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. Toa 
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 régime, 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 
fill 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 still 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 
