could guess that the peach and nectarine, for instance, were cultivated varieties of the wild almond, or that the various breeds of dogs have a common and, geologically speaking, very recent ancestry.
It may be objected however, and it often is objected, that natural selection is not the same thing as artificial selection; but the objection cannot be sustained, for in effect it is the same thing, artificial selection being merely natural selection with man as the governing agent. Man, for instance, has caused the evolution of speed in the greyhound and in the race-horse by breeding, on the whole, from the swiftest animals of each species; in like manner the carnivora have caused the evolution of speed in the hare and the antelope by permitting, other things equal, only the swiftest to continue the race. Artificially caused evolution differs from naturally caused evolution only in that it is usually more rapid; for man, in his endeavours to produce a wished-for evolution, fixes his attention on but a few traits, and breeds with the intention of developing those traits only. Thus in the case of the greyhound he has bred, generally speaking, with the intention of producing a very swift animal with sight keen enough to see the prey, and jaws and teeth adapted to seize and kill it. In the case of the racehorse he has bred with the intention of producing another swift animal, strong enough and tractable enough to carry him. But natural selection in the hare and the antelope has developed not only speed, but also hearing, watchfulness, and many other traits which are as essential.
Other things—i.e. other essential traits—equal, preeminence in one or more essential traits is favourable to survival. But because in a state of nature many traits are essential, evolution by natural selection must proceed along many lines, and, in consequence, be corre-
