People have always been curious about the plants and animals with which they coexist. Primitive cultures identified edible and poisonous plants by a process of trial and error, and then began to exploit the toxic materials for hunting, euthanasia, executions and murder. Other plants were found to have stimulatory or hallucinogenic effects: these not only formed the basis of magico-religious rites, they also encouraged experimentation which led to the identification of plants with useful medicinal properties. This account of the evolution of modern medicine from its roots in folk medicine aims to entertain and inform both scientist and general reader alike. It explains the chemical basis of modern pharmacology and provides a description of how the use and abuse of natural products in various societies throughout the ages has led to the development of many of the drugs we now take for granted. Many plant and animal species remain undiscovered, and much native folk medicine has yet to be investigated.