The summer before last, I worked for a while with a young man from La Paz named Salvador. We were building a series of retaining walls. Neither of us knew what we were doing at first, but we figured it out as the walls grew longer and taller. I was eating oatmeal with raisins every morning. The fiber was supposed to lower my cholesterol and keep me healthy. As anyone who has tried this knows, regular cooked oatmeal is a time bomb waiting to happen, and until Monsanto bioengineers clean burning oats, it produces large quantities of sometimes unexpected gas.

I was easing a block into place, concentrating on center of gravity and lifting with my legs — I'm not young anymore, so I tend to be more careful than people in their twenties — and what I thought might be a tiny incident turned out to be a booming fart. "Dees gus ting," he said, making a face. "What," I demanded, "Mexicans don't fart?" "No," he replied, cutting an enormous fart of his own. "Dey do dees."