The Origin of Species

characters be ever so slight, has had its wild prototype. At this rate

  there must have existed at least a score of species of wild cattle, as many

  sheep, and several goats in Europe alone, and several even within Great

  Britain. One author believes that there formerly existed in Great Britain

  eleven wild species of sheep peculiar to it! When we bear in mind that

  Britain has now hardly one peculiar mammal, and France but few distinct

  from those of Germany and conversely, and so with Hungary, Spain, &c., but

  that each of these kingdoms possesses several peculiar breeds of cattle,

  sheep, &c., we must admit that many domestic breeds have originated in

  Europe; for whence could they have been derived, as these several countries

  do not possess a number of peculiar species as distinct parent-stocks? So

  it is in India. Even in the case of the domestic dogs of the whole world,

  which I fully admit have probably descended from several wild species, I

  cannot doubt that there has been an immense amount of inherited variation.

  Who can believe that animals closely resembling the Italian greyhound, the

  bloodhound, the bull-dog, or Blenheim spaniel, &c.--so unlike all wild

  Canidae--ever existed freely in a state of nature? It has often been

  loosely said that all our races of dogs have been produced by the crossing

  of a few aboriginal species; but by crossing we can get only forms in some

  degree intermediate between their parents; and if we account for our

  several domestic races by this process, we must admit the former existence

  of the most extreme forms, as the Italian greyhound, bloodhound, bull-dog,

  &c., in the wild state. Moreover, the possibility of making distinct races

  by crossing has been greatly exaggerated. There can be no doubt that a

  race may be modified by occasional crosses, if aided by the careful

  selection of those individual mongrels, which present any desired

  character; but that a race could be obtained nearly intermediate between

  two extremely different races or species, I can hardly believe. Sir J.

  Sebright expressly experimentised for this object, and failed. The

  offspring from the first cross between two pure breeds is tolerably and

  sometimes (as I have found with pigeons) extremely uniform, and everything

  seems simple enough; but when these mongrels are crossed one with another

  for several generations, hardly two of them will be alike, and then the

  extreme difficulty, or rather utter hopelessness, of the task becomes

  apparent. Certainly, a breed intermediate between two very distinct breeds

  could not be got without extreme care and long-continued selection; nor can

  I find a single case on record of a permanent race having been thus formed.

  On the Breeds of the Domestic Pigeon. -- Believing that it is always best

  to study some special group, I have, after deliberation, taken up domestic

  pigeons. I have kept every breed which I could purchase or obtain, and

  have been most kindly favoured with skins from several quarters of the

  world, more especially by the Hon. W. Elliot from India, and by the Hon. C.

  Murray from Persia. Many treatises in different languages have been

  published on pigeons, and some of them are very important, as being of

  considerably antiquity. I have associated with several eminent fanciers,

  and have been permitted to join two of the London Pigeon Clubs. The

  diversity of the breeds is something astonishing. Compare the English

  carrier and the short-faced tumbler, and see the wonderful difference in

  their beaks, entailing corresponding differences in their skulls. The

  carrier, more especially the male bird, is also remarkable from the

  wonderful development of the carunculated skin about the head, and this is

  accompanied by greatly elongated eyelids, very large external orifices to

  the nostrils, and a wide gape of mouth. The short-faced tumbler has a beak

  in outline almost like that of a finch; and the common tumbler has the

  singular and strictly inherited habit of flying at a great height in a

  compact flock, and tumbling in the air head over heels. The runt is a bird

  of great size, with long, massive beak and large feet; some of the

  sub-breeds of runts have very long necks, others very long wings and tails,

  others singularly short tails. The barb is allied to the carrier, but,

  instead of a very long beak, has a very short and very broad one. The

  pouter has a much elongated body, wings, and legs; and its enormously

  developed crop, which it glories in inflating, may well excite astonishment

  and even laughter. The turbit has a very short and conical beak, with a

  line of reversed feathers down the breast; and it has the habit of

  continually expanding slightly the upper part of the oesophagus. The

  Jacobin has the feathers so much reversed along the back of the neck that

  they form a hood, and it has, proportionally to its size, much elongated

  wing and tail feathers. The trumpeter and laugher, as their names express,

  utter a very different coo from the other breeds. The fantail has thirty

  or even forty tail-feathers, instead of twelve or fourteen, the normal

  number in all members of the great pigeon family; and these feathers are

  kept expanded, and are carried so erect that in good birds the head and

  tail touch; the oil-gland is quite aborted. Several other less distinct

  breeds might have been specified.

  In the skeletons of the several breeds, the development of the bones of the

  face in length and breadth and curvature differs enormously. The shape, as

  well as the breadth and length of the ramus of the lower jaw, varies in a

  highly remarkable manner. The number of the caudal and sacral vertebrae

  vary; as does the number of the ribs, together with their relative breadth

  and the presence of processes. The size and shape of the apertures in the

  sternum are highly variable; so is the degree of divergence and relative

  size of the two arms of the furcula. The proportional width of the gape of

  mouth, the proportional length of the eyelids, of the orifice of the

  nostrils, of the tongue (not always in strict correlation with the length

  of beak), the size of the crop and of the upper part of the oesophagus; the

  development and abortion of the oil-gland; the number of the primary wing

  and caudal feathers; the relative length of wing and tail to each other and

  to the body; the relative length of leg and of the feet; the number of

  scutellae on the toes, the development of skin between the toes, are all

  points of structure which are variable. The period at which the perfect

  plumage is acquired varies, as does the state of the down with which the

  nestling birds are clothed when hatched. The shape and size of the eggs

  vary. The manner of flight differs remarkably; as does in some breeds the

  voice and disposition. Lastly, in certain breeds, the males and females

  have come to differ to a slight degree from each other.

  Altogether at least a score of pigeons might be chosen, which if shown to

  an ornithologist, and he were told that they were wild birds, would

  certainly, I think, be ranked by him as well-defined species. Moreover, I

  do not believe that any ornithologist would
place the English carrier, the

  short-faced tumbler, the runt, the barb, pouter, and fantail in the same

  genus; more especially as in each of these breeds several truly-inherited

  sub-breeds, or species as he might have called them, could be shown him.

  Great as the differences are between the breeds of pigeons, I am fully

  convinced that the common opinion of naturalists is correct, namely, that

  all have descended from the rock-pigeon (Columba livia), including under

  this term several geographical races or sub-species, which differ from each

  other in the most trifling respects. As several of the reasons which have

  led me to this belief are in some degree applicable in other cases, I will

  here briefly give them. If the several breeds are not varieties, and have

  not proceeded from the rock-pigeon, they must have descended from at least

  seven or eight aboriginal stocks; for it is impossible to make the present

  domestic breeds by the crossing of any lesser number: how, for instance,

  could a pouter be produced by crossing two breeds unless one of the

  parent-stocks possessed the characteristic enormous crop? The supposed

  aboriginal stocks must all have been rock-pigeons, that is, not breeding or

  willingly perching on trees. But besides C. livia, with its geographical

  sub-species, only two or three other species of rock-pigeons are known; and

  these have not any of the characters of the domestic breeds. Hence the

  supposed aboriginal stocks must either still exist in the countries where

  they were originally domesticated, and yet be unknown to ornithologists;

  and this, considering their size, habits, and remarkable characters, seems

  very improbable; or they must have become extinct in the wild state. But

  birds breeding on precipices, and good fliers, are unlikely to be

  exterminated; and the common rock-pigeon, which has the same habits with

  the domestic breeds, has not been exterminated even on several of the

  smaller British islets, or on the shores of the Mediterranean. Hence the

  supposed extermination of so many species having similar habits with the

  rock-pigeon seems to me a very rash assumption. Moreover, the several

  above-named domesticated breeds have been transported to all parts of the

  world, and, therefore, some of them must have been carried back again into

  their native country; but not one has ever become wild or feral, though the

  dovecot-pigeon, which is the rock-pigeon in a very slightly altered state,

  has become feral in several places. Again, all recent experience shows

  that it is most difficult to get any wild animal to breed freely under

  domestication; yet on the hypothesis of the multiple origin of our pigeons,

  it must be assumed that at least seven or eight species were so thoroughly

  domesticated in ancient times by half-civilized man, as to be quite

  prolific under confinement.

  An argument, as it seems to me, of great weight, and applicable in several

  other cases, is, that the above-specified breeds, though agreeing generally

  in constitution, habits, voice, colouring, and in most parts of their

  structure, with the wild rock-pigeon, yet are certainly highly abnormal in

  other parts of their structure: we may look in vain throughout the whole

  great family of Columbidae for a beak like that of the English carrier, or

  that of the short-faced tumbler, or barb; for reversed feathers like those

  of the jacobin; for a crop like that of the pouter; for tail-feathers like

  those of the fantail. Hence it must be assumed not only that

  half-civilized man succeeded in thoroughly domesticating several species,

  but that he intentionally or by chance picked out extraordinarily abnormal

  species; and further, that these very species have since all become extinct

  or unknown. So many strange contingencies seem to me improbable in the

  highest degree.

  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 Indian sub-species, C. intermedia of Strickland, having it bluish);

  the tail has a terminal dark bar, with the bases of the outer feathers

  externally edged with white; the wings have two black bars; some

  semi-domestic breeds and some apparently truly wild breeds have, besides

  the two black bars, the wings chequered with black. These several marks do

  not occur together in any other species of the whole family. Now, in every

  one of the domestic breeds, taking thoroughly well-bred birds, all the

  above marks, even to the white edging of the outer tail-feathers, sometimes

  concur perfectly developed. Moreover, when two birds belonging to two

  distinct breeds are crossed, neither of which is blue or has any of the

  above-specified marks, the mongrel offspring are very apt suddenly to

  acquire these characters; for instance, I crossed some uniformly white

  fantails with some uniformly black barbs, and they produced mottled brown

  and black birds; these I again crossed together, and one grandchild of the

  pure white fantail and pure black barb was of as beautiful a blue colour,

  with the white rump, double black wing-bar, and barred and white-edged

  tail-feathers, as any wild rock-pigeon! We can understand these facts, on

  the well-known principle of reversion to ancestral characters, if all the

  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 and marked like the rock-pigeon, although no other existing

  species is thus coloured and marked, so that in each separate breed there

  might be a tendency to revert to the very same colours and markings. Or,

  secondly, that each breed, even the purest, has within a dozen or, at most,

  within a score of generations, been crossed by the rock-pigeon: I say

  within a dozen or twenty generations, for we know of no fact countenancing

  the belief that the child ever reverts to some one ancestor, removed by a

  greater number of generations. In a breed which has been crossed only once

  with some distinct breed, the tendency to reversion to any character

  derived from such cross will naturally become less and less, as in each

  succeeding generation there will be less of the foreign blood; but when

  there has been no cross with a distinct breed, and there is a tendency in

  both parents to revert to a character, which has been lost during some

  former generation, this tendency, for all that we can see to the contrary,

  may be transmitted undiminished for an indefinite number of generations.

  These two distinct cases are often confounded in treatises on inheritance.

  Lastly, the hybrids or mongrels from between all the domestic breeds of

  pigeons are perfectly fertile. I can state this from my own observations,

  purposely made on the most distinct breeds. Now, it is difficult, perhaps

  impossible, to bring forward one case of the hybrid offspring of two

  animals clearly distinct being themselves perfectly fertile. Some authors

  believe that long-continued domestication eliminates this strong tendency

  to sterility: from the history of
the dog I think there is some

  probability in this hypothesis, if applied to species closely related

  together, though it is unsupported by a single experiment. But to extend

  the hypothesis so far as to suppose that species, aboriginally as distinct

  as carriers, tumblers, pouters, and fantails now are, should yield

  offspring perfectly fertile, inter se, seems to me rash in the extreme.

  From these several reasons, namely, the improbability of man having

  formerly got seven or eight supposed species of pigeons to breed freely

  under domestication; these supposed species being quite unknown in a wild

  state, and their becoming nowhere feral; these species having very abnormal

  characters in certain respects, as compared with all other Columbidae,

  though so like in most other respects to the rock-pigeon; the blue colour

  and various marks occasionally appearing in all the breeds, both when kept

  pure and when crossed; the mongrel offspring being perfectly fertile;--from

  these several reasons, taken together, I can feel no doubt that all our

  domestic breeds have descended from the Columba livia with its geographical

  sub-species.

  In favour of this view, I may add, firstly, that C. livia, or the

  rock-pigeon, has been found capable of domestication in Europe and in

  India; and that it agrees in habits and in a great number of points of

  structure with all the domestic breeds. Secondly, although an English

  carrier or short-faced tumbler differs immensely in certain characters from

  the rock-pigeon, yet by comparing the several sub-breeds of these breeds,

  more especially those brought from distant countries, we can make an almost

  perfect series between the extremes of structure. Thirdly, those

  characters which are mainly distinctive of each breed, for instance the

  wattle and length of beak of the carrier, the shortness of that of the

  tumbler, and the number of tail-feathers in the fantail, are in each breed

  eminently variable; and the explanation of this fact will be obvious when

  we come to treat of selection. Fourthly, pigeons have been watched, and

  tended with the utmost care, and loved by many people. They have been

  domesticated for thousands of years in several quarters of the world; the

  earliest known record of pigeons is in the fifth Aegyptian dynasty, about

  3000 B.C., as was pointed out to me by Professor Lepsius; but Mr. Birch

  informs me that pigeons are given in a bill of fare in the previous

  dynasty. In the time of the Romans, as we hear from Pliny, immense prices

  were given for pigeons; 'nay, they are come to this pass, that they can

  reckon up their pedigree and race.' Pigeons were much valued by Akber Khan

  in India, about the year 1600; never less than 20,000 pigeons were taken

  with the court. 'The monarchs of Iran and Turan sent him some very rare

  birds;' and, continues the courtly historian, 'His Majesty by crossing the

  breeds, which method was never practised before, has improved them

  astonishingly.' About this same period the Dutch were as eager about

  pigeons as were the old Romans. The paramount importance of these

  considerations in explaining the immense amount of variation which pigeons

  have undergone, will be obvious when we treat of Selection. We shall then,

  also, see how it is that the breeds so often have a somewhat monstrous

  character. It is also a most favourable circumstance for the production of

  distinct breeds, that male and female pigeons can be easily mated for life;

  and thus different breeds can be kept together in the same aviary.

  I have discussed the probable origin of domestic pigeons at some, yet quite

  insufficient, length; because when I first kept pigeons and watched the

  several kinds, knowing well how true they bred, I felt fully as much

  difficulty in believing that they could ever have descended from a common

  parent, as any naturalist could in coming to a similar conclusion in regard

  to the many species of finches, or other large groups of birds, in nature.