Breeds And Breeding

Breeds And Breeding. Breeds may be defined as domestic varieties of animals or plants which man has been able to bring into existence and to maintain in existence. The process of breeding includes all the modifying influences which man may bring to bear on a wild stock for the purpose, conscious or unconscious, of establishing and maintaining breeds. Charles Darwin’s Variation of Animals and Plants under Domestication (1868) was the starting-point of exact knowledge on this subject; when it appeared, it contained not only the best collection of empirical facts, but the only rational theory of the facts. The first relations between man and domesticated animals and plants were due to unconscious or accidental selection of wild stocks that tolerated the vicinity of man and that were useful or attractive to him. The new conditions must have produced modifications in these stocks, whether these were caused by a survival in each generation of individuals with the power of response to the new environment, or were due to a conscious selection of individuals capable of such favourable response. The essence of the process, however, came to be a conscious selection in each generation of the best individuals, that is to say, of those individuals that seemed to man to be most adapted to his wants. The possibility of establishing a breed depended, therefore, in the first place on the natural variability of wild animals and plants, then on the variations induced in animals and plants under subjection to the new conditions brought about by man’s interference, next on the extent to which these variations, natural or artificial, persisted through the series of generations, and finally on man’s intelligence in altering or maintaining the conditions of the environment, and in selective mating. The theory of breeds and breeding depends, in fact, on knowledge of variation, of modification by the environment, and of heredity. Any attempt to give an account of what actually has been done by man in establishing breeds would be little more than an imperfect summary of Darwin’s work. The articles Heredity, Mendelism and Variation and Selection show that what may be called the theoretical and experimental knowledge of variation and heredity is far in advance of the practical art of breeding. Even horticulturists, who have been much more successful than those who deal with animals, are still far from being able to predict the result of their selections and crossings. None the less it may be stated definitely that such prediction is already so nearly within the power of the practical breeder that it would be a waste of time to give a summary of the existing rule-of-thumb methods. The art of breeding is so immediately destined to become a science of breeding that existing knowledge and conceptions must be dismissed as of no more than historical interest.