In the SF classic “The Marching Morons,” by Cyril Kornbluth (published in 1951, when clinical use of the terms “idiot” and “moron” for persons falling within certain low IQ ranges was not considered offensive), a sleeper wakes in a future where the prudent, childbirth-delaying habits of the more intelligent people, combined with the rampant reproduction of everybody else (made possibly by industrialization and technological progress), has produced a world of, well, morons. Everyone is congenitally stupid, except for a secret society of selectively-bred geniuses, who work slavishly hard behind the scenes (as personal assistants, etc., to the apparent decisonmakers) to keep things working. One time the geniuses experimented with simply going on vacation, retreating to their secret base in Antarctica, and things started falling apart right away.
This kind of thinking was not unusual at the time the story was written. Eugenics had been an intermittenly fashionable cause from the late 19th Century, attracting a lot of truly great minds to its banner – though it was based, then, on imperfect and sometimes pseudoscientific understandings of genetics; and it was always tinged with racism, in some forms inseparable from it. To some, “eugenics” simply meant encouraging negroes to use contraception. And then to the Nazis it meant a great deal more . . . (Kornbluth, at least, gave no hint that differential reproduction of different “races” played any part in Moron World, which seemed to have roughly the same racial makeup of the world of 1951.)
In this ongoing thread on overpopulation, soulmurk posted:
Based on later posts, it appears soulmurk is talking not just about stupidity but about people with congenital physical defects – who, in earlier generations, would have been quickly culled from the gene pool because nobody had the power to save them.
But . . . is any of this a real problem, or is it superstition? I mean, is there any hard evidence that any form of “dysgenic pressure” has been causing the general genetic quality of humanity, or of any particular society, to degenerate by any standard or in any respect, physical or intellectual?