1 66 THE EVOLUTION OF MAN 



plete reversal by man of some of the most important principles 

 which have guided evolution in the past. For the first time in 

 the history of life upon the earth, a single species now has the 

 power of controlling to a large extent its own evolution, and 

 it has begun by radically changing some of the conditions of 

 progress which have prevailed hitherto. A large part of the 

 human race is now engaged in the most stupendous and dan- 

 gerous experimentation upon itself; without any adequate 

 knowledge of the mechanism of evolution it has begun to tinker 

 with that mechanism, throwing certain parts out of gear, de- 

 stroying others, and in general paying little or no attention to 

 the results. 



Decreasing Influence of Natural Selection. In spite of some 

 notable exceptions, the leading biologists of the world agree 

 that natural selection has been the most important guiding 

 and perfecting principle in past evolution, and on the whole 

 it has made for progress. At every step in the past course of 

 evolution it has sifted the unfit from the fit, and while it has 

 not originated fitness, it has preserved it, and in general it has 

 directed evolution into paths of progress by closing up other 

 paths. Those whose only conception of natural selection is 

 that of a life and death struggle between individuals of the 

 same species may well rejoice that mankind is to a certain 

 extent freed from this struggle, and that in human society 

 cooperation is becoming a more important means of progress 

 than competition. But natural selection in its widest sense 

 means the elimination of the unfit, whether these are reactions, 

 instincts, customs, persons, races, or species; and if in human 

 society cooperation is more beneficial than competition, co- 

 operation rather than competition will be favored by natural 

 selection. And in similar manner if intelligence is more bene- 

 ficial than brute strength or cunning or instinct, intelligence 

 will be favored. In short, there are many kinds of fitness in 

 different lines, and in the case of man, if natural selection were 



