366 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
This reasoning applies also to any relaxation of selection that may 
result from sociological progress. There is supposed to exist a danger 
of loss or “erosion” of genes for high intelligence, owing to the higher 
reproductive rates of the social classes in which such genes are sup- 
posedly rare. Cook (1951, p. 260) describes this danger in the fol- 
lowing way: 
As this process continues . .. the average level of intelligence and the pro- 
portion of gifted individuals decline. Should the feeble-minded level be 
reached, most of the plus-genes will have been eliminated. But before that 
time growing inefliciency and incompetence would cause the collapse of modern 
industrial society. The Dark Ages which spread over Europe with the fall of 
Rome were a cultural blackout that lasted for a thousand years. The Dark 
Ages which would be caused by continued gene erosion could last five to ten 
times as long. 
It would not be appropriate here to discuss how far this eschatology 
is justified by available evidence. It should, however, be pointed out 
that the fearsome process, if it actually occurs, means that in our 
society high intelligence decreases the average biological fitness of its 
possessors, while less intelligent people tend to be more fit. This 
appalling circumstance would be due not to the cessation of natural 
selection, but to the relative intensification of selection for personality 
traits other than intelligence. It would be unfortunate only insofar 
as the most favored genotypes gave rise to certain characteristics 
which could be regarded as undesirable on other grounds. If the 
humble and the meek inherit the earth, it will mean simply that 
under social conditions which obtain in modern industrial civilizations 
humility and meekness are favored by natural selection, while pride 
and egotism are discriminated against. 
It should be noted that relaxation of natural selection does not by 
itself change the genetic composition of populations; it does so only 
in conjunction with mutation. The process of mutation constantly 
and irresistibly generates genetic variations, and most of the mutants 
are deleterious to the organism. Increase of mutation rates would, 
then, lower the fitness of the population even if the selection pressure 
remained constant. But the relaxation of selection would necessarily 
mean that the “bad” genes will have become rather less dreadful than 
they were. 
SELECTION AND ADAPTEDNESS 
More than half a century ago, in the heat of polemics, Weissmann 
wrote about the “omnipotence of natural selection.” This unfortu- 
nate exaggeration is not wholly absent in the writings of some modern 
authors. Natural selection is a remarkable enough phenomenon, since 
it is the sole method known at present which begets adaptedness to 
the environment in living matter. But it has its limitations. As 
pointed out above, it is opportunistic and lacking in foresight. More- 
