the corals at a depth not exceeding 120 feet. It cannot be imagined that there were innumerable submarine mountain ranges with their summits all exactly at this height; therefore, they must have been brought to the required level by subsidence, and he found evidence for it in drowned villages in the Caroline Islands. This has since been confirmed by deep borings at Funafuti, at Bikini, and at Eniwetok, where evidence has been found of over 4,600 feet of coral rock produced by shallow-water organisms during prolonged subsidence.

In addition to atolls or lagoon-islands, there are also barrier reefs, like the Great Barrier Reef of Australia, which is known to have been erected by coral polyps on the down-faulted coastal edge of northeast Australia. Darwin observed a third type of coral reef, the fringing reefs or shore-reefs that surround an island which projects high above the sea, and these reefs are often found lifted above sea level. Fringing reefs are therefore the result of coral action on platforms that are either stationary or have undergone elevation. With all this evidence, Darwin drew a map. He found that large zones of the Pacific Ocean have atolls and barrier reefs and have undergone subsidence, while other zones, parallel to these, have fringing reefs and have undergone elevation. Now the most extraordinary correlation with these facts, bearing in mind Darwin’s observations of the connection between land elevation and volcanic activity, was the distribution of active volcanoes in the Pacific: all of them are situated in the zone of fringing reefs, not one of them in the zone of atolls or barrier reefs. Darwin’s book on Coral Reefs, published in 1842, still remains the accepted explanation, except for a slight addition in the form of R. A. Daly’s glacial control theory. This is based on the fact that during the recent Ice Ages, the amount of water immobilized in icecaps reduced the level of the oceans by 150 feet, which would have exposed the atolls to the air and cut down their height by wave-action. But when the Ice Age came to an end and the sea level rose again, the platforms were there for coral polyps to make new atolls.

The evidence which Darwin obtained in South America and in atolls for changes of sea level was later responsible for leading him into error. In 1838 in attempting to explain the Parallel Roads of Glen Roy in Scotland, Darwin imagined that the land had sunk by over 1,000 feet and that the so-called roads were marine beaches. In 1862 it was shown by T. F. Jamieson that the glaciers of Ben Nevis had dammed back the waters of a lake, the level of which dropped twice as outlets were formed, and that the roads were lake beaches. Darwin admitted defeat in words which have an important message for all scientific research workers: “How rash it is in science to argue because any case is not one thing, it must be some second thing, which happens to be known to the writer…. My error has been a good lesson to me never to trust in science to the principle of exclusion”.

Darwin’s trilogy of geological books was completed by the publication in 1844 of Volcanic Island, and at the end of 1846 by Geological Observations on South America. The supremacy of the position which geology occupied in Darwin’s mind shortly after his return from the voyage of the Beagle is shown by the order of subjects in the title of the first edition, published in August 1839, of his Journal of Researches into the Geology and Natural History of the Various Countries Visited by H. M. S. Beagle. In the second edition, published in August 1845, natural history and geology have changed places. The reason for this is to be found in the progressive orientation of Darwin’s mind toward the problem of evolution.

Evolution and Natural Selection. When Darwin sailed in the Beagle, he had no reason to call in question the accepted view that the species of plants and animals alive on earth were as they had always been since the creation. It was only gradually that doubts began. They arose from four kinds of evidence. The first was that in some areas species had become extinct. Darwin himself had found gigantic fossil armadillos (and other forms) in South America; but armadillos of similar but not identical form also live in South America. This meant that “extinct animals have a close relation in form with extinct species.” Why was this?

Second, in adjacent areas of South America, Darwin found one species replaced by different, although very similar, species. On the pampas he observed and collected specimens of the South American ostrich (rhea), but when he went farther south into Patagonia, he found a very similar but smaller species (Rhea darwinii). But why were the two species of rheas built on the same plan, different from that of the African ostriches? Why were the agoutis and vizcachas of South America built on the same plan as other South American rodents and not on that of North American or European hares and rabbits?

The third doubt was evoked by the fact that inhabitants of oceanic islands tended to resemble species found in the neighboring continents; African-like species in the Cape Verde Islands, South American-like species in the Galápagos archipelago. At the same time, although the geological and physical features of the Cape Verde and Galápagos Islands are very similar, their faunas are quite different. Why was this?

Finally, the different Galápagos islands, identical in climate and physical features, and very close to each other, might be expected to have identical species, but they had not. On different islands he observed that the finches characteristic of the Galápagos group differed in structure and food habits. Some ate insects, others ate seeds, and their sizes and their bills differed in relation to their diets and mode of life. Darwin suspected that they were only varieties of a single species. The local inhabitants could also tell at sight from which island any of the giant tortoises had come. Was all this arbitrary and meaningless or could a pattern of meaning be discerned?

The answer gradually came to Darwin: All these questions, and many more, could be rationally answered if species did not remain immutable but changed into other species, and diverged, so that one species could have given rise to two or more. It is because they had a common ancestor in South America that fossil armadillos resemble living armadillos, that agoutis resemble capybaras, and that the Galápagos birds resemble South American birds, while the Cape Verde birds resemble African birds with which in each case they had a common ancestor. But why did the finches and other birds of each Galápagos island differ from one another? “One might really fancy that, from an original paucity of birds in this archipelago, one species had been taken and modified for different ends,” Darwin wrote. These “ends” are very important; they fit the animals for their mode of life, they are adaptations; and the isolation of each species on each island plays an important part.

Gradually, only a few months after his return to England, these ideas began to crystallize in Darwin’s mind: “Animals, our fellow brethren in pain, disease, death, suffering and famine—our slaves in the most laborious works, our companions in our amusements—they may partake of our origin in one common ancestor—we may be all netted together.”

In July 1837 Darwin started writing down his ideas at random in his Notebook on Transmutation of Species. He soon found that if change of species had occurred, there was a ready explanation for a number of otherwise arbitrary and inexplicable facts. Why are the bones of the arm of a man, the foreleg of a dog and a horse, the wing of a bat, and the flipper of a seal built on the same general plan, with the different bones corresponding, each to each? Why are young embryos of lizards, chicks, and rabbits so similar to each other, while their adults are so distinct? Why do some animals have useless rudiments of organs? Why do particular regions of the earth have their characteristic plants and animals? Why do organisms fall into groups, namely, species, that may be arranged in larger groups, namely, genera, that in turn may be arranged in still larger groups, namely, families, and so on? Why is there this apparent relationship of species instead of a random distribution of forms across the whole field of possibilities? Why do more or less similar organisms behave in similar ways? For instance, why do both horses and men yawn; why do both orangutans and men show emotional distress by weeping? Why do fossils in early geological formations differ greatly from those living today, while those from more recent formations differ only slightly?

All these questions could be meaningfully answered if species were related by descent from common ancesters, but not otherwise. It is important to note Darwin’s form of argument. He never claimed to demonstrate the change of one species into another, and in his letters constantly repeated that he was tired of impressing this fact on his readers and critics; all that he claimed was that if evolution has occurred, it explains a host of otherwise inexplicable facts. But after he had satisfied himself that evolution had occurred, he kept his views to himself because he saw the great obstacles that lay ahead. Evolution he already saw as the change that species undergo in relation to their adaptation to their environment. A woodpecker differs from other birds in that it has two claws of its feet directed backward, with which it secures a firm grasp on the trunk of a tree, stiff tail feathers with which it supports itself against the tree, a stout bill with which it chisels a hole in the bark, and a very long tongue which it projects through the chiseled hole to extract the grubs beneath the bark. The woodpecker must have evolved these adaptations. How?

In considering this question of how evolution might have occurred, Darwin noticed that the cultivation of plants and the domestication and breeding of animals, both of which man has practiced since the Neolithic period, were the result of selection. Man deliberately chose the parents of the next generation of his plants and animals, to perpetuate and improve the qualities in them which he required. But how did, or could, selection operate in nature, where there had been no man to direct it, since the beginning of life on earth? Darwin had already observed that some species are better adapted than others to life in particular environments, and thus are likely to leave more descendants, while the less well adapted may diminish and become extinct (Notebook 1, MS. p. 37, notebook finished in February 1838). In other words, he had already grasped the principle of natural selection before he saw how it was enforced in nature.

The solution to this problem came to him on 28 September 1838 when he read Thomas Robert Malthus’ Essay on the Principle of Population. Malthus, whose whole line of thought was tinged with opposition to the principles of egalitarianism displayed by the French Revolution, argued that since the potential rate of increase in man was geometrical, and that his population could double in twenty-five years, while the increase of available foodstuffs could not increase so fast, there was bound to be misery, poverty, starvation, and death among the poor unless the rate of population increase in man was checked by war, famine, disease, or voluntary restraint (which would diminish the incentive to work among the poor).

Malthus, therefore, demonstrated the relentless pressure which human populations, by their boundless tendency to grow, maintain on their requirements for life whatever the level of their resources may be. If the food supply and other requirements for life can be increased, a population will tend to grow until its growth presses against the limits of the enlarged supply of food. Malthus also observed that in many countries the population did not grow and much of his book is taken up with a study of the means by which the numbers of people were limited in different countries. These ranged from exposure of infants, infanticide, and the intermittent reduction of the population by famine in China, to delayed marriage and strict sexual morality in Norway. But Malthus was able to show that in every country the tendency of a human population to grow was under some form of severe and continued restraint.

Darwin pounced on the argument and applied it, not to man, but to plants and animals in nature, and saw that they are in no position to increase their food supplies, but must die if they outstrip them by their own numbers. Here were the sanctions that made natural selection work.

Like most flashes of genius, it was very simple, and T. H. Huxley said later, “How extremely stupid not to have thought of that.” It marked a turning point, not only in the history of science, but in the history of ideas in general, for there is no field of human intellectual endeavor that has not been influenced by the thought and fact of evolution. By good fortune, the note that Darwin scribbled down immediately when the flash struck him has been preserved. It is of such importance that it deserves quotation:

28th [September 1838] We ought to be far from wondering of changes in numbers of species, from small changes in nature of locality. Even the energetic language of De Candolle does not convey the warring of species as inference from Malthus. Increase of brutes must be prevented solely by positive checks, excepting that famine may stop desire. In Nature production does not increase, whilst no check prevail, but the positive check of famine and consequently death. I do not doubt every one till he thinks deeply has assumed that increase of animals exactly proportionate to the number that can live.

Population is increase at geometrical ratio in FAR SHORTER time than 25 years, yet until the one sentence of Malthus no one clearly perceived the great check amongst men. There is [a] spring, like food used for other purposes as wheat for making brandy. Even a few years plenty makes population in man increase and an ordinun crop causes a dearth. Take Europe, on an average every species must have same number killed year with year by hawks, by cold etc. even one species of hawk decreasing in number must affect instantaneously all the rest. The final cause of all this wedging, must be to sort out proper structure, and adapt it to changes, to do that for form which Malthus shows is the final effect (by means however of volition) of this populousness on the energy of man. One may say there is a force like a hundred thousand wedges trying to force every kind of adapted structure into the gaps in the oeconomy of nature, or rather forming gaps by thrusting out weaker ones.

This passage, in which Darwin’s thought penetrates through a jungle of ideas, following on his reading of Candolle’s description of the war of nature and Malthus’ book, is remarkable for a number of reasons. In the first place it pinpoints the notion that evolution does not take place in a vacuum, but each individual, if it is lucky, lodges in its fortified position in the economy of nature, in what is now called its ecological niche, in dynamic equilibrium not only with the physical factors of the environment, but with the other living organisms of the habitat. It is because Darwin recognized this fact so clearly that he can be reckoned as the founder of the science of ecology.

Second, this passage shows that evolution is not a process that goes on in single individuals, or even in Paris, but which proceeds in populations and consists of some individuals becoming better adapted, under the pressure of natural selection, which is the third lesson of this passage. Ernst Mayr has pointed out that one of the most important recent advances in biology has been the realization that the real units are populations, which have objective existence, and not types (which are only imaginary abstractions), and that Darwin was more responsible than anyone else for the substitution of “population-thinking” for “typological thinking.” The change to a different species is nothing but a by-product of the process of a species becoming better adapted, after a certain point of divergence has been reached. The explanation of the fact of divergence itself is foreshadowed in the passage. As Darwin later wrote, “The more diversified the descendants of any one species become in structure, constitution and habits, by so much will they be better enabled to seize on many and widely diversified places in the polity of nature.” Again, it is the ecological niches which supply the key to the problem.

Darwin’s argument can be formulated as follows: (1) The numbers of individuals in species in nature remain more or less constant. (2) There is an enormous overproduction of pollen, seeds, eggs, larvae. (3) Therefore, there must be high mortality. (4) All individuals in a species are not identical, but show variation and differ from one another in innumerable anatomical, physiological, and behavioristic respects. (5) Therefore, some will be better adapted than others to their conditions of life and to the ecological niches which they could occupy, will survive more frequently in the competition for existence, will leave more off-spring, and will contribute most of the parents that will produce the next generation. (6) Hereditary resemblance between parents and offspring is a fact. (7) Therefore, successive generations will not only maintain but improve their degree of adaptation to their modes of life, i.e., to the conditions of their environments, and as these conditions vary in different places, successive generations will not only come to differ from their parents, but also from each other and give rise to divergent stocks issuing from common ancestors.

This is the formal theory of evolution by natural selection, which recent observation and controlled experiment have proved to be correct in all cases. What modern biology has done is to provide answers to the two questions which, in the state of knowledge of his time, Darwin could not answer: what is the nature of hereditary transmission between parents (and grandparents, and so forth) and offspring? And what is the nature of the origin of heritable variation? Without heritable variation, natural selection could achieve nothing. In Darwin’s day, no clear distinction was made between what was heritable and what was not, and few doubted the inheritance of characters acquired by a parent during its own life.

The problem was completely solved (unknown to Darwin, or to the world before 1900) by Gregor Mendel, who proved that the basis of inheritance takes the form of particulate characters, distributed between parents and offspring in accordance with a simple law (since proved by cytology and the behavior of chromosomes) known as Mendel’s law of segregation. The inception of a heritable novelty was a sport, now known as a mutation, a random, nonadaptive change in the chemical structure of a particular character, now known as a gene. The application of Mendelian genetics to Darwinian selection was effected by the work of J. B. S. Haldane and Sir Ronald Fisher by 1930. Since then the synthetic theory of evolution by natural selection has been generally accepted by biologists. It is remarkable that even without the knowledge that these advances represent, to say nothing of those achieved in comparative biochemistry, serology, parasitology, and cytogenetics, Darwin was nevertheless able to construct a coherent theory which made general acceptance of evolution possible—and a mechanism to account for it, namely, natural selection. Although long considered inadequate, natural selection is now proved to be the basis for biological change and for the production of all the diverse structures and functions of living organisms.

Shortly before Darwin died, his son Leonard asked him how long he thought that it would be before positive evidence of natural selection would be forthcoming. Darwin replied, about fifty years. It was a remarkably accurate forecast, for it was in the 1930’s that Sir Ronald Fisher showed how expression of a gene, in the form of the bodily character that it controls, is itself the effect of selection. Shortly afterward, E. B. Ford demonstrated that mimetic resemblance in butterflies is adaptive, confers survival value, and originates from heritable variation. The researches of H. B. D. Kettlewell on industrial melanism in moths, P. M. Sheppard and A. J. Cain in snails, T. Dobzhansky on geographical races of fruit flies, and A. C. Allison on sickle cell in man have provided experimental evidence not only of natural selection but of the pressure at which it works, and have permitted actuarial estimates of the longevity of different genetic types. This follows the mathematical studies of Sir Ronald Fisher, Sewall Wright, and J. B. S. Haldane on the effects of selection at different intensities on the composition of populations.

Studies on what B. Rensch has called “ring-races” has shown species in the act of splitting into new species, in gulls, tits, and salamanders, when geographical isolation of portions of populations enables them to evolve independently of each other, so that they become adapted in different directions and eventually no longer interbreed. This speciation is what T. H. Huxley regarded as necessary for the final confirmation of Darwin’s views.

Paleontology has been a trap for biologists and others who have neglected David Hume’s warning that the existence of a state of affairs does not in itself justify conclusions on how it came about.

Darwin claimed that the fossil record, as known to him, was compatible with evolution; but that if fossils ever provided any evidence contrary to his theory, such, for instance, as to prove that the Cambrian fossils were the first organisms that ever lived, or that a mammal was “created” later than those earliest known mammals of the Stonesfield Slate of the Jurassic period, his theory of evolution must be abandoned. However, he never adduced any evidence from fossils to bear on the problem of the principle of natural selection.

Although the recognition of fossils as former living beings goes back four centuries, it is only recently that paleontology has come into its own as a science, largely as a result of the researches of George G. Simpson. Fully aware that the mechanism of evolution can be interpreted only in terms of genetics, ecology, selection, and population studies, Simpson has shown that evolutionary sequences previously claimed as “straight” are not straight at all. For example, the evolutionary history of the horse has followed a zigzag course, first in the direction of many-toed browsers on leaves, then in that of many-toed grazers on grass, and finally in that of one-toed grazers on grass. In general the horse increased in size, but some species became smaller. Each lap of the course can be correlated with the environmental conditions of the period: soft or hard ground, leafy or grassy (siliceous) vegetation. At all times the trend has been toward favorable adaptations, to ecological niches which paleontologists are now in a position to describe; in other words, it has been compatible with the requirements of natural selection and has been opportunistic and devoid of any predetermined program. Furthermore, the rate of evolution, now measurable by radioactive dating, is not correlated with variability, nor with fertility (years per generation). In this manner, Simpson has been able to show that natural selection under changing environmental conditions accounts for evolution, and explains why in terrestrial forms evolution has generally been rapid, while in marine forms it has been slow or stationary.

It is regrettable that Darwin in later years allowed himself to be persuaded to accept Herbert Spencer’s inappropriate expression “survival of the fittest.” This stresses survival when the important thing is the greater fecundity of the better adapted; it emphasizes a superlative “fittest” when it is the slightest comparative superiority of adaptation that confers advantage. It lays the subject open to the taunt of tautology: Who survive? The fittest. Which are the fittest? Those who survive. This is a form of argument which neglects entirely the fundamental fact that forms better adapted to their environment leave more offspring. Finally, the phrase conveys no inkling that the automatic choice exerted by nature in ramming the better adapted variants into their ecological niches is the efficient cause of adaptation. It was not the first (or last) time that so-called philosophers of science have encumbered scientists with their help.

After Darwin had developed his new theory of the origin of species by natural selection in 1838, he did not publish it, or even discuss it with his friends. In 1842 he drew up a rough sketch of his argument, which in 1844 he expanded into an essay but never published. In 1845 when he had finished preparing for publication the results of his geological work on the Beagle voyage, he put the species question aside and started on eight tedious years’ study of the structure and classification of living and fossil barnacles. In the course of this work he acquired firsthand knowledge of the amount of variation that is found in nature, and he also made a striking discovery, that of complemental males, small parasitic males found under the mantle of larger hermaphrodite or female individuals.

After his return to England in 1836 Darwin became close friends with Charles Lyell and Joseph Dalton Hooker. They did not accept evolution, which was known to them only in the form of Lamarck’s exposition. Lamarck’s views were in many ways similar to those of Erasmus Darwin, who posited that there was a “natural tendency” to perfection, and the “inner a feelings” of an animal caused it to provide the organs required to meet its needs. In 1844 Robert Chambers published Vestiges of the Natural History of Creation, which only brought the subject into disrepute by its amateurish ignorance.

In April 1856 Darwin described his theory of natural selection to Lyell, who urged him to write a book describing his views on species. He began the work in the summer of 1856. On 18 June 1858 Darwin received a letter from Alfred Russel Wallace containing a perfect summary of the views which he had worked out during the preceding twenty years. Thanks to Lyell and to Hooker, Darwin’s and Wallace’s papers were read together before the Linnean Society of London on 1 July 1858 and published on 20 August of that year.

Darwin then set about writing an “abstract” of his larger work, and On the Origin of Species was published on 24 November 1859. The fat was then in the fire. Old-fashioned biologists protested that Darwin indulged in hypotheses that he could not prove (and he did not pretend to prove them). Theologians were aghast at two consequences of Darwin’s work; the first was that man and the apes must have had a common ancestor, which dislodged man from his privileged position as created by God in his own image. The second arose from the consideration that if Darwin’s views on the origins of plants and animals, including man, by natural selection were true, then much of the argument for the existence of God based on the presence of design in nature was destroyed. The theologian William Paley had argued that highly specialized and coordinated adaptations, such as the tongue, beak, claws, and tail of the woodpecker, or the human hand, manifested a complex design which required one to postulate the presence of a designer in nature. If, however, these same adaptations could be accounted for by natural selection acting on random variations, a designer was no longer needed. Since natural theology, as represented by Paley, had enjoyed enormous influence in England, the destruction of its very foundations was greeted with dismay and outrage.

Matters came to a head at the celebrated Oxford meeting of the British Association for the Advancement of Science on 30 June 1860, when the Reverend Samuel Wilberforce, bishop of Oxford (who knew little of natural history but was coached by the anatomist Richard Owen, who was jealous at what he felt already was Darwin’s ascendancy over himself), twitted Darwin’s friend Thomas Henry Huxley with the question whether it was through his father or his mother that he claimed descent from an ape. Huxley replied that he was not ashamed to be descended from an ape but he would be ashamed of an ancestor who used great gifts and eloquence in the service of falsehood. Wilberforce was annihilated by Huxley and Hooker, and Darwin’s views on evolution started their conquest of the world. In the United States, Darwin’s friend, the botanist Asa Gray, had already won a victory over the anatomist and paleontologist Louis Agassiz, who was never able to accept Darwin’s theory.

After the Origin of Species, Darwin wrote three more books expanding different aspects of the work. The Variation of Animals and Plants Under Domestication (1868) took up in detail that subject which had been confined to one chapter of the Origin. It contained his hypothesis of pangenesis, by means of which Darwin tried to frame an explanation of hereditary resemblance, inheritance of acquired characters, atavism, and regeneration. It was a brave attempt to account for a number of phenomena which were beyond the bounds of scientific knowledge in his day, such as fertilization by the union of sperm with egg, the mechanism of chromosomal inheritance, and the development of the embryo by successive cell division. His hypothesis of pangenesis could not therefore give a permanently acceptable account of the multitude of phenomena it was designed to explain. It was, however, a point of departure for particulate theories of inheritance in the later nineteenth century.

Darwin’s next book, The Descent of Man (1871), filled in what was only adumbrated in the Origin. T. H. Huxley and W. H. Flower had shown already that the body of man differs less from that of an ape than the latter does from that of a monkey. It is important to remember that Darwin never claimed that man was descended from apes, but that man’s ancestor, if alive today, would be classified among the Primates, and would be even lower in the scale than the apes. Man and apes are subject to similar psychological and physiological processes in courtship, reproduction, menstruation, gestation, birth, lactation, and childhood. At early stages of embryonic development the human fetus has a tail, inherited from ancestors who not only had a tail as embryos but also as adults and were quadrupedal. Darwin wrote, “The time will before long come when it will be thought wonderful, that naturalists, who were well acquainted with the comparative structure and development of man and other animals, should have believed that each was the work of a separate act of creation.”

Having proved his point with man’s body, Darwin then turned to the most difficult aspect, man’s mind. Here he showed that the gap, however enormous between man and the highest animal, is not unbridgeable, by the principle of gradation. Man shares with animals the urge to self-preservation, sexual love, maternal affection, paternal protection, and the senses of pleasure, pain, courage, pride, shame, excitement, boredom, wonder, curiosity, imitation, attention, and memory. As for the moral sense, Darwin concluded that it, also, arose gradually, through evolution, and that any animal endowed with social instincts, which man’s ancestors undoubtedly possessed, would acquire a moral sense as soon as its intellectual powers had developed (by natural selection) to an extent comparable with those of man and was able to appreciate the survival value of collaboration and mutual affection. Borrowing from Marcus Aurelius the view that social instincts are the prime principles of man’s moral constitution, Darwin concluded that these, with the aid of intellectual powers and the effects of new tradition and habits, would lead naturally to the Golden Rule: “As ye would that men should do to you, do ye to them likewise.”

In this book Darwin added an essay on a related subject: sexual selection, the preferential chances of mating that some individuals of one sex (usually the male) have over their rivals because of special structures, colors, and types of behavior used in courtship displays, leading them to leave more offspring and accentuate their characters: for example, antlers in deer, trains in peacocks, feathers in birds of paradise, color in sticklebacks. There is no need to assume a power of aesthetic choice in either sex; the characters act as sexual stimulants, real aphrodisiacs, so that mating follows more quickly, occurs more often, and there are more progeny. In man, there can be no doubt that the differences between the sexes in respect of distribution of hair on face and body and of fat in local accumulations under the skin are the result of sexual selection.

Darwin did not explain how the preference of females for particular structures, colors, and courtship displays was related to natural selection, although female preferences themselves must be subject to natural selection. Perhaps Darwin’s greatest contribution in this area was to show that secondary sexual characteristics had evolved in relation to a complex pattern of reproductive behavior, which must itself be the product of natural selection.

The last of Darwin’s books in this series, The Expression of the Emotions in Man and Animals (1872), contains studies of facial muscles and means of expression in man and mammals, emission of sounds, erection of hair, and so forth, and their correlation with suffering, sobbing, anxiety, grief, despair, joy, love, devotion, reflection, meditation, sulking, hatred, anger, pride, disdain, shame, surprise, fear, horror, acceptance (affirmation), and rejection (negation). With this book Darwin founded the study of ethology (animal behavior) and conveyance of information (communication theory) and made a major contribution to psychology.

Botanical Works. From the first Darwin interested himself in adaptations of plants to cross-pollination. He found that trees (with countless flowers) tend to have flowers of one sex, while small plants have hermaphrodite flowers, and he showed that the unisexuality of trees would tend to prevent self-pollination. He concluded that “flowers are adapted to be crossed, at least occasionally, by pollen from a different plant.” Here was a general principle which must have a wide meaning, and he set out to study it. His attention was first directed to orchids, which have elaborate adaptations for cross-pollination, making the bees that visit their flowers carry away the pollen sacs with them and pollinate the next flowers that they visit. His book on the Fertilization of Orchids (1862) showed that plants are in no way behind animals in the marvels of the adaptations that they show. Darwin further observed that flowers that are pollinated by wind have no colors; it is only those that are pollinated by insects that have bright colors in their petals and sweet-smelling nectaries.

Presently Darwin noticed that in some species flowers differ by the lengths of their anthers and styles, like the primroses, which show two conditions, or loosestrife, which shows three. This is also an adaptation for cross-pollination, and these observations formed the basis of Different Forms of Flowers on Plants of the Same Species (1877). The problem continued to fascinate him, and he raised two large beds of seedlings of Linaria vuglaris, the one cross-pollinated and the other self-pollinated, all from the same plant. “To my surprise, the crossed plants when fully grown were plainly taller and more vigorous than the self-fertilized ones.” Darwin had experimentally discovered and demonstrated the fact of hybrid vigor, or heterosis, which is completely explained by Mendelian genetics. These experiments, conducted over twelve years on fifty-seven species, led to the publication of Effects of Cross and Self Fertilization (1876). The demonstration of the advantage that accrues from cross-fertilization explains not only why sexual reproduction (as distinct from asexual budding) increases heritable variation (through recombination of genes), but also reveals the basis for the survival value conferred by the existence of different sexes in a species. This adaptation (for that is what it is) is a very old one, for it was inherited by plants and animals before they diverged from one another.

Darwin’s interest in climbing plants was not that of a systematic botanist but an attempt to discover what adaptive value the habit of climbing has. He found that “climbing” is a result of the process of nutation; the apex of the plant’s stem bends to one side while it grows and the plane of the bend itself revolves, clockwise or counterclockwise, so that the apex describes circular sweeping movements. In the hop plant—in hot weather, during daylight hours—it takes a little over two hours for each revolution. If the growing stem hits nothing, it continues to circle; if it hits an object it wraps itself around it by twining, Twining thus enables a young and feeble plant, in one season, to raise its growing point and leaves much higher from the ground, with more exposure to sunlight and air, without expending time and energy in the synthesis of woody supporting tissues. There is a further delicate adaptation here; a twining plant will not twine around an object larger than approximately six inches in diameter. This adaptation prevents it from climbing up a large tree, where it would be deprived of air and sun by the tree’s own leaves.

Some plants climb by a modification of this method and have stalks and leaves that clasp other objects, and intermediate forms show that leaf-climbers evolved from twiners. In others, such as the Virginia creeper, the leaf tendrils end in little discs full of resinous fluid which anchor the plant to its support. These researches were described in Climbing Plants (1875).

The behavior of climbing plants and the bending of their shoots led Darwin to investigate the mechanical cause of such bending. The fact that a stem bends toward the light because it grows faster on the unilluminated than on the illuminated side of the stem had been known for some time. By means of simple but ingenious experiments, Darwin showed that the tip of the shoot was sensitive to light and that the bending was caused by growth of the stem on the side away from the light but some way down from the apex. Furthermore, this growth was due to a substance that comes down from the apex, “some matter in the upper part which is acted upon by light, and which transmits its effects to the lower part.” From these researches and experiments (reported in Power of Movement in Plants, 1880) has sprung the whole science of growth hormones in plants.

Darwin’s chance observation of the number of flies caught on the leaf of the common sundew (Drosera rotundifolia) was the starting point for a series of observations and experiments which showed not only how insects are caught, but how their bodies are digested and ingested, and what the significance of this carnivorous habit is for the life of the plant. By feeding one bed of sundew plants with meat and depriving another bed, he found that the fed plants had larger leaves, taller flowerstalks, and more numerous seed capsules. This remarkable adaptation, which insures survival of the plants, explains why sundew plants, which have very few roots, through which only small supplies of nitrogen can be obtained, can live on extremely poor soil. Darwin was particularly impressed by the fact that the living cells of plants possess a capacity for irritability and response similar to that of the nerve and muscle cells of animals. His work on Insectivorous Plants was published in 1875.

Darwin’s last book connected with plants was The Formation of Vegetable Mould Through the Action of Worms (1881). This was published only six months before his death but covers a subject that he had studied for more than fifty years. He showed the services performed by earthworms in eating leaves and grinding earth in their gizzards and turning it into fertile soil, which they constantly sift and turn over down to a depth of twenty inches from the surface, thereby aerating it. He calculated from the weight of worm-castings that on one acre in one year’s time eighteen tons of soil are brought up to the surface by worms. This was a pioneer study in quantitative ecology.

Darwin was elected to fellowship of the Royal Society in 1839 at the age of twenty-nine; three foreign universities awarded him honorary doctorates; and fifty-seven leading foreign learned societies elected him to honorary or corresponding membership—the French Academy of Sciences only in 1878, for his views have never been really appreciated in France. The Prussian government awarded him the highly coveted Ordre pour le mérite, but from the British sovereign and the British government he never received any recognition. His demonstration of the fact of evolution, and of the automatic mechanism of natural selection which causes it, was unpalatable to the orthodox views of the Church of England. When he died, however, twenty members of Parliament asked the dean of Westminster to allow his burial in Westminster Abbey, an honor which was readily granted. Darwin himself would have been highly amused, for, with his genial sense of humor he once said, “Considering how fiercely I have been attacked by the orthodox, it seems ludicrous that I once intended to be a clergyman.” At his funeral there were present not only his friends Hooker, Huxley, and Wallace, but also James Russell Lowell, the American ambassador, as well as diplomats representing France, Germany, Italy, Spain, and Russia.

BIBLIOGRAPHY

I. Books. Journal of Researches into the Geology and Natural History of the Various Countries Visited by H. M. S. Beagle (London, 1839); facs. repr. (New York, 1952); 2nd ed., Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage of H. M. S. Beagle (London, 1845); repr., intro. by Sir Gavin de Beer (New York, 1956); The Structure and Distribution of Coral Reefs (London, 1842; 2nd ed., 1874); Geological Observations on the Volcanic Islands Visited During the Voyage of H. M. S. Beagle (London, 1844); Geological Observations on South America (London, 1846); A Monograph of the Subclass Cirripedia, 2 vols. (London, 1851, 1854); A Monograph of the Fossil Lepadidae, or Pedunculated Cirripedes of Great Britain (London, 1851); A Monograph of the Fossil Balanidae and Verrucidae (London, 1854); On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (London, 1859; 2nd ed., 1860; 3rd ed., 1861; 4th ed., 1866; 5th ed., 1869; 6th ed., 1872); repr., intro. by Sir Gavin de Beer (London, 1963); 1st American ed. (New York, 1860); variorum text, Morse Peckham, ed. (Philadelphia, 1959); facs. repr. of 1st ed. (Cambridge, Mass., 1964); On the Various Contrivances by Which British and Foreign Orchids are Fertilized by Insects, and on the Good Effects of Intercrossing (London, 1862, 2nd ed., 1877); The Variation of Animals and Plants Under Domestication (London, 1868; 2nd ed., 1875); The Descent of Man, and Selection in Relation to Sex (London, 1871; 2nd ed., 1874); The Expression of the Emotions in Man and Animals (London, 1872); Insectivorous Plants (London, 1875); Climbing Plants (London, 1875); The Effects of Cross and Self Fertilization in the Vegetable Kingdom (London, 1876); The Different Forms of Flowers on Plants of the Same Species (London, 1877); The Power of Movement in Plants, assisted by Francis Darwin (London, 1880); The Formation of Vegetable Mould, Through the Action of Worms, With Observations on Their Habits (London, 1881); repr., intro. by Sir Albert Howard (London, 1961); and a preliminary notice in Ernst Krause, Erasmus Darwin, W. S. Dallas, trans. (London, 1879).

Posthumously published writings include Life and Letters of Charles Darwin, Francis Darwin, ed. (London, 1887); Autobiography (London, 1887), unexpurgated ed., Nora Barlow, ed. (London, 1958); More Letters of Charles Darwin, Francis Darwin and A. C. Seward, eds. (London, 1903); “Sketch” of 1842 and “Essay” of 1844, in Evolution by Natural Selection, foreword by Sir Gavin de Beer (Cambridge, 1958); and the notebooks on transmutation of species, Sir Gavin de Beer, ed., in Bulletin of the British Museum (Natural History), Historical Ser., 2 (1960), 23–200, and 3 (1967), 129–176.

II. Bibliographies. Handlist of the Darwin Papers at the University Library Cambridge (Cambridge, 1960); R. B. Freeman, The Works of Charles Darwin. An Annotated Bibliographical Handlist (London, 1965).

III. Secondary Literature. See Sir Gavin de Beer, “Darwin’s Views on the Relations Between Embryology and Evolution,” in Journal of the Linnean Society of London, 66 (1958), 15–23; “The Origins of Darwin’s Ideas on Evolution and Natural Selection,” in Proceedings of the Royal Society, 155B , 321–338; “Mendel, Darwin, and Fisher,” in Notes and Records of the Royal Society, 19 (1964), 192–226; 21 (1966), 64–71; Atlas of Evolution (London, 1964); and Charles Darwin. A Scientific Biography (New York, 1965).

Also of interest are W. E. Le Gros Clark, Man-Apes or Ape-Men? (New York, 1967); A. Cronquist, The Evolution and Classification of Flowering Plants (London, 1967); T. Dobzhansky, Genetics and the Origin of Species (New York, 1937; 4th ed., 1959); Mankind Evolving (New Haven, 1962); R. A. Fisher, The Genetical Theory of Natural Selection (Oxford, 1930); E. B. Ford, Ecological Genetics (New York, 1964); Bentley Glass, Owsei Temkin, and William R. Strauss, eds., Forerunners of Darwin (Baltimore, 1959); Gerald L. Geison, “Darwin and Heredity: the Evolution of His Hypothesis of Pangenesis,” in Journal of the History of Medicine, 24 (1969), 375–411; Michael T. Ghiselin, The Triumph of the Darwinian Method (Berkeley, 1969); John C. Greene, The Death of Adam. Evolution and Its Impact on Western Thought (Ames, Iowa, 1959); J. B. S. Haldane, The Causes of Evolution (London, 1932); Garett Hardin, Nature and Man’s Fate (London, 1960); Julian Huxley, A. C. Hardy, and E. B. Ford, eds., Evolution as a Process (London, 1954); Julian Huxley, Evolution. The Modern Synthesis (London, 1942; repr., 1963); Ernst Mayr, Animal Species and Evolution (Cambridge, Mass., 1963); Milton Millhauser, Just Before Darwin. Robert Chambers and Vestiges (Middletown, Conn., 1959); Bernard Rensch, Evolution above the Species Level (London, 1959); and Anne Roe and George Gaylord Simpson, eds., Behavior and Evolution (New Haven, 1958).

See also George Gaylord Simpson, The Meaning of Evolution. A Study of the History of Life and of its Significance for Man (London, 1950); Horses. The Story of the Horse Family in the Modern World and Through Sixty Million Years of History (New york, 1951); The Major Features of Evolution (New York, 1953); This View of Life. The World of an Evolutionist (New York, 1964); The Geography of Evolution (Philadelphia-New York, 1965); G. Ledyard Stebbins, Variation and Evolution in Plants (New York, 1957); and Sol Tax, ed., Evolution After Darwin, 3 vols (Chicago, 1960).

On Darwin’s health see Saul Adler, “Darwin’s Illness,” in Nature, 184 (1959), 1102–1103.

Gavin de Beer

Darwin, Charles 1809-1882

DARWIN’S FINCHES AND THE LOGIC OF NATURAL SELECTION

SOME MISCONCEPTIONS ABOUT DARWIN’S THEORY

EVOLUTIONARY PSYCHOLOGY

CONTROVERSIES ABOUT DARWINISM AND HUMAN BEHAVIOR

BIBLIOGRAPHY

Charles Robert Darwin is regarded as one of the greatest scientists who ever lived. He was the son of a wealthy provincial British doctor and entered into the study of medicine at Edinburgh University, but did not like it. He was then expected by his family to become a clergyman and graduated from Cambridge University. However, he was unenthused about pursuing a career in the church.

Fortunately for him, as well as the world of the biological sciences, he was offered an unpaid position assisting the captain of the British survey ship Beagle. From this little ship, Darwin spent the next five years exploring the natural world. His observations fostered a deep interest in biology and geology and motivated him to pursue the sciences as a career and eventually develop the theory of natural selection.

Charles Darwin’s theory of evolution by natural selection is the only scientific explanation for the nature and variety of life on our planet. Moreover, if life in other parts of our galaxy is governed by the same natural laws that govern it here, then Darwin’s logic also explains the verities of life in distant parts of our galaxy. However, it does not explain the origin of life itself. Darwin’s theory leaves the very beginning of life—the formation of the first primitive organic molecules—to chemists, physicists, and maybe even theologians. This entry focuses on the logic of how natural selection shapes the tools that enable organisms to survive the challenges of their environment, on some misconceptions about the theory of evolution, and on how evolutionary theory can help us understand human behavior. Finally, it briefly mentions some of the scientific and political controversies associated with current evolutionary thinking. Those interested in the vast evidence for Darwin’s theory should consult Mark Pagel’s Encyclopedia of Evolution (2002).

DARWIN’S FINCHES AND THE LOGIC OF NATURAL SELECTION

The Galapagos Archipelago is a group of islands off the coast of Peru. Eons ago, a single species of finch landed on one of the islands. Because resources for survival and reproduction were limited, the finches began competing for them. Some finches migrated to other islands. Since the environments of the islands differed, various biological tools, such as the shape of the birds’ beaks, differed in their effectiveness for dealing with these environments. Over time, fourteen species of finches evolved in the archipelago. Although the species vary in many ways, such as in size and coloration, differences in their beaks are particularly salient. The study of how the beaks of Galapagos finches contribute to survival and reproduction in the environments of the different islands has contributed greatly to the development of evolutionary theory (Weiner 1994).

Biological tools that contribute to an individual’s survival and reproduction are called adaptations. An adaptation is a trait—an anatomical structure, physiological process, or behavior pattern—that contributes more to an individual’s ability to survive, grow, or reproduce in comparison with alternate traits in the population. The large, powerful beak of the Geospiza magnirostris finch, useful for cracking large seeds, and the small, delicate beak of Certhidea olivacea, useful for extracting insects from the bark of trees, provide examples. Natural selection is the differential contribution of offspring to the next generation by genetically different members of a population, that is, the number of progeny of finches with genes for different beaks. The logic of natural selection can be explained in terms of assumptions and inferences that follow from the assumptions (Crawford 1998).

Assumption 1: The number of descendents of organisms in a population can grow exponentially.

Assumption 2: Resources enabling individuals in a population to exist can expand only arithmetically.

Assumption 3: The size of a population of individuals remains relatively stable across time.

Inference A: Competition for survival and reproduction ensues between individuals in a population.

Assumption 4: Individuals differ on traits that enable them to survive and reproduce.

Assumption 5: Some of the variation in these traits is genetic in origin.

Inference B: There is “differential contribution of offspring to the next generation by genetically different members of a population” (natural selection, by definition).

Inference C: Over many generations, “anatomical structures, physiological processes or behavior patterns that contribute more to individuals’ ability to survive, grow and reproduce in comparison with alternate traits in the population” (adaptations, by definition) are created.

In summary, some feature of the environment—for example, the arrival of a new predator or a change in climate—poses a problem for organisms in a population. A solution (e.g., longer legs, thicker fur) aids survival and reproduction. The above assumptions and inferences explain how natural selection provides the solution. Preexisting adaptations, sometimes called preadaptations, provide both stepping stones and limits to the solutions natural selection can provide (Pagel 2002).

SOME MISCONCEPTIONS ABOUT DARWIN’S THEORY

Assumptions 1, 2, and 3 do not require nature to be “red in tooth and claw,” as the poet Alfred Tennyson described it in In Memoriam (1850). A variety of subtle, and not so subtle, adaptations help individuals survive and reproduce. For example, animals in herds, such as wildebeests, may minimize the relative risk of predation by maneuvering to place other animals between themselves and predators (Hamilton 1971). Many types of camouflage coloration have evolved to protect organisms from their predators (Pagel 2002).

Although genes are involved in the development of all adaptations, assumptions 4 and 5 do not require that differences between individuals in evolved traits are genetically preprogrammed. Traits whose development is influenced by environmental factors are called facultative traits. Although male white-crowned sparrows, for example, cannot learn the song of another species, when they are nestlings they must hear an adult male of their own species sing and then themselves sing as juveniles if they are to sing a full song as adults (Konishi 1965).

Organisms do not evolve to act for the good of their species or the groups with which they live (Williams 1966). Since an organism’s time and energy are limited, an organism that helped a member of its species or group would pay a reproductive cost (i.e., have fewer offspring) to do the helping. Hence, one of its competitors who did not help would leave more offspring, and its kind would spread through the group or species at the expense of the helpers. However, modern Darwinists have two methods of explaining the widespread helping behavior seen in nature. The first is the evolution of cooperation, in which both parties increase their reproductive success by helping the other (Trivers 1971). The second is through helping genetic kin (Hamilton 1964). Genetic kin, such as brothers and sisters, have copies of genes that are identical to those of common ancestors. If a brother inherited a gene from his mother that predisposes him to help his sister produce offspring, that helping gene can spread through the sister’s offspring (his nieces and nephews) even though it reduces the brother’s own reproductive success. The reason is that the sister has a fifty-fifty chance of inheriting the same helping gene from their mother and passing it on to her children, her brother’s nieces and nephews.

Finally, natural selection does not have a goal. It is a purely mechanical process: traits that contribute more to survival and reproduction spread at the expense of traits that contribute less to survival and reproduction. Humans may evolve to be godlike creatures in the distant future. However, if this happens it will not be because natural selection had the goal of producing such beings.

EVOLUTIONARY PSYCHOLOGY

Evolutionary psychology uses the principles of natural selection to understand the origin and functioning of the cognitive and emotional adaptations that helped us deal with problems in our ancestral environment, known as the environment of evolutionary adaptedness, and how those mechanisms function now (Crawford and Anderson 1989).

Mating of close genetic relatives, for example, can be detrimental to reproduction and survival because it brings together deleterious recessive alleles, such as those causing some genetic diseases, in the offspring of such mates. Some Darwinists have argued that intimate rearing of brothers and sisters during their first few years, which reduces or eliminates adult sexual attraction between them, may reflect one mechanism humans evolved to avoid this problem (Westermarck 1891). This argument is supported by evidence from: (1) boys and girls reared in the same children’s houses in Israeli kibbutzim, who rarely find each other sexually attractive as adults (Shepher 1983); (2) the reduced success of Chinese shim pau marriages, in which a genetically unrelated baby girl is adopted into a family at birth with the expectation that she will marry a son of the family at their sexual maturity (Wolf 1995); and (3) sexual attraction between adult genetic siblings who were separated at birth (Bevc and Silverman 2000).

In the upper panel of Figure 1, the assumption is that brothers and sisters with genes enabling them to develop psychological mechanisms to avoid incest had greater lifetime reproductive success across evolutionary time than those who did not. The result is the ancestral genotype for the avoidance mental mechanism. The ancestral developmental environment—intimate rearing with genetic siblings—produced the genetically organized ancestral cognitive and emotional mechanism(s) (the ancestral phenotype) that reduced sexual attraction between adult childhood intimates. The ancestral immediate environment refers to encounters between sexually mature, ancestral, opposite-sex individuals. Finally, natural selection favored the genes that enabled the development of the avoidance mental mechanisms.

The bottom panel represents an infinitesimal segment of evolutionary time—a few years in an Israeli kibbutz or a Chinese sim pau marriage or the meeting of an adult brother and sister who were reared apart from birth. In all cases, the putative adaptation functions as it evolved to function with respect to childhood intimates. However, because it functions in novel environments, its decision processes produce consequences that do not serve its evolutionary purpose. That is, it does nothing to prevent the mating of the genetic siblings, while reducing the likelihood of the success of the kibbutz and shim pau marriages.

Finally, evolutionary psychology is concerned with: (1) the problems that our hominid and primate ancestors encountered in their daily lives; (2) the psychological adaptations that natural selection shaped to help deal with those problems; and (3) the way the resulting evolved adaptations function in current environments (Crawford and Anderson, 1989).

CONTROVERSIES ABOUT DARWINISM AND HUMAN BEHAVIOR

Because of the great explanatory potential of Darwin’s theory of evolution, it engenders continuing scientific, religious, political, and social controversy. For example, if biologically based race, gender, and social class differences in anatomy, physiology, or behavior exist, then evolutionary theory helps explain their origin and significance (Degler 1991; Pagel 2002). However, the most salient issue—the one that underlies most controversies—is the degree of genetic specialization of evolved cognitive and emotional behavior–producing mechanisms. If natural selection produced primarily general-purpose psychological

mechanisms, as many social anthropologists and social activists argue, then evolutionary theory is of limited use in understanding human behavior. However, if it produced genetically highly-specialized psychological mechanisms, as most evolutionary psychologists argue (Barkow et al. 1992), then it is invaluable for understanding

human mind and behavior and in developing solutions to social problems.

Table 1 shows the consequences for social policy of these two perspectives. The assumption underlying the table is that although specialized peripheral, information-processing mechanisms produce behavior, these specialized mechanisms can be assumed to develop from either a low or a high degree of innate genetic specialization of development. The columns under “Possible States of Nature” describe the possible states of the ancestral genotype shown in Figure 1. The rows indicate the two approaches to developing scientific explanations. Note that several different scientific approaches are listed in each row. The four cells in the table enumerate the outcomes of pairs of possibilities, that is, of pairing a high degree of genetic specialization with the scientific belief in a low degree of genetic specialization. Two cells describe valid outcomes. The two cells labeled “Evolutionary Psychologists’ Risk” and “Social Constructionists’ Risk” describe invalid outcomes. Many social activists, such as feminists and social constructionists, assume that the consequences of either making an evolutionary psychologist’s error or living in a society where ancestral evolved adaptations have an impact on current life, liberty, and happiness are so grave that they reject the possibility of the scientific explanations in the bottom row of the table.

Evolutionary psychologists reject this view. First, they worry about the suffering that could be caused by the social constructionist errors shown in Table 1. Second, they claim that accurate scientific knowledge about the human mind is crucial for developing more caring and harmonious societies. Third, they claim that natural selection has given the human species many evolved cognitive and emotional mechanisms, such as those underlying reciprocity and kinship, which if their functioning is understood can help us produce a better world. Fourth, they claim that evolutionary psychology is in fact an environmentalist discipline (Crawford and Anderson 1989)—the specialized psychological mechanisms that produce behavior, described in Figure 1, evolved to help humans deal with problems and stresses in their environments. Hence, understanding how these evolved cognitive and emotional mechanisms work can help us create better places to pursue life, liberty, and happiness.

SEE ALSO Darwinism, Social; Natural Selection

BIBLIOGRAPHY

Barkow, Jerome, Leda Cosmides, and John Tooby. 1992. The Adapted Mind: Evolutionary Psychology and the Generation of Culture. New York: Oxford University Press.

Bevc, Irene, and Irwin Silverman. 2000. Early Separation and Sibling Incest: A Test of the Revised Westermarck Theory. Evolution and Human Behavior 21: 151-161.

Crawford, Charles. 1998. The Theory of Evolution in the Study of Human Behavior: An Introduction and Overview. In Handbook of Evolutionary Psychology: Ideas, Issues, and Applications, eds. Charles Crawford and Dennis Krebs, 3-42. Mahwah, NJ: Erlbaum.

Crawford, Charles, and Catherine Salmon. 2004. The Essence of Evolutionary Psychology: An Introduction. In Evolutionary Psychology, Public Policy, and Personal Decisions, eds. Charles Crawford and Catherine Salmon, 23-50. Mahwah, NJ: Erlbaum.

Crawford, Charles, and Judith Anderson. 1989. Sociobiology: An Environmentalist Discipline? American Psychologist 44: 1449-1459.

Degler, Carl. 1991. In Search of Human Nature: The Decline and Revival of Darwinism in American Social Thought. New York: Oxford University Press.

Hamilton, William D. 1964. The Genetical Evolution of Social Behavior, I and II. Journal of Theoretical Biology 7: 1-52.

Hamilton, William D. 1971. Geometry of the Selfish Herd. Journal of Theoretical Biology 31: 295-311.

Konishi, M. 1965. The Role of Auditory Feedback in the Control of Vocalization in the White-Crowned Sparrow. Zeitschrift für Tierpsychologie 22: 770-783.

Pagel, Mark. 2002. Encyclopedia of Evolution. Oxford: Oxford University Press.

Shepher, Joseph. 1983. Incest: A Biosocial View. New York: Academic Press.

Trivers, Robert L. 1971. The Evolution of Reciprocal Altruism. The Quarterly Review of Biology 46: 35-57.

Weiner, Jonathan. 1994. The Beak of the Finch: A Story of Evolution in our Time. New York: Knopf.

Westermarck, Edward A. 1891. The History of Human Marriage. New York: Macmillan.

Williams, George C. 1966. Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought. Princeton, NJ: Princeton University Press.

Wolf, Arthur P. 1995. Sexual Attraction and Childhood Association: A Chinese Brief for Edward Westermarck. Stanford, CA: Stanford University Press.

Charles Crawford

Darwin, Charles

WORKS BY DARWIN

SUPPLEMENTARY BIBLIOGRAPHY

Charles Robert Darwin was born in 1809 at Shrewsbury and died in 1882 in Down House in Kent. He was the next to youngest child in a family of four sisters and an older brother. His father, Robert Darwin, was a physician of imposing presence and severe character. His paternal grandfather, Erasmus, had also been a doctor by profession. By avocation, however, Erasmus Darwin was a naturalist, whose Zoönomia, a disquisition in verse on the course of nature, has usually been considered, quite incorrectly, to have been an anticipation of Charles Darwin’s theory of evolution. Darwin’s maternal grandfather was Josiah Wedgwood, founder of the pottery firm and friend of Erasmus Darwin in the Birmingham scientific circle known as the Lunar Society. Darwin belonged, in short, to a provincial family of means and intelligence which associated itself with the professions, intellectual pursuits, and commerce. Although his father expected him to choose a profession, he never needed to earn a living. In 1839 Darwin, too, married a Wedgwood, his cousin Emma. The seven (of ten) children who survived infancy and their descendants have sustained the notable literary and scientific tradition which distinguishes the family.

Originally intended for medicine in his turn, Darwin detested the study of it at the University of Edinburgh. His father allowed him to move to Cambridge, with a view to his becoming a clergyman. At both universities the hobby of natural history absorbed him. He read; he collected beetles and prepared specimens; he went on geological and entomological forays. He might have become a clerical naturalist like Gilbert White, whose Natural History and Antiquities of Selborne had charmed him in boyhood. Instead, a decisive opportunity intervened. In 1831 he was offered the (unpaid) post of naturalist aboard H. M. S. Beagle, then outfitting for a voyage to collect geographical information. This was to be no mere trip around the world. The expedition lasted five years. It was the making of Darwin as a scientist, and it cost him his health. Sir Gavin de Beer’s biography has established the strong probability that the chronic physical prostration which debilitated Darwin throughout the rest of his life was the manifestation of Chagas’ disease, a malady identified only in 1909, which involves infestation of the heart muscle and intestines by Trypanosoma cruzi. These bacteria are carried by the great black bug of the pampas, benchuca (Triatoma infestans), and while in Peru Darwin recorded having watched with careful interest one of these insects biting his finger and engorging itself on his blood.

Darwin returned to England in 1836. On the Origin of Species appeared in 1859. In the interval of over twenty years Darwin published descriptive accounts of the zoological and geological findings of the voyage. His Journal of Researches in 1839 was followed by a series of geological treatises: one on coral reefs in 1842, a second on volcanic islands in 1844, and a third on South America in 1846. These writings won him the reputation of an accurate, thorough, and reliable naturalist. In the early 1850s he published in four volumes a complete study of fossil and living barnacles. Here his work was that of a descriptive biologist of great finesse, capable also in experimental inquiry. Meanwhile, he was quietly maturing his views on evolution, these too deriving from observations and reflections started on the voyage of the Beagle.

Theory in biology. The theoretical originality of Darwin’s central work is more difficult to appreciate than its content is difficult to understand. On the Origin of Species does not on the face of it read like a book animated by theory, either abstruse or abstract. Paragraphs follow one out of another setting forth evidence for the mutability of animals. That notion was not in itself a new one. Intimations and even evidence of the transformation of species had often before been adduced—by Lamarck, by Darwin’s grandfather, and by many others. Certainly Darwin marshaled his materials with a fidelity to fact and a range of relevance that proved telling. Nevertheless, what was original was not the assertion but the explanation of evolution in the theory of natural selection. For that theory constituted a new notion of biological order. Although Darwin’s mundane style tended to obscure its novelty, the Origin is in fact a work of theory; it changed the way of seeing the phenomena of life.

Prior to the assimilation of Darwin’s work, no consensus existed about the mode of biological explanation. Only in the early nineteenth century did biology as a professional discipline emerge from the combination of the tradition of natural history with that of the medical or mechanistic study of anatomy and physiology. In Darwin’s youth two distinct traditions governed the modeling of theory—the one organismic and the other teleological. The former arose in eighteenth-century romantic feeling about nature and harked back to ancient Stoicism. According to that philosophy, nature is the source of vitality, morality, and destiny. Goethe’s vision of universal metamorphosis exemplified this cast of mind, and its foremost scientific exponent was Lamarck. In post-Darwinian polemics Lamarck has often been represented by those hostile to the theory of natural selection as the predecessor who had formulated whatever was original and valid in the doctrine of evolution. That argument is untrue to the facts and unfair to the thought of both Lamarck and Darwin. In Lamarck’s view, cyclic equilibrium obtains in the world between the continuously constitutive forms of activity (electricity, fire, life itself) and the perpetually disintegrating tendency of the physical environment. The innate self-perfecting drive of living beings never altogether prevails over the dead hand of inorganic matter, and the tableau of animals each in its kind represents the highest point to which every species has attained in the continuous process of becoming. Assertions of the inheritance of acquired characters and the law of use and disuse (these are later terms) may, indeed, be found in Lamarck’s writings, although only as incidental to his view of flux and process in the progression of life, not as explaining actual evidence of variations.

Over against this conception of life as plastic power, novel in emphasis and appeal if not in principle, persisted the strong tradition of teleology. Engrained since Aristotle, that habit of mind had survived the scientific revolution of the seventeenth century with its scope reduced to the degree that it had become the mode of explanation appropriate to the description of organisms. Within this restricted domain teleology had if anything been fortified by the popularity in eighteenth-century natural theology of the argument from design, which held that the existence of God is demonstrable in the ease and skill with which He had specially created each species to fit its own environment and manner of life. In scientific practice, moreover, teleology answered in detail to the problems of functional analysis of anatomical structure, exhibiting how in plants and animals the part serves in exact respects the purposes of the whole. Such was Cuvier’s method in comparative anatomy.

Background of “Origin of Species.” The problem of adaptation, in short, was the crux of biological explanation. Aboard the Beagle Darwin already saw it to be so. Leaving home a believer in the fixity of species, like Cuvier or Paley, he had the facts of geographical variation of species continuously borne in upon him throughout the extensive experience of the voyage. He told in his Autobiography what lines of evidence led him first to doubt and then to change his mind:

… I had been deeply impressed by discovering in the Pampean formation great fossil animals covered with armour like that on the existing armadillos; secondly, by the manner in which closely allied animals replace one another in proceeding southwards over the [South American] Continent; and thirdly, by the South American character of most of the productions of the Galapagos archipelago, and more especially by the manner in which they differ slightly on each island of the group. ([1876a] 1958, p. 118)

Upon these manifold indications of variation of species in geographical space the new science of geology superimposed evidence of their modification in time. Stratigraphy had become a definitive science in the decades between 1810 and 1830. The first truly historical science, stratigraphy systematically ordered the geological succession according to the fossil population characteristic of the several formations and systems of the rocks. While an undergraduate, Darwin had worked one summer as assistant to one of the founders of stratigraphy, the Reverend Adam Sedgwick, a professor at Cambridge. Sedgwick, like many among the early geologists, held that the evidence for geological revolutions confirmed Biblical accounts of the Creation and the Flood. That view proved venial scientifically, however, for their intensive study of the fossil record made clear the progression of forms of life in the course of the ages.

Catastrophists of Sedgwick’s persuasion took those ages to be brief and punctuated by cataclysms. Increasingly, however, skeptical critics came to think of the span of the past as very long—long enough for all changes to come about gradually. Indeed, the mentor to whom Darwin professed the deepest of his scientific obligations was not a biologist at all. He was Sir Charles Lyell, whose Principles of Geology, published in three volumes between 1830 and 1833, was the earliest fully comprehensive work in that science. It combated the doctrine of geological catastrophes in the name of the uniformity and virtual eternity of nature and taught Darwin to think of the cumulative efficacy of minute changes operating progressively across vast reaches of time.

Further insights came to Darwin as he puzzled over the problem of species in the months following his return to England in the autumn of 1836. Soon thereafter he started a notebook on the subject, the first in what was to become a voluminous series. He worked the while, so he later said, on Baconian principles, collecting facts wholesale. One of his concerns was inheritable modifications. Such modifications are not to be confused with characteristics acquired, in the Neo-Lamarckian sense, as a consequence of a creature’s individual necessities—the biceps in a blacksmith’s arm, for example. Any theory of evolution must, of course, suppose that the variations which are its subject matter are cumulative over generations. From the outset Darwin had the wit to see that if a theory of evolution were not to beg the question, variations must be supposed random in origin, cumulative in effect, and indefinite in extent. In thinking about how they may be accumulated, Darwin meditated often upon the way in which kennel owners, cattle farmers, stablemen, nurserymen, and pigeon fanciers select stock for breeding—how, operating upon successive generations of domesticated animals and plants, the breeder picks for reproduction those individuals that exhibit the characters desired and thus appears to mold the species.

As early as 1837, then, Darwin had all this: geographical evidence of variation; geological proof of succession; a uniformitarian sense of the history of nature; and the notion of random, heritable, and cumulative modifications in form, modifications produced by a process of selection, albeit an artificial one. Even so, he saw no prospect of oversetting by means of such indirect evidence the well-nigh universal conviction that species are fixed in nature itself, based as that belief was on the universal observation that within the experience of everyone like reproduces like, as well as on the plausible supposition that the adaptation of species to all sorts of specialized lives argues the creation of each to lead just that life we see it living.

Darwin disposed of a set of facts and ideas, in other words, and needed a theory; indeed, he was constantly looking for one. It came in one of those flashes of insight which is better called catalytic than coincidental or subconscious. In October 1838 he chanced to read for distraction Maithus’ essay on population. The argument persuaded him at once [seePopulation, article onpopulation theories; and the biography ofalthus]. It must, indeed, have been familiar, for it was one of the commonplaces of contemporary political economy, requiring only to be brought together with Darwin’s problem for its relevance to flash into his mind:

… being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work. ([1876a] 1958, p. 120)

He worked for twenty years before publishing, although he did write out a draft in 1844 for circulation among friends and colleagues, notably Lyell and J. D. Hooker, the botanist. In May 1856 he at last began writing on an exhaustive scale and completed some ten or eleven chapters in the next year and a half. He thought to call the work “Natural Selection.” Then on June 18, 1858, Darwin had the shock of receiving from Alfred Russel Wallace, a young naturalist who had been investigating the flora and fauna of the Malayan jungle, the manuscript of an evolutionary theory identical with his own although based on much less extensive material, together with a request to send it along to Lyell if it should seem worthy. This coincidence precipitated Darwin’s decision to come before the public. On the advice of Lyell and Hooker he prepared a brief summary of his views to be published jointly with Wallace’s paper. Thereupon he settled down to compose an account that should be full enough to do justice to his materials although reduced in scale from what he had initially intended. It took eight months to write the Origin of Species, which appeared in November 1859.

The circumstances of the publication of the Origin belong, of course, to Darwin’s personal history, not to an account of his science. Suffice it to say that his behavior throughout was entirely honorable. It offers no grounds for the imputation repeated by detractors that he slighted Wallace. (For a general discussion of multiple discoveries in science, see Merton 1961.)

“Origin of Species.” The full title summarizes the argument: On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Addressing himself to the general public, Darwin began with the most familiar matter, the great variations evident among domesticated animals. He thereby called attention to the variability which exists within what are commonly taken to be fixed species and observed that in the breeder’s hands they are malleable: “The key is man’s power of accumulative selection: nature gives successive variations; man adds them up in certain directions useful to him” ([1859] 1964, p. 105). The second chapter extends consideration of the ambiguity of species into nature, and the third attributes the function of selection to the struggle for existence. “Owing to this struggle, variations, however slight, and from whatever cause proceeding, if they be in any degree profitable to the individuals of a species, in their infinitely complex relations to other organic beings and to their physical conditions of life, will tend to the preservation of such individuals, and will generally be inherited by the offspring” (p. 145). Within the species the proportion of favored individuals will increase in successive generations, since by definition these individuals have characteristics with survival value that enable their possessors, merely by living longer than less favored competitors, to produce more descendants similarly equipped. Thus will species alter as time goes on.

The middle chapters of the Origin discuss the laws of variation. Darwin’s masterful control over detail is particularly evident here. There are acute observations on the effects of use and disuse of organs, on the influence of climate, and on the greater variability of species than of genera, the last offering a consideration peculiarly difficult to comprehend on any basis other than his. Darwin expressly excluded the problem of cause. Given the evidence that variations have in fact occurred and are heritable, the theory of natural selection explains the course of variation or change. Indeed, the success of the theory turned on dropping the question of cause, not as uninteresting, but as currently unanswerable, although not necessarily forever so.

In the later chapters Darwin anticipated difficulties and objections. He dealt with instinct, which hardly seems a bodily matter. He acknowledged the problem of extreme specialization and discussed the spectacular beauty of the male in certain species of birds as an extravagance that seems to surpass the humdrum effects of selection. He ascribed the absence of transitional forms to the imperfection of the geological record. He treated sexual preferences and choices as a special case of natural selection rather than as an auxiliary or extraneous factor. In summary let it be said that contemporary evolutionists bear him out on all essential matters. The degree of confirmation of his reasoning and its fidelity to vast reaches of fact is extraordinary when it is also considered that he was necessarily unaware of the twentieth-century discoveries about the fine structure and workings of heredity.

Publication of the Origin was the great event, indeed the raison d’être, of Darwin’s career. His single-mindedness invested the book with a kind of power—a power deriving from the scope as well as from the depth of his thought. Iconoclastic critics have sometimes described the book as dull. Nor does it invite stylistic appreciation. It will repay structural analysis, however, and this is the way to understand Darwin’s merit as a theorist. For this is a work of theory, even though any given sentence expresses only fact or deduction. The art lies in the deployment, not in the expression, and it creates its effect in the way a mosaic does rather than a painting. Each element is a mere bit of stone, every sentence a mere statement; yet a design governs the arrangement and the disposition. There are not many books in just this genre. Burckhardt’s Civilization of the Renaissance in Italy, for example, and perhaps Marx’s Capital (setting aside the disgust which often overlays statements in Marx) are also works in the mid-nineteenth-century mode of factual argumentation which, in the literature of science, Darwin represents at its most powerful.

Darwin did not abandon further science in order to defend his views in the discussion that followed the publication of the Origin, although the pattern of the remaining half of his career was inevitably determined by the response to his book. He followed criticism closely and modified later editions of the Origin in numerous respects which either met or accepted objections without abandoning the position. Not all the revisions proved fortunate. Least felicitous was one he introduced into the subtitle as well as into the text. At Wallace’s urging he substituted Herbert Spencer’s formula, “survival of the fittest,” for his own phrase, “preservation of favoured races” to describe what transpires in the struggle for life in consequence of natural selection. Both the tautology—i.e., survival in a struggle for life—and the ambiguity of the superlative “fittest” confused his proper meaning and obscured the point he had originally emphasized: that the essential feature in the operation of natural selection is not mere survival for its own sake. It is the differential reproductivity of individuals favored adaptively by chance variation, which effect entails an increasing proportion of similarly constituted offspring in a population.

Darwin’s later work. Thenceforth, Darwin was more effective in his other writings, both in substantiation of the theory of natural selection and in affirmation of his remarkable virtuosity in research. He chose problems which combined an appeal to his taste with relevance to evolution. Three major books develop central evolutionary themes more fully than does the Origin. The Variation of Plants and Animals Under Domestication (1868) tells in full zoological and archeological detail how man has bent to his uses very variable breeds—dog and horse, for example, sheep and goat, peacock and guinea fowl—and attributes the contrasting stability of the goose to its never having been taken in as a pet or servant and of the donkey to its having served only the classes of society whose members cannot afford experiments [seeDomestication, article onAnimal domestication]. By way of excursion, at the end of his book Darwin advanced the hypothesis of pangenesis to account for the phenomena of heredity. Here he addressed himself to the complaint that he had not explained how variations are transmitted. The speculation with which he met the criticism has only increased his vulnerability before later critics, for in imagining that the basis of heredity might be generalized throughout the organism (“gemmules” in each structure and organ governing the formation of its counterpart in the offspring), Darwin appeared to have conceded inheritance of acquired characters taken in a Lamarckian sense. It is to be appreciated, however, that Darwin suggested this speculation as a parenthetical aside.

In The Descent of Man (1871) Darwin directed his theory explicitly to the single species Homo sapiens. Much of the book is devoted to developing the evolutionary significance of sexual selection— i.e., the preferential choice of reproductive partner. Apart from that, the argument follows two main lines. The first is physical. The immediate evolutionary forebears of mankind are unknown. Darwin never represented man as deriving from apes. He did establish that man must in all probability be descended from species that are classified among primates, and further, that man and the higher apes resemble each other anatomically more closely than the latter resemble the lower primates.

The second line of argument is behavioristic. Intellectual and social faculties are themselves adaptive and in their variations make for the greater or lesser survival of the creatures that possess them. Other species besides man subsist with the aid of rudimentary or developed forms of social organization and communication, and Darwin could see only differences of degree between these and the characteristics of human community and moral awareness.

The last of Darwin’s expressly evolutionary treatises carries behavioristic comparisons even further. Probably The Expression of the Emotions in Man and Animals (1872) is the most dated of Darwin’s writings. Nevertheless, in comparing phenomena like the physical manifestation of hostility in dog and master—the similarity of the snarling jaw to the drawn lip—and many other states of temper, Darwin did carry biology into treatment of faculties traditionally reserved for moral studies. Reciprocally, he introduced the study of animal behavior into psychology [seeSocial behavior, animal].

In the last decade of his life Darwin put in hand a train of experimental researches mainly botanical in character and published a final series of monographs exhibiting a great variety of novel observations and phenomena. He had already brought out a study of fertilization in orchids—in 1862; in 1877 he issued a second edition, much enlarged in detail. In the same year he published a very acute work on hermaphroditic reproduction in trees and plants. Two years previously, in 1875, he had issued two quite new studies, one on climbing plants (first published in journal form in 1865) and one on insectivorous plants. In 1880 he generalized the former in a book about the power of movement in plants as it resides in root, leaf, stem, and flower. In 1881 he concluded his lifework with an account of the process by which earthworms contribute to the formation of humus: the originality of the subject is characteristic of his acumen, while its choice reflects the modesty of his temperament.

To appreciate the full range of Darwin’s accomplishment as a scientist one must read in these experimental writings as well as in the Origin. The comparison to Newton is often adduced. It is justified. Notable scientists normally excel either in theoretical insight or in experimental virtuosity. Newton and Darwin were capable as very few have ever been, and perhaps none in equal measure, of combining those veins and thereby achieving the foremost stature in all aspects that distinguish science. It is true that, given the state of the science, comprehensiveness had to do the work in theory for Darwin that mathematical power did for Newton, which is only to say that the one was suited by his abilities to accomplish for biology what the other had done for physics, and that both of them made the most of those abilities.

Professional response to the “Origin.” The theory of natural selection polarized opinion among biologists more radically than is the common effect of scientific theories. Those who adopted it tended to do so straightaway in something like a conversion. “How extremely stupid not to have thought of that,” was T. H. Huxley’s often quoted reaction as the pieces suddenly fell into place on reading Darwin. Yet even the professional response was influenced by philosophical taste and cultural tradition. Then, as now, the English-speaking scientific world was empirically minded after the manner of Bacon, Locke, and Mill. In Darwin’s own milieu, what immediately persuaded was his resolution of the question of biological adaptation. Not that he solved the problem. He did better. He dispelled it, by turning adaptation from final cause into present effect. Instead of a wonder so intricate as to bespeak Providence or purpose, adaptation became merely the outcome of the whole life history of the species in its relation to circumstance and environment, a phenomenon or set of phenomena to be analyzed and explained in evolutionary terms. In Huxley’s hands, therefore, Darwin became the protagonist of the drama of scientific fact undoing theological prejudice.

In Germany, where Darwin’s work enjoyed a success if anything more influential than in England and the United States, what appealed was less its empiricism than its historicism. The sense of history as indwelling process, whether in the successive versions of Herder, Hegel, or Marx, had in the course of the romantic movement of thought become deeply engrained in the German sense of the world. Philosophically speaking, such historiography treats the past in a mode exactly counter to Darwin’s, the one being a realist and the other a nominalist approach to nature. Oblivious to these distinctions, German historicists misread Darwin and took him for their own. It is well known that Marx spoke of dedicating the second book of Capital to Darwin, an intention which makes a curious contrast to the Lamarckian position of some subsequent Marxists. The professional champion and self-appointed spokesman, however, was Ernst Haeckel, who tried to make over all biology into the study of evolution. He governed his embryology, for example, by the doctrine that the development of every individual in the womb recapitulates the evolution of the species. Not only does evolution govern all biology, but all truth too: Haeckel’s Riddle of the Universe is the cardinal document of the movement to make something like a religion out of evolutionary thought itself.

Only in France was Darwin’s work initially greeted by indifference (except among anthropologists who did take it up with very great benefit to their science). Not so the biologists. Among them the writ of Cuvier still ran. There was also a problem of language. In French, the word évolution refers to the development of an individual; transformisme connotes the doctrine as affecting species in general, and at that time involved visionary connotations. A self-defeating semantic objection also supervened—to explain the origin of species in a book which questioned their reality seemed an inadmissible mode of discourse. The greatest of physiologists, Claude Bernard, never even seized the differences between the Darwinian theory and its speculative predecessors. “We must doubtless admire,” he wrote disdainfully, “those great horizons dimly seen by the genius of a Goethe, an Oken, a Carus, a Geoffrey Saint-Hilaire, a Darwin, in which a general conception shows us all living beings as the expression of types ceaselessly transformed in the evolution of organisms and species, —types in which every living being individually disappears like a reflection of the whole to which it belongs” ([1865] 1957, pp. 91–92). In general, Darwin expressed himself pragmatically in a manner characteristically English and characteristically unconvincing, not to say irritating, to the French.

The nonprofessional response. Darwin himself took no part in the social Darwinist movement of ideas and gave it no countenance [see Social Darwinism]. Something must here be said, nevertheless, about the pattern of nonprofessional response, insofar as it has been hostile, for these attitudes greatly amplified for a time certain scientific difficulties left unresolved by Darwin, and they have also contributed to persistent misunderstandings of the status of the theory in science—misunderstandings arising from repugnance toward its political and social derivations.

The pattern has two distinct aspects, theological and moralistic, which turn on different implications of the theory of evolution. The former, the theological issue between the Biblical story of the Creation and the Darwinian account of the origin of species, is the more famous. It is also the more literal and has proved the more ephemeral, concerned as it is with the wide historical fact of evolution rather than with the theory of natural selection, by which Darwin explained and thereby established the fact. The science of geology had, indeed, already faced theology with the necessity of regarding the scriptural account of earth history in an allegorical fashion, and the confrontation between Darwinists and religious believers settled rather than initiated that matter among informed persons. The Origin of Species did cause additional shock and distress, of course, chiefly in regard to the question of whether the reality of a spiritual component of human existence requires that man be biologically unique and specially created. This is a dilemma which may be resolved in one of two ways: either by considering the whole universe as contingent and composed of physical and spiritual aspects; or, in a more restricted way, by appreciating that the theory of evolution treats man as an evolved animal, but it does not and in principle cannot assert that he is nothing but an animal. At all events, within a relatively short space of time theologians learned to contemplate evolution without dismay, as clearly a matter of fact; significant religious minds have not felt impelled to gird against the facts, although fundamentalist rejection of them persists in diminishing backwaters.

What has persisted in recurrent and often serious manifestations is a second aspect of resistance to Darwin’s work. This kind of resistance is serious because it obtains among educated persons and reveals the occasional inability of highly intelligent people to respect the force and limitations of scientific demonstration. In this tradition the tenor has been to accept and even celebrate the phenomenon of evolution while denigrating the theory of natural selection. Sometimes this denigration has taken the form of an attack on Darwin’s character and probity, as in the instances of Barzun (1941) and Himmelfarb (1959). Sometimes it has taken the form of a revival, more or less garbled, of the views of Lamarck, as in the writings of Samuel Butler and George Bernard Shaw. Sometimes it has taken the form of proposing an alternative formula, metaphorical in character, for the purpose of replenishing evolution with intelligence, will, or choice. Such were the notions of “creative evolution,” the elan vital of Bergson, or entelechy of Driesch. Sometimes it has taken on ideological and political dress, as in the refusal of Lysenko’s adherents to admit the irrelevance to heredity of manipulation of the physical and social environment. As, indeed, in any complex of opinions, some proportion of these several elements, some mixture of these motivations, may be discerned in all types of educated refusal to be persuaded by the theory of natural selection.

What unifies these hostile views into a tradition of romantic resistance is the common complaint that the theory of natural selection deprives the history of nature of any sanctions for man as a social or moral being. These critics hold a different conception of the function of a scientific explanation. They want more out of nature than Darwin, or science generally, has found there. They want reasons, and Darwin gave them circumstance. They want causes, and he gave them accidental variation. They want purpose and direction, and he gave them an indefinite sequence of indifferent results. They want a science which seizes on unity and deep process, and he fragmented nature into a congeries of discrete events connected only by proximity and happenstance. What has proved profound, therefore, is not the incompatibility between evolutionary science and theology, considered intellectually at least. Much deeper and more persistent, partly because of common commitment to the natural with different understandings of what it signifies, has been the incompatibility between the Darwinian theory and any form of naturalistic social or moral philosophy. For the moralist knows what sort of nature he requires of science. And the theory of natural selection has succeeded precisely in consequence of limiting its purview to the indifferent event. While the present state of scientific understanding is not the touchstone by which to judge theories of the past, it is important to emphasize, nevertheless, that the theory of natural selection is part of working evolutionary thought. To refuse to admit its force is not only to question the actual state of scientific knowledge, but it is also to impugn the current mode of scientific explanation.

Charles C. Gillispie

[Directly related are the entriesEvolution; Genetics; Race. Other relevant material may be found in the biographies ofCooley; Galton; Giddings; Lubbock; Morgan, Lewis Henry; Spencer; Tylor.]

WORKS BY DARWIN

(1839) 1952 Journal of Researches Into the Geology and Natural History of the Various Countries Visited by H.M.S. Beagle. New York: Hafner. → A facsimile reprint of the first edition. A second edition was published in 1845.

(1842) 1962 The Structure and Distribution of Coral Reefs. Berkeley: Univ. of California Press. → A second edition was published in 1874.

(1842–1858) 1958 Darwin, Charles R.; and Wallace, Alfred R. Evolution by Natural Selection. With a foreword by Gavin de Beer. Cambridge Univ. Press. → The Darwin and Wallace papers of 1858, together with Darwin’s other early drafts.

(1844–1846) 1900 Geological Observations on the Volcanic Islands and Parts of South America Visited During the Voyage of H.M.S. “Beagle.” 3d ed. New York: Appleton. → First published as Geological Observations on the Volcanic Islands, Visited During the Voyage of H.M.S. Beagle (1844) and Geological Observations of South America (1846).

1851 A Monograph on the Fossil Lepadidae: Or, Pedunculated Cirripedes of Great Britain. London: Palaeontological Society.

1851–1854 A Monograph on the Sub-class Cirripedia, With Figures of All the Species. 2 vols. London: Ray Society. → Volume 1: The Lepadidae: or, Pedunculated Cirripedes. Volume 2: The Balanidae (or Sessile Cirripedes), the Verrucidae, etc.

1854 A Monograph on the Fossil Balanidae and Verrucidae of Great Britain. London: Palaeontological Society.

(1859) 1964 On the Origin of Species. Cambridge, Mass.: Harvard Univ. Press. → A facsimile of the first edition. Numerous editions have been published, including a reprint of the sixth edition in 1927 by Macmillan, and a variorum text edited by Morse Peckham, published by the Univ. of Pennsylvania Press in 1959.

(1862) 1903 The Various Contrivances by Which Orchids Are Fertilized by Insects. 2d ed., rev. New York: Appleton. → First published as On the Various Contrivances by Which British and Foreign Orchids Are Fertilised by Insects.

(1865) 1893 The Movements and Habits of Climbing Plants. 2d ed., rev. New York: Appleton. → First published in Volume 9 of the Journal of the Linnean Society.

(1868) 1900 The Variation of Animals and Plants Under Domestication. New York: Appleton.

(1871) 1930 The Descent of Man and Selection in Relation to Sex. 2d ed., rev. enl. New York: Appleton.

(1872) 1965 The Expression of the Emotions in Man and Animals. Edited by Francis Darwin. Univ. of Chicago Press.

(1875) 1900 Insectivorous Plants. 2d ed., rev. Edited by Francis Darwin. New York: Appleton.

(1876a) 1958 Autobiography of Charles Darwin, 1809–1882. Edited by his granddaughter Nora Barlow. London: Collins. → Written in 1876; first published posthumously in 1887.

(1876b) 1902 The Effects of Cross and Self Fertilisation in the Vegetable Kingdom. New York: Appleton.

(1877) 1896 The Different Forms of Flowers on Plants of the Same Species. New York: Appleton.

1880 The Power of Movement in Plants. London: Murray.

(1881) 1892 The Formation of Vegetable Mould Through the Action of Worms, With Observations on Their Habits. New York: Appleton.

(1887) 1959 The Life and Letters of Charles Darwin. 2 vols. New York: Basic Books. → Includes an autobiographical chapter, edited by Francis Darwin.

SUPPLEMENTARY BIBLIOGRAPHY

Barzun, Jacques (1941) 1958 Darwin, Marx, and Wagner: Critique of a Heritage. 2d ed. Garden City, N.Y.: Doubleday.

Bernard, Claude (1865) 1957 An Introduction to the Study of Experimental Medicine. New York: Dover. → First published in French.

De Beer, Gavin R. 1964 Charles Darwin: Evolution by Natural Selection. New York: Doubleday. → The most authoritative biography.

Eiseley, Loren 1959 Darwin’s Century: Evolution and the Men Who Discovered It. Garden City, N.Y.: Doubleday.

Gillispie, Charles C. 1951 Genesis and Geology: A Study in the Relations of Scientific Thought, Natural Theology, and Social Opinion in Great Britain, 1790–1850. Harvard Historical Studies, Vol. 58. Cambridge, Mass.: Harvard Univ. Press. → A paperback edition was published in 1959 by Harper.

Glass, Bentley (editor) 1959 Forerunners of Darwin: 1745–1859. Baltimore: Johns Hopkins Press.

Himmelfarb, Gertrude 1959 Darwin and the Darwinian Revolution. Garden City, N.Y.: Doubleday.

Merton, Robert K. 1961 Singletons and Multiples in Scientific Discovery: A Chapter in the Sociology of Science. American Philosophical Society, Proceedings 105:470–486.

DARWIN, CHARLES ROBERT

(b. The Mount, Shrewsbury, England, 12 February 1809;

d. Down House, Downe, Kent, England, 19 April 1882),natural history, geology, evolution. For the original article on Darwin see DSB, vol. 3 (note error in date of birth given there).

When Gavin de Beer wrote the article on Darwin in the original DSB there were only a handful of historical studies available, including his own biography. Over the next few decades there was an explosion of interest in the process by which Darwin developed his theory of evolution by natural selection, fueled by the publication of his notebooks, edited by de Beer himself. There have also been many studies of the impact of Darwin’s ideas, inspired in part by a recognition that earlier perceptions had been shaped by the success of the selection theory in the mid-twentieth century. Michael Ruse coined the term “Darwin industry” to denote the group of historians who devoted themselves to the study of his work. Many of Darwin’s papers have since been published, including a combined volume of the notebooks originally edited by de Beer. There are editions of his diaries, of the marginalia he scribbled in the books he read, and an ongoing project to publish his whole correspondence. Both the Origin of Species and the notebooks have been provided with a concordance. The flow of technical literature has slackened off, but the flood of biographical studies has continued unabated, those by Janet Browne and by Adrian Desmond and James Moore having attracted particular attention.

There have been important developments in the understanding of many aspects of Darwin’s work and its implications. Historians such as Jonathan Hodge have alerted scholars to the strong thread that runs through Darwin’s work based on a traditional view of heredity and reproduction. There have been major debates on the role of ideology in his thinking and new developments in the understanding of his changing religious views. De Beer’s effort to trace a straightforward link between Darwin’s original theory and modern Darwinism have come under suspicion as researchers have become more aware of the existence of alternative ideas about how evolution might work.

Darwin’s Early Career . Darwin’s period of medical study at Edinburgh has traditionally been dismissed as of little significance. But he also worked on natural history there, and this has led Hodge and Phillip R. Sloan to challenge the impression given in his autobiography that these were wasted years. Darwin claimed to have been unimpressed by the Lamarckian anatomist Robert Grant, although it is now known that the two worked closely together, and that Darwin was impressed by Grant’s claim that the “zoophytes” (Hydrozoa and corals) serve as a bridge between the plant and animal kingdoms. Darwin’s early reading focused his attention on issues that would shape his later thinking, especially his ideas about generation or sexual reproduction. He became committed to the view that reproduction is a creative activity of the vital forces in the body, a position quite unlike the modern focus on the rigid transmission of genetic units. Here his thinking reflects the fascination with the creativity of sex that ran through his grandfather Erasmus Darwin’s theories.

Sandra Herbert has made a major study of Darwin’s geological work and has shown how he turned the methodology of Charles Lyell into a theoretical program for understanding all Earth movements. There have been important studies of Darwin’s biogeographical work on the Beagle voyage. Working on Darwin’s original notes, Frank Sulloway has undermined the myth of a “eureka” experience on the Galápagos Islands by showing that the finches there could not have played such a crucial role. Darwin’s own specimens were not even labeled to show which island they were collected on, and he had to rely on collections made by others on the ship to reconstruct the distribution. Only after his return to England, when the ornithologist John Gould informed him that the finches really did constitute a group of distinct but closely related species, did Darwin realize their full significance.

Herbert and Martin Rudwick have made detailed studies of Darwin’s active role in the London geological community following his return, including his abortive theory on the parallel roads of Glen Roy. But behind the scenes he had begun to think hard about the question of transmutation. Sulloway argues that the insights that led Darwin to the idea of branching evolution were probably arrived at after the Beagle had returned to England in October 1836, although a few historians speculate that he may have accepted transmutation during the later part of the voyage. Ernst Mayr called this the first Darwinian revolution: The Galápagos results convinced him that new species are formed by the natural transformation of old ones, although as yet he had no idea what the process of change might be. Over the next few years he searched for a plausible mechanism, and his development of the theory of natural selection constitutes a second revolution.

The Discovery of Natural Selection . Howard Gruber has explored Darwin’s notebooks from this period to argue that the discovery of the selection theory can be seen as a major example of creative thinking. Darwin sometimes projected an image of himself as a patient observer, and his opponents have always accused him of being incapable of deep thought. But he also said that the Origin was “one long argument,” and Mayr among others has stressed that he was anything but a simple fact-gatherer. Ruse and Silvan Schweber focus on Darwin’s desire to appear a good scientist as defined by contemporary discussions of the scientific method by Sir John Frederick William Herschel and William Whewell. They argue that he developed natural selection by a creative process of synthesis and testing. David J. Depew and Bruce H. Weber see the selection theory as the product of a new statistical mode of explanation and also stress his innovative work in the area of methodology. Darwin wanted to create a theory based on natural law in the Newtonian tradition, but by the very nature of the problems he addressed he was forced to transform this program by introducing statistical and historical elements into his explanations. Robert J. Richards sees the historical element as derived from German idealist philosophy, but others, including Hodge, relate it to Lyell’s uniformitarian methodology.

Darwin started from his knowledge of biogeography, and with a conviction that evolution must be a branching process in which one species is divided by geographical barriers and the separate populations then become transformed in different directions. He wondered if species might be “born” with a built-in lifespan, after which they become extinct. He soon realized, however, that some more active mechanism of change was needed and by July 1837 he was convinced that transmutation must come about by the accumulation of individual variations over many generations. He explored the direction already taken by Jean-Baptiste de Lamarck and Erasmus Darwin: Might a change in the environment produce modifications either by affecting the reproductive process or by changing the organisms’ habits? He soon decided that Lamarckism was inadequate. For a variety of reasons, he decided that although the environment might well be the stimulus, the majority of the changes it produced were not purposeful.

Studies by Hodge, David Kohn, and Phillip Sloan have revealed the extent to which Darwin was influenced by his views on “generation” or reproduction. The key to transmutation was the creative power of sexual reproduction. The theory of heredity he later called “pangenesis” (published in 1868) was formulated at this early stage. Older studies lament Darwin’s “failure” to anticipate genetics, on the assumption that if he had developed the concept of the gene he would have avoided the problems that beset the selection theory in the late nineteenth century. Modern scholars accept that the foundations of his thought lie in a premodern concept of heredity.

James Secord and Peter J. Vorzimmer show how the C notebook shows Darwin studying work of animal breeders, where changes could actually be observed within a species. He later suggested that he observed the breeders applying a process of artificial selection and then saw how this model could be transferred to natural evolution. L. T. (Lloyd Thomas) Evans and Ruse have explored the analogy between artificial and natural selection because—as Darwin himself later realized—it offers such a neat model for how natural selection operates. But although the process of selection seems clearly illustrated in such cases, Darwin’s notebooks show that there was no direct borrowing of the selection model from the breeders. Throughout the C and D notebooks he remained convinced that adaptive variations must somehow be elicited automatically in a changed environment (Lamarckism), and did not see the breeders work as a useful analogy. Accounts of the discovery of the selection mechanism by Camille Limoges, Herbert, and Richard A. Richards have argued that he could not have been inspired by the model of artificial selection. Darwin became so used to citing the work of animal breeders as a model in his later accounts of the theory that he actually came to believe that this was how he was led to the idea of selection.

At this point he read Thomas Robert Malthus on population and realized the significance of the struggle for existence. Here the discussion enters the debate over the extent to which his thinking reflected the ideology of free-enterprise capitalism. Robert M. Young has been the most powerful advocate of the view that the selection theory does reflect the prevailing ideology of the time, a position backed up in the biography by Desmond and Moore. Schweber argues for an influence derived from the individualism of Adam Smith’s economics, while noting that scientific factors had already begun to make Darwin think in terms of individual variation within a population—the innovation that Mayr calls “population thinking”—the transition from seeing a species as based on an ideal type to seeing it as a population of distinct individuals. Depew and Weber see the rise of Darwinism as the creation of a statistical mode of explanation as opposed to the old Newtonian view of causation based on law. The claim for a direct input from Darwin’s social environment must be balanced against the evidence for a growing awareness that for science to tackle certain kinds of questions, a new type of explanation based on statistically modeled changes was needed.

De Beer’s account minimized the influence of Malthus, treating the population principle as only a catalyst helping Darwin to put together insights already gained from his observations of nature. The connection is certainly not as direct as is sometimes implied: Peter J. Bowler showed that Darwin’s concept of the struggle for existence does not appear in Malthus’s work, and in this sense he had to think creatively with the insight provided by the population principle. Malthus did not anticipate the logic of what became known as social Darwinism, and thus could not provide the whole model for the selection theory. Edward Manier and Schweber point to the breadth of Darwin’s reading, which reveals other ways in which the ideology of the time could have filtered into his thinking. He read Smith and also David Brewster’s review of Auguste Comte’s positivist philosophy, which argued for the need to base all theories on mathematical foundations—exactly what was provided by the arithmetical logic of the population principle. Looking for a way of measuring variation, he turned to the work of the Belgian anthropologist Lambert Quételet, who pioneered the application of statistics to the human population. Darwin’s theory was not a slavish copy of Malthus’s political philosophy, but it may nevertheless have been steeped in the ideology of the time. As Desmond and Moore stress, this was a time of social conflict in Britain, so Darwin could see on the streets the struggle that the political economists were trying to understand.

Studies by Gruber and Herbert show the M and N notebooks revealing Darwin’s adoption of a materialist perspective, at least on how his theory would apply to humankind. These notes anticipate many of the topics later articulated in the Descent of Man. Darwin saw no room for the traditional notion of a soul existing on a purely spiritual plane: The mind was a product of the material activity of the brain, just as the phrenologists held. He suspected that much of human unconscious behavior may be instinctive, programmed into human brains by the effect of evolution on humanity’s ancestors. The ways in which individuals express their emotions reveal their animal ancestry, as in the case of snarling to express anger. He was convinced that evolution would throw light on moral values by showing how certain forms of social behavior have been programmed into humans by natural selection. Morality was merely a rationalization of these social instincts. Such ideas would undermine the whole traditional view of human nature.

Yet Darwin still felt that the laws of nature were instituted by a wise and perhaps even benevolent God. Far from recognizing the full horror of a worldview based on struggle, he stressed that the end result of evolution was to keep species well adapted to their environments in an ever-changing world. As Walter Cannon and Young argue, he transformed rather than destroyed the old natural

theology of William Paley (1743–1805). Even struggle and death had a positive value in the divine plan. Robert Richards argues that Darwin was also committed to the idea of progress. He suggests that historians influenced by modern Darwinism have failed to appreciate that Darwin still saw evolution as a steady pressure to mount the scale of organization. Selection was a force that would tend to raise the standard of organization whenever the circumstances were appropriate. But he was also aware that the advance could take place in a number of directions, not just along a single line leading toward humanity.

Development of the Theory . Over the next twenty years Darwin worked on his theory, soon moving to live in the countryside at Downe. He was not a complete recluse, however, and the vast extent of the correspondence network he built up (later published) provided him with sources of information on subjects relevant to his theorizing. As Manier argues, he was trying to build up a community of scientists who would speak the new language of evolution.

Darwin’s work on barnacles provided him with many insights, including the importance of embryological characters for determining relationships. His thinking incorporated an element of what would later be called the recapitulation theory, although the extent to which he can be associated with the full-blown version of this theory is controversial. Richards has argued that Darwin adopted the “law of parallelism,” whose influence had been charted by Stephen Jay Gould. This form of recapitulation theory implies a linear model of evolution, with the lower animals being treated as immature versions of the more perfect human form. Many historians are suspicious of Richards’s effort to tie Darwin in with the developmental way of thinking so prevalent in Germany.

An important change took place in Darwin’s thinking in the 1850s. It has often been assumed that as soon as he formulated the selection theory, he must have recognized that it implied a much harsher vision of nature as a scene of unrelenting struggle and suffering. But Dov Ospovat argued that the early form of the theory still revealed its roots in Paley’s vision of natural theology. Only in the 1850s did he realize that a compromise could not be maintained. The principle of population implies that the struggle for existence continues even in a stable environment, so there can never be any escape from the relentless threat of death. As Frank Burch Brown, Kohn, and Neal Gillespie show, Darwin’s worldview thus became gradually more pessimistic. Moore notes how this move was encouraged by the death of his beloved daughter Anne in 1851.

Ospovat also notes that this growing recognition of the power of struggle allowed Darwin to explain the trends toward divergence and specialization being discovered by Richard Owen in the fossil record. Both Owen and William B. Carpenter recognized this trend by comparing the fossil sequences with the process of embryological specialization observed by Karl Ernst von Baer. In effect, Darwin applied the principle of the “division of labor” to explain why it was advantageous for species to diversify. Browne and Kohn note that biogeography also transformed Darwin’s thinking on this issue. His “principle of divergence” arose from a recognition that successful genera expand and diversify, wiping out the species that had previously occupied the territory. Here again Darwin came face to face with the relentless pressure of natural selection. Sulloway notes that by focusing on the pressure to specialize, Darwin was led to marginalize his early emphasis on the role of geographical isolation in speciation, as in the Galápagos. Nevertheless, by 1856 he had created a much more sophisticated theory and had amassed a vast amount of supportive evidence and had begun to write a “big book” on the topic, now published and edited by Robert Stauffer. This was the project interrupted by the arrival of Alfred Russel Wallace’s paper in 1858. There has been much debate over the degree of similarity between the two men’s theories of natural selection, summarized by Malcolm Kottler. Some scholars argue that there were significant differences between them, but no one disputes that Darwin recognized important parallels and began writing the Origin of Species.

The Reception of Darwin’s Theory . Surveying the recent work on the reception of the Origin of Species moves into broader realms of the interactions between Darwin and the scientific, cultural, and social developments of the time. A survey of the Darwinian revolution by Ruse provides a useful overview, as do the biographies of Darwin by Browne and Desmond and Moore. Recent studies of the early Darwinians such as Thomas Henry Huxley should also be consulted.

For the scientific debate, David Hull edited and commented on a collection of reviews of the Origin. Scholars such as Vorzimmer, Jean Gayon, and William Provine have traced the debates over natural selection from Darwin’s time into the era of modern genetics. The emergence of the so-called modern synthesis of Darwinism and genetics was the topic of an important collection of essays edited by Mayr and Provine. Here is a complex series of debates centered on challenges to the traditional assumption that Darwin’s “failure” to recognize the significance of Gregor Mendel’s laws of heredity left him vulnerable to attacks such as the one launched by Fleeming Jenkin in 1867. In the early 2000s, recognition of the role played by a pregenetical model of heredity and variation in Darwin’s thinking about selection makes it difficult to imagine how he could have appreciated the potential value of Mendelism. Nor is it clear that his theory of pangenesis necessarily undermined the credibility of the selection mechanism, although Jenkin’s attack did force him to question his longstanding assumption that favorable variations were very rare. The process by which the theory of natural selection was synthesized with genetics was long and complex because it involved the destruction of a developmental viewpoint in which the transmission of characters was thought to be inextricably connected with the mechanism by which those characters are generated in the embryo.

Many modern historians would accept that it was the prevalence of this developmental model in late nineteenth-century biology, not a specific problem associated with “blending inheritance” that accounts for the widespread reluctance to take the theory of natural selection seriously during Darwin’s own lifetime. Peter Bowler has outlined several alternative theories of evolution developed in the late nineteenth-century “eclipse of Darwinism.” In particular he develops Gould’s account of the ways in which the recapitulation theory was used to imply that evolution must be directed along predefined channels, just like the development of the embryo. Bowler has also suggested that an appreciation of the extent to which Darwin’s own explanation of the process was rejected must force us to reconsider the reasons why the basic idea of evolution became popular at the time. Darwinism was translated into a theory of necessary progress, and the more radical implications of the selection theory remained dormant until the twentieth century. Along similar lines, Ruse has written a provocative book arguing that Darwinism succeeded only because the theory of evolution piggybacked on the rising tide of enthusiasm for the idea of progress.

In terms of the wider public response, Alvar Ellegard provided a detailed study of the reaction to Darwin in the British periodical press. Gillian Beer has pioneered the study of Darwin’s influence in the literary sphere. Moore has challenged the established view that evolutionism became sucked into a “war” between science and religion, noting the extent to which liberal Christians welcomed the theory because they saw it as a model for social progress in the modern world. The challenges posed by this vision to the more traditional Christian view of the origin of humanity were highlighted in Darwin’s own study of human origins, the Descent of Man. Richards has written a detailed account of the development of evolutionary explanations of the human mind, which compares Darwin’s ideas on the topic with those of other thinkers such as Herbert Spencer. He stresses the extent to which Darwin and Spencer saw themselves as providing morality with a new foundation, certainly not as destroying all traditional values. Darwin did, however, come to accept the prevailing view that the nonwhite races retain more traces of humanity’s ape ancestry, although initially he had adopted more liberal views on this issue.

Curiously, however, there have been comparatively few attempts to integrate Darwin’s ideas on human origins with the history of paleoanthropology, although a survey by Bowler stresses the innovative nature of his belief that the development of an upright posture was the key breakthrough in the separation of the first hominids from the apes. Virtually all other commentators before the mid-twentieth century took it for granted that it was the expansion of the human brain that drove the separation— Darwin was the first to suggest that the initial step might have been triggered by an adaptive change necessitated by the hominids’ move onto the open plains.

There have been endless debates about the role played by Darwin’s theory in the promotion of “social Darwinism.” Historians such as Young, who stress the ideological input into Darwin’s own thinking, have naturally pointed to the use of Darwinian rhetoric to justify policies in which struggle is the driving force of progress. There have been many accounts of social Darwinism making the same point, from the classic study by Richard Hofstadter to more recent work by Mike Hawkins. But historians such as Robert Bannister and Bowler have urged caution, noting that some appeals to the metaphor of the struggle for existence did not depend on the application of the selection theory, even when Darwin’s name was invoked. Spencer’s enthusiasm for individual competition was linked to a Lamarckian mechanism of self-improvement, for all that he coined the term “survival of the fittest.”

There have been comparatively few accounts of the detailed biological investigations Darwin carried out in the later part of his life, apart from those contained in the biographies. Helena Cronin and Kottler have written on the theory of sexual selection, especially Darwin’s longstanding debate with Wallace on the topic (significantly in the context of the “eclipse” of Darwinism; few other biologists took that theory seriously until the mid-twentieth century). On a more personal level, Ralph Colp has written on Darwin’s illness. Moore has discredited the story, popular among modern creationists, that he underwent a deathbed conversion back to Christianity. Moore has also provided an analysis of the symbolism associated with the events surrounding his funeral. When he died in 1882 the scientific community was anxious to exploit his status as the most famous biologist of the century to obtain for him the honor of being buried in Westminster Abbey.

SUPPLEMENTARY BIBLIOGRAPHY

There have been many modern editions of The Origin of Species, usually based on either the first or the sixth editions, and translations into most major languages.

WORKS BY DARWIN

Charles Darwin’s Natural Selection: Being the Second Part of His Big Species Book Written from 1856 to 1858. Edited by Robert C. Stauffer. London: Cambridge University Press, 1975.

The Collected Papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago: University of Chicago Press, 1977.

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Peter J. Bowler

DARWIN, CHARLES

DARWIN, CHARLES (1809–1882), English naturalist.

Born in Shrewsbury, England, on 12 February 1809, Charles Darwin was the grandson of a physician, Erasmus Darwin (1731–1802). His father, Robert Waring Darwin, was also a physician; his mother, Susannah Wedgwood Darwin, was a member of the noted English pottery family. From 1818 to 1825, Darwin attended boarding school but was not a top-notch student. In 1825 Darwin was sent to Edinburgh University, which featured the best medical school in Britain. When Darwin recoiled from the idea of surgery and rejected becoming a physician, his father arranged for extra tutoring to prepare him for study at Cambridge University. Darwin enrolled at Christ's College at Cambridge in 1828. Darwin's father hoped that he would study theology at Cambridge and prepare for a comfortable life as a country parson. Instead, Darwin spent much of his time gambling and riding horses, and his father complained that he was interested only in "shooting, dogs, and rat catching." Yet Darwin eventually proved to be a successful student at Cambridge, ranking tenth out of 178 students on the final bachelor's examination and impressing his teachers, including the botantist Robert Henslow.

voyage of the beagle

When the Cambridge University faculty was asked to recommend a student to serve as ship's naturalist aboard a British surveying ship, Henslow recommended Darwin. The ship, the H.M.S. Beagle, was scheduled to make a five-year voyage through the South Pacific and along the coast of South America. Paying the deference to his father that was expected from sons in upper-class Victorian families, the twenty-two-year-old Darwin asked his father's permission to apply for the job. Although his father thought the work "useless" and initially rejected the idea, permission was granted after an uncle intervened.

darwin on natural selection and human origins

In his On the Origin of Species and The Descent of Man, Darwin made an effort to take the most optimistic view possible of natural selection, which most of his contemporaries feared was a "blind" process whose future outcome was uncertain and unpredictable.

Judging from the past, we may safely infer that not one living species will transmit its unaltered likeness to a distant futurity … it will be the common and widely-spread species, belonging to the larger and dominant groups, which will ultimately prevail and procreate new and dominant species…. Hence we may look with some confidence to a secure future of equally inappreciable length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress toward perfection. (Origin of Species, 1st ed., p. 489)

In regard to bodily size or strength, we do not know whether man is descended from some small species, like the chimpanzee, or from one as powerful as the gorilla; and therefore, we cannot say whether man has become larger or stronger, or smaller and weaker, than his ancestors … an animal possessing great size, strength, and ferocity … like the gorilla, could defend itself from all enemies, [and] would not have perhaps become social; and this would most effectually have checked the acquirement of the higher mental qualities such as sympathy and the love of his fellows. Hence it might have been an immense advantage to man to have sprung from some comparatively weak creature. (The Descent of Man, p. 65)

The voyage, which lasted from 1831 through 1836, proved to be the most formative event in Darwin's professional career. Darwin was haunted by his discoveries during the voyage. He returned to Britain with a large collection of fossils and animal and plant specimens, many of which he distributed to universities and scientific institutions. The fossils that he collected appeared to show that a large number of species had become extinct, but they did not answer the central question of why that had happened. The voyage of the Beagle also impressed on Darwin how geography had influenced species. He was struck by the similarities, as well as the differences, between species from nearby islands, particularly in the chain of Galépagos Islands. Reasoning that plants and animals had developed somewhat differently at different geographical locales, Darwin, by the end of the voyage, was willing to conclude that species were not "immutable." When his diary aboard the Beagle was published as Journals andRemarks, 1832–1836 (1839), it did not raise the issue of "transmutation," the term used at the time to describe species change. Yet his "Red Notebook," done during the last months of his Beagle voyage, and his "B" notebook, began after his return, did discuss transmutation. Darwin had begun the voyage believing in the "permanence of the species," but he ended it with "vague doubts."

problems for evolution

Yet it was twenty-three years from the time that the Beagle returned to Britain until the appearance of Darwin's famous book that proposed his version of evolution, On the Origin of Species (1859). Why did it take him so long? Why did he not rush to publication? The answer appears to be that he was acutely aware that his theories on evolution would jar the Victorian world and risked making him a social outcast and a religious pariah. Since the late twentieth century increasing attention has been given (by Adrian Desmond and James Moore, among others) to the mysterious illness that afflicted Darwin for many years after the voyage of the Beagle, leaving him with frequent bouts of fatigue and a "nervous stomach." One explanation is that he was aware that his work might not only alienate him from some of his friends but also reopen what one contemporary termed "the warfare between science and religion."

the oxford debate

Darwin's defenders frequently framed the issue of evolution as the search for scientific truth. In 1860, the year after the publication of the Origin, Darwin's friend Thomas Henry Huxley publicly debated the merits of the book with a bishop of the Church of England, Samuel Wilberforce. The occasion was a meeting of the British Association for the Advancement of Science at Oxford University. It pitted one of the most talented speakers among the English bishops—whose nickname was "soapy Sam"—against Darwin's most spirited defender—whose nickname would become "Darwin's bull-dog." The bishop, speaking first, diverged from his scheduled topic to ask whether Darwin claimed ancestry through an ape grandfather or an ape grandmother. Huxley felt compelled to respond. After all, Darwin had written that the details of human origins were uncertain, but he had added that apes and human beings probably shared a common ancestor. While there are a number of accounts of what Huxley said, they are generally similar.

An Oxford undergraduate who was present wrote a friend that Huxley had replied:

I asserted—and I repeat—that a man has no reason to be ashamed of having an ape for his grandfather. If there were an ancestor whom I should feel shame in recalling it would rather be a man—a man of restless and versatile intellect—who, not content with an equivocal success in his own sphere of activity, plunges into scientific questions with which he has no real acquaintance, only to obscure them by an aimless rhetoric, and distract the attention of his hearers from the real point at issue by eloquent digressions and skilled appeals to religious prejudice.

An instructor at Oxford wrote this account to Huxley's son:

The Bishop had rallied your father as to the descent from a monkey, asking as a sort of joke how recent this had been, whether it was his grandfather, or further back. Your father … then went to this effect—'But if this question is treated, not as a matter of calm investigation of science, but as a matter of sentiment, and if I am asked whether I would choose to be descended from the poor animal of low intelligence and stooping gait, who grins and chatters as we pass, or for man, endowed with great ability and splendid position, who should use these gifts (here, as the point became clear, there was a great outburst of applause, which mostly drowned out the end of the sentence) to discredit and crush humble seekers after truth, I hesitate what answer to make.'

A third person who was present added:

Thomas Henry Huxley, edited by Leonard Huxley [New York, 1901], p. 199)">

No one doubted his meaning, and the effect was tremendous. One lady fainted, and had to be carried out; I, for one, jumped out of my seat. (Life and Letters of Thomas Henry Huxley, edited by Leonard Huxley [New York, 1901], p. 199)

While Darwin worried about the impact of his theories of evolution, he was also wrestling with serious scientific problems for his ideas. Darwin and his colleagues did not take seriously the Biblical account of the earth's creation in six days, and they also dismissed the ideas of the Irish bishop James Ussher (1581–1656), who had totaled the number of generations represented in the Bible and had announced, on the basis of such calculations, that the creation of the universe began on 23 October 4004 b.c.e. Much more respect was given to the work of the noted British mathematician and physicist Lord Kelvin. Assuming that the earth began as a fiery ball, Kelvin had used the laws of thermodynamics to determine that the age of the earth did not exceed some 200 million years. That was not sufficient time for a true evolution.

The necessary long time frame for the history of the earth was furnished by geology. Until the early nineteenth century, most geologists were "catastrophists," who believed that the earth's surface had been shaped by periodic cataclysms such as floods. "Catastrophism" fit with the Biblical story of a great flood. It also allowed writers to explain fossils without resorting to evolution. The doctrine of "Special Creation" held that God re-created life on Earth following periodic catastrophes; fossils were seen as evidence of what life was like before the previous Creation.

By the 1820s, however, a new school of geology, uniformitarianism, emerged. Uniformitarians held that the laws of nature operated "uniformly" in time throughout the earth—great mountains, for example, were produced by forces operating gradually, in processes such as erosion. The new theory argued that the same slow forces seen shaping the earth today had also operated in the past. During the voyage of the Beagle, the ship's captain (and Darwin's closest friend during the voyage), Robert FitzRoy, gave him a copy of the first volume of a major uniformitarian book—Charles Lyell's Principles of Geology (1830–1833). Because Lyell and other uniformitarians assumed a much longer time span for the history of the earth than previously believed, Darwin later commented that his own evolutionary book On the Origin of Species "half came out of Lyell's brain."

What was lacking, until Darwin, was a plausible explanation of the mechanism of evolution—the "how" of the process that drove and shaped species change. There had been previous attempts, none of which was considered successful, to explain "transmutation." The most significant evolutionary theory before Darwin came from the French naturalist Jean-Baptiste Lamarck, who speculated that animals might deliberately acquire characteristics or organs that they needed in order to survive in their environment. These new characteristics—a fish forced to live on land coming to acquire lungs, for example—might then be passed down to following generations. How this might occur remained a puzzle, since the science of genetics would not emerge until the late nineteenth and early twentieth centuries.

Larmarck's theory, called the theory of the "inheritance of acquired characteristics," received less attention among scientists on the European continent after fellow French naturalist Georges Cuvier ridiculed the idea at a scientific conference in 1830. For much of the first half of the nineteenth century, evolution became the province of philosophy, as the German philosophers Lorenz Oken and Friedrich von Schelling promoted the idea that an inner force or "vital spirit" drove all living matter to self-improvement. Their evolutionary philosophy, named Naturphilosophie (nature philosophy), gained little acceptance among scientists outside of Germany.

the influence of malthus and spencer

In September 1838, Darwin read the Essay on the Principle of Population (1798) by the English economist Thomas Malthus. Malthus held that human population was growing faster than the supply of available food, with the result that there would always be competition among human beings for the "means of subsistence." Darwin had come to believe that new traits or "variations" constantly appeared among plants and animals. Some traits or "variations" condemned an animal to a short life; others might be more "favorable," allowing the animal to live a longer life. Darwin concluded that what Malthus called the "struggle for existence" might be used to explain how, in evolution, "favorable variations" would tend to be preserved and "unfavorables ones" destroyed.

Darwin also would eventually accept a phrase from the philosopher Herbert Spencer, a nonscientist who was the most popular writer on evolution

in mid-nineteenth-century Britain. Darwin and his friends held little respect for Spencer's system of evolution—which Spencer said proceeded from the simple to the complex, or from the "homogeneous" to the "heterogeneous"—since it was based on philosophic speculation rather than science. When Spencer treated Darwin rather arrogantly at their first meeting, Darwin's friend Thomas Henry Huxley retaliated by quipping that Spencer's idea of tragedy was "a deduction killed by fact." Yet Darwin eventually came to accept a phrase used by Spencer after Darwin's own theories were published—"survival of the fittest"—to describe evolution.

the slow path to the origin

Darwin did not prepare to publish his theories until he received a letter in 1858 from a biologist with similar ideas, but he had long been at work producing a number of unpublished writings on the subject. By the 1840s, he was writing that "I am almost convinced … that species are not … immutable," adding that "it is almost like confessing a murder." In 1842 he produced a thirty-five-page description of what he termed "natural selection" to explain evolution, and in February of 1844, he gave his wife a 231-page manuscript on evolution, with instructions that it be published after his death. Darwin began writing his groundbreaking book, On the Origin of Species, in May 1856. At first he intended to write for scientists alone. By now he had abandoned the idea that evolution occurred only when conditions, or the environment that an animal lived in, changed. Now he favored the idea that nature was a place of constant struggle, with new "variations" continually appearing.

Alfred Wallace, a less accomplished biologist, forced Darwin to make his ideas public. Wallace wrote to Darwin in June 1858, proposing, from his own travels and from also reading Malthus, that changes in species were driven by competition and overpopulation. Typically generous, Darwin refused to try to deny recognition to Wallace (even considering, for a time, allowing Wallace to garner much of the initial credit). In July 1858, at a time when Darwin was too ill to appear, two colleagues in the scientific community, Huxley and Joseph Hooker, presented Darwin's 1844 essay, along with a paper by Wallace, to the Linnean Society; both were later published together.

When Darwin's book On the Origin of Species appeared in 1859, it demonstrated the influence of Malthus and the impact of the voyage of the H.M.S.Beagle. The book's distinctive idea of "natural selection" was based on the belief that as plants and animals overproduced, the resulting struggle for resources tested which plants and animals best "fit" in their environment. In "natural selection," nature selected from variations that regularly appeared. The survivors lived longer, founded new species, and produced the most offspring. The Origin proved to be Darwin's most celebrated book, one that was translated into at least thirty-six languages in his lifetime and is still read widely.

Since the late twentieth century writers such as Dov Ospovat have traced Darwin's efforts to achieve a more optimistic view of the "struggle for existence" than Malthus had presented. Darwin first proposed that animals, in responding to changes in their environment, would create a new "stable" relationship with the environment and that the "struggle for existence" would cease. He later changed his mind, however, deciding that struggle was a constant part of nature. Another assessment of Darwin, by the writer Robert Young, concludes that Darwin attempted to prove that evolution represented "progress" by reasoning that natural selection led to greater "complexity" in nature, which Darwin considered desirable.

The last chapter of the Origin drew much attention, since it included the statement that "light" would soon be thrown on "human origins." Darwin fulfilled that promise in 1871, when he published The Descent of Man. The Descent made human beings part of the process of natural selection, arguing that early humans were hairy beings with large ears and that human beings, monkeys, and apes probably shared a common ancestor. In the Descent Darwin wrote that human mental and moral abilities differed from those of animals only by degrees. The implication was that the moral standards of human society were patterns of behavior that human beings had utilized, in evolution, in order to survive.

Darwin's book The Expression of Emotion in Animals (1872) extended the argument, attempting to establish connections between the emotional and intellectual life of human beings and animals. During the last twenty years of his life Darwin also worked to explain how natural selection operated in the plant world. Scholars have recently paid much more attention to his writings on this subject, since

Darwin appeared to believe that his readers were more likely to accept the concept of natural selection if it was applied to plants rather than to animals.

Wealthy from investments and from inheritances, Darwin and his wife, his first cousin Emma Wedgwood (whom he married in 1839), were able to live a comfortable life. Eventually they had ten children. Because of Darwin's frequent fits of nervousness, his wife often protected him from uninvited visitors to his home in Down, England, sometimes claiming that she could not locate her husband. Some honors were bestowed on Darwin, although far fewer than might be expected from a man considered one of the scientific greats of the nineteenth century. When he died on 19 April 1882, however, his friends, including Huxley, were able to arrange for burial in Westminster Abbey, close to a monument to another scientific giant, Isaac Newton.

popular and scientific reception

Outside of the scientific community, much of the early reaction to the Origin and the Descent focused on the issue of human origins. The British humor magazine Punch published a famous cartoon showing monkeys discussing their human relatives. The playwright George Bernard Shaw declared that no decent-minded person could believe Darwin's theories. Behind public debates over Darwinism lay deeper fears among the Victorians, who were repulsed by the idea of nature as a battleground between individuals that was filled with misery and suffering. Late-twentieth and early-twenty-first-century writers on Darwin such as Michael Ruse have pointed out that "Darwinism" raised major philosophic questions. Many of Darwin's contemporaries worried that there were no standards of conduct or accountablity for individual actions in an evolutionary world.

The American writer Henry Adams was not quite accurate when he said that "evolution pleases every-one—except curates and bishops"—but his words underlined the degree to which "Darwinism" became a cause in itself, since it raised the possibility that Nature operated on its own, without divine guidance. Ernst Mayr, a twentieth-century biologist, has argued that until about 1940, "Darwinism" meant the idea that the world might be explained only through natural processes (and that only after that time did Darwinism signify "natural selection"). The poet Alfred, Lord Tennyson wrote that if Darwin's version of Nature was God's creation, God had to be "disease, murder, and rapine." Even Darwin's wife worried that her husband's work "puts God further off." Nevertheless, when Tennyson said to Darwin, "Your theory of evolution does not make against Christianity," Darwin replied, "No, certainly not." Some liberal Protestant clergy in Darwin's time, such as Charles Kingsley, would come to accept evolution in general (although not necessarily natural selection), with Kingsley approving the concept that "God created primeval forms capable of self government." Darwin himself seemed to encourage such views, conceding that the idea that "this grand and wondrous universe could not have arisen through chance" was the "chief argument for the existence of God."

Even within the scientific community, religious and philosophic issues played a role in determining whether Darwin's ideas were accepted or rejected. A major opponent was the director of the Kensington Natural History Museum, Richard Owen, who insisted that Nature Philosophy was correct in describing evolution as the operation of a "vital force" in organisms. In the United States, the Harvard geologist Louis Agassiz insisted that species, once created by God, are fixed and unchangeable, although another prominent American biologist in the late nineteenth century, Asa Gray, defended the Origin. In general, scientists in Darwin's time were more likely to accept the idea of evolution than the concept of natural selection. Huxley himself accepted evolution but said that natural selection remained unproved.

Darwin's theories of evolution were generally accepted within the scientific community in the early decades of the twentieth century, but with major modifications. The "Neo-Darwinians" of the first half of the century combined natural selection with newer genetic theories. The work of the Dutch geneticist Hugo De Vries provided an explanation for the cause of Darwin's important "variations"—continual genetic mutations in organisms. Not every aspect of Darwin's ideas has been accepted, however. The biologist Stephen Jay Gould has been one of the advocates of the theory of "punctuated equilibrium," which holds that species, rather than undergoing the very gradual changes described by Darwin, actually undergo rapid genetic alterations or "genetic jumps," followed by long periods of little or no change.

the social darwinians

The Social Darwinians, largely nonscientists, were social and political commentators who cited Darwin to buttress their own preconceived ideas. Darwin had provided little guidance regarding the meaning of his system of evolution for political or social issues. One exception was the theory of laissez-faire, the name of the nineteenth-century economic belief that governments should not interfere in the operations of the business world. Darwin favored the concept of laissez-faire, opposing a proposal by British trade unions that factory workers should be paid by the hour rather than by the piece. He wrote that it meant "excluding competition," which, in turn, would be a "great evil for the future progress of mankind." Such comments led Karl Marx to describe the Origin as an example of "British greed morality."

The majority of Social Darwinians claimed to see in natural selection a justification for laissez-faire, nationalistic beliefs, or theories of racial superiority. To the American writer William Graham Sumner, life was a constant struggle, and humanitarian efforts to eliminate poverty were "ill conceived." On the continent of Europe, the German historian Heinrich von Treitschke saw war as a Darwinian testing ground that led to the "utter annihilation of puny man," separating the "wheat" from the "chaff." As European nations came to dominate large areas of Asia and Africa in the late nineteenth century, some Social Darwinians sought to justify these colonial adventures by asserting white racial superiority.

A smaller group of Social Darwinians thought that the struggle for existence, instead of being a struggle between individuals, was a struggle of whole groups of animals against their environment. The most prominent member of this school of thought was the Russian writer Peter Kropotkin. Using his own observations of the behavior of animals in the harsh winters of Siberia, Kropotkin insisted that the "struggle for survival" was a joint struggle of animals against their own environment; the "fittest" animals were those who supported each other through what he termed "mutual aid."

Social Darwinism took a fateful turn in the twentieth century with the emergence of the eugenics and "racial hygiene" movements. Darwin's cousin Francis Galton had coined the term eugenics to describe "selective efforts at human improvement." Although Darwin did not endorse his cousin's ideas, Darwin's theories were cited during the early twentieth century by members of eugenics societies in Europe and the United States. Some of these societies promoted the forced sterilization of the "feeble-minded," the insane, the criminal, and the deaf.

During the 1930s and early 1940s the German dictator Adolf Hitler and his National Socialist movement used a crude Social Darwinism to justify their racial policies and glorify war. The ultimate result of Nazi "racial hygiene" was the death of eleven million people in concentration camps. No "racial hygienist" was an internationally respected scientist, however, and Darwin had consistently rejected prowar analogies drawn from his theories. Darwin argued, in fact, that the earliest human beings emerged in Africa rather than in Europe or North America. Modern anthropologists tend to agree.

See alsoAgassiz, Louis; Eugenics; Evolution; Great Britain; Haeckel, Ernst Heinrich; Humboldt, Alexander and Wilhelm von; Lamarck, Jean-Baptiste; Mendel, Gregor; Science and Technology; Wallace, Alfred Russel.

bibliography

Primary Sources

Burkhardt, Frederick, and Sydney Smith. The Correspondence of Charles Darwin Cambridge, U.K., 1985–. This, the most complete publication of Darwin's letters, will fill an anticipated thirty-two volumes and supersedes The Life and Letters of Charles Darwin (3 vols., 1887) and More Letters of Charles Darwin (2 vols., 1903), edited by Darwin's son Francis.

Darwin, Charles. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. London, 1859. Numerous reprintings.

——. The Descent of Man and Selection in Relation to Sex. 2 vols. London, 1871. Numerous reprintings.

——. Autobiography. Edited by Nora Barlow. London and New York, 1958. Reprint, 1993. This edition of Darwin's autobiography restored passages, omitted from an earlier edition by Darwin's wife, in which Darwin wrote that the existence of God might be neither proved nor disproved, a position known as agnosticism.

——. Diary of the Voyage of the H.M.S. Beagle. Edited by Richard Darwin Keynes. Cambridge, U.K., and New York, 1988. Reprint, 2001.

Secondary Sources

Aydon, Cyril. Charles Darwin: The Naturalist Who Started a Scientific Revolution. London and New York, 2002. Darwin's life and theories explained for the general reader.

Bowler, Peter J. Evolution: The History of an Idea. Berkeley, Calif., 1989. 3rd ed., 2003. Authoritative in its description of the development of various evolutionary theories.

Browne, Janet. Charles Darwin: Voyaging and Charles Darwin: The Power of Place. Princeton, N.J., 1996, and New York, 2002. This two-volume biography uses new material from family archives.

Desmond, Adrian, James Moore, and James R. Moore. Darwin: The Life of a Tormented Evolutionist. London and New York, 1992. Reprint, 1994. Part of this book deals with Darwin's fears that the Origin would engender so much controversy that its scientific merit would be ignored.

Eiseley, Loren. Darwin's Century: Evolution and Men who Discovered It. New York, 1958. Reprint, 1961. This book, by an anthropologist, treats Darwinism as the central event in the history of evolutionary theories, and makes other figures, such as Buffon and the Swedish botanist Carl Linnaeus, into "precursors" of Darwin.

Glick, Thomas F., ed. The Comparative Reception of Darwinism. Chicago, 1988. Reprint, 2003. Glick's book covers not only Europe and the United States but also areas such as Mexico and the Islamic world.

Gould, Stephen Jay. The Structure of Evolutionary Theory. Cambridge, Mass., 2002. Evolution presented by a biologist who was a major twentieth-century dissenter from some of Darwin's theories.

Greene, John C. The Death of Adam: Evolution and Its Impact on Western Thought. Ames, Iowa, 1959. Reprint, 1961, 1996. Focuses on Darwinism as a materialist threat to the older view of nature as a tool of God.

Himmelfarb, Gertrude. Darwin and the Darwinian Revolution. London and Garden City, New York, 1959. Reprint, 1996. Distinctive among Darwin biographies for its critical tone toward both Darwin's personality and scientific work.

Hull, David. Darwin and His Critics: The Reception of Darwin's Theory of Evolution by the Scientific Community. Cambridge, Mass., 1973. Reprint, 1993. Contrasts with the Glick book by focusing more on the debates over the scientific merits of Darwin's theories.

Kohn, David, ed. The Darwinian Heritage: Including Proceedings of the Charles Darwin Centenary Conference. Princeton, N.J., 1985. Reprint, 1988. Thirty-two leading scholars assess the social and cultural impact of Darwin.

Mayr, Ernst. One Long Argument: Charles Darwin and the Genesis of Modern Evolutionary Thought. Cambridge, Mass., 1991. Reprint, 1993. A modern view of Darwin by a major twentieth-century biologist.

Ospovat, Dov. The Development of Darwin's Theory: Natural History, Natural Theology, and Natural Selection, 1838–1859. Cambridge, U.K., and New York, 1981. An influential book that concentrates on the period when Darwin was formulating his theory of natural selection.

Rogers, James Allen. "Darwinism and Social Darwinism." Journal of the History of Ideas 33 (1972): 265–280. A groundbreaking article which argues that the Social Darwinians, by using "unnecessary concepts," which Darwin borrowed from Malthus and Spencer, distorted the essence of Darwin's theories

Ruse, Michael. The Darwinian Revolution: Science Red in Tooth and Claw. Chicago, 1979. Reprint, 1981, 1999. Ruse's book concludes that while many scientists came to accept "evolution," many did not accept "natural selection."

Russett, Cynthia Eagle. Darwin in America: The Intellectual Response, 1865–1912. San Francisco, 1976. An important book that focuses on the reaction to Darwin's theories by major American thinkers of his time.

Young, Robert M. Darwin's Metaphor: Nature's Place in Victorian Culture. Cambridge, U.K., and New York, 1985. Examines the implications of, and the debate over, the significance of Darwin's work for the place of human beings in nature at large.

Niles R. Holt