Claims about dysgenics usually quickly degenerate into a big debate about nature vs. nurture. Steve Sailer interestingly argues that both sides are missing the deeper point:
It's important to realize that for evaluating the likelihood of Idiocracy or Freakonomics, it doesn't particularly matter whether nature or nurture is the driving force in molding the next generation.
If dim people are having more babies than smart people, the average American in the next generation will end up with a relatively worse upbringing or worse genes or both. As I explained to Levitt in Slate in 1999, a long line of both conservative and progressive nail-biters have worried that a bourgeoisie that's self-disciplined and responsible enough to use abstinence or contraception will someday be demographically swamped by a working class too sexually indulgent and disorganized to prevent pregnancies.
The “eugenicists” feared the spread of the lower orders' inadequate genes. The “euculturalists” dreaded their cruder culture. And agnostics on the subject realized that while disentangling nature and nurture was extremely difficult, the precise mechanism mattered surprisingly little.
This is all obvious once you think about it, but I can't recall hearing it before. Ultimately, though, the Flynn effect ("countervailing but poorly understood" according to Sailer) is strong evidence that, conservative and progressive nail-biters notwithstanding, culture is getting better, or, to be more precise, smarter.
Absurd? Hardly. Would you rather be a nerd in 1987 or 2007?