Corn

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Corn, Indian corn, or maize is one of three grasses that account for almost half of all human calories consumed. The seed of these grasses are called cereals and each developed in a distinct part of the world: corn in the Americas, specifically Mexico/Guatemala (where its name is derived from the Arawak-Carib word mahiz, when Christopher Columbus first encountered the grain on the island of Cuba), and wheat and rice in the Old World. Corn was and still is the most important food plant for the indigenous people of the Americas. Its cultivation stretched from the Gaspé Peninsula of eastern Canada to Chile in South America. It is grown from sea level to elevations of ten thousand feet in the Andes.

Most of the corn grown in the developed world is from improved hybrid seed while subsistence farmers plant mostly open-pollinated farmer-selected varieties called landraces. There are approximately three hundred landraces of corn, each with its own geographic/climatic zone where it is most productive. Even commercial hybrid corn in the United States belongs to a recognized landrace, which is called Corn Belt Dent.

Three distinct views on the origin of corn exist within the scientific community: 1) corn evolved from an extinct wild corn, 2) corn evolved from its closest relative, teosinte, and 3) corn evolved after hybridization of either wild corn or teosinte with a more distant relative in the genus Trip-sacum. During the 1960s there was widespread support for the idea of wild corn as the ancestor of the domesticated form. In contrast, in the 1980s the theory holding greatest currency was that of teosinte as the progenitor of corn. Recent research suggests that Tripsacum has had a role.

Although there are distinctly different hypotheses regarding the ancestry of corn, all agree on the basic circumstances surrounding its origin. The ecosystem that gave rise to corn had almost frost-free, seasonally dry winters alternating with summer rains, and highland (above 1,500 meters). Sometime between 5000 and 3000 B. C. E., corn appeared in Mesoamerica (Mexico and Guatemala), most probably along the western escarpment of south central Mexico in an arc within five hundred kilometers of present-day Mexico City. This location also describes the major area occupied by the closest relatives of corn, both annual and perennial teosinte, and numerousspecies in the genus Tripsacum. Corn and teosinte are unique among the grasses because the male and female flowers are borne in separate structures: the ear, or female seed-bearing cob, is carried half way down the stem while the male central spike, or tassel, is at the top of the stem. In the early stages of domestication the ear was small (one to three centimeters) yielding no more than fifty small, hard, popcornlike seeds. Archaeo-logical corn remains, from cave sites dating back to 3000 B. C. E.in Tehuacán, Mexico, match the above description perfectly. In contrast, modern corn yields a massive ear (25 to 30 centimeters) producing more than 750 seeds. This modern corn plant is unable to disperse its seed because of the unique husk and cob structure where the seed do not fall free at maturity as in all wild plants. Humans must harvest, shell, and plant the seed for maize to exist.

Modern corn is a single species, Zea mays, with five kinds of seeds based primarily on the storage starch of the endosperm. The earliest corns were popcorn types with a hard protein rind that held moisture in the starch, and when heated they exploded. Seeds that have a soft starch are called flour corns; sugary varieties are called sweet corn, which are often eaten immature when the sugar content is highest relative to starch; hard-starch varieties are called flint corn; and dent corn, which is intermediate between flour and flint, has a characteristic small dent or dimple at the top of the kernel. Dent corn is the most common form grown in the Corn Belt of the United States (ac-counting for one-half of the world's total production, valued at fifteen billiondollars). On commodity markets it is called #2 yellow dent. Much of this goes into animal feeds or is used in the chemical and processing industries.

Corn seed is used industrially to make ethyl, butyl, or propyl alcohol; acetaldehyde; acetone; glycerol; and acetic, citric, or lactic acids by fermentation then distillation. Wet milling produces zein, a protein used to make polyurethane, corn starch, and specialty corn products such as high fructose corn syrup (widely used as a sweetener and replacement for sucrose or cane sugar in candies and baked and processed foods).

In the Americas (excluding the United States and Canada) corn is the mainstay of the diet and the preferred cereal. This is also true for east Africa, south Africa, and regions around the Mediterranean and southeastern Europe. More than half of the dietary calories in both Guatemala and Kenya are accounted for by corn alone. In Mexico corn is eaten in tortillas (an un-leavened, griddle-toasted flat bread), tamales (dough steamed in corn husks and often stuffed with meat and chilies), atole (roasted, ground corn flour beverage) or elotes (roasted or steamed ears). In the southern United States it is consumed as grits (boiled, cracked endosperm from which the bran and embryo or germ have been separated), hominy (entire kernels soaked in lye, then washed and boiled). Corn on the cob and corn chips are eaten nationwide. Cornflakes, invented in the United States, are made from toasted rolled grits; they started the boxed cold cereal breakfast a century ago. Popcorn is both an ancient form of consuming corn and a modern one as it comes freshly popped from the microwave. In Andean countries corn is fermented by first a salivation process to convert starch to sugar and then fermentation by yeast to produce Chicha. Pombay beer is made from corn in Africa; whiskey made from corn is called bourbon whiskey.

Corn kernels or seeds are much larger than either rice or wheat but on a per-weight basis the three supply approximately the same energy as measured in calories. Corn has less protein than wheat and is deficient in the essential amino acids tryptophan and lysine. In the ancient civilizations of Mesoamerica this deficiency never appeared because corn and beans were eaten together and the combination formed a complementary protein supplying all the essential amino acids. Only when corn alone forms a major part of the diet, as in diets of poverty, do we see malnutrition. The corn kernel, especially the germ or embryo, is rich in oil and the grain is a good source of the B vitamins except for niacin. The low content of niacin can lead to the deficiency disease pellagra, historically prevalent in the South until the 1930s and still common in parts of Africa where corn is consumed. Corn grain is an outstanding feed for pigs, cattle, and chickens; the entire plant cut up and made into silage is a major food for milk cows. Americans consume much more corn as pork, beef, eggs, and milk than we do from corn products directly. Corn is the largest harvest in the United States and the most valuable crop, but it is also Mexico's most significant gift to the world.

Agriculture, History Of; Agriculture, Modern; Economic Importance of Plants; Fertilizer; Grains.

Mangelsdorf, Paul C. Corn: Its Origin, Evolution and Improvement. Cambridge, MA: Harvard University Press, 1974.

Purseglove, J. W. Tropical Crops: Monocotyledons. London: Longman, 1972.

Wallace, Henry A., and William L. Brown. Corn and Its Early Fathers, rev. ed. Ames, IA: Iowa State University Press, 1988.

Weatherax, Paul. Indian Corn in Old America. New York: Macmillan, 1955.

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