152 SUMMARY AND CONCLUSION. 



though there can be no doubt that it is sometimes operative. Social 

 organization is often affected by the conditions in the environment ; 

 but though the environment remains unchanged, vast changes in 

 social organization may take place. For example, while remaining in 

 the same region, and without special change in the environment, a 

 tribe of men may pass from the hunter stage of life, through some- 

 thing of pastoral life, into agricultural and diversified industrial life. 

 This has probably been the experience of the Chinese race. 



(6) That endonomic selection, resting on the power of different 

 individuals of the same species to deal with the same environment in 

 different ways, is a fruitful cause of divergent evolution in isolated 

 sections of the same species. This diversity of power is sometimes 

 due to diversity of aptitudes, producing what I call aptitudinal selec- 

 tion ; and sometimes to diversity of training and of habitudes, pro- 



^ducing what I call habitudinal selection ; and at still other times to 

 different methods of using the same aptitudes and habitudes, for 

 which a suitable name has not yet been suggested. 



(7) That organic (or coincident) selection is of great importance in 

 securing a new adjustment when the organism is suddenly exposed to 

 an environment very different from that to which it was previously 

 adjusted. 



(8) That the indiscriminate isolation of a small fragment of a species 

 leads directly to the modification of type in the descendants of the 

 isolated fragment, for the character of a single individual (or even 

 the average character of several individuals) seldom if ever represents 

 the average character of the original stock in every respect. 



(9) That indiscriminate isolation of a large section of a species 

 interrupts the unifying influences of tradition and of heredity between 



separated branches of the original stock ; and, even though the environ- 

 ment surrounding each branch is the same, the traditional method of 

 dealing with the environment may in one or in both branches become 

 modified, and the separate branches be thus subjected to divergent 

 forms of endonomic selection. 



( i o) That the indiscriminate elimination of all but a small fragment 

 of an intergenerating group may be an important factor in introducing 

 transformation, for one or two individuals may not be able to transmit 

 all the traditions of the original group, or to reproduce in the innate 

 characters of their offspring the unchanged average character of the 

 original stock. 



(i i) That advancing powers of accommodation, cooperating with 

 higher degrees of altruistic social organization, are in an ever-increasing 

 measure setting aside both environal and dominational selection, and 

 so lowering the racial standards of civilized man. 



