240 Heredity and Environment 



poor health. Genius is frequently associated with physical de- 

 fects. Great specialization is associated with corresponding limi- 

 tations in other directions. Society needs the genius and the 

 specialist, but for the general good of mankind the generalized 

 type is needed even more than the specialized. 



No given environment or training can be good for every in- 

 dividual, nor for the same individual at every stage of develop- 

 ment. Every individual is unique and if the best results are to 

 be had he must have unique environment and training, which 

 must be supplied by omniscient intelligence. Such an ideal may 

 not be practicable but the impossibility of securing the absolutely 

 best conditions of development need not prevent society from 

 securing better conditions than those which now prevail. 



Relative Importance of Heredity, Environment, Education. It 

 is plain that environment and education play a greater part in the 

 development of man than in that of other animals> whereas hered- 

 ity plays the same part; but it is difficult if not impossible to de- 

 termine the relative importance of these three factors. In the 

 field of intellect and morals most persons are inclined to place 

 greater weight upon the extrinsic than upon the intrinsic factors, 

 but this opinion is not based upon demonstrable evidence. So far 

 as organisms below man are concerned there is general agreement 

 that heredity is the most important factor, and this opinion is held 

 also for man by those who have made a thorough study of hered- 

 ity. Galton has made the best scientific study of this subject in 

 the case of identical twins, in which as we know heredity is the 

 same in the two, both individuals having come from the same 

 oosperm (Fig. 81). In bodily and mental characters such twins 

 are remarkable alike; the differences which exist are slight and 

 may usually be traced to different environmental and educational 

 influences, and particularly to different illnesses. Galton sums 

 up his study with these words: "There is no escape from the 

 conclusion that nature prevails enormously over nurture when the 

 differences of nurture do not exceed what is commonly to be 

 found among persons of the same rank of society and in the same 

 country." 



