Societies do collapse, sometimes suddenly. Nevertheless, prophets of their darkest predictions have been, on the whole, a little premature. In 1968, Paul Ehrlich, a lepidopterist, and his largely uncredited wife, Anne, published a best-seller called "The Population Bomb." For centuries, economists had worried that the world's food supply could not possibly be expected to keep pace with the growing mobs of people. Now there was no postponing our fate. "The battle to feed all of humanity is over," Ehrlich wrote. "In the 1970s the world will undergo famines-hundreds of millions of people are going to starve to death."This was the received wisdom of the era: a decade earlier, an only slightly flippant article in Science estimated that in November, 2026, the global population would approach infinity. Ehrlich prescribed a few sane proposals-the legalization of abortion, investments in contraception research, and sex education but he also floated the idea of spiking the water supply with temporary sterilants. Americans might protest such extreme measures, he allowed, but people in foreign countries should have no choice. It was only reasonable that food aid be conditioned on the developing world's ability to exhibit civilized restraint. Nations that tolerated a free-forall of unrepentant copulation-he singled out India-would be left to fend for themselves.