88 DOMESTICATED ANIMALS AND PLANTS 



and stops. Nature does not aim at perfection, but every species 

 is just as good as competition makes it, and no better. 



Writers when discussing this topic often overstate the facts. 

 They are impressed by the niceties of adjustment so frequently 

 seen in nature, and rush to the assumption that everything is 

 perfectly adjusted and perfectly adaptive. It is better to under- 

 stand that upon the whole characters are and must be highly 

 but not perfectly adaptive ; that such adaptations are achieved 

 at great distress to individuals and temporary danger to the 

 species, and that they will never be more numerous or closer 

 than circumstances compel ; so that each species generally sur- 

 vives with one or more handicaps, in which the fatalities are 

 not sufficient to force a fit upon the one hand or bring about 

 extinctio7i tipon the other. 



Looked at in this way, the animals and plants of the forest as 

 we see them, even in a state of nature, represent a choice but 

 not a perfect lot, born, upon the whole, as they are, from a 

 highly selected though not perfect ancestry ; that is, from the 

 standpoint of nature these species were already highly bred 

 when first domesticated by our forefathers. 



Our standards of selection differ from those of nature. In 

 nature selection is based only on the struggle for existence. 

 Nothing avails that does not bear upon the supreme issue of 

 mere ability to live and reproduce fast enough to keep ahead of 

 the death rate and thus maintain the balance of life in favor 

 of the species. Natural selection is thus based on anything and 

 everything that affects the mere question of life, death, and 

 reproduction, and nothing else. It secures, of course, great vigor, 

 comparatively long life, 1 and at least a reasonable degree of 

 fecundity together with the extreme development of whatever 

 physical part or trait of character is directly concerned with the 

 preservation and sustenance of life, and there it will stop. 



1 See Fig. 12. This is the same burro shown on page 7 in his working out- 

 fit, when engaged in building the Pikes Peak Railroad many years ago. His 

 labors are done and he is now kept for photographic purposes. He illustrates 

 the longevity of rare individuals. 



