RETROSPECT AND PROSPECT 379 



rather extensive changes had taken place it is doubtful if the fact 

 could be established by the kind of records which have been 

 compiled. We can only judge of the present trend of our bio- 

 logical development by a study of the forces which are now pro- 

 ducing modifications in the inherited qualities of mankind. In 

 our study of these forces it has been found that some of them are 

 working in the direction of racial improvement, while others are 

 quite evidently having an opposed influence. 'What the re- 

 sultant effect will be can be determined only by some estimate of 

 their relative potency. How these forces are working, we have 

 discussed in previous chapters and our main conclusions may be 

 stated somewhat categorically as follows: The one agency which 

 appears to be most clearly working toward racial improvement is 

 natural selection. At any rate there is a large amount of evidence 

 that it is favoring the maintenance of physical vigor and keenness 

 of mind. Sexual selection is in a more doubtful position. To a 

 certain extent it retains what might be considered its primitive 

 function of denying the privilege of parenthood to the poorer or 

 uglier individuals of the species, but the more capable and inde- 

 pendent spirits, especially among the women, are coming to be 

 denied this privilege also. The influence of group selection 

 as manifested in war and otherwise, may also retain some of its 

 original racial benefits, but, under our present regime, its dys- 

 genic effects not improbably outweigh whatever it may contrib- 

 ute to racial improvement. The general influence of reproductive 

 selection or differential fecundity is quite evidently pernicious. 

 It tends to extinguish the posterity of the most capable and to 

 fiU the world with the subnormal and inefficient, thereby con- 

 stituting the most serious menace of all the forces which are 

 influencing human heredity. Religious selection while formerly 

 eliminating through persecution many of the better minds and 

 while stin continuing the racial evil of a celibate clergy in the 

 Catholic church, now exercises its effects mainly upon the birth 

 rate of different stocks. Its influence in maintaining the high 

 birth rate of the Jews who are certainly endowed with an unusual 

 degree of intelligence and energy is rapidly waning and the 



