HERMANN J. MULLER 
have a lower than average number of children, in order that 
they may obtain higher benefits for those children that they do 
have, as well as for themselves and others near to them. More- 
over, persons who experience failure in their work, their home 
life, or their health, are especially likely to seek compensatory 
gratification in having children. At the same time, as regards 
success in limiting conception to the extent aimed at, it is 
evident that ability enters in here in a negative way, in that 
those who are clumsier, slacker, less provident, and less thought- 
ful are the very ones most likely to fail in keeping the number of 
their children down to whatever quota they may have set. It 
is possible, therefore, that selection based on differences 
in reproductive rate is today not merely inadequate to main- 
tain genetic fitness against the pressure of mutation (using the 
word fitness here in its larger sense, that of having a consti- 
tution valuable for the population as a whole), but that such 
selection is today working actively in reverse, so as to decrease 
fitness. 
THE HUMAN GENETIC PREDICAMENT 
This is an ironical situation. Cultural evolution has at long 
last given rise to science and its technologies. It has thereby 
endowed itself with powers that—according to the manner 
in which they are used—could either wreck the human enter- 
prise or carry it upward to unprecedented heights of being 
and of doing. To steer his course under these circumstances man 
will need his greatest collective wisdom, humanity, will to 
co-operate, and self-control. Moreover, he cannot muster these 
faculties in sufficient measure collectively unless he also possesses 
them in considerable measure individually. Yet in this very 
epoch cultural evolution has undermined the process of genetic 
selection in man, a process whose active continuance is necessary 
for the mere maintenance of man’s faculties at their present 
none-too-adequate level. What we need instead, at this junc- 
ture, is a means of enhancing genetic selection. 
True, there are specialists who believe that equivalent or even 
better results than selection could provide may be obtained by 
ais 
