The Origin of Species
From Wikipedia, the free encyclopedia.
First published on 24 November 1859, The Origin of Species (full title On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) by British naturalist Charles Darwin is one of the pivotal works in scientific history, and arguably the pre-eminent work in biology. In it, Darwin makes "one long argument" for his theory that "groups" of organisms, (which we now call populations) rather than individual organisms, gradually evolve through the process of natural selection—a mechanism effectively introduced to the public at large by the book. The work presents detailed scientific evidence he had accumulated both on the Voyage of the Beagle in the 1830s and since his return, painstakingly laying out his theory and refuting the doctrine of "Created kinds" underlying the theories of Creation biology which were then widely accepted.
Even for the non-specialist the book was quite readable (as it still is), and it attracted widespread interest. Although the ideas presented in it are now supported by overwhelming scientific evidence and are widely accepted by scientists today, they are still highly controversial particulary among non-scientists who perceive it to contradict literal interpretations of various religious texts (see Creation-evolution controversy).
Contents |
Background
Before "The Origin"
- Main article: history of evolutionary thought
The idea of biological evolution was supported in Classical times by the Greek and Roman atomists, notably Lucretius. With the dominance of Christianity came belief in the Biblical story of creation according to Genesis, with the doctrine that God had directly "Created kinds" of organisms which were immutable. Other ideas resurfaced, and in 17th century English the word evolution (from the Latin word "evolutio", meaning "unroll like a scroll") began to be used in to refer to an orderly sequence of events, particularly one in which the outcome was somehow contained within it from the start.
Natural history aiming to investigate and catalogue the wonders of God's works developed greatly in the 18th century. Discoveries showing the extinction of species were explained by catastrophism, the belief that animals and plants were periodically annihilated as a result of natural catastrophes and that their places were taken by new species created ex nihilo (out of nothing). Countering this, James Hutton's uniformitarian theory of 1785 envisioned gradual development over aeons of time.
By 1796 Charles Darwin's grandfather Erasmus Darwin had put forward ideas of common descent with organisms "acquiring new parts" in response to stimuli then passing these changes to their offspring, and in 1802 he hinted at natural selection. In 1809 Jean-Baptiste Lamarck developed a similar theory, with "needed" traits being acquired then passed on. These theories of Transmutation were developed by Radicals in Britain like Robert Edmund Grant. At this time the work of Thomas Malthus showing that human populations increased to exceed resources influenced liberal thinking, resulting in the Whig Poor Law of the 1830s.
Various ideas were developed to reconcile Creation biology with scientific findings, including Charles Lyell's uniformitarian idea that each species had its "centre of creation" and was designed for the habitat, but would go extinct when the habitat changed. Charles Babbage believed God set up laws that operated to produce species, as a divine programmer, and Richard Owen followed Johannes Peter Müller in thinking that living matter had an "organising energy", a life-force that directed the growth of tissues and also determined the lifespan of the individual and of the species.
Inception of Darwin's theory
- Main article: inception of Darwin's theory
Charles Darwin's education at the University of Edinburgh gave him direct involvement in Robert Edmund Grant's evolutionist developments of the ideas of Erasmus Darwin and Jean-Baptiste Lamarck. Then at Cambridge University his theology studies convinced him of William Paley's argument of "design" by a Creator while his interest in natural history was increased by the botanist John Stevens Henslow and the geologist Adam Sedgwick, both of whom believed strongly in divine creation and in a uniformitarian ancient earth. During the Voyage of the Beagle Charles Darwin became convinced by Charles Lyell's uniformitarianism, and puzzled over how various theories of creation fit the evidence he saw. On his return Richard Owen showed that fossils Darwin had found were of extinct species related to current species in the same locality, and John Gould startlingly revealed that completely different birds from the Galápagos Islands were species of finches distinct to each island.
By early 1837 Darwin was speculating on transmutation in a series of secret notebooks. He investigated the breeding of domestic animals, consulting William Yarrell and reading a pamphlet by Yarrell's friend Sir John Sebright which commented that "A severe winter, or a scarcity of food, by destroying the weak and the unhealthy, has all the good effects of the most skilful selection." At the zoo in 1838 he had his first sight of an ape, and the orang-utan's antics impressed him as being "just like a naughty child" which from his experience of the natives of Tierra del Fuego made him think that there was little gulf between man and animals despite the theological doctrine that only mankind possessed a soul.
In late September 1838 he began reading the 6th edition of Malthus's Essay on the Principle of Population which reminded him of Malthus's statistical proof that human populations breed beyond their means and compete to survive, at a time when he was primed to apply these ideas to animal species. Darwin applied to his search for the Creator's laws the Whig social thinking of struggle for survival with no hand-outs. By December 1838 he was seeing a similarity between breeders selecting traits and a Malthusian Nature selecting from variants thrown up by chance so that "every part of newly acquired structure is fully practised and perfected", thinking this "the most beautiful part of my theory".
First writings on the theory
- Main article: development of Darwin's theory
Darwin was well aware of the implication the theory had for the origin of humanity and the real danger to his career and reputation as an eminent geologist of being convicted of blasphemy. He worked in secret to consider all objections and prepare overwhelming evidence supporting his theory. He increasingly wanted to discuss his ideas with his colleagues, and in January 1842 sent a tentative description of his ideas in a letter to Lyell, who was then touring America. Lyell, dismayed that his erstwhile ally had become a Transmutationist, noted that Darwin "denies seeing a beginning to each crop of species".
Despite problems with illness, Darwin formulated a 35 page "Pencil Sketch" of his theory in June 1842 then worked it up into a larger "essay". The botanist Joseph Dalton Hooker became Darwin's mainstay, and late in 1845 Darwin offered his "rough Sketch" for comments without immediate success, but in January 1847 when Darwin was particularly ill Hooker took away a copy of the "Sketch". After some delays he sent a page of notes, giving Darwin the calm critical feedback that he needed. Darwin made a huge study of barnacles which established his credentials as a biologist and provided more evidence supporting his theory.
Publication
- Main article: publication of Darwin's theory
In the spring of 1856 Lyell drew Darwin's attention to a paper on the "introduction" of species written by Alfred Russel Wallace, a naturalist working in Borneo, and urged Darwin to publish to establish priority. Darwin was now torn between the desire to set out a full and convincing account, and the pressure to quickly produce a short paper. He ruled out exposing himself to an editor or counsel which would have been required to publish in an academic journal. On 14 May 1856 he began a "sketch" account, then by July had decided to produce a full technical treatise on species.
Darwin pressed on, overworking, and was throwing himself into his work with his book on Natural Selection well under way, when on 18 June 1858 he received a parcel from Wallace enclosing about twenty pages describing an evolutionary mechanism, an unexpected response to Darwin's recent encouragement, with a request to send it on to Lyell. Darwin wrote to Lyell that "your words have come true with a vengeance,... forestalled" and he would, "of course, at once write and offer to send [it] to any journal" that Wallace chose, adding that "all my originality, whatever it may amount to, will be smashed". Lyell and Hooker agreed that a joint paper should be presented at the Linnean Society, and on 1 July 1858 the Wallace and Darwin papers entitled respectively On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection were read out, to surprisingly little reaction.
Darwin now worked hard on an "abstract" trimmed from his Natural Selection, writing much of it from memory. Lyell made arrangements with the publisher John Murray, who agreed to publish the manuscript sight unseen, and to pay Darwin two-thirds of the net proceeds. Darwin had decided to call his book An Abstract of an Essay on the Origin of Species and Varieties through Natural Selection, but with Murray's persuasion it was eventually reduced to the snappier On the Origin of Species through Natural Selection
Publication of The Origin
The Origin was first published on 24 November 1859, price fifteen shillings, and was oversubscribed, so that all 1250 copies were claimed by booksellers that day. The second edition came out on 7 January 1860, and during Darwin's lifetime the book went through six editions, with cumulative changes and revisions to deal with counter-arguments raised.
In January 1871 Mivart published On the Genesis of Species, the cleverest and most devastating critique of natural selection in Darwin's lifetime. Darwin took it personally and from April to the end of the year made extensive revisions to the Origin, using the word "evolution" for the first time and adding a new chapter to refute Mivart. Other changes included adding Herbert Spencer's phrase "survival of the fittest", and adding "by the Creator" into the closing sentence, making it read "There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone circling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved."
He told Murray of working men in Lancashire clubbing together to buy the 5th edition at fifteen shillings, and he wanted a new cheap edition to make it more widely available. The 6th edition of Origin of Species was published by Murray on 19 February 1872 at a price kept down to 7s. 6d. by using minute print, and sales increased from 60 to 250 a month.
Darwin's theory, as presented
A firm base
Darwin's theory of evolution is based on five key observations and inferences drawn from them, as summarized by the biologist Ernst Mayr:
- Species have great fertility. They make more offspring than can grow to adulthood.
- Populations remain roughly the same size, with modest fluctuations.
- Food resources are limited, but are relatively constant most of the time. From these three observations it may be inferred that in such an environment there will be a struggle for survival among individuals.
- In sexually reproducing species, generally no two individuals are identical. Variation is rampant.
- Much of this variation is heritable.
From this Darwin infers: In a world of stable populations where each individual must struggle to survive, those with the "best" characteristics will be more likely to survive, and those desirable traits will be passed to their offspring; and that these advantageous characteristics are inherited by following generations, becoming dominant among the population through time. This is natural selection.
Darwin further infers that natural selection, if carried far enough, makes changes in a population, eventually leading to new species. He puts forward myriad observations as demonstrations of this, and also claims that the fossil record can be interpreted as supporting these observations. Darwin imagined it might be possible that all life is descended from an original species from ancient times. Modern DNA evidence is consistent with this idea.
A minor mistake - or precaution
One of the chief difficulties for Darwin in his time was the development of a model of heredity which would allow for the specific requirements of his theory of speciation. Darwin's relatively loose understanding of inheritance had many connections to Lamarckian theories which stressed that use and disuse alone could result in inherited traits. For example, in the first edition, he states, "When the first tendency was once displayed, methodical selection and the inherited effects of compulsory training in each successive generation would soon complete the work". Darwin later worked out a more elaborate model of heredity (which he dubbed "Pangenesis") which incorporated various aspects of Lamarckian inheritance as well, though was also key in influencing early non-Lamarckian theories of heredity (such as the biometric model developed by his cousin Francis Galton). Lamarckian inheritance would not be conclusively disproved until after Darwin's death, and Mendelian genetics would not be (re)discovered until the twentieth century.
Public reaction
- Main article: reaction to Darwin's theory
After the publication of Darwin's book, evolution by means of natural selection was widely discussed and debated. As well as attracting attention from naturalists and learned religious people, Huxley's "working-men's lectures" proved very popular and the 6th edition was halved in price, successfully increasing sales to meet this demand.
The book was highly controversial when first published, as it contradicted the then-prevailing theory of establishment scientists, of immediate, divine design in nature, and conflicted with a literal reading of the biblical creation stories in the Book of Genesis. Though Darwin was supported by some scientists (e.g., T.H. Huxley), others hesitated to accept the theory due to the unexplained ability of individuals to pass their special abilities to their offspring (though Darwin put forth his own theory of heredity—pangenesis—it was unconvincing, and the lack of a coherent mechanism was a difficult aspect of his theory until the re-discovery of the work of Gregor Mendel in the early 20th century). On the whole, however, his greatest accomplishment was to move the idea of evolution into the realm of serious scientific debate.
In 1874, the theologian Charles Hodge accused Darwin of denying the existence of God by defining humans to be a result of a natural process rather than a creation designed by God. This is an argument that had been made by many almost immediately after Darwin's first publication. Evolution is in complete contradiction with literal readings of many of the legendary or religious stories of how the world's life originated; therefore, those who accepted the theory grew more skeptical of the Bible or other religious sources. As Hodge pointed out, evolution does not seem to originate from a divine source, and some viewed God as a less powerful force in the universe.
Darwin's theory changed the way humans saw themselves and their world. If one accepted that humans were descended from animals, it became clear that humans also are animals. The natural world took on a darker tinge in the minds of many, as animals in the wild are understood to be in a constant state of deadly competition with one another. The world was also seen in a less permanent fashion; since the world was apparently much different millions of years ago, it dawned on many that the impact of human beings would lessen and perhaps disappear altogether over time.
From the 1860s up until the 1930s, Darwinian "selectionist" evolution was not universally accepted by scientists, while evolution of some form generally was (a variety of evolutionary theories competed for scientific approval, including neo-Darwinism, neo-Lamarkism, orthogenesis, and mutation theory). In the 1930s, the work of a number of biologists and statisticians (especially R. A. Fisher) created the modern synthesis of evolution, which merged Darwinian selection theory with Mendelian genetics.
Today, whilst the overwhelming majority of biologists (over 99%) consider Darwin's basic theory correct[1], a significant fraction of the general population, particularly in the United States, disagree mainly on religious grounds [2] (see creationism).
Misconceptions, and comparison to Wallace's theory
Contrary to popular understanding, Darwin did not "discover" evolution as is clear from the history of evolutionary thought. Even in his own day it was a well-known concept, although not one defended by the scientific community. As he subsequently acknowledged, others before him published brief statements outlining the principle of natural selection, but he was not aware of these little known statements until after publication of the Origin. Instead, he and Wallace put forth the first convincing and coherent mechanism of evolution: natural selection. Darwin's work, through its long list of facts and its support by prominent naturalists, established for most that evolution of some form did occur—that there was no fixity of species—even if there was considerable disagreement on the mechanism. Also contrary to a common understanding, Darwin did not invent the phrase "survival of the fittest", but added this in the 6th edition of The Origin of Species, giving due credit to the philosopher Herbert Spencer (who had used the phrase in his 1851 work Social Statics) and usually using the phrase "Natural Selection, or the Survival of the Fittest". Other aspects of Darwin's overall theory which themselves evolved over time were: common descent, sexual selection, gradualism, and pangenesis.
Darwin's explanation of natural selection was slightly different from that given by Wallace. Darwin used comparison to selective breeding and artificial selection as a means for understanding natural selection. No such connection between selective breeding and natural selection was made by Wallace; he expressed it simply as a basic process of nature and did not think the phenomena were in any way related. On Wallace's own first edition of The Origin of Species, he crossed out every instance of the phrase "natural selection" and replaced with it Spencer's "survival of the fittest." He also ruled out much of the ideas of Lamarckian inheritance present in Darwin's work, calling it "quite unnecessary." Darwin and Wallace would disagree on many substantive issues later in their lives especially, most bitterly on the question of whether human consciousness had itself evolved (to Darwin's horror, Wallace eventually turned against this and towards spiritualism).
Philosophical implications
According to Ernst Mayr, Darwin's evolutionary thinking rests on a rejection of essentialism, which assumes the existence of some perfect, essential form for any particular class of existent, and treats differences between individuals as imperfections or deviations away from the perfect essential form. Darwin embraced instead what Mayr calls population thinking, which denies the existence of any essential form and holds that a class is the conceptualization of the numerous unique individuals. Individuals, in short, are real in an objective sense, while the class is an abstraction, an artifact of epistemology. This emphasis on the importance of individual differences is necessary if one believes that the mechanism of evolution, natural selection, operates on individual differences.
Mayr claims essentialism had dominated Western thinking for two thousand years, and that Darwin's theories thus represent an important and radical break from traditional Western philosophy. Ripples of Darwin's thought can now be seen in fields such as economics and complexity theory, suggesting that Darwin's influence extends well beyond the field of biology.
References
- Darwin, Charles (1859) On the Origin of Species. John Murray, London.
- Darwin, Charles & Huxley, Julian (2003). The Origin of Species. Signet Classics. ISBN 0-45-152906-5.
- Jones, Steve (1999). Almost Like a Whale. Doubleday. ISBN 0-38-540985-0. (contemporary introduction to The Origin of Species)
- Clark, Ronald W. (1984). The Survival of Charles Darwin. New York: Avon Books. ISBN 0-380-69991-5
- Desmond, Adrian & Moore, James (1991). Darwin. London: the Penguin Group. ISBN 0-7181-3430-3
External links
- Origin of Species, 1st edn. (1859) (British Library)
- Origin of Species, 6th edn. (1872) (British Library)
- Full text in pdf format
- Free eBook of Origin of Species, 1st Edition at Project Gutenberg
- Free eBook of Origin of Species, 6th Edition at Project Gutenberg
See also
| Basic topics in evolutionary biology |
|---|
| Processes of evolution: evidence - macroevolution - microevolution - speciation |
| Mechanisms: selection - genetic drift - gene flow - mutation |
| Modes: anagenesis - catagenesis - cladogenesis |
| History: History of evolutionary thought - Charles Darwin - The Origin of Species - modern evolutionary synthesis |
| Subfields: population genetics - ecological genetics - human evolution - molecular evolution - phylogenetics - systematics - evo-devo |
| List of evolutionary biology topics | Timeline of evolution | Timeline of human evolution |
