The result, of course, was disastrous. There was worldwide famine (presumably also obliterating grazing animals and the pandas; bamboo is a grass). Starving people formed bands of marauders. In England—where the story is set—farms savvy enough to have concentrated on such non-grass crops as cabbages and potatoes turned themselves into armed fortresses and shot desperate people who tried to breach their stockades.

It’s not all that outlandish a scenario. Wheat, the staple crop that provides 20 percent of the world’s calories, is the major component of the staff of life: bread. For much of history, the bulk of the human diet has consisted of bread—and when people are deprived of it, all hell breaks loose. The French and Russian Revolutions both