Food is energy. Not much thought is given to it, but every time that we eat, our bodies convert food calories into a fuel that powers everything that we do, from typing at a computer, making art, walking or biking into town, fixing a house, or digging a garden bed.

Over the past 10,000 years, humans have developed agriculture -- the cultivation of land and active management of crops and animals to increase the food-calories available for growing human populations.