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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 considerable 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. Com-
pare 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 won-
derful development of the carunculated skin about the head; and this is ac-
companied 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
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 long beak, has a very short and broad
one. The pouter has a much elongated body, wings and legs; and its enor-
mously developed crop, which it glories in inflating, many well excite astonish-



VARIATION UNDER DOMESTICATION 13

ment and even laughter. The turbit has a 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, 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, in-
stead of twelve or fourteen — the normal number in all the members of the
great pigeon family; 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 be 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 caudal and sacral vertebrae vary in number;
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 eyeUds, 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 rela-
tive length of the wing and tail to each other and to the body; the relative
length of the leg and foot; the number of scutellae on the toes, the develop-
ment 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, and in some breeds
the voice and disposition, differ remarkably. Lastly, in certain breeds, the
males and females have come to differ in 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
be ranked by him as well-defined species. Moreover, I do not believe that
any ornithologist would in this case 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 would call them, could be shown him.

Great as are the differences between the breeds of the pigeon, I am fully
convinced that the common opinion of naturalists is correct, namely, that
all are 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 pro-
ceeded from the rock-pigeon, they must have descended from at least seven



14 THE ORIGIN OF SPECIES

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, they did not breed or willingly
perch on trees. But besides G. 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 improbable ; or they must
have become extinct in the wild state. But birds breeding on precipices, and
good flyers, are unlikely to be exterminated; and the common rock-pigeon,
which has the same habits with the domestic breeds, has not been ex-
terminated 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 a very rash assumption.

Moreover, the several above-named domesticated breeds have been trans-
ported 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 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 difficult to get wild animals 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 of great weight and applicable in several other cases, is,
that the above-specified breeds, though agreeing generally with the wild
rock-pigeon in constitution, habits, voice, coloring, and in most parts of
their structure, yet are certainly highly abnormal in other parts; we may
look in vain through the whole great family of Golumbidae 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 are improbable in the highest
degree.

Some facts in regard to the coloring of pigeons well deserve consideration.
The rock-pigeon is of a slaty-blue, with white loins; but the Indian sub-
species, G. intermedia of Strickland, has this part bluish. The tail has a
terminal dark bar, with the outer feathers externally edged at the base with
white. The wings have two black bars. Some semi-domestic breeds, and some
truly wild breeds, have, besides the two black bars, the wings checkered with



VARIATION UNDER DOMESTICATION 15

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 birds
belonging to two or more distinct breeds are crossed, none of which are blue
or have any of the above-specified marks, the mongrel offspring are very
apt suddenly to acquire these characters. To give one instance out of several
which I have observed : I crossed some white f antails, which breed very true,
with some black barbs — and it so happens that blue varieties of barbs are so
rare that I never heard of an instance in England; and the mongrels were
black, brown, and mottled. I also crossed a barb with a spot, which is a white
bird with a red tail and red spot on the forehead, and which notoriously breeds
very true; the mongrels were dusky and mottled. I then crossed one of the
mongrel barb-fantails with a mongrel barb-spot, and they produced a bird
of as beautiful a blue color, with the white loins, 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 are descended from the rock-pigeon.
But, if we deny this, we must make one of the two following highly im-
probable suppositions. Either, first, that all the several imagined aboriginal
stocks were colored and marked like the rock-pigeon, although no other
existing species is thus colored and marked, so that in each separate breed
there might be a tendency to revert to the very same colors 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 no instance is known of crossed
<iescendants reverting to an ancestor of foreign blood, removed by a greater
number of generations. In a breed which has been crossed only once the
tendency to revert to any character derived from such a 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, and there is a tendency
in the breed to revert to a character which was 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 of reversion are often confounded together by those who
liave written on inheritance.

Lastly, the hybrids or mongrels from between all the breeds of the pigeon
are perfectly fertile, as I can state from my own observations, purposely
made, on the most distinct breeds. Now, hardly any cases have been as-
certained with certainty of hybrids from two quite distinct species of animals
being perfectly fertile. Some authors believe that long-continued domestica-
tion eliminates this strong tendency to sterility in species. From the history
of the dog, and of some other domestic animals, this conclusion is probably
quite correct, if applied to species closely related to each other. But to extend
_it so far as to suppose that species, aboriginally as distinct as carriers,



]6 THE ORIGIN OF SPECIES

tumblers, pouters, and fantails now are, should yield offspring perfectly
fertile inter se, would be rash in the extreme.

From these several reasons, namely, the improbability of man having
formerly made seven or eight supposed species of pigeons to breed freely
under domestication — these supposed species being quite unknown in a wild
state, and their not having become anywhere feral — these species presenting
certain very abnormal characters, as compared with all other Columbidae,
though so like the rock-pigeon in most respects — the occasional reappear-
ance of the blue color and various black marks in all the breeds, both when
kept pure and when crossed — and lastly, the mongrel offspring being per-
fectly fertile — from these several reasons, taken together, we may safely con-
clude that all our domestic breeds are descended from the rock-pigeon or
Columba livia with its geographical sub-species.

In favor of this view, I may add, firstly, that the wild G. livia 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, that although an English carrier or a short-faced tumbler
differs immensely in certain characters from the rock-pigeon, yet that by
comparing the several sub-breeds of these two races, more especially those
brought from distant countries, we can make, between them and the rock-
pigeon, an almost perfect series; so we can in some other cases, but not with
all the breeds. Thirdly, those characters which are mainly distinctive of
each breed are in each eminently variable, 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: and the explanation of this fact will
be obvious when we 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 Egyptian 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 explain-
ing the immense amount of variation which pigeons have undergone, will
likewise be obvious when we treat of selection. We shall then, also, see how
it is that the several breeds so often have a somewhat monstrous character.
It is also a most favorable 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.



VARIATION UNDER DOMESTICATION 17

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, well knowing how truly they breed, I felt fully as much
difficulty in believing that since they had been domesticated they had all
proceeded from a common parent, as any naturalist could in coming to a
similar conclusion in regard to the many species of finches, or other groups
of birds, in nature. One circumstance has struck me much; namely, that
nearly all the breeders of the various domestic animals and the cultivators
of plants, with whom I have conversed, or whose treatises I have read, are
firmly convinced that the several breeds to which each has attended, are
descended from so many aboriginally distinct species. Ask, as I have asked, a
celebrated raiser of Hereford cattle, whether his cattle might not have
descended from Long-horns, or both from a common parent-stock, and he
will laugh you to scorn. I have never met a pigeon, or poultry, or duck, or
rabbit fancier, who was not fully convinced that each main breed was
descended from a distinct species. Van Mons, in his treatise on pears and
apples, shows how utterly he disbelieves that the several sorts, for instance, a
Ribston-pippin or Codlin-apple, could ever have proceeded from the seeds
of the same tree. Innumerable other examples could be given. The explana-
tion, I think, is simple : from long-continued study they are strongly impressed
with the differences between the several races; and though they well know
that each race varies slightly, for they win their prizes by selecting such
slight differences, yet they ignore all general arguments, and refuse to sum
up in their minds slight differences accumulated during many successive
generations. May not those naturalists who, knowing far less of the laws
of inheritance than does the breeder, and knowing no more than he does of
the intermediate links in the long lines of descent, yet admit that many of
our domestic races are descended from the same parents — ^may they not
learn a lesson of caution, when they deride the idea of species in a state of
nature being lineal descendants of other species?

PRINCIPLES OF SELECTION ANCIENTLY FOLLOWED, AND THEIR EFFECTS

Let us now briefly consider the steps by which domestic races have been
produced, either from one or from several allied species. Some effect may
be attributed to the direct and definite action of the external conditions of
life, and some to habit; but he would be a bold man who would account by
such agencies for the differences between a dray- and race-horse, a greyhound
and bloodhound, a carrier and tumbler pigeon. One of the most remarkable
features in our domesticated races is that we see in them adaptation, not
indeed to the animal's or plant's own good, but to man's use or fancy. Some
variations useful to him have probably arisen suddenly, or by one step ; many
botanists, for instance, believe that the fuller's teasel, with its hooks, which
cannot be rivalled by any mechanical contrivance, is only a variety of the
wild Dipsacus; and this amount of change may have suddenly arisen in a
seedling. So it has probably been with the turnspit dog; and this is known



18 THE ORIGIN OF SPECIES

to have been the case with the ancon sheep. But when we compare the dray-
horse and race-horse, the dromedary and camel, the various breeds of sheep
fitted either for cultivated land or mountain pasture, with the wool of one
breed good for one purpose, and that of another breed for another purpose;
when we compare the many breeds of dogs, each good for man in different
ways; when we compare the game-cock, so pertinacious in battle, with
other breeds so little quarrelsome, with "everlasting layers" which never
desire to sit, and with the bantam so small and elegant; when we compare
the host of agricultural, culinary, orchard, and flower-garden races of plants,
most useful to man at different seasons and for different purposes, or so
beautiful in his eyes, we must, I think, look further than to mere variability.
We cannot suppose that all the breeds were suddenly produced as perfect
and as useful as we now see them; indeed, in many cases, we know that this
has not been their history. The key is man's power of accumulative selec-
tion: nature gives successive variations; man adds them up in certain
directions useful to him. In this sense he may be said to have made for
himself useful breeds.

The great power of this principle of selection is not hypothetical. It is
certain that several of our eminent breeders have, even within a single
lifetime, modified to a large extent their breeds of cattle and sheep. In
order fully to realize what they have done, it is almost necessary to read
several of the many treatises devoted to this subject, and to inspect the
animals. Breeders habitually speak of an animal's organization as something
plastic, which they can model almost as they please. If I had space I could
quote numerous passages to this effect from highly competent authorities.
Youatt, who was probably better acquainted with the works of agriculturists
than almost any other individual, and who was himself a very good judge
of animals, speaks of the principle of selection as "that which enables the
agriculturist, not only to modify the character of his flock, but to change it
altogether. It is the magician's wand, by means of which he may summon
into life whatever form and mould he pleases." Lord Somerville, speaking
of what breeders have done for sheep, says : "It would seem as if they had
chalked out upon a wall a form perfect in itself, and then had given it
existence." In Saxony the importance of the principle of selection in regard
to merino sheep is so fully recognized that men follow it as a trade: the
sheep are placed on a table and are studied, like a picture by a connoisseur :
this is done three times at intervals of months, and the sheep are each time
marked and classed, so that the very best may ultimately be selected for
breeding.

What English breeders have actually effected is proved by the enormous
prices given for animals with a good pedigree; and these have been exported
to almost every quarter of the world. The improvement is by no means
generally due to crossing different breeds; all the best breeders are strongly
opposed to this practice, except sometimes among closely allied sub-breeds.
And when a cross has been made, the closest selection is far more indis-
pensable even than in ordinary cases. If selection consisted merely in separat-



VARIATION UNDER DOMESTICATION 19

ing some very distinct variety, and breeding from it, the principle would
be so obvious as hardly to be worth notice; but its importance consists in
the great effect produced by the accumulation in one direction, during
successive generations, of differences absolutely inappreciable by an un-
educated eye — differences which I for one have vainly attempted to
appreciate. Not one man in a thousand has accuracy of eye and judgment
sufficient to become an eminent breeder. If gifted with these qualities, and
he studies his subject for years, and devotes his lifetime to it with indomitable
perseverance, he will succeed, and may make great improvements; if he
wants any of these qualities, he will assuredly fail. Few would readily believe
in the natural capacity and years of practice requisite to become even a
skilful pigeon-fancier.

The same principles are followed by horticulturists ; but the variations are
here often more abrupt. No one supposes that our choicest productions have
been produced by a single variation from the aboriginal stock. We have
proofs that this has not been so in several cases in which exact records have
been kept; thus, to give a very trifling instance, the steadily increasing size
of the common gooseberry may be quoted. We see an astonishing improve-
ment in many florists' flowers, when the flowers of the present day are com-
pared with drawings made only twenty or thirty years ago. When a race of
plants is once pretty well established, the seed-raisers do not pick out the
best plants, but merely go over their seed-beds, and pull up the "rogues," as
they call the plants that deviate from the proper standard. With animals
this kind of selection is, in fact, likewise followed; for hardly any one is so
careless as to breed from his worst animals.

In regard to plants, there is another means of observing the accumulated
effects of selection — namely, by comparing the diversity of flowers in the
different varieties of the same species in the flower garden; the diversity of
leaves, pods, or tubers, or whatever part is valued, in the kitchen-garden, in
comparison with the flowers of the same varieties; and the diversity of fruit
of the same species in the orchard, in comparison with the leaves and flowers
of the same set of varieties. See how different the leaves of the cabbage are,
and how extremely alike the flowers; how unlike the flowers of the heart' s-
ease are, and how alike the leaves; how much the fruit of the different kinds
of gooseberries differ in size, color, shape, and hairiness, and yet the flowers
present very slight differences. It is not that the varieties which differ largely
in some one point do not differ at all in other points; this is hardly ever — I
speak after careful observation — perhaps never, the case. The law of corre-



Online LibraryCharles DarwinThe origin of species → online text (page 3 of 50)