A few decades ago, when the climate crisis du jour was global cooling, people were admonished to achieve zero population growth by having fewer children. "The battle to feed all of humanity is over," biologist Paul Ehrlich proclaimed in 1968. "In the 1970s ... hundreds of millions of people are going to starve to death." It never happened, of course. But since then Western birthrates have plummeted, producing demographic challenges large and small. Fast-forward to the present. A new cohort of climate experts is now advising us to have "one fewer child" as a means of reducing CO2 emissions—backed by the usual media cheerleaders. If only we still had Charlton Heston to sound the alarm.