The only center of domestication of maize, Zea mays ssp. mays, worldwide is Mesoamerica, the region of central and southern Mexico and adjacent areas of Central America. The prairies, open woodlands, and roadsides of Mesoamerica also are the only native habitat of several closely related wild Zea species that are called teosintes, a common name derived from the Aztec language of Guatemala ⁽¹⁾. Teosinte species such as Zea mays ssp. parviglumis and Zea mays ssp. mexicana are the closest relatives of maize and the probable ancestors of domesticated maize ⁽²⁾.

Origin of Maize

In central Mexico, Zea mays ssp. mexicana is a troublesome weed of maize fields where, until flowering, the plant can be difficult to distinguish from domesticated maize ⁽³⁾. The ears and seeds of teosintes and maize, however, are profoundly different. Whereas the maize ear bears hundreds of naked seeds that remain attached to the ear at maturity, teosinte species bear about a dozen seeds in an ear that shatters at maturity. Each teosinte seed is completely covered by a very hard and lustrous triangular fruitcase, giving it the general appearance of a small gray or brown pebble.

Despite differences in ear and seed morphology, teosinte and maize are genetically closely related. All species of teosinte can form hybrids with maize under natural conditions. Crosses of maize with the annual teosintes Z. mays ssp. mexicana and parviglumis are highly fertile, and progeny demonstrate a range of morphological traits intermediate between the parents. Maize geneticist John Doebley and colleagues have used crosses of maize and teosinte to show that relatively few genes, with large effects on traits such as seed shattering and the size of seeds and fruitcases, are involved in transformation of the teosinte ear into the maize ear ⁽⁴⁾. Such genetic evidence supports the close relationship between teosinte and maize that was first proposed by 19^th century European botanists who first studied teosinte. Joseph Hooker grew teosinte plants in the greenhouse of the Royal Gardens at Kew, England in 1878. Hooker wrote "that from a botanical point of view Euchlaena (teosinte) is a most interesting genus, from its being the nearest congener of maize, whose American origin it thus supports" ⁽⁵⁾.

Darwin on Maize in Peru

Nineteenth century botanists also proposed the great antiquity of maize cultivation in the Americas. During his 5-year voyage around the world on HMS Beagle, Charles Darwin found ancient heads of maize on the coast of Peru. Darwin later wrote in Animals and Plants under Domestication that "Zea mays...is undoubtedly of American origin, and was grown by the aborigines throughout the continent from New England to Chili. Its cultivation must have been extremely ancient, for Tschudi describes two kinds, now extinct or not known in Peru, which were taken from the tombs apparently prior to the dynasty of the Incas. But there is even stronger evidence of antiquity, for I found on the coast of Peru heads of maize, together with eighteen species of recent sea-shell, embedded in a beach which had been raised at least 85 feet above the level of the sea. In accordance with this ancient cultivation, numerous American varieties have arisen.maize has varied in an extraordinary and conspicuous manner" ⁽⁶⁾. Recent archaeobiological studies of maize cobs and pollen, and of maize phytoliths (microscopic structures of silica) in food residues in potsherds and on ancient human teeth, indicate that Native Americans domesticated maize in Mexico more than 6200 years ago ⁽⁷⁾.

Aztec Records of Maize and Teosinte

Despite the early domestication of maize in Mesoamerica and its widespread cultivation by Native Americans, written records of maize and of teosinte are rare in pre-Columbian America. The Incas of Peru and the other native South Americans had no known system of writing, and the written literature of the Maya civilization of Yucatan and Guatemala was almost completely destroyed by Friar Diego de Landa in a great bonfire in 1562. Surviving pre-Columbian documents in the Nahuatl language of the Aztecs of Mexico occasionally mention cincocopi (teosinte), as in "Quezacoatl put his wife, Chalchiuhtlicue, to be the sun. During the time Chalchiuhtlicue was the sun, the people ate a seed like maize which they called cincocopi" ⁽⁸⁾. Aztec documents from this era also contain numerous figures of the maize plant and of agricultural practices connected with it, along with stylized representations of maize and deities such as the maize god Cinteotl and goddess Chicomecoatl ⁽⁹⁾.

Among the early Spanish explorers to the Americas were priests, government officials, and other educated men who wrote substantial accounts of the significance of maize in Native American life ⁽¹⁰⁾. The Spanish Friar Bernardino de Sahagun arrived in Mexico in 1529 and, during the remaining 60 years of his life there, learned the Nahuatl language of the Aztecs, compiled Nahuatl documents, and translated them into Spanish. His Historia general de las cosas de Nueva Espana was completed in 1576 and contains a description and illustration of teosinte. "There is a plant very similar to maize called cocopi.this herb grows in the maize field, it is not sown, some grow before planting, and others after planting. It grows in-between maize like rye-grass in a wheat field" ⁽¹¹⁾. Sahagun's Historia and another old manuscript El primer nueva coronica y bien gobierno, which is illustrated with many drawings, describe maize, as well as agricultural practices, use of food plants, and other aspects of everyday life among the Aztecs.