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01 - Variations Under Domestication 01-09 - Principles of Selection anciently followed, and their Effects 30 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 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, 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.

pigeon
pigeon
01 - Variations Under Domestication 01-10 - Methodical and Unconscious Selection 30 Youatt gives an excellent illustration of the effects of a course of selection, which may be considered as unconscious, in so far that the breeders could never have expected, or even wished, to produce 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 remarks, "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."

sheep
sheep
01 - Variations Under Domestication 01-11 - Unknown Origin of our Domestic Productions 30 On the view here given of the important part which selection by man has played, it becomes at once obvious, how it is that our domestic races show adaptation in their structure or in their habits to man's wants or fancies.

We can, I think, further understand the frequently abnormal characters of our domestic races, and likewise their differences being so great in external characters, and relatively so slight in internal parts or organs.

Man can hardly select, or only with much difficulty, any deviation of structure excepting such as is externally visible; and indeed he rarely cares for what is internal.

He can never act by selection, excepting on variations which are first given to him in some slight degree by nature. No man would ever try to make a fantail till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter till he saw a pigeon with a crop of somewhat unusual size; and the more abnormal or unusual any character was when it first appeared, the more likely it would be to catch his attention.

Fantail Pigeon
Fantail Pigeon


But to use such an expression as trying to make a fantail, is, I have no doubt, in most cases, utterly incorrect.

The man who first selected a pigeon with a slightly larger tail, never dreamed what the descendants of that pigeon would become through long-continued, partly unconscious and partly methodical, selection. Perhaps the parent-bird of all fantails had only fourteen tail-feathers somewhat expanded, like the present Java fantail, or like individuals of other and distinct breeds, in which as many as seventeen tail-feathers have been counted.

Perhaps the first pouter-pigeon did not inflate its crop much more than the turbit now does the upper part of its oesophagus,- a habit which is disregarded by all fanciers, as it is not one of the points of the breed.

Pouter Pigeon
Pouter Pigeon
01 - Variations Under Domestication 01-12 - Circumstances favourable to Man's Power of Selection 30 But the goose, under the conditions to which it is exposed when domesticated seems to have a singularly inflexible organisation, though it has varied to a slight extent, as I have elsewhere described.

goose
goose


Some authors have maintained that the amount of variation in our domestic productions is soon reached, and can never afterwards be exceeded.

It would be somewhat rash to assert that the limit has been attained in any one case; for almost all our animals and plants have been greatly improved in many ways within a recent period; and this implies variation.

It would be equally rash to assert that characters now increased to their utmost limit, could not, after remaining fixed for many centuries, again vary under new conditions of life.

No doubt, as Mr. Wallace has remarked with much truth, a limit will be at last reached. For instance, there must be a limit to the fleetness of any terrestrial animal, as this will be determined by the friction to be overcome, the weight of body to be carried, and the power of contraction in the muscular
fibres.

Alfred Russel Wallace
Alfred Russel Wallace


But what concerns us is that the domestic varieties of the same species differ from each other in almost every character, which man has attended to and selected, more than do the distinct species of the same genera.

Isidore Geoffroy St-Hilaire has proved this in regard to size, and so it is with colour and probably with the length of hair.

With respect to fleetness, which depends on many bodily characters, Eclipse was far fleeter, and a dray-horse is incomparably stronger than any two natural species belonging to the same genus.

So with plants, the seeds of the different varieties of the bean or maize probably differ more in size, than do the seeds of the distinct species in any one genus in the same two families. The same remark holds good in regard to the fruit of the several varieties of the plum, and still more strongly with the melon, as well as in many other analogous cases.

maize
maize

plum
plum

melon
melon