Whenever like mates with like (genetically), the statistical distribution curve, which describes the frequency of the purely fortuitous combinations of genes, is flattened out, its mode is depressed, and its extremes are increased. The reduces the number of the mediocre produced and increases the numbers both of the sub-normal and the talented groups. It is possible that, without this increase in the number of extreme variants, no nation, race or group could produce enough superior individuals to maintain a complex culture. Certainly not enough to operate or advance a civilization. ...Any number of social customs have stood, and still stand, in the way of an optimum amount of selective matings. In a feudal society, opportunities are denied to many able men who, consequently, never develop to the high level of their biological potential and thus they remain among the undistinguished. Such able men (and women) might also be diffused throughout an "ideal" classless society and, lacking the means to separate themselves from the generality, or to develop their peculiar talents, would be effectively swamped. In such a society they could hardly segregate in groups. In fact, only a few of the able males might ever meet an able female who appealed to them erotically. Obviously an open society—one in which the able may rise and the dim-wits sick, and where like intelligences have a greater chance of meeting and mating—has advantages that other societies do not have. Our own society today—incidentally and without design—is providing more and more opportunities for intelligent matrimonial discrimination. It is possible that our co-educational colleges, where highly-selected males and females meet when young, are as important in their function of bringing together the parents of our future superior individuals as they are in educating the present crop.
"Some Biological Aspects of Individualism," Essays on Individuality (Philadelphia: 1958), pp. 59-61