Evolutionary genetics / edited by D.L. Jameson.

Date:
[1977], ©1977
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Evolutionary genetics / edited by D.L. Jameson. Source: Wellcome Collection.

    49/360 (page 29)
    60 MESSES. С. DAEWTN AND A. WALLACE ON THE ita body that is not called into daily and hourly activity ; there is no sense or faculty that is not strengthened by continual exercise. The domestic animal, on the other hand, has food provided for it, is sheltered, and often confined, to guard it against the vicissitudes of the seasons, is carefully secured from the attacks of its natura] enemies, and seldom even rears its young without human assistance. Half of its senses and faculties are quite useless ; and the other half are but occasionally called into feeble exercise, while even its muscular system is only irregularly called iato action. Now when a variety of such an animal occurs, having increased power or capacity in any organ or sense, such increase is to¬ tally useless, is never caUed into action, and may even exist without the animal ever becoming aware of it. In the wild animal, on the contrary, all its faculties and powers being brought into full action for the necessities of existence, any increase becomes immediately available, is strengthened by exercise, and must even slightly mo¬ dify the food, the habits, and the whole economy of the race. It creates as it were a new animal, one of superior powers, and which will necessarily increase in numbers and outlive those inferior to it. Again, in the domesticated animal all variations have an equal chance of continuance ; and those which would decidedly render a wild animal unable to compete with its fellows and continue its existence are no disadvantage whatever in a state of domesticity. Our quickly fattening pigs, short-legged sheep, pouter pigeons, and poodle dogs could never have come into existence in a state of nature, because the very first step towards such inferior forms would have led to the rapid extinction of the race ; still less could they now exist in competition with their wild allies. The great speed but slight endurance of the race horse, the unwieldy strength of the ploughman's team, would both be useless in a state of nature. If turned wild on the pampas, such animals would probably soon become extinct, or under favourable circumstances might each lose those extreme qualities which would never be called into action, and in a few generations woidd revert to a common type,'which must be that in which the various powers and faculties are so proportioned to each other as to be best adapted to procure food and seciire safety,—^that in which by the fidi exercise of every part of his organization the animal can alone continue to live. Domestic varieties, when turned wüd, must return to something near the type of the original wild stock, or become altogetJier extinct. 29