The distribution and uses of the tropical cultivated plants support the belief of ethnologists in the truly indigenous character of the peoples, agricultures and civilizations of the new world, but they also testify to a very early colonization of the islands of the Pacific and Indian oceans from tropical America. The comparative deficiency of the western continent in fruits and animals suitable for food was compensated by numerous starchy root-crops. The primitive culture peoples of the tropical regions of ancient America were accustomed to the cooking, grinding, and storing of vegetable food, and were thus prepared to appreciate and utilize the cereals by agricultural experience lacking among the fruit-eating aborigines of the old world, who developed instead the arts of the chase, the domestication of animals, and the use of milk. But fruit, meat and milk do not complete the agricultural series, and do not include its essential members, since civilizations have nowhere developed without the assistance of the farinaceous root-crops and cereals, the use and cultivation of which are habits acquired by primitive man in America and carried in remote times westward across the Pacific, together with the social organization and constructive arts which appear only in settled communities supported by the tillage of the soil.
By means of agricultural facts it is possible thus to choose between the rival theories of the ethnologists, and in addition to gain a suggestion of the history of agriculture among primitive peoples. If we may not know where man first began to encourage the growth of the plants which furnished his food, we are not without numerous indications that agriculture proper, together with the agricultural organization of human society which lay behind modern civilization, originated in America and has now completed the circuit of the globe.