Humankind's evolutionary ancestors were walking the earth for millions of years before modern man came along. These ancestors were hunter/gatherers, surviving on animal kills and what- ever edible plants they could find.

About ten thousand years ago, however, that lifestyle changed when humans learned how to prepare and eat grains, legumes,

and other plant products. People quickly realized that these new foods were not only tasty, they were also much more convenient than the traditional diet. Soon humans were deliberately planting fields full of wheat, rice, beans, and other food crops to supplement their hunting activities, and before long, organized agriculture had become a way of life. The hunter/gatherer days were mostly forgotten, and humankind became dependent on crops for its survival.

For the most part this dependence has worked out well. But it has also created one big problem. Crops, like humans, can get sick...