Page:Philosophical Review Volume 19.djvu/138

124 of man are wholly inadequate to describe those processes after his appearance. So far as man is a product of the preceding stages of evolution, he maybe regarded merely as one term among many of an indefinitely continued series; but, so far as he is the dominant factor in the course of his own development, giving character and determination to it, he is unique, and in this respect at least cannot be grouped with any other order of animal, however closely they may resemble him in form and function, or in the crude exercise of a rudimentary intelligence. What such a man as Charles Darwin alone has accomplished in modifying the character of the race far transcends our powers of estimation, or of conjecture.

Not only has man determined in a large measure the course of his own development, but the evolution of the human factor in the series has also modified in many essential features the process of the series itself. Man's occupation of the earth has changed the natural environment both of plants and of animals. Entire species have been exterminated; others have been protected and cultivated. Deserts have been turned into fertile fields, and fertile fields into waste places. Fauna and flora alike are affected by the introduction of the human factor into their environment. Man has become a directive force in evolution. The process of natural selection is being constantly modified by human selection. The experiments in agriculture on a large scale, the selective breeding of domestic animals, the preservation of game, the special culture of fish in almost every stream and lake in the civilized world, the domestication of wild animals, the production of new varieties of fruits and vegetables—all indicate that man's control of the phenomena of life exerts an influence upon the evolutionary series of a permanent and essential character.

This then is the paradox of evolution, that a process giving no evidence of intelligent purpose develops a product whose characteristic feature is purposeful activity; that what is a product, becomes a determining factor in the subsequent development of the process; and that natural selection produces an effect, capable of modifying and at times defeating the influences of natural selection itself by reason of that very selective faculty which these influences originally evolved.