In C. M. Kornbluth's 1951 sci fi short, The Marching Morons, a modern day huckster takes a one way trip to the future and discovers that progress didn't quite go as expected.  The breeding rate of smart, educated people versus that of the not-so-bright underclass has left the world with an average IQ less than the temperature of Milwaukee in January, and only said conman can save the few smarties left from moronic domination.  The story is racist, classist, elitist, terribly dated, and really quite funny.

But of course, Kornbluth got everything wrong -- well, everything but the results   Because if some researchers are right, America is facing a huge shortage of a resource that can't be fixed no matter how many national parks we're willing to drill, or how many old growth trees we chop down.  We're running out of smart people.