Charles Darwin: Origin Of Species
On 5 April, Darwin sent Murray the first three chapters, and a proposal for the book's title. An early draft title page suggests On the Mutability of Species. Murray cautiously asked Whitwell Elwin to review the chapters. At Lyell's suggestion, Elwin recommended that, rather than "put forth the theory without the evidence", the book should focus on observations upon pigeons, briefly stating how these illustrated Darwin's general principles and preparing the way for the larger work expected shortly: "Every body is interested in pigeons." Darwin responded that this was impractical: he had only the last chapter still to write. In September the main title still included "An essay on the origin of species and varieties", but Darwin now proposed dropping "varieties".
Charles Darwin: Origin of Species
Page ii contains quotations by William Whewell and Francis Bacon on the theology of natural laws, harmonising science and religion in accordance with Isaac Newton's belief in a rational God who established a law-abiding cosmos. In the second edition, Darwin added an epigraph from Joseph Butler affirming that God could work through scientific laws as much as through miracles, in a nod to the religious concerns of his oldest friends. The Introduction establishes Darwin's credentials as a naturalist and author, then refers to John Herschel's letter suggesting that the origin of species "would be found to be a natural in contradistinction to a miraculous process":
Chapter I covers animal husbandry and plant breeding, going back to ancient Egypt. Darwin discusses contemporary opinions on the origins of different breeds under cultivation to argue that many have been produced from common ancestors by selective breeding. As an illustration of artificial selection, he describes fancy pigeon breeding, noting that "[t]he diversity of the breeds is something astonishing", yet all were descended from one species of rock pigeon. Darwin saw two distinct kinds of variation: (1) rare abrupt changes he called "sports" or "monstrosities" (example: Ancon sheep with short legs), and (2) ubiquitous small differences (example: slightly shorter or longer bill of pigeons). Both types of hereditary changes can be used by breeders. However, for Darwin the small changes were most important in evolution. In this chapter Darwin expresses his erroneous belief that environmental change is necessary to generate variation.
Darwin proposes sexual selection, driven by competition between males for mates, to explain sexually dimorphic features such as lion manes, deer antlers, peacock tails, bird songs, and the bright plumage of some male birds. He analysed sexual selection more fully in The Descent of Man, and Selection in Relation to Sex (1871). Natural selection was expected to work very slowly in forming new species, but given the effectiveness of artificial selection, he could "see no limit to the amount of change, to the beauty and infinite complexity of the coadaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection". Using a tree diagram and calculations, he indicates the "divergence of character" from original species into new species and genera. He describes branches falling off as extinction occurred, while new branches formed in "the great Tree of life ... with its ever branching and beautiful ramifications".
The leading naturalist in Britain was the anatomist Richard Owen, an idealist who had shifted to the view in the 1850s that the history of life was the gradual unfolding of a divine plan. Owen's review of the Origin in the April 1860 Edinburgh Review bitterly attacked Huxley, Hooker and Darwin, but also signalled acceptance of a kind of evolution as a teleological plan in a continuous "ordained becoming", with new species appearing by natural birth. Others that rejected natural selection, but supported "creation by birth", included the Duke of Argyll who explained beauty in plumage by design. Since 1858, Huxley had emphasised anatomical similarities between apes and humans, contesting Owen's view that humans were a separate sub-class. Their disagreement over human origins came to the fore at the British Association for the Advancement of Science meeting featuring the legendary 1860 Oxford evolution debate. In two years of acrimonious public dispute that Charles Kingsley satirised as the "Great Hippocampus Question" and parodied in The Water-Babies as the "great hippopotamus test", Huxley showed that Owen was incorrect in asserting that ape brains lacked a structure present in human brains. Others, including Charles Lyell and Alfred Russel Wallace, thought that humans shared a common ancestor with apes, but higher mental faculties could not have evolved through a purely material process. Darwin published his own explanation in the Descent of Man (1871).
The whole subject must, I think, remain vague; nevertheless, I may, withouthere entering on any details, state that, from geographical and otherconsiderations, I think it highly probable that our domestic dogs havedescended from several wild species. In regard to sheep and goats I can form noopinion. I should think, from facts communicated to me by Mr. Blyth, on thehabits, voice, and constitution, etc., of the humped Indian cattle, that thesehad descended from a different aboriginal stock from our European cattle; andseveral competent judges believe that these latter have had more than one wildparent. With respect to horses, from reasons which I cannot give here, I amdoubtfully inclined to believe, in opposition to several authors, that all theraces have descended from one wild stock. Mr. Blyth, whose opinion, from hislarge and varied stores of knowledge, I should value more than that of almostany one, thinks that all the breeds of poultry have proceeded from the commonwildIndian fowl (Gallus bankiva). In regard to ducks and rabbits, the breeds ofwhich differ considerably from each other in structure, I do not doubt thatthey all have descended from the common wild duck and rabbit.
Great as the differences are between the breeds of pigeons, I am fullyconvinced that the common opinion of naturalists is correct, namely, that allhave descended from the rock-pigeon (Columba livia), including under this termseveral geographical races or sub-species, which differ from each other in themost trifling respects. As several of the reasons which have led me to thisbelief are in some degree applicable in other cases, I will here briefly givethem. If the several breeds are not varieties, and have not proceeded from therock-pigeon, they must have descended from at least seven or eight aboriginalstocks; for it is impossible to make the present domestic breeds by thecrossing of any lesser number: how, for instance, could a pouter be produced bycrossing two breeds unless one of the parent-stocks possessed thecharacteristic enormous crop? The supposed aboriginal stocks must all have beenrock-pigeons, that is, not breeding or willingly perching on trees. But besidesC. livia, with its geographical sub-species, only two or three other species ofrock-pigeons are known; and these have not any of the characters of thedomestic breeds. Hence the supposed aboriginal stocks must either still existin the countries where they were originally domesticated, and yet be unknown toornithologists; and this, considering their size, habits, and remarkablecharacters, seems very improbable; or they must have become extinct in the wildstate. But birds breeding on precipices, and good fliers, are unlikely to beexterminated; and the common rock-pigeon, which has the same habits with thedomestic breeds, has not been exterminatedeven on several of the smaller British islets, or on the shores of theMediterranean. Hence the supposed extermination of so many species havingsimilar habits with the rock-pigeon seems to me a very rash assumption.Moreover, the several above-named domesticated breeds have been transported toall parts of the world, and, therefore, some of them must have been carriedback again into their native country; but not one has ever become wild orferal, though the dovecot-pigeon, which is the rock-pigeon in a very slightlyaltered state, has become feral in several places. Again, all recent experienceshows that it is most difficult to get any wild animal to breed freely underdomestication; yet on the hypothesis of the multiple origin of our pigeons, itmust be assumed that at least seven or eight species were so thoroughlydomesticated in ancient times by half-civilized man, as to be quite prolificunder confinement.
Some facts in regard to the colouring of pigeons well deserve consideration.The rock-pigeon is of a slaty-blue, and has a white rump (the Indiansub-species, C. intermedia of Strickland, having it bluish); the tail has aterminal dark bar, with the bases of the outer feathers externally edged withwhite; the wings have two black bars; some semi-domestic breeds and someapparently truly wild breeds have, besides the two black bars, the wingschequered with black. These several marks do not occur together in any otherspecies of the whole family. Now, in every one of the domestic breeds, takingthoroughly well-bred birds, all the above marks, even to the white edging ofthe outer tail-feathers, sometimes concur perfectly developed. Moreover, whentwo birds belonging to two distinct breeds are crossed, neither of which isblue or has any of the above-specified marks, the mongrel offspring are veryapt suddenly to acquire these characters; for instance, I crossed someuniformly white fantails with some uniformly black barbs, and they producedmottled brown and black birds; these I again crossed together, and onegrandchild of the pure white fantail and pure black barb was of as beautiful ablue colour, with the white rump, double black wing-bar, and barred andwhite-edged tail-feathers, as any wild rock-pigeon! We can understand thesefacts, on the well-known principle of reversion to ancestral characters, if allthe domestic breeds have descended from the rock-pigeon. But if we deny this,we must make one of the two following highly improbable suppositions. Either,firstly, that all the several imagined aboriginal stocks were coloured andmarked like the rock-pigeon, although no other existing species is thuscoloured and marked, so that in each separate breed there might be a tendencyto revert to the very same colours and markings. Or, secondly,that each breed, even the purest, has within a dozen or, at most, within ascore of generations, been crossed by the rock-pigeon: I say within a dozen ortwenty generations, for we know of no fact countenancing the belief that thechild ever reverts to some one ancestor, removed by a greater number ofgenerations. In a breed which has been crossed only once with some distinctbreed, the tendency to reversion to any character derived from such cross willnaturally become less and less, as in each succeeding generation there will beless of the foreign blood; but when there has been no cross with a distinctbreed, and there is a tendency in both parents to revert to a character, whichhas been lost during some former generation, this tendency, for all that we cansee to the contrary, may be transmitted undiminished for an indefinite numberof generations. These two distinct cases are often confounded in treatises oninheritance. 041b061a72