As someone who thinks systematically about the future for a living, I frequently read science fiction with an eye for what it reveals about how today's real fears are being projected upon tomorrow's imagined landscapes. The books behind the 1973 movie "Soylent Green" (too many people!) and the 2006 movie "Children of Men" (no more babies!) make for a good example. Compare their central premises and you've basically captured the 180-degree turn the popular imagination has experienced on population growth over my lifetime.