On the Origin of Species
On the Origin of Species (or, more completely, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life), published on 24 November 1859, is a work of scientific literature by Charles Darwin which is considered to be the foundation of evolutionary biology. Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection. It presented a body of evidence that the diversity of life arose by common descent through a branching pattern of evolution. Darwin included evidence that he had gathered on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence, and experimentation.
Epigrams
“But with regard to the material world, we can at least go so far as this—we can perceive that ev...
Introduction
When on board H.M.S. 'Beagle,' as naturalist, I was much struck with certain facts in the distrib...
Variation under Domestication
Causes of Variability
When we look to the individuals of the same variety or sub-variety of our older cultivated plants...
Effects of Habit and the Use or Disuse of Parts; Correlated Variation; Inheritance.
Changed habits produce an inherited effect as in the period of the flowering of plants when trans...
Character of Domestic Varieties; difficulty of distinguishing between Varieties and Species; origin of Domestic Varieties from one or more Species.
When we look to the hereditary varieties or races of our domestic animals and plants, and compare...
Breeds of the Domestic Pigeon, their Differences and Origin.
Believing that it is always best to study some special group, I have, after deliberation, taken u...
Principles of Selection anciently followed, and their Effects.
Let us now briefly consider the steps by which domestic races have been produced, either from one...
Unconscious Selection.
At the present time, eminent breeders try by methodical selection, with a distinct object in view...
Circumstances favourable to Man's power of Selection.
I will now say a few words on the circumstances, favourable or the reverse, to man's power of sel...
Variation under Nature
Before applying the principles arrived at in the last chapter to organic beings in a state of nat...
Individual Differences
The many slight differences which appear in the offspring from the same parents, or which it may ...
Doubtful Species
The forms which possess in some considerable degree the character of species, but which are so cl...
Wide-ranging, much-diffused, and common Species vary most.
Guided by theoretical considerations, I thought that some interesting results might be obtained i...
Species of the Larger Genera in each Country vary more frequently than the Species of the Smaller Genera.
If the plants inhabiting a country as described in any Flora, be divided into two equal masses, a...
Many of the Species included within the Larger Genera resemble Varieties in being very closely, but unequally, related to each other, and in having restricted ranges.
There are other relations between the species of large genera and their recorded varieties which ...
Summary.
Finally, varieties cannot be distinguished from species,— except, first, by the discovery of inte...
Struggle for Existence
The Bearing of Struggle for Existence on Natural Selection
Before entering on the subject of this chapter, I must make a few preliminary remarks to show how...
The Term, Struggle for Existence, Used in a Large Sense
I should premise that I use this term in a large and metaphorical sense, including dependence of ...
Geometrical Ratio of Increase.
A struggle for existence inevitably follows from the high rate at which all organic beings tend t...
Nature of the Checks to Increase.
The causes which check the natural tendency of each species to increase are most obscure. Look at...
Complex Relations of all Animals and Plants to Each Other in the Struggle for Existence.
Many cases are on record showing how complex and unexpected are the checks and relations between ...
Struggle for Life most severe between Individuals and Varieties of the same Species.
As the species of the same genus usually have, though by no means invariably, much similarity in ...
Natural Selection; or the Survival of the Fittest
Natural Selection: Its Power Compared with Man’s Selection
How will the struggle for existence, briefly discussed in the last chapter, act in regard to vari...
Sexual Selection.
Inasmuch as peculiarities often appear under domestication in one sex and become hereditarily att...
Illustrations of the Action of Natural Selection, or the Survival of the Fittest.
In order to make it clear how, as I believe, natural selection acts, I must beg permission to giv...
On the Intercrossing of Individuals.
I must here introduce a short digression. In the case of animals and plants with separated sexes,...
Circumstances favourable for the production of new forms through Natural Selection.
This is an extremely intricate subject. A great amount of variability, under which term individua...
Extinction caused by Natural Selection.
This subject will be more fully discussed in our chapter on Geology; but it must here be alluded ...
Divergence of Character.
The principle, which I have designated by this term, is of high importance, and explains, as I be...
The Probable Effects of the Action of Natural Selection through Divergence of Character and Extinction, on the Descendants of a Common Ancestor.
After the foregoing discussion, which has been much compressed, we may assume that the modified d...
On the degree to which organisation tends to advance.
Natural selection acts exclusively by the preservation and accumulation of variations, which are ...
Convergence of Character.
Mr. H. C. Watson thinks that I have overrated the importance of divergence of character (in which...
Summary of Chapter.
If under changing conditions of life organic beings present individual differences in almost ever...
Laws of Variation
Effects of Changed Conditions
I have hitherto sometimes spoken as if the variations — so common and multiform with organic bein...
Effects of the increased use and disuse of parts, as controlled by natural selection.
From the facts alluded to in the first chapter, I think there can be no doubt that use in our dom...
Acclimatisation.
Habit is hereditary with plants, as in the period of flowering, in the time of sleep, in the amou...
Correlated variation.
I mean by this expression that the whole organisation is so tied together, during its growth and ...
Compensation and Economy of Growth.
The elder Geoffroy and Goethe propounded, at about the same time, their law of compensation or ba...
Multiple, Rudimentary, and Lowly-organised Structures are Variable.
It seems to be a rule, as remarked by Is. Geoffroy St. Hilaire, both with varieties and species, ...
A Part developed in any Species in an extraordinary degree or manner, in comparison with the same Part in allied Species, tends to be highly variable.
Several years ago I was much struck by a remark to the above effect made by Mr. Waterhouse. Profe...
Specific characters more variable than generic characters.
The principle discussed under the last heading may be applied to our present subject. It is notor...
Summary.
Our ignorance of the laws of variation is profound. Not in one case out of a hundred can we prete...
Difficulties of the Theory
Difficulties of the Theory of Descent with Modification
Long before the reader has arrived at this part of my work, a crowd of difficulties will have occ...
On the absence or rarity of transitional varieties.
As natural selection acts solely by the preservation of profitable modifications, each new form w...
On the Origin and Transition of Organic Beings with peculiar Habits and Structure.
It has been asked by the opponents of such views as I hold, how, for instance, could a land carni...
Organs of extreme Perfection and Complication.
To suppose that the eye with all its inimitable contrivances for adjusting the focus to different...
Modes of transition.
If it could be demonstrated that any complex organ existed, which could not possibly have been fo...
Special difficulties of the theory of natural selection.
Although we must be extremely cautious in concluding that any organ could not have been produced ...
Organs of little apparent Importance, as affected by Natural Selection.
As natural selection acts by life and death,— by the survival of the fittest, and by the destruct...
Utilitarian Doctrine, how far true: Beauty, how acquired.
The foregoing remarks lead me to say a few words on the protest lately made by some naturalists a...
Summary: The Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection.
We have in this chapter discussed some of the difficulties and objections which may be urged agai...
Miscellaneous Objections to the Theory of Natural Selection
I will devote this chapter to the consideration of various miscellaneous objections which have be...
Instinct
Instincts Comparable with Habits, but Different in Their Origin
Many instincts are so wonderful that their development will probably appear to the reader a diffi...
Inherited Changes of Habit or Instinct in Domesticated Animals.
The possibility, or even probability, of inherited variations of instinct in a state of nature wi...
Special Instincts.
We shall, perhaps, best understand how instincts in a state of nature have become modified by sel...
Objections to the Theory of Natural Selection as applied to Instincts: Neuter and Sterile Insects.
It has been objected to the foregoing view of the origin of instincts that "the variations of str...
Summary.
I have endeavoured in this chapter briefly to show that the mental qualities of our domestic anim...
Hybridism
Distinction between the Sterility of First Crosses and of Hybrids
The view commonly entertained by naturalists is that species, when intercrossed, have been specia...
Laws governing the Sterility of first Crosses and of Hybrids.
We will now consider a little more in detail the laws governing the sterility of first crosses an...
Origin and Causes of the Sterility of first Crosses and of Hybrids.
At one time it appeared to me probable, as it has to others, that the sterility of first crosses ...
Reciprocal Dimorphism and Trimorphism.
This subject may be here briefly discussed, and will be found to throw some light on hybridism. S...
Fertility of Varieties when Crossed, and of their Mongrel Offspring, not universal.
It may be urged as an overwhelming argument that there must be some essential distinction between...
Hybrids and Mongrels compared, independently of their fertility.
Independently of the question of fertility, the offspring of species and of varieties when crosse...
Summary of Chapter.
First crosses between forms, sufficiently distinct to be ranked as species, and their hybrids, ar...
On the Imperfection of the Geological Record
On the Absence of Intermediate Varieties at the Present Day.
In the sixth chapter I enumerated the chief objections which might be justly urged against the vi...
On the Lapse of Time, as inferred from the rate of Deposition and extent of Denudatym.
Independently of our not finding fossil remains of such infinitely numerous connecting links, it ...
On the Poorness of our Palæontological Collections.
Now let us turn to our richest museums, and what a paltry display we behold! That our collections...
On the Absence of Numerous Intermediate Varieties in any Single Formation.
From these several considerations it cannot be doubted that the geological record, viewed as a wh...
On the sudden Appearance of whole Groups of allied Species.
The abrupt manner in which whole groups of species suddenly appear in certain formations, has bee...
On the sudden Appearance of Groups of allied Species in the lowest known Fossiliferous Strata.
There is another and allied difficulty, which is much more serious. I allude to the manner in whi...
On the Geological Succession of Organic Beings
On the Slow and Successive Appearance of New Species
Let us now see whether the several facts and laws relating to the geological succession of organi...
On Extinction.
We have as yet only spoken incidentally of the disappearance of species and of groups of species....
On the Farms of Life changing almost simultaneously throughout the World.
Scarcely any palæontological discovery is more striking than the fact that the forms of life chan...
On the Affinities of Extinct Species to each other, and to Living Forms.
Let us now look to the mutual affinities of extinct and living species. All fall into a few grand...
On the State of Development of Ancient compared with Living Forms.
We have seen in the fourth chapter that the degree of differentiation and specialisation of the p...
On the Succession of the same Types within the same Areas, during the later Tertiary periods.
Mr. Clift many years ago showed that the fossil mammals from the Australian caves were closely al...
Summary of the preceding and present Chapters.
I have attempted to show that the geological record is extremely imperfect; that only a small por...
Geographical Distribution
Present Distribution Cannot Be Accounted for by Differences in Physical Conditions
In considering the distribution of organic beings over the face of the globe, the first great fac...
Means of Dispersal.
Sir C. Lyell and other authors have ably treated this subject. I can give here only the briefest ...
Dispersal during the Glacial Period.
The identity of many plants and animals, on mountain-summits, separated from each other by hundre...
Alternate Glacial Periods in the North and South.
But we must return to our more immediate subject. I am convinced that Forbes's view may be largel...
Geographical Distribution—Continued
Fresh-water Productions
As lakes and river-systems are separated from each other by barriers of land, it might have been ...
On the Inhabitants of Oceanic Islands.
We now come to the last of the three classes of facts, which I have selected as presenting the gr...
Absence of Batrachians and Terrestrial Mammals on Oceanic Islands.
With respect to the absence of whole orders of animals on oceanic islands, Bory St. Vincent long ...
On the Relation of the Inhabitants of Islands to those of the nearest Mainland.
The most striking and important fact for us is the affinity of the species which inhabit islands ...
Summary of the last and present Chapters.
In these chapters I have endeavoured to show that if we make due allowance for our ignorance of t...
Mutual Affinities of Organic Beings: Morphology—Embryology—Rudimentary Organs
Classification.
From the most remote period in the history of the world organic beings have been found to resembl...
Analogical Resemblances.
We can understand why a species or a group of species may depart from its allies, in several of i...
On the Nature of the Affinities Connecting Organic Beings.
As the modified descendants of dominant species, belonging to the larger genera, tend to inherit ...
Morphology.
We have seen that the members of the same class, independently of their habits of life, resemble ...
Development and Embryology.
This is one of the most important subjects in the whole round of natural history. The metamorphos...
Rudimentary, Atrophied, and Aborted Organs.
Organs or parts in this strange condition, bearing the plain stamp of inutility, are extremely co...
Summary.
In this chapter I have attempted to show that the arrangement of all organic beings throughout al...
Recapitulation and Conclusion
As this whole volume is one long argument, it may be convenient to the reader to have the leading...