Ignorance Breeds Ignorance...

... and it has nothing to do with genetics. I've never read "The Marching Morons", but I feel safe in deferring to Ben Bova's summary:

The most prescient — and chilling — of all the science fiction stories ever written, though, is “The Marching Morons,” by Cyril M. Kornbluth, first published in 1951. It should be required reading in every school on Earth.

The point that Kornbluth makes is simple, and scary: dumbbells have more children than geniuses. In “The Marching Morons” he carries that idea to its extreme, but logical, conclusion.

Kornbluth tells of a future world that is overrun with dummies: men and women who don’t know anything beyond their own shallow personal interests. They don’t know how their society works, or who is running it. All they care about is their personal — and immediate — gratification.

I don't know why PZ Meyers thinks this has something to do with biology. Kornbluth (and, by extension, Mr. Bova) look to me to be arguing that ignorance is culturally transmitted. Mr. Bova goes on to complain about a "moron in a sports car", hardly your typical representative of a genetic underclass. He's worried about a bread-and-circuses culture full of unenlightened people; there's not even a whiff of genetic determinism about the piece.

The belief that ignorance begets ignorance is hardly revolutionary; PZ supports it, but he tends to limit his criticisms in this area to Christians. PZ is certainly not arguing that Christians are less intelligent than non-Christians. Instead, he merely points out that the Christian home-schooling system perpetuates a particular worldview which seems to be at odds with reality. If you accept that people whose parents read the NY Times are more likely to become newspaper readers themselves, while people whose parents watch reality TV are less likely to do so, then Ben Bova's thesis becomes much more plausible. If you further accept that birth rates fall as education level rises (and that "moronitude" varies inversely with education level) then Ben's concerns about drowning in a sea of morons suddenly seems quite reasonable.

Note that at no point in the above discussion is it necessary to believe that some people are genetically inferior/superior to others. All you need to believe is

1. Parents transmit their culture to their children.
2. Some cultures foster ignorance better than others.
3. Ignorance (however you choose to measure it) is positively correlated with birth rates.