Jacob Abbott 
Genghis Khan [EPUB ebook] 

There are four several methods by which the various communities into which the human race is divided obtain their subsistence from the productions of the earth, each of which leads to its own peculiar system of social organization, distinct in its leading characteristics from those of all the rest. Each tends to its own peculiar form of government, gives rise to its own manners and customs, and forms, in a word, a distinctive and characteristic type of life.
These methods are the following:
1. By hunting wild animals in a state of nature.
2. By rearing tame animals in pasturages.
3. By gathering fruits and vegetables which grow spontaneously in a state of nature.
4. By rearing fruits and grains and other vegetables by artificial tillage in cultivated ground.
By the two former methods man subsists on animal food. By the two latter on vegetable food.