A sweet tooth is a powerful thing. Babies everywhere seem to smile when tasting sweetness for the first time, a trait inherited, perhaps, from our ancestors who foraged for sweet foods that were generally safer to eat than their bitter counterparts. But the "science of sweet" is only the beginning of a fascinating story, because it is not basic human need or simple biological impulse that prompts us to decorate elaborate wedding cakes, scoop ice cream into a cone, or drop sugar cubes into coffee. These are matters of culture and aesthetics, of history and society, and we might ask many other...