On Food and Cooking

strong-tasting, sometimes poisonous warning
signals that discourage bacteria, fungi,
insects, and us from attacking them. A partial
list of their chemical warfare agents would
include irritating compounds like mustard oil,
hot-chilli capsaicin, and the tear-inducing
factor in onions; bitter and toxic alkaloids like
caffeine in coffee and solanine in potatoes;
the cyanide compounds found in lima beans
and many fruit seeds; and substances that
interfere with the digestive process, including
astringent tannins and inhibitors of digestive
enzymes.
If plants are so well endowed with their
own natural pesticides, then why isn’t the
world littered with the corpses of their
victims? Because animals have learned to
recognize and avoid potentially harmful
plants with the help of their senses of smell
and taste, which can detect chemical
compounds in very small concentrations.
Animals have developed appropriate innate