By William McGurn, Wall Street Journal - Fifty years ago this month, Mr. Ehrlich published “The Population Bomb.” In it he portended global cataclysm—unless the world could be persuaded to stop producing so many . . . well . . . people. The book sketched out possible scenarios of the hell Mr. Ehrlich believed imminent: hundreds of millions dying from starvation, England disappearing by the year 2000, India doomed, the average American’s lifespan falling to 42 by 1980....