'On the Origin of Species': natural selection as the mechanism of species formation

24 November 1859 Life and health theory

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A mechanism for the origin of species: since more are born than can survive, any heritable deviation that gives even a slight advantage will more often be preserved and any injurious one destroyed, and over thousands of generations this accumulation turns varieties into species.

The mechanism is set out in the 'Origin of Species' (1859) by the Englishman Charles Darwin. He joined three things: from the breeders he took selection as a force that accumulates small differences; from Malthus, the overproduction of offspring from which a struggle for existence follows; from Lyell, deep time and the rule of explaining the past by slowly acting present causes. The book was written in haste as an 'abstract' of a larger work after Wallace had sent him the same idea.

The mechanism of inheritance Darwin could not explain, and that remained the chief gap in the theory until the rediscovery of Mendel.

Why this date

The date follows the first edition of 'On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life' (London, John Murray): according to Sloan in the Stanford Encyclopedia the book was issued on 24 November 1859, while Britannica gives 22 November as the day it was sold to the trade. Natural selection had been printed in condensed form earlier, on 20 August 1858, in the joint Linnean Society publication with Wallace, but the full statement with its evidence and its treatment of difficulties is the book of 1859. The subject here is chapters III and IV of the book, the struggle for existence and natural selection; the argument from domestic breeds (chapter I) is described separately.

What it grew from

• 'An Essay on the Principle of Population': population outruns subsistence

  influenced · Confidence: high

  Darwin already knew from the breeders that selection accumulates characters, but did not see how selection could act in nature; reading Malthus in the autumn of 1838 gave him the missing link, the overproduction of offspring and the struggle for existence, and he himself repeatedly called this the moment when he 'had at last got a theory by which to work'.

  Dispute: Neither the reading of Malthus nor its turning-point character is contested; the argument is over what exactly Darwin took from him and how decisive that was. One line of historiography (Young, 'Darwin's Metaphor', 1985; Desmond and Moore) derives the theory from British political economy and stresses that Malthusian ideas were commonplace in Darwin's circle long before 1838: Desmond in Britannica calls it 'a seminal moment' but adds at once that Malthusianism 'had long permeated his Whig circle'. Another line (Bowler, 'Malthus, Darwin, and the concept of struggle', Journal of the History of Ideas 37, 1976; Schweber, Journal of the History of Biology 13, 1980) insists that Malthus's 'struggle' and Darwin's are not the same thing, and that by September 1838 Darwin already had most of the components of the theory, so that Malthus supplied a trigger rather than content. Sloan in the Stanford Encyclopedia notes that recent manuscript-based work has 'de-emphasized some of the novelty of Darwin's views'. The date is also inconsistent: Darwin in the Autobiography writes 'October 1838', Desmond in Britannica gives September 1838, Sloan August 1838; by Notebook D the reading is placed on 28 September 1838.

  Link sources

  • Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 20 Sep 2026

    This concern with a causal theory of life was then replaced by a new emphasis on external forces controlling population, a thesis developed from his reading of Thomas Malthus's (1766–1834) Essay on the Principle of Population (6th ed. 1826).

  • Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 20 Sep 2026

    The impact of Darwin's reading of this edition of the Essay in August of 1838, was dramatic. It enabled him to theorize the existence of a constantly-acting dynamic force behind the transformation of species. Darwin's innovation was to universalize the Malthusian "principle of population" to apply to all of nature.

  • Charles Darwin, Evolution by natural selection: the London years, 1836-42, Encyclopaedia Britannica (Adrian J. Desmond) (2026) Verified 24 Sep 2026

    But he only saw the complete congruity between the way nature operated and the way fanciers produced new breeds upon reading the economist Thomas Malthus's Essay on the Principle of Population in September 1838.

  • Charles Darwin, Evolution by natural selection: the London years, 1836-42, Encyclopaedia Britannica (Adrian J. Desmond) (2026) Verified 24 Sep 2026

    Darwin realized that population explosions would lead to a struggle for resources and that the ensuing competition would weed out the unfit. It was an idea he now applied to nature (he had previously thought that animal populations remained stable in the wild). Darwin called his modified Malthusian mechanism "natural selection."

  • Nora Barlow (ed.), The Autobiography of Charles Darwin 1809-1882, London: Collins, p. 120 (Darwin Online, F1497) (1958) Verified 20 Sep 2026

    In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement Malthus on Population, and 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

  • Charles Darwin to A. R. Wallace, 6 April 1859, Darwin Correspondence Project, DCP-LETT-2449 (1859) Verified 20 Sep 2026

    You are right, that I came to conclusion that Selection was the principle of change from study of domesticated productions; & then reading Malthus I saw at once how to apply this principle.

  • Charles Darwin, On the Origin of Species, 1st ed., Introduction, p. 5 (Darwin Online, F373) (1859) Verified 20 Sep 2026

    This is the doctrine of Malthus, applied to the whole animal and vegetable kingdoms.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• 'Principles of Geology': the Earth's past explained by causes now in operation and by vast time

  influenced · Confidence: high

  Lyell gave Darwin not a theory of species but a way of thinking: to explain the past by slow present causes and to allow incomparably long time; Darwin carried the first volume on the Beagle, wrote that his books came 'half out of Lyell's brains', and in the Origin invited anyone who does not admit the vastness of past ages to close the book.

  Dispute: The influence is not contested, but its nature is discussed. The Principles of Geology contain neither evolution nor selection: the second volume explicitly refutes Lamarck, and Lyell, according to Britannica, 'had never shared his protégé's belief in evolution' up to 1859. The link therefore runs through method (actualism, the accumulation of small changes) and through deep time, not through the content of the theory. Sloan assigns the Lyellian explanation to a 'predominantly anglophone historiography' (Hodge, Herbert) and sets against it the social-constructivist line (Young) that derives Darwin from political economy, and recent work that has lowered the estimate of the novelty of his views.

  Link sources

  • Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 20 Sep 2026

    His conversion to the uniformitarian geology of Charles Lyell and to Lyell's advocacy of "deep" geological time during the voyage of the HMS Beagle (December 1831–October 1836), has been seen as fundamental in his formation (Norman 2013; Herbert 2005; Hodge 1983).

  • Charles Lyell, Encyclopaedia Britannica (Richard W. Macomber) (2024)

    Although Darwin drew heavily on Lyell's Principles of Geology both for style and content, Lyell had never shared his protégé's belief in evolution.

  • Charles Darwin, Evolution by natural selection: the London years, 1836-42, Encyclopaedia Britannica (Adrian J. Desmond) (2026) Verified 24 Sep 2026

    That was the way a species kept pace with the Lyellian evolution of Earth.

  • Nora Barlow (ed.), The Autobiography of Charles Darwin 1809-1882, London: Collins, p. 77 (Darwin Online, F1497) (1958) Verified 20 Sep 2026

    I had brought with me the first volume of Lyell's Principles of Geology, which I studied attentively; and this book was of the highest service to me in many ways.

  • Charles Darwin to Leonard Horner, 29 August [1844], Darwin Correspondence Project, DCP-LETT-771 (1844) Verified 5 Oct 2026

    I always feel as if my books came half out of Lyell's brains & that I never acknowledge this sufficiently, nor do I know how I can, without saying so in so many words

  • Charles Darwin, On the Origin of Species, 1st ed., chapter IX, p. 282 (Darwin Online, F373) (1859) Verified 20 Sep 2026

    He who can read Sir Charles Lyell's grand work on the Principles of Geology, which the future historian will recognise as having produced a revolution in natural science, yet does not admit how incomprehensibly vast have been the past periods of time, may at once close this volume.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

What grew out of it

• Regression to the mean and correlation: heredity as statistics

  influenced · Confidence: high

  Magnello asserts the link directly: as soon as Darwin introduced continuous variation into biology, his cousin Galton set about devising statistical methods to measure that variation. Stigler describes the same dependence more precisely in substance: Galton's Aberdeen address of 1885 solved a puzzle left in the Origin of Species, and multivariate analysis came out of that solution.

  Link sources

  • M. Eileen Magnello, Karl Pearson and the Origins of Modern Statistics: An Elastician becomes a Statistician, The Rutherford Journal 1 (2005) Verified 20 Sep 2026

    Once Darwin introduced the idea of continuous variation into biological discourse, his cousin, Francis Galton, began to devise statistical methods to measure this variation.

  • Stephen M. Stigler, Darwin, Galton and the Statistical Enlightenment, Journal of the Royal Statistical Society A 173 (3), 469-482 (2010)

    On September 10th, 1885, Francis Galton ushered in a new era of Statistical Enlightenment with an address to the British Association for the Advancement of Science in Aberdeen. In the process of solving a puzzle that had lain dormant in Darwin's Origin of Species, Galton introduced multivariate analysis and paved the way towards modern Bayesian statistics.

  • J. J. O'Connor, E. F. Robertson, Francis Galton, MacTutor History of Mathematics Archive, University of St Andrews (2003) Verified 20 Sep 2026

    Perhaps it was the publication of Charles Darwin's Origin of the species in 1859 which marked a change in direction of Galton's interests.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

• Pearson's correlation coefficient and the chi-square test

  influenced · Confidence: medium

  Magnello asserts that Pearsonian mathematical statistics was built on Darwin's understanding of a species as a set of 'statistical populations' with individual variation, and that Pearson saw in every Darwinian notion, from variation to inheritance, a demand for statistical analysis.

  Dispute: In Magnello the Darwinian influence on Pearson runs not directly from the book but through the zoologist Weldon, who brought Pearson the Darwinian questions and the Naples crab data. A direct reading of the Origin of Species as the impulse to the method is not asserted here, hence the medium confidence.

  Link sources

  • M. Eileen Magnello, Karl Pearson and the Origins of Modern Statistics: An Elastician becomes a Statistician, The Rutherford Journal 1 (2005) Verified 20 Sep 2026

    Pearsonian mathematical statistics was thus built upon Charles Darwin’s recognition that species comprised different sets of ‘statistical populations’ underpinned by individual variation.

  • M. Eileen Magnello, Karl Pearson and the Origins of Modern Statistics: An Elastician becomes a Statistician, The Rutherford Journal 1 (2005) Verified 20 Sep 2026

    Pearson recognized the fundamental statistical concepts in Darwin’s work, as ‘every idea of Darwin, from variation, natural selection, inheritance to reversion, seemed to demand statistical analyses’.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Other links

• Wallace, 'On the Tendency of Varieties to Depart Indefinitely from the Original Type': natural selection found independently

  parallel to · Confidence: high

  Wallace arrived at natural selection independently of Darwin, who had been working on the same idea since 1838; the receipt of the Ternate paper on 18 June 1858 made Darwin abandon his large work and write the Origin of Species in a year and a half, and the joint reading at the Linnean Society on 1 July 1858 secured priority for both.

  Dispute: Nobody contests the independence of Wallace's discovery; the argument is about Darwin's conduct in June 1858. Brackman ('A Delicate Arrangement', 1980), Brooks (1984) and Davies ('The Darwin Conspiracy', 2008; Biological Journal of the Linnean Society 105, 2012 and 109, 2013) claim that Darwin received the paper two weeks before he told Lyell and had time to borrow the principle of divergence from it; Smith summarises their position as 'Darwin was up to no good in the weeks that followed'. Van Wyhe and Rookmaaker (Biological Journal of the Linnean Society 105, 2012) reconstructed the mail routes and date the receipt to 17-18 June, removing the charge; the Darwin Correspondence Project states plainly 'Darwin didn't steal it'. Smith (2014) takes a middle position: he finds theft 'improbable' but admits the question is not fully closed. The 'delicate arrangement' itself is discussed separately: the reading was arranged without Wallace's knowledge and Darwin's extracts were placed first (McKinney, Britannica); Wallace himself, in a letter to Hooker in October 1858, approved the decision.

  Link sources

  • Alfred Russel Wallace, Darwin Correspondence Project (2024) Verified 20 Sep 2026

    Independently formulated a theory of evolution by natural selection in 1858.

  • James T. Costa, Engaging with Lyell: Alfred Russel Wallace's Sarawak Law and Ternate papers as reactions to Charles Lyell's Principles of Geology, Theory in Biosciences 132 (4), 225-237 (2013) Verified 20 Sep 2026

    Accordingly, much attention has focused on their relationship, from their independent development of the principle of natural selection to the receipt by Darwin of Wallace's essay from Ternate in the spring of 1858, and the subsequent reading of the Wallace and Darwin papers at the Linnean Society on 1 July 1858.

  • Fake Darwin: myths and misconceptions, Darwin Correspondence Project (2024) Verified 20 Sep 2026

    Wallace came to similar conclusions about the mechanism for evolution (which Darwin termed 'natural selection'). The surviving historical evidence makes it clear, however, that Darwin had spent years developing the theory, amassing the evidence, and had written it out in draft form years earlier in 1842. Darwin didn't steal it.

  • Alfred Russel Wallace, Encyclopaedia Britannica (2024) Verified 24 Sep 2026

    In early 1858 he sent a paper outlining these ideas to Darwin, who saw such a striking coincidence to his own theory that he consulted his closest colleagues, the geologist Charles Lyell and the botanist Joseph Dalton Hooker.

  • Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 5 Oct 2026

    The hurried preparation and publication of the Origin between the summer of 1858 and November of 1859 was prompted by the receipt on June 18 of 1858 of a letter and manuscript from Alfred Russel Wallace (1823–1913) that outlined his remarkably similar views on the possibility of continuous species change under the action of a selection upon natural variation

  • Charles Darwin to Charles Lyell, 18 [June 1858], Darwin Correspondence Project, Fake Darwin (1858) Verified 20 Sep 2026

    I never saw a more striking coincidence. if Wallace had my M.S. sketch written out in 1842 he could not have made a better short abstract! Even his terms now stand as Heads of my Chapters.

  • Nora Barlow (ed.), The Autobiography of Charles Darwin 1809-1882, London: Collins, p. 121 (Darwin Online, F1497) (1958) Verified 20 Sep 2026

    early in the summer of 1858 Mr Wallace, who was then in the Malay archipelago, sent me an essay On the Tendency of Varieties to depart indefinitely from the Original Type; and this essay contained exactly the same theory as mine.

  "Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

Node sources

• Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 5 Oct 2026

  The Origin of Species by Means of Natural Selection, or the Preservaton of Favoured Races in the Struggle for Life was issued in London by the publishing house of John Murray on November 24, 1859 (Darwin 1859 [1964]).

• Charles Darwin, On the Origin of Species, 1st ed., London: John Murray, chapter IV, pp. 80-81 (Darwin Online, F373) (1859) Verified 5 Oct 2026

  If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed.

• Charles Darwin, On the Origin of Species, 1st ed., London: John Murray, Introduction, p. 5 (Darwin Online, F373) (1859) Verified 5 Oct 2026

  In the next chapter the Struggle for Existence amongst all organic beings throughout the world, which inevitably follows from their high geometrical powers of increase, will be treated of. This is the doctrine of Malthus, applied to the whole animal and vegetable kingdoms.

• Charles Darwin, Evolution, Natural Selection, Species, Encyclopaedia Britannica (Adrian J. Desmond) (2026) Verified 24 Sep 2026

  Darwin hastily began an "abstract" of Natural Selection, which grew into a more-accessible book, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Suffering from a terrible bout of nausea, Darwin, now 50, was secreted away at a spa on the desolate Yorkshire moors when the book was sold to the trade on November 22, 1859.

• Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 5 Oct 2026

  The hurried preparation and publication of the Origin between the summer of 1858 and November of 1859 was prompted by the receipt on June 18 of 1858 of a letter and manuscript from Alfred Russel Wallace (1823–1913) that outlined his remarkably similar views on the possibility of continuous species change under the action of a selection upon natural variation

"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.

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