Variation under Domestication

Artificial selection has shown how our domestic races have adaptations in their structure or habits based on human design.

Humans can only select externally visible features. We rarely care for what is internal.

A man will only try to make a fantail if he saw a pigeon with an unusual tail.

The more unusual any feature, the more likely it would be to catch human attention.

The man who first selected a pigeon with a larger tail, never dreamed what its descendants would look like through long-continued, partly unconscious and partly methodical selection.

Many slight differences might arise amongst pigeons which are rejected as faults or deviations from the perfection of each breed.

We know nothing about the origin or history of any of our domestic breeds.

A breed, like a dialect of a language, can hardly have a definite origin.

A man either breeds:

• from an individual with a slight deviation of structure, or
• from his best animals and thus improves them

The improved breeds do not get a distinct name and their history will be disregarded because they have little value.

When further improved by the same slow and gradual process, they will spread more widely and get recognised as something distinct and valuable and so get a provincial name.

A high degree of variability is obviously favourable as it freely gives the materials for selection to work on.

When the individuals of any species are scanty, all the individuals will be allowed to breed.

• This prevents selection.

Most importantly, the organism should be so highly valued by man that the closest attention should be paid to the slightest deviation in the qualities or structure of each individual.

Unless such attention be paid nothing can be effected.

The strawberry began to vary just when gardeners began to attend closely to it.

The strawberry had always varied since it was cultivated. But the slight varieties had been neglected.

However, gardeners picked out individual plants with slightly larger, earlier, or better fruit, and raised seedlings from them. They again picked out the best seedlings and bred from them.

There appeared (aided by some crossing with distinct species) those many admirable strawberry varieties.

In the case of animals with separate sexes, preventing crosses is important in creating new races.

• This is true at least, in a country which is already stocked with other races.

In this respect, enclosure of the land plays a part.

Wandering savages or the inhabitants of open plains rarely possess more than one breed of the same species.

Pigeons can be mated for life. This is a great convenience to the breeder so that many races may be kept true, though mingled in the same aviary. This has favoured the improvement and formation of new breeds.

Pigeons can be propagated in great numbers quickly. Inferior birds may be freely rejected, as when killed they serve for food.

On the other hand, cats cannot be matched because of their nocturnal rambling habits.

We hardly ever see a distinct breed kept up. Such breeds are usually imported, often from islands.

The rarity or absence of distinct breeds of cat, donkey, peacock, goose, &c. is from selection not being brought into play.

• Cats are difficult to pair. There are only a few donkeys kept by poor people.
• Little attention paid to their breeding.
• Peacocks are not easily reared and a large stock not kept.
• Geese are valuable only for food and feathers.

To sum up on the origin of our Domestic Races of animals and plants. I believe that

The most important cause of variability is the conditions of life on the reproductive system.

Variability is not an inherent and necessary contingency under all circumstances with all organic beings.

The effects of variability are modified by various degrees of inheritance and of reversion.

Variability is governed by many unknown laws, more especially by that of correlation of growth.

Something may be attributed to:

• the direct action of the conditions of life.
• use and disuse

The final result is thus rendered infinitely complex.

In some cases, the intercrossing of species, aboriginally distinct, has played an important part in the origin of our domestic productions.

When in any country several domestic breeds have once been established, their occasional intercrossing, with the aid of selection, has largely aided the formation of new sub-breeds.

But the importance of the crossing of varieties has been greatly exaggerated, both in regard to animals and to plants propagated by seed.

In plants which are temporarily propagated by cuttings, buds, &c., the importance of the crossing both of distinct species and of varieties is immense.

The cultivator here quite disregards the extreme variability both of hybrids and mongrels, and the frequent sterility of hybrids.

But the cases of plants not propagated by seed are of little importance to us, for their endurance is only temporary.

The accumulative action of Selection is by far the predominant Power over all these causes of Change whether applied:

• methodically and more quickly, or
• unconsciously and more slowly, but more efficiently