The Origin of Species

One circumstance has struck me much; namely, that all the breeders of the

  various domestic animals and the cultivators of plants, with whom I have

  ever 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, 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 explanation, 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 have 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?

  Selection. -- Let us now briefly consider the steps by which domestic races

  have been produced, either from one or from several allied species. Some

  little effect may, perhaps, be attributed to the direct action of the

  external conditions of life, and some little to habit; but he would be a

  bold man who would account by such agencies for the differences of 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 teazle, 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 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 very 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 several cases, we

  know that this has not been their history. The key is man's power of

  accumulative selection: nature gives successive variations; man adds them

  up in certain directions useful to him. In this sense he may be said to

  make 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 some breeds of cattle and sheep. In

  order fully to realise 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 organisation as

  something quite 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 agriculturalists than almost any other individual, and who was

  himself a very good judge of an animal, 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.' That most skilful breeder,

  Sir John Sebright, used to say, with respect to pigeons, that 'he would

  produce any given feather in three years, but it would take him six years

  to obtain head and beak.' In Saxony the importance of the principle of

  selection in regard to merino sheep is so fully recognised, 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 now 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 amongst closely allied

  sub-breeds. And when a cross has been made, the closest selection is far

  more indispensable even than in ordinary cases. If selection consisted

  merely in separating 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 uneducated 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 b
y 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 is not so in some 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 improvement

  in many florists' flowers, when the flowers of the present day are compared

  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, also followed; for hardly any one is so

  careless as to allow his worst animals to breed.

  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 heartsease are, and how alike the

  leaves; how much the fruit of the different kinds of gooseberries differ in

  size, colour, 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, perhaps

  never, the case. The laws of correlation of growth, the importance of

  which should never be overlooked, will ensure some differences; but, as a

  general rule, I cannot doubt that the continued selection of slight

  variations, either in the leaves, the flowers, or the fruit, will produce

  races differing from each other chiefly in these characters.

  It may be objected that the principle of selection has been reduced to

  methodical practice for scarcely more than three-quarters of a century; it

  has certainly been more attended to of late years, and many treatises have

  been published on the subject; and the result, I may add, has been, in a

  corresponding degree, rapid and important. But it is very far from true

  that the principle is a modern discovery. I could give several references

  to the full acknowledgment of the importance of the principle in works of

  high antiquity. In rude and barbarous periods of English history choice

  animals were often imported, and laws were passed to prevent their

  exportation: the destruction of horses under a certain size was ordered,

  and this may be compared to the 'roguing' of plants by nurserymen. The

  principle of selection I find distinctly given in an ancient Chinese

  encyclopaedia. Explicit rules are laid down by some of the Roman classical

  writers. From passages in Genesis, it is clear that the colour of domestic

  animals was at that early period attended to. Savages now sometimes cross

  their dogs with wild canine animals, to improve the breed, and they

  formerly did so, as is attested by passages in Pliny. The savages in South

  Africa match their draught cattle by colour, as do some of the Esquimaux

  their teams of dogs. Livingstone shows how much good domestic breeds are

  valued by the negroes of the interior of Africa who have not associated

  with Europeans. Some of these facts do not show actual selection, but they

  show that the breeding of domestic animals was carefully attended to in

  ancient times, and is now attended to by the lowest savages. It would,

  indeed, have been a strange fact, had attention not been paid to breeding,

  for the inheritance of good and bad qualities is so obvious.

  At the present time, eminent breeders try by methodical selection, with a

  distinct object in view, to make a new strain or sub-breed, superior to

  anything existing in the country. But, for our purpose, a kind of

  Selection, which may be called Unconscious, and which results from every

  one trying to possess and breed from the best individual animals, is more

  important. Thus, a man who intends keeping pointers naturally tries to get

  as good dogs as he can, and afterwards breeds from his own best dogs, but

  he has no wish or expectation of permanently altering the breed.

  Nevertheless I cannot doubt that this process, continued during centuries,

  would improve and modify any breed, in the same way as Bakewell, Collins,

  &c., by this very same process, only carried on more methodically, did

  greatly modify, even during their own lifetimes, the forms and qualities of

  their cattle. Slow and insensible changes of this kind could never be

  recognised unless actual measurements or careful drawings of the breeds in

  question had been made long ago, which might serve for comparison. In some

  cases, however, unchanged or but little changed individuals of the same

  breed may be found in less civilised districts, where the breed has been

  less improved. There is reason to believe that King Charles's spaniel has

  been unconsciously modified to a large extent since the time of that

  monarch. Some highly competent authorities are convinced that the setter

  is directly derived from the spaniel, and has probably been slowly altered

  from it. It is known that the English pointer has been greatly changed

  within the last century, and in this case the change has, it is believed,

  been chiefly effected by crosses with the fox-hound; but what concerns us

  is, that the change has been effected unconsciously and gradually, and yet

  so effectually, that, though the old Spanish pointer certainly came from

  Spain, Mr. Borrow has not seen, as I am informed by him, any native dog in

  Spain like our pointer.

  By a similar process of selection, and by careful training, the whole body

  of English racehorses have come to surpass in fleetness and size the parent

  Arab stock, so that the latter, by the regulations for the Goodwood Races,

  are favoured in the weights they carry. Lord Spencer and others have shown

  how the cattle of England have increased in weight and in early maturity,

  compared with the stock formerly kept in this country. By comparing the

  accounts given in old pigeon treatises of carriers and tumblers with these

  breeds as now existing in Britain, India, and Persia, we can, I think,

  clearly trace the stages through which they have insensibly passed, and

  come to differ so greatly from the rock-pigeon.

  Youatt gives an excellent illustration of the effects of a course of

  selection, which may be considered as unconsciously followed, in so far

  that the breeders could never have expected or even have wished to have

  produced the result which ensued--namely, the production of two distinct

  strains. The two flocks of Leicester sheep kept by Mr. Buckley and Mr.

  Burgess, as Mr. Youatt re
marks, 'have been purely bred from the original

  stock of Mr. Bakewell for upwards of fifty years. There is not a suspicion

  existing in the mind of any one at all acquainted with the subject that the

  owner of either of them has deviated in any one instance from the pure

  blood of Mr. Bakewell's flock, and yet the difference between the sheep

  possessed by these two gentlemen is so great that they have the appearance

  of being quite different varieties.'

  If there exist savages so barbarous as never to think of the inherited

  character of the offspring of their domestic animals, yet any one animal

  particularly useful to them, for any special purpose, would be carefully

  preserved during famines and other accidents, to which savages are so

  liable, and such choice animals would thus generally leave more offspring

  than the inferior ones; so that in this case there would be a kind of

  unconscious selection going on. We see the value set on animals even by

  the barbarians of Tierra del Fuego, by their killing and devouring their

  old women, in times of dearth, as of less value than their dogs.

  In plants the same gradual process of improvement, through the occasional

  preservation of the best individuals, whether or not sufficiently distinct

  to be ranked at their first appearance as distinct varieties, and whether

  or not two or more species or races have become blended together by

  crossing, may plainly be recognised in the increased size and beauty which

  we now see in the varieties of the heartsease, rose, pelargonium, dahlia,

  and other plants, when compared with the older varieties or with their

  parent-stocks. No one would ever expect to get a first-rate heartsease or

  dahlia from the seed of a wild plant. No one would expect to raise a

  first-rate melting pear from the seed of a wild pear, though he might

  succeed from a poor seedling growing wild, if it had come from a

  garden-stock. The pear, though cultivated in classical times, appears,

  from Pliny's description, to have been a fruit of very inferior quality. I

  have seen great surprise expressed in horticultural works at the wonderful

  skill of gardeners, in having produced such splendid results from such poor

  materials; but the art, I cannot doubt, has been simple, and, as far as the

  final result is concerned, has been followed almost unconsciously. It has

  consisted in always cultivating the best known variety, sowing its seeds,

  and, when a slightly better variety has chanced to appear, selecting it,

  and so onwards. But the gardeners of the classical period, who cultivated

  the best pear they could procure, never thought what splendid fruit we

  should eat; though we owe our excellent fruit, in some small degree, to

  their having naturally chosen and preserved the best varieties they could

  anywhere find.

  A large amount of change in our cultivated plants, thus slowly and

  unconsciously accumulated, explains, as I believe, the well-known fact,

  that in a vast number of cases we cannot recognise, and therefore do not

  know, the wild parent-stocks of the plants which have been longest

  cultivated in our flower and kitchen gardens. If it has taken centuries or

  thousands of years to improve or modify most of our plants up to their

  present standard of usefulness to man, we can understand how it is that

  neither Australia, the Cape of Good Hope, nor any other region inhabited by

  quite uncivilised man, has afforded us a single plant worth culture. It is

  not that these countries, so rich in species, do not by a strange chance

  possess the aboriginal stocks of any useful plants, but that the native

  plants have not been improved by continued selection up to a standard of

  perfection comparable with that given to the plants in countries anciently

  civilised.

  In regard to the domestic animals kept by uncivilised man, it should not be