2o8 Changing Human Nature 



that the most extensive changes take place in those structures 

 that are most variable. Whether we compare different stages 

 in human development or different species in the larger group 

 of primates, the same is found to be true. 



Dr. Adolph H. Schultz of the Johns Hopkins Univer- 

 sity, who has made thousands of such studies on very extensive 

 material, points out that in the evolution of species as well 

 as in the individual development three kinds of changes are 

 possible, theoretically: 



(i) The changes may be consistently divergent — 

 that is, as time goes on one individual, or one species, comes 

 to differ more and more from another. 



(2) The changes may be strictly parallel to each other, 

 so that species or individuals remain equally distinct from 

 one another at every stage of evolution or of development. 



(3) The changes may be convergent, so that with the 

 passing of time the individuals of a species, or the species of 

 a family, become more and more alike. 



The actual studies, including thousands of comparative 

 measurements of human and other primate individuals at 

 all stages, show strikingly consistent results. In not a single 

 instance has there been convergence — that is, in no case do 

 the parts compared show a tendency to become more alike, 

 whether among individuals, or between different races of 

 mankind, or between different species of primates. " All 

 human racial differences and all differences between man and 

 apes or monkeys increase during some periods of growth and 

 remain the same during other periods, but they never become 

 less with advancing development." 



Human Races 



The evidence that the human race has changed with the 

 passing of time is necessarily scattered and fragmentary. 

 The archeological and paleontological evidence can, however, 

 be supplemented by a study of man as found upon the earth 

 today. It we undertake to classify the whole human popu- 



