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Perhaps the most readable and accessible of the great works of scientific imagination, The Origin of Species sold out on the day it was published in 1859. Theologians quickly labeled Charles Darwin the most dangerous man in England, and, as the Saturday Review noted, the uproar over the book quickly "passed beyond the bounds of the study and lecture-room into the drawing-room and the public street." Yet, after reading it, Darwin's friend and colleague T. H. Huxley had a different reaction: "How extremely stupid not to have thought of that." Based largely on Darwin's experience as a naturalist while on a five-year voyage aboard H.M.S. Beagle, The Origin of Species set forth a theory of evolution and natural selection that challenged contemporary beliefs about divine providence and the immutability of species. A landmark contribution to philosophical and scientific thought, this edition also includes an introductory historical sketch and a glossary Darwin later added to the original text. Charles Darwin grew up considered, by his own account, "a very ordinary boy, rather below the common standard of intellect." A quirk of fate kept him from the career his father had deemed appropriate--that of a country parson--when a botanist recommended Darwin for an appointment as a naturalist aboard H.M.S. Beagle from 1831 to 1836. Darwin is also the author of the five-volume work Zoology of the Voyage of the Beagle (1839) and The Descent of Man (1871). From the Trade Paperback edition.

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CHARLES ROBERT DARWIN was born in 1809 in Shrewsbury, England, to a wealthy intellectual family, his grandfather being the famous physician Erasmus Darwin. At Cambridge University he formed a friendship with J. S. Henslow, a professor of botany, and that association, along with his enthusiasm for collecting beetles, led to “a burning zeal,” as he wrote in his Autobiography, for the natural sciences. When Henslow obtained for him the post of naturalist on H.M.S. Beagle, the course of his life was fixed. The five-year-long voyage to the Southern Hemisphere between 1831 and 1836 would lay the foundation for his ideas about evolution and natural selection. Upon his return Darwin lived in London before retiring to his residence at Down, a secluded village in Kent. For the next forty years he conducted his research there and wrote the works that would change human understanding forever. Knowing of the resistance from the orthodox scientific and religious communities, Darwin published The Origin of Species in 1859 only when another naturalist, Alfred Russel Wallace, independently reached the same conclusions. His other works include The Descent of Man, and Selection in Relation to Sex (1871) and Recollections of My Mind and Character, also titled Autobiography (1887). Charles Darwin’s Diary of the Voyage of the H.M.S. Beagle was published posthumously in 1933. Darwin died in 1882; he is buried in Westminster Abbey.

From the Paperback edition.

AN HISTORICAL SKETCH

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INTRODUCTION

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CHAPTER I VARIATION UNDER DOMESTICATION Causes of Variability-Effects of Habit and the use or disuse of Parts-Correlated Variation-Inheritance-Character of Domestic Varieties-Difficulty of distinguishing between Varieties and Species-Origin of Domestic Varieties from one or more Species-Domestic Pigeons, their Differences and Origin-Principles of Selection, anciently followed, their Effects-Methodical and Unconscious Selection-Unknown Origin of our Domestic Productions-Circumstances favourable to Man's power of Selection

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CHAPTER II VARIATION UNDER NATURE Variability-Individual differences-Doubtful species-Wide ranging, much diffused, and common species vary most-Species of the larger genera in each country vary more frequently than the Species of the smaller genera-Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges

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CHAPTER III STRUGGLE FOR EXISTENCE Its bearing on natural selection-The term used in a wide sense-Geometrical ratio of the increase-Rapid increase of naturalised animals and plants-Nature of the checks to increase-Competition universal-Effects of Climate-Protection from the number of individuals-Complex relations of all animals and plants throughout nature-Struggle for life most servere between individuals and varieties of the same species: Often severe between species of the same genus-The relation of organism to organism the most important of all relations

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CHAPTER IV NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST Natural Selection-its power compared with man's selection-its power on characters of trifling importance-its power at all ages and on both sexes-Sexual Selection-On the generality of intercrosses between individuals of the same species-Circumstances favourable and unfavourable to the results of Natural Selection, namely, intercrossing, isolation, number of individuals-Slow action-Extinction caused by Natural Selection-Divergence of Character, related to the diversity of inhabitants of any small area, and to naturalisation-Action of Natural Selection, through Divergence of Character, and Extinction, on the descendants from a comman parent-Explains the grouping of all organic beings-Advance in organisation-Low forms preserved-Convergence of character-Indefinite multiplication of species-Summary

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CHAPTER V LAWS OF VARIATION Effects of changed conditions-Use and disuse, combined with natural selection; organs of flight and of vision-Acclimatisation-Correlated variation-Compensation and economy of growth-False correlations-Multiple, rudimentary and lowly organised structures variable-Parts developed in an unusual manner are highly variable; specific characters more variable than generic: secondary sexual characters variable-Species of the same genus vary in an analogous manner Reversions to long-lost characters-Summary

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CHAPTER VI DIFFICULTIES OF THE THEORY Difficulties of the theory of descent with modification-Absence or rarity of transitional varieties-Transitions in habits of life-Diversified habits in the same species-Species with habits widely different from those of their allies-Organs of extreme perfection-Modes of transition-Cases of difficulty-Naturanon facit saltum-Organs of small importance-Organs not in all cases absolutely perfect-The law of Unity of Type and of the Conditions of Existence embraced by the theory of Natural Selection

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CHAPTER VII MISCELLANEOUS OBJECTIONS TO THE THEORY OF NATURAL SELECTION Longevity-Modifications not necessarily simultaneous-Modifications apparently of no direct service-Progressive development-Characters of small functional importance, the most constant-Supposed incompetence of natural selection to account for the incipient stages of useful structures-Causes which interfere with the acquisition through natural selection of useful structures-Gradations of structure with changed functions Widely different organs in members of the same class, developed from one and the same source-Reasons for disbelieving in great and abrupt modifications

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CHAPTER VIII INSTINCT Instincts comparable with habits, but different in their origin-Instincts graduated-Aphides and ants-Instincts variable-Domestic instincts, their origin-Natural instincts of the cuckoo, molothrus, ostrich, and parasitic bees Slave-making ants-Hive-bee, its cell-making instinct-Changes of instinct and structure not necessarily simultaneous-Difficulties of the theory of the Natural Selection of instincts-Neuter or sterile insects-Summary

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CHAPTER IX HYBRIDISM Distinction between the Sterility of first crosses and of hybrids-Sterility various in degree, not universal, affected by close interbreeding, removed by domestication-Laws governing the sterility of hybrids-Sterility not a special endowment, but incidental on other differences, not accumulated by natural selection-Causes of the sterility of first crosses and of hybrids-Parallelism between the effects of changed conditions of life and of crossing-Dimorphism and trimorphism-Fertility of varieties when crossed and of their mongrel offspring not universal-Hybrids and mongrels compared independently of their fertility-Summary

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CHAPTER X ON THE IMPERFECTION OF THE GEOLOGICAL RECORD On the absence of intermediate varieties at the present day--On the nature of extinct intermediate varieties; on their number--On the lapse of time, as estimated by years--On the poorness of our palaeontological collections--On the intermittence of geological formations--On the denudation of granitic areas--On the absence of intermediate varieties in any one formation--On the sudden appearance in the lowest known fossiliferous strata--Antiquity the habitable earth

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CHAPTER XI ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS On the slow and successive appearance of new species--On their different rates of change--Species once lost do not reappear--Groups of species follow the same general rules in their appearance and disappearance as do single species--On extinction--On simultaneous changes in the forms of life throughout the world--On the affinities of extinct species to each other and to living species--On the state of development of ancient forms--On the state the same types within the same areas--Summary of preceding and present chapter

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CHAPTER XII GEOGRAPHICAL DISTRIBUTION Present distribution cannot be accounted for by differences in physical conditions--Importance of barriers--Affinity of the productions of the same continent--Centres of creation--Means of dispersal by changes of climate and of the level of the land, and by occasional means--Dispersal during the Glacial period--Alternate Glacial periods in the North and South

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CHAPTER XIII GEOGRAPHICAL DISTRIBUTION--continued Distribution of fresh-water productions--On the inhabitants of oceanic islands--Absence of Batrachians and of terrestrial Mammals--On the relation of the inhabitants of islands to those of the nearest mainland--On colonisation from the nearest source with subsequent modification--Summary of the last and present chapter

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CHAPTER XIV MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: EMBRYOLOGY: RUDIMENTARY ORGANS Classification, groups subordinate to groups--Natural system--Rules and difficulties in classification, explained on the theory of descent with modification --Classification of varieties--Descent always used in classification--Analogical or adaptive characters--Affinities, general, complex, and radiating--Extinction separates and defines groups--MORPHOLOGY, between members of the same class, between parts of same individual--EMBRYOLOGY, laws of, explained by variations not supervening at an early age, and being inherited at a corresponding age--RUDIMENTARY ORGANS; their origin explained--Summary

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CHAPTER XV RECAPITULATION AND CONCLUSION Recapitulation of the objections to the theory of Natural Selection--Recapitulation of the general and special circumstances in its favour--Causes of the general belief in the immutability of species--How far the theory of Natural Selection may be extended--Effects of its adoption on the study of Natural History--Concluding remarks

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GLOSSARY OF SCIENTIFIC TERMS

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INDEX

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Chapter One

Variation Under Domestication

Causes of Variability—Effects of Habit—Correlation of Growth—Inheritance—Character of Domestic Varieties—Difficulty of distinguishing between Varieties and Species—Origin of Domestic Varieties from one or more Species—Domestic Pigeons, their Differences and Origin—Principle of Selection anciently followed, its Effects—Methodical and Unconscious Selection—Unknown Origin of our Domestic Productions—Circumstances favourable to Man's power of Selection

WHEN WE look to the individuals of the same variety or sub-variety of our older cultivated plants and animals, one of the first points which strikes us, is, that they generally differ much more from each other, than do the individuals of any one species or variety in a state of nature. When we reflect on the vast diversity of the plants and animals which have been cultivated, and which have varied during all ages under the most different climates and treatment, I think we are driven to conclude that this greater variability is simply due to our domestic productions having been raised under conditions of life not so uniform as, and somewhat different from, those to which the parent species have been exposed under nature. There is, also, I think, some probability in the view propounded by Andrew Knight, that this variability may be partly connected with excess of food. It seems pretty clear that organic beings must be exposed during several generations to the new conditions of life to cause any appreciable amount of variation; and that when the organisation has once begun to vary, it generally continues to vary for many generations. No case is on record of a variable being ceasing to be variable under cultivation. Our oldest cultivated plants, such as wheat, still often yield new varieties: our oldest domesticated animals are still capable of rapid improvement or modification.
It has been disputed at what period of life the causes of variability, whatever they may be, generally act; whether during the early or late period of development of the embryo, or at the instant of conception. Geoffroy St Hilaire's experiments show that unnatural treatment of the embryo causes monstrosities; and monstrosities cannot be separated by any clear line of distinction from mere variations. But I am strongly inclined to suspect that the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of conception. Several reasons make me believe in this; but the chief one is the remarkable effect which confinement or cultivation has on the functions of the reproductive system; this system appearing to be far more susceptible than any other part of the organization, to the action of any change in the conditions of life. Nothing is more easy than to tame an animal, and few things more difficult than to get it to breed freely under confinement, even in the many cases when the male and female unite. How many animals there are which will not breed, though living long under not very close confinement in their native country! This is generally attributed to vitiated instincts; but how many cultivated plants display the utmost vigour, and yet rarely or never seed! In some few such cases it has been found out that very trifling changes, such as a little more or less water at some particular period of growth, will determine whether or not the plant sets a seed. I cannot here enter on the copious details which I have collected on this curious subject; but to show how singular the laws are which determine the reproduction of animals under confinement, I may just mention that carnivorous animals, even from the tropics, breed in this country pretty freely under confinement, with the exception of the plantigrades or bear family; whereas, carnivorous birds, with the rarest exceptions, hardly ever lay fertile eggs. Many exotic plants have pollen utterly worthless, in the same exact condition as in the most sterile hybrids. When, on the one hand, we see domesticated animals and plants, though often weak and sickly, yet breeding quite freely under confinement; and when, on the other hand, we see individuals, though taken young from a state of nature, perfectly tamed, long-lived, and healthy (of which I could give numerous instances), yet having their reproductive system so seriously affected by unperceived causes as to fail in acting, we need not be surprised at this system, when it does act under confinement, acting not quite regularly, and producing offspring not perfectly like their parents or variable.

Sterility has been said to be the bane of horticulture; but on this view we owe variability to the same cause which produces sterility; and variability is the source of all the choicest productions of the garden. I may add, that as some organisms will breed most freely under the most unnatural conditions (for instance, the rabbit and ferret kept in hutches), showing that their reproductive system has not been thus affected; so will some animals and plants withstand domestication or cultivation, and vary very slightly—perhaps hardly more than in a state of nature.

A long list could easily be given of 'sporting plants;' by this term gardeners mean a single bud or offset, which suddenly assumes a new and sometimes very different character from that of the rest of the plant. Such buds can be propagated by grafting, &c., and sometimes by seed. These 'sports' are extremely rare under nature, but far from rare under cultivation; and in this case we see that the treatment of the parent has affected a bud or offset, and not the ovules or pollen. But it is the opinion of most physiologists that there is no essential difference between a bud and an ovule in their earliest stages of formation; so that, in fact, 'sports' support my view, that variability may be largely attributed to the ovules or pollen, or to both, having been affected by the treatment of the parent prior to the act of conception. These cases anyhow show that variation is not necessarily connected, as some authors have supposed, with the act of generation.

Seedlings from the same fruit, and the young of the same litter, sometimes differ considerably from each other, though both the young and the parents, as Mxller has remarked, have apparently been exposed to exactly the same conditions of life; and this shows how unimportant the direct effects of the conditions of life are in comparison with the laws of reproduction, and of growth, and of inheritance; for had the action of the conditions been direct, if any of the young had varied, all would probably have varied in the same manner. To judge how much, in the case of any variation, we should attribute to the direct action of heat, moisture, light, food, &c., is most difficult: my impression is, that with animals such agencies have produced very little direct effect, though apparently more in the case of plants. Under this point of view, Mr Buckman's recent experiments on plants seem extremely valuable. When all or nearly all the individuals exposed to certain conditions are affected in the same way, the change at first appears to be directly due to such conditions; but in some cases it can be shown that quite opposite conditions produce similar changes of structure. Nevertheless some slight amount of change may, I think, be attributed to the direct action of the conditions of life—as, in some cases, increased size from amount of food, colour from particular kinds of food and from light, and perhaps the thickness of fur from climate.

Habit also has a deciding influence, as in the period of flowering with plants when transported from one climate to another. In animals it has a more marked effect; for instance, I find in the domestic duck that the bones of the wing weigh less and the bones of the leg more, in proportion to the whole skeleton, than do the same bones in the wild-duck; and I presume that this change may be safely attributed to the domestic duck flying much less, and walking more, than its wild parent. The great and inherited development of the udders in cows and goats in countries where they are habitually milked, in comparison with the state of these organs in other countries, is another instance of the effect of use. Not a single domestic animal can be named which has not in some country drooping ears; and the view suggested by some authors, that the drooping is due to the disuse of the muscles of the ear, from the animals not being much alarmed by danger, seems probable.

There are many laws regulating variation, some few of which can be dimly seen, and will be hereafter briefly mentioned. I will here only allude to what may be called correlation of growth. Any change in the embryo or larva will almost certainly entail changes in the mature animal. In monstrosities, the correlations between quite distinct parts are very curious; and many instances are given in Isidore Geoffroy St Hilaire's great work on this subject. Breeders believe that long limbs are almost always accompanied by an elongated head. Some instances of correlation are quite whimsical; thus cats with blue eyes are invariably deaf; colour and constitutional peculiarities go together, of which many remarkable cases could be given amongst animals and plants. From the facts collected by Heusinger, it appears that white sheep and pigs are differently affected from coloured individuals by certain vegetable poisons. Hairless dogs have imperfect teeth; long-haired and coarse-haired animals are apt to have, as is asserted, long or many horns; pigeons with feathered feet have skin between their outer toes; pigeons with short beaks have small feet, and those with long beaks large feet. Hence, if man goes on selecting, and thus augmenting, any peculiarity, he will almost certainly unconsciously modify other parts of the structure, owing to the mysterious laws of the correlation of growth.

The result of the various, quite unknown, or dimly seen laws of variation is infinitely complex and diversified. It is well worth while carefully to study the several treatises published on some of our old cultivated plants, as on the hyacinth, potato, even the dahlia, &c.; and it is really surprising to note the endless points in structure and constitution in which the varieties and subvarieties differ slightly from each other. The whole organization seems to have become plastic, and tends to depart in some small degree from that of the parental type.

Any variation which is not inherited is unimportant for us. But the number and diversity of inheritable deviations of structure, both those of slight and those of considerable physiological importance, is endless. Dr Prosper Lucas's treatise, in two large volumes, is the fullest and the best on this subject. No breeder doubts how strong is the tendency to inheritance: like produces like is his fundamental belief: doubts have been thrown on this principle by theoretical writers alone. When a deviation appears not unfrequently, and we see it in the father and child, we cannot tell whether it may not be due to the same original cause acting on both; but when amongst individuals, apparently exposed to the same conditions, any very rare deviation, due to some extraordinary combination of circumstances, appears in the parent—say, once amongst several million individuals—and it reappears in the child, the mere doctrine of chances almost compels us to attribute its reappearance to inheritance. Every one must have heard of cases of albinism, prickly skin, hairy bodies, &c., appearing in several members of the same family. If strange and rare deviations of structure are truly inherited, less strange and commoner deviations may be freely admitted to be inheritable. Perhaps the correct way of viewing the whole subject, would be, to look at the inheritance of every character what ever as the rule, and non-inheritance as the anomaly.

The laws governing inheritance are quite unknown; no one can say why the same peculiarity in different individuals of the same species, and in individuals of different species, is sometimes inherited and sometimes not so; why the child often reverts in certain characters to its grandfather or grandmother or other much more remote ancestor; why a peculiarity is often transmitted from one sex to both sexes, or to one sex alone, more commonly but not exclusively to the like sex. It is a fact of some little importance to us, that peculiarities appearing in the males of our domestic breed are often transmitted either exclusively, or in a much greater degree, to males alone. A much more important rule, which I think may be trusted, is that, whatever period of life a peculiarity first appears in, it tends to appear in the offspring at a corresponding age, though sometimes earlier. In many cases this could not be otherwise; thus the inherited peculiarities in the horns of cattle could appear only in the offspring when nearly mature; peculiarities in the silkworm are known to appear at the corresponding caterpillar or cocoon stage. But hereditary diseases and some other facts make me believe that the rule has a wider extension, and that when there is no apparent reason why a peculiarity should appear at any particular age, yet that it does tend to appear in the offspring at the same period at which it first appeared in the parent. I believe this rule to be of the highest importance in explaining the laws of embryology. These remarks are of course confined to the first appearance of the peculiarity, and not to its primary cause, which may have acted on the ovules or male element; in nearly the same manner as in the crossed offspring from a short-horned cow by a long-horned bull, the greater length of horn, though appearing late in life, is clearly due to the male element.

Having alluded to the subject of reversion, I may here refer to a statement often made by naturalists—namely, that our domestic varieties, when run wild, gradually but certainly revert in character to their aboriginal stocks. Hence it has been argued that no deductions can be drawn from domestic races to species in a state of nature. I have in vain endeavoured to discover on what decisive facts the above statement has so often and so boldly been made. There would be great difficulty in proving its truth: we may safely conclude that very many of the most strongly-marked domestic varieties could not possibly live in a wild state. In many cases we do not know what the aboriginal stock was, and so could not tell whether or not nearly perfect reversion had ensued. It would be quite necessary, in order to prevent the effects of intercrossing, that only a single variety should be turned loose in its new home. Nevertheless, as our varieties certainly do occasionally revert in some of their characters to ancestral forms, it seems to me not improbable, that if we could succeed in naturalising, or were to cultivate, during many generations, the several races, for instance, of the cabbage, in very poor soil (in which case, however, some effect would have to be attributed to the direct action of the poor soil), that they would to a large extent, or even wholly, revert to the wild aboriginal stock. Whether or not the experiment would succeed, is not of great importance for our line of argument; for by the experiment itself the conditions of life are changed. If it could be shown that our domestic varieties manifested a strong tendency to reversion,—that is, to lose their acquired characters, whilst kept under unchanged conditions, and whilst kept in a considerable body, so that free intercrossing might check, by blending together, any slight deviations of structure, in such case, I grant that we could deduce nothing from domestic varieties in regard to species. But there is not a shadow of evidence in favour of this view: to assert that we could not breed our cart and race-horses, long and short-horned cattle, and poultry of various breeds, and esculent vegetables, for an almost infinite number of generations, would be opposed to all experience. I may add, that when under nature the conditions of life do change, variations and reversions of character probably do occur; but natural selection, as will hereafter be explained, will determine how far the new characters thus arising shall be preserved.

From the Paperback edition.

Excerpted from The Origin of Species: By Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life by Charles Darwin
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The Origin of Species

The Origin of Species

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