210 



SCIENCE 



[N. S. Vol. XXXI. No. 789 



through his own advantages replaces by 

 means of his offspring the rest of the pop- 

 ulation. Rather do we find that the pro- 

 gressive races are those in which the 

 environment causes deiinite variation in 

 the largest number of advantageous direc- 

 tions. The race advances by the accumu- 

 lation of these variations. Many indi- 

 viduals of the race contribute towards its 

 maintenance by adding to its advantages, 

 some in one way, some in another. And 

 they do so, not by supplanting their fel- 

 lows, for each advantage to be gained, but 

 by combining with them. The new varia- 

 tions are the products of the environment. 

 Their perpetuation by grafting on to the 

 race raises the race to a level from which 

 further variations in the same direction 

 are possible. Sexual reproduction comes 

 to have an unexpected meaning, for 

 through it the contributions of the indi- 

 viduals are added to the race. It seems to 

 me that some such interpretation as this is 

 more nearly in accord with our present 

 knowledge of the origin of adaptation. 

 If so, we should expect advance in the 

 human races to take place not by every 

 man's hand being raised against his 

 neighbor, nor by the picking out of a few 

 choice individuals in the way the breeder 

 produces new varieties of corn, horses, 

 pigeons and pigs, but we should expect ad- 

 vance to take place in those parts of the 

 world where there is a good stock to start 

 with, and an environment that calls forth 

 in that stock favorable variations in excess 

 of unfavorable ones. 



It seems preposterous to us that so 

 highly organized a machine as the human 

 body could have evolved by undirected 

 variations and chance combinations from 

 a formless mass of living matter. But 

 such a statement of the problem gives a 

 false impression, if, as I have tried to show, 

 each step that the organism has taken 



^arantees further responses in the same 

 direction. And, since the steps that count 

 are the adaptive ones, the very essence of 

 the process of evolution is such that the 

 organism is carried along adaptive lines. 

 The mechanism of survival (if I may be 

 pardoned the expression) is such that it 

 insures success where it is most called for. 

 To repeat a familiar epigram : In evolution 

 nothing succeeds like success. 



In conclusion, I owe you, I fear, an apol- 

 ogy for attempting to discuss so serious a 

 theme at this time and occasion, when high 

 living may not be conducive to plain think- 

 ing. In the detail of every-day work in 

 'which we are plunged we are apt to lose 

 sight of the relative value of the problems 

 at which we work. It seemed to me, there- 

 fore, that it might not be inappropriate 

 this evening to focus our attention on the 

 large problem^ of organic adaptation, which 

 is still, I think, the central problem of the 

 naturalist; and if in attempting an analy- 

 sis of the present situation I have allowed 

 my imagination too free rein, I submit, in 

 defense, that the human mind has an 

 ineradicable tendency to probe into the 

 unknown, and that the fires of the imagi- 

 nation, kept alive by human curiosity, may 

 also serve a purpose in the progress of hu- 

 man thought, provided the imagination is 

 controlled at every advance by an appeal 

 to experience, and is used as a tool and not 

 as an end in itself. But I frankly confess 

 that I feel, as no doubt every one does who 

 tries to keep in touch with modern work, 

 that the time is past when it will be any 

 longer possible to speculate light-heartedly 

 about the possibilities of evolution, for an 

 army of able and acute investigators is 

 carefully weighing by experimental tests 

 the evidence on which all theories of evo- 

 lution and adaptation must rest. To them 

 belongs the future. T. H. IMorgak 



Columbia Univehsity 



