ORGANIC EVOLUTION — PHYSICAL 11 



could guess that tbe peach and nectarine, for instance, 

 were cultivated vaiieties of the wild almond, or that 

 the various breeds of dogs have a common and, geolo- 

 gically 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 breed- 

 ing, 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 race- 

 horse he has bred with the intention of producing 

 another swift animal, strong enough and tractable 

 enough to cany 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, pre- 

 eminence in one or more essential traits is favourable 

 to survival. But because in a state of nature many 

 traits ai-e essential, evolution by natural selection must 

 proceed along many hues, and, in consequence, be corre- 



