On the Origin of Species On the Origin of Species, published on 24 November 1859, is a worof scientific literature b! "harles #arwin which is considered to be the foundation of evolutionar! biolog!$ %ts full title was On the Origin of Species b! &eans of Natural Selection, or the 'reservation of (avoured )aces in the Struggle for *ife$ (or the si+th edition of 182, the short title was changed to -he Origin of Species$ #arwin.s boointroduced the scientific theor! that populations evolve over the course of generations through a process of natural selection$ %t presented a bod! of evidence that the diversit! of life arose b! common descent through a branching pattern of evolution$ #arwin included evidence that he had gathered on the /eagle e+pedition in the 180s and his subseuent findings from research, correspondence, and e+perimentation$ 3a rious evolutionar! ideas had alread! been proposed to e+plain new findings in biolog!$ -here was growing support for such ideas among dissident anatomists and the general public, but during the first half of the 19th centur! the nglish scientific establishment was closel! tied to the "hurch of ngland, while science was part of natural theolog!$ %deas about the transmutation of species were controversial as the! conflicted with the beliefs that species were unchanging parts of a designed hierarch! and that humans were uniue, unrelated to other animals$ -he political and theological implications were intensel! debated, but transmutation was not accepted b ! the scientific mainstream$ -he boowas written for nonspecialist readers and attracted widespread interest upon its publication$ 6s #arwin was an eminent scientist, his findings were taen seriousl! and the evidence he presented generated scientific, philosophical, and religious discussion$ -he debate over the boocontributed to the campaign b! -$ 7$ 7u+le! and his fellow members of the "lub to secularise science b! promoting scientific naturalism$ ithin two decades there was widespread scientific agreement that evolution, with a branching pattern of common descent, had occurred, but scientists were slow to give natural selection the significance that #arwin thought appropriate$ #uring the :eclipse of #arwinism: from the 188s to the 190s, various other mechanisms of evolution were given more credit$ ith the development of the modern evolutionar! s!nthesis in the 190s and 194s, #arwin.s concept of evolutionar! adaptation through natural selection became central to modern evolutionar! theor! , now the unif!ing concept of the life sciences$
On the Origin of Species, published on 24 November 1859, is a wor of scientific literature b!"harles #arwin which is considered to be the foundation of evolutionar! biolog!$ %ts full title wasOn the Origin of Species b! &eans of Natural Selection, or the 'reservation of (avoured )acesin the Struggle for *ife$ (or the si+th edition of 182, the short title was changed to -he Origin ofSpecies$ #arwin.s boo introduced the scientific theor! that populations evolve over the course ofgenerations through a process of natural selection$ %t presented a bod! of evidence that thediversit! of life arose b! common descent through a branching pattern of evolution$ #arwinincluded evidence that he had gathered on the /eagle e+pedition in the 180s and hissubseuent findings from research, correspondence, and e+perimentation$3arious evolutionar! ideas had alread! been proposed to e+plain new findings in biolog!$ -herewas growing support for such ideas among dissident anatomists and the general public, butduring the first half of the 19th centur! the nglish scientific establishment was closel! tied to the"hurch of ngland, while science was part of natural theolog!$ %deas about the transmutation ofspecies were controversial as the! conflicted with the beliefs that species were unchanging partsof a designed hierarch! and that humans were uniue, unrelated to other animals$ -he politicaland theological implications were intensel! debated, but transmutation was not accepted b! thescientific mainstream$-he boo was written for nonspecialist readers and attracted widespread interest upon its
publication$ 6s #arwin was an eminent scientist, his findings were taen seriousl! and theevidence he presented generated scientific, philosophical, and religious discussion$ -he debateover the boo contributed to the campaign b! -$7$ 7u+le! and his fellow members of the "lubto secularise science b! promoting scientific naturalism$ ithin two decades there waswidespread scientific agreement that evolution, with a branching pattern of common descent, hadoccurred, but scientists were slow to give natural selection the significance that #arwin thoughtappropriate$ #uring the :eclipse of #arwinism: from the 188s to the 190s, various othermechanisms of evolution were given more credit$ ith the development of the modernevolutionar! s!nthesis in the 190s and 194s, #arwin.s concept of evolutionar! adaptationthrough natural selection became central to modern evolutionar! theor!, now the unif!ing conceptof the life sciences$
#arwin.s theor! of evolution is based on e! facts and the inferences drawn from them, whichbiologist rnst &a!r summarised as follows;
ver! species is fertile enough that if all offspring survived to reproduce the population wouldgrow <fact=$
#espite periodic fluctuations, populations remain roughl! the same si>e <fact=$)esources such as food are limited and are relativel! stable over time <fact=$ 6 struggle for survival ensues <inference=$%ndividuals in a population var! significantl! from one another <fact=$&uch of this variation is inheritable <fact=$%ndividuals less suited to the environment are less liel! to survive and less liel! to reproduce?individuals more suited to the environment are more liel! to survive and more liel! to reproduceand leave their inheritable traits to future generations, which produces the process of naturalselection <inference=$-his slowl! effected process results in populations changing to adapt to their environments, and
ultimatel!, these variations accumulate over time to form new species <inference=$
Background
Developments before Darwin's theory
%n later editions of the boo, #arwin traced evolutionar! ideas as far bac as 6ristotle?@4A the te+the cites is a summar! b! 6ristotle of the ideas of the earlier Bree philosopher mpedocles$@5Aarl! "hristian "hurch (athers and &edieval uropean scholars interpreted the Benesis creationnarrative allegoricall! rather than as a literal historical account?@CA organisms were described b!their m!thological and heraldic significance as well as b! their ph!sical form$ Nature was widel!believed to be unstable and capricious, with monstrous births from union between species, andspontaneous generation of life$
he 'rotestant )eformation inspired a literal interpretation of the /ible, with concepts of creationthat conflicted with the findings of an emerging science seeing e+planations congruent with themechanical philosoph! of )enD #escartes and the empiricism of the /aconian method$ 6fter theturmoil of the nglish "ivil ar, the )o!al Societ! wanted to show that science did not threatenreligious and political stabilit!$ Eohn )a! developed an influential natural theolog! of rationalorder? in his ta+onom!, species were static and fi+ed, their adaptation and comple+it! designed b!
Bod, and varieties showed minor differences caused b! local conditions$ %n Bod.s benevolentdesign, carnivores caused mercifull! swift death, but the suffering caused b! parasitism was apu>>ling problem$ -he biological classification introduced b! "arolus *innaeus in 105 alsoviewed species as fi+ed according to the divine plan$ %n 1CC, Beorges /uffon suggested thatsome similar species, such as horses and asses, or lions, tigers, and leopards, might be varietiesdescended from a common ancestor$ -he Fssher chronolog! of the 1C5s had calculatedcreation at 44 /", but b! the 18s geologists assumed a much older world$ erneriansthought strata were deposits from shrining seas, but Eames 7utton proposed a selfmaintaininginfinite c!cle, anticipating uniformitarianism$"harles #arwin.s grandfather rasmus #arwin outlined a h!pothesis of transmutation of speciesin the 19s, and Eean/aptiste *amarc published a more developed theor! in 189$ /othenvisaged that spontaneous generation produced simple forms of life that progressivel!developed greater comple+it!, adapting to the environment b! inheriting changes in adults caused
b! use or disuse$ -his process was later called *amarcism$ *amarc thought there was aninherent progressive tendenc! driving organisms continuousl! towards greater comple+it!, inparallel but separate lineages with no e+tinction$ Beoffro! contended that embr!onic developmentrecapitulated transformations of organisms in past eras when the environment acted on embr!os,and that animal structures were determined b! a constant plan as demonstrated b! homologies$Beorges "uvier strongl! disputed such ideas, holding that unrelated, fi+ed species showedsimilarities that reflected a design for functional needs$ 7is palGontological wor in the 19s hadestablished the realit! of e+tinction, which he e+plained b! local catastrophes, followed b!repopulation of the affected areas b! other species$%n /ritain, illiam 'ale!.s Natural -heolog! saw adaptation as evidence of beneficial :design: b!the "reator acting through natural laws$ 6ll naturalists in nglish universities were "hurch ofngland clerg!men, and science became a search for these laws$ Beologists adaptedcatastrophism to show repeated worldwide annihilation and creation of new fi+ed species adapted
to a changed environment, initiall! identif!ing the most recent catastrophe as the biblical flood$Some anatomists such as )obert Brant were influenced b! *amarc and Beoffro!, but mostnaturalists regarded their ideas of transmutation as a threat to divinel! appointed social order$
Content
Title pages and introduction
Eohn Bould.s illustration of #arwin.s )hea was published in 1841$ -he e+istence of two rhea
species with overlapping ranges influenced #arwin$
'age ii contains uotations b! illiam hewell and (rancis /acon on the theolog! of naturallaws, harmonising science and religion in accordance with %saac Newton.s belief in a rational Bodwho established a lawabiding cosmos$ %n the second edition, #arwin added an epigraph fromEoseph /utler affirming that Bod could wor through scientific laws as much as through miracles,in a nod to the religious concerns of his oldest friends$ -he %ntroduction establishes #arwin.scredentials as a naturalist and author, then refers to Eohn 7erschel.s letter suggesting that theorigin of species "would be found to be a natural in contradistinction to a miraculous process:;7N on board 7$&$S$ ./eagle,. as naturalist, % was much struc with certain facts in thedistribution of the inhabitants of South 6merica, and in the geological relations of the present tothe past inhabitants of that continent$ -hese facts seemed to me to throw some light on the originof speciesHthat m!ster! of m!steries, as it has been called b! one of our greatest philosophers$#arwin refers specificall! to the distribution of the species rheas, and to that of the BalIpagostortoises and mocingbirds$ 7e mentions his !ears of wor on his theor!, and the arrival ofallace at the same conclusion, which led him to :publish this 6bstract: of his incomplete wor$7e outlines his ideas, and sets out the essence of his theor!;
6s man! more individuals of each species are born than can possibl! survive? and as,conseuentl!, there is a freuentl! recurring struggle for e+istence, it follows that an! being, if itvar! however slightl! in an! manner profitable to itself, under the comple+ and sometimes var!ing
conditions of life, will have a better chance of surviving, and thus be naturall! selected$ (rom thestrong principle of inheritance, an! selected variet! will tend to propagate its new and modifiedform$
Starting with the third edition, #arwin prefaced the introduction with a setch of the historicaldevelopment of evolutionar! ideas$ %n that setch he acnowledged that 'atric &atthew had,unnown to allace or himself, anticipated the concept of natural selection in an appendi+ to aboo published in 1801? in the fourth edition he mentioned that illiam "harles ells had doneso as earl! as 1810$3ariation under domestication and under nature@edit source J editbetaA"hapter % covers animal husbandr! and plant breeding, going bac to ancient g!pt$ #arwindiscusses contemporar! opinions on the origins of different breeds under cultivation to argue thatman! have been produced from common ancestors b! selective breeding$@84A 6s an illustration of
artificial selection, he describes fanc! pigeon breeding,@85A noting that :@tAhe diversit! of thebreeds is something astonishing:, !et all were descended from one species of roc pigeon$@8CA#arwin saw two distinct inds of variation; <1= rare abrupt changes he called :sports: or:monstrosities: <e+ample; ancon sheep with short legs=, and <2= ubiuitous small differences<e+ample; slightl! shorter or longer bill of pigeons=$@8A /oth t!pes of hereditar! changes can beused b! breeders$ 7owever, for #arwin the small changes were most important in evolution$%n "hapter %%, #arwin specifies that the distinction between species and varieties is arbitrar!, withe+perts disagreeing and changing their decisions when new forms were found$ 7e concludes that:a wellmared variet! ma! be Kustl! called an incipient species: and that :species are onl!strongl! mared and permanent varieties:$@88A 7e argues for the ubiuit! of variation in nature$@89A 7istorians have noted that naturalists had long been aware that the individuals of a speciesdiffered from one another, but had generall! considered such variations to be limited andunimportant deviations from the archet!pe of each species, that archet!pe being a f i+ed ideal in
the mind of Bod$ #arwin and allace made variation among individuals of the same speciescentral to understanding the natural world$Struggle for e+istence, natural selection, and divergence@edit source J editbetaA%n "hapter %%%, #arwin ass how varieties :which % have called incipient species: become distinctspecies, and in answer introduces the e! concept he calls :natural selection:? in the fifth editionhe adds, :/ut the e+pression often used b! &r$ 7erbert Spencer, of the Survival of the (ittest, ismore accurate, and is sometimes euall! convenient$:Owing to this struggle for life, an! variation, however slight and from whatever cause proceeding,if it be in an! degree profitable to an individual of an! species, in its infinitel! comple+ relations toother organic beings and to e+ternal nature, will tend to the preservation of that individual, and will
generall! be inherited b! its offspring $$$ % have called this principle, b! which each slight variation,if useful, is preserved, b! the term of Natural Selection, in order to mar its relation to man.spower of selection$7e notes that both 6$ '$ de "andolle and "harles *!ell had stated that all organisms are e+posedto severe competition$ #arwin emphasi>es that he used the phrase :struggle for e+istence: in :alarge and metaphorical sense, including dependence of one being on another:? he givese+amples ranging from plants struggling against drought to plants competing for birds to eat theirfruit and disseminate their seeds$ 7e describes the struggle resulting from population growth; :%tis the doctrine of &althus applied with manifold force to the whole animal and vegetableingdoms$: 7e discusses checs to such increase including comple+ ecologicalinterdependencies, and notes that competition is most severe between closel! related forms:which fill nearl! the same place in the econom! of nature:$"hapter %3 details natural selection under the :infinitel! comple+ and closefitting $$$ mutualrelations of all organic beings to each other and to their ph!sical conditions of life:$@90A #arwintaes as an e+ample a countr! where a change in conditions led to e+tinction of some species,immigration of others and, where suitable variations occurred, descendants of some speciesbecame adapted to new conditions$ 7e remars that the artificial selection practised b! animalbreeders freuentl! produced sharp divergence in character between breeds, and suggests thatnatural selection might do the same, sa!ing;/ut how, it ma! be ased, can an! analogous principle appl! in natureL % believe it can and does
appl! most efficientl!, from the simple circumstance that the more diversified the descendantsfrom an! one species become in structure, constitution, and habits, b! so much will the! be better enabled to sei>e on man! and widel! diversified places in the polit! of nature, and so be enabledto increase in numbers$
This tree diagram, used to show the diergence of species, is the only illustration in the Origin ofSpecies!
7istorians have remared that here #arwin anticipated the modern concept of an ecologicalniche$ 7e did not suggest that ever! favourable variation must be selected, nor that the favouredanimals were better or higher, but merel! more adapted to their surroundings$
#arwin proposes se+ual selection, driven b! competition between males for mates, to e+plainse+uall! dimorphic features such as lion manes, deer antlers, peacoc tails, bird songs, and the
bright plumage of some male birds$@9CA 7e anal!sed se+ual selection more full! in -he #escentof &an, and Selection in )elation to Se+ <181=$ Natural selection was e+pected to wor ver!slowl! in forming new species, but given the effectiveness of artificial selection, he could :see nolimit to the amount of change, to the beaut! and infinite comple+it! of the coadaptations betweenall organic beings, one with another and with their ph!sical conditions of life, which ma! beeffected in the long course of time b! nature.s power of selection:$ Fsing a tree diagram andcalculations, he indicates the :divergence of character: from original species into new speciesand genera$ 7e describes branches falling off as e+tinction occurred, while new branches formedin :the great -ree of life $$$ with its ever branching and beautiful ramifications:$
