Page:Through the Brazilian Wilderness by Theodore Roosevelt (1925).djvu/60

 another set of cases, in the development and preservation of species. Courage, intelligence, adaptability, prowess, bodily vigor, speed, alertness, ability to hide, ability to build structures which will protect the young while they are helpless, fecundity—all, and many more like them, have their several places; and behind all these visible causes there are at work other and often more potent causes of which as yet science can say nothing. Some species owe much to a given attribute which may be wholly lacking in influence on other species; and every one of the attributes above enumerated is a survival factor in some species, while in others it has no sur- vival value whatever, and in yet others, although of benefit, it is not of sufficient benefit to offset the benefit conferred on foes or rivals by totally different attri- butes. Intelligence, for instance, is of course a survival factor; but to-day there exist multitudes of animals with very little intelligence which have persisted through im- mense periods of geologic time either unchanged or else without any change in the direction of increased intelli- gence; and during their species-life they have witnessed the death of countless other species of far greater in- telligence but in other ways less adapted to succeed in the environmental complex. The same statement can be made of all the many, many other known factors in de- velopment, from fecundity to concealing coloration; and behind them lie forces as to which we veil our ignorance by the use of high-sounding nomenclature—as when we use such a convenient but far from satisfactory term as orthogenesis.