Maize is a gigantic domesticated grass [Zea mays ssp. mays] of tropical Mexican origin. The plant is used to produce grain and fodder that are the basis of a number of food, feed, pharmaceutical and industrial manufactures. Cultivation of maize and the elaboration of its food products are inextricably bound with the rise of pre-Colombian Mesoamerican civilizations. Due to its adaptability and productivity the culture of maize spread rapidly around the globe after Spaniards and other Europeans exported the plant from the Americas in the 15th and 16th centuries. Maize is currently produced in most countries of the world and is the third most planted field crop (after wheat and rice). The bulk of maize production occurs in the United States, Peoples Republic of China, and Brazil, which together account for 73% of the annual global production of 456.2 million tons. Mexico, the world's fourth largest producer of maize, currently produces approximately 14 million tons of grain annually on 6.5 million hectares (3% of world production on 5% of the world's land devoted to maize production).

Maize is a tall, determinate annual plant producing large, narrow, opposing leaves (about a tenth as wide as they are long), borne alternately along the length of a solid stem. Aside from its size, a distinguishing feature of this grass is the separation of the sexes among its flowering structures. Unlike other grasses, which produce perfect (bisexual) flowers, maize produces male inflorescences (tassels) which crown the plant at the stem apex, and female inflorescences (ears) which are borne at the apex of condensed lateral branches protruding from leaf axils. The male (staminate) inflorescence, a loose panicle, produces pairs of free spikelets each enclosing a fertile and a sterile floret. The female (pistillate) inflorescence, a spike, produces pairs of spikelets on the surface of a highly condensed rachis (central axis, or "cob"). Each of the female spikelets encloses two fertile florets, one of whose ovaries will mature into a maize kernel once sexually fertilized by wind-blown pollen.

The individual maize grain is botanically a caryopsis, a dry fruit containing a single seed fused to the inner tissues of the fruit case. The seed contains two sister structures, a germ from which a new plant will develop, and an endosperm which will provide nutrients for that germinating seedling until the seedling establishes sufficient leaf area to become autotrophic.

The germ consists of a miniature plant axis, including approximately five embryonic leaves, a radicle, from which the root system will develop, and an attached seed leaf (scutellum). The germ is the source of maize "vegetable oil" (total oil content of maize grain is 4% by weight). The endosperm occupies about two thirds of a maize kernel's volume and accounts for approximately 86% of its dry weight. The primary component of endosperm is starch, together with 10% bound protein (gluten), and this stored starch is the basis of the maize kernel's nutritional uses. Whole, ground maize meal has an energetic value of 3,578 calories per kilogram.

The vaunted productivity of maize is due to its large leaf area and to a modification of its photosynthetic pathway. This modification (shared by other tropical species adapted to survive periods of drought stress), is known as the "C4 syndrome," and consists of an efficient mechanism for the exchange of water vapor for atmospheric carbon dioxide. As a result of this mechanism, C4 species can produce more dry matter per unit of water transpired than can plants endowed with the conventional (C3) photosynthetic pathway.

Maize is primarily a cross-pollinating species, a feature that has contributed to its broad morphological variability and geographic adaptability. Maize varieties may range from 0.5 to 5 meters standing height at flowering, mature in 60 to 330 days from planting, produce 1 to 4 ears per plant, 10 to 1,800 kernels per ear and yield from 0.5 to 23.5 tons of grain per hectare. Kernels may be colorless (white) or yellow, red, blue or variegated with these colors in mottled or striated patterns. The crop, which is produced from 50° latitude N to 40° S, is adapted to desertic and high rainfall environments, and to elevations ranging from 0 to 4,000 meters above sea level.

The variable feature of maize that relates most closely with its food uses is endosperm composition, a trait usually controlled by one or a few simply inherited genes. A common utilitarian classification of maize based on endosperm characteristics distinguishes five types:

Currently, major maize production areas are located in temperate regions of the globe, and turn out primarily animal feed and industrial materials. However, in Mexico the culture of maize remains predominantly a subsistence enterprise. Industrial maize varieties are hybrids that tend toward uniformity due to the requirements of mechanized production and their common ancestry (in almost all cases related to germplasm developed in the maize belt of the north central United States.) It is in this region that the technique of hybridizing inbred lines of corn to produce high-yielding cultivars was perfected in the first third of the 20th century. Because most maize produced in Mexico is for direct human consumption, and because it is produced by self-provisioning farmers in small-scale settings, the expensive, uniform, high-yielding dent hybrids of the north central United States are not suited to the highly variable production conditions or nutritional requirements of most Mexican producers. Although important niches of hybrid production exist in various areas, notably in the western states of Jalisco and Sinaloa, almost all Mexican maize production is based on small populations of open-pollinates. These populations are maintained by peasant farmers and are under constant selection pressure for adaptation to the microclimates of the myriad mountain valleys where these farmers subsist.

Consequently, there is high genetic biodiversity in the Mexican maize pool, a factor of great importance for the breeding of current and future maize cultivars. In a classic study of this variability conducted during the 1940s, 32 races grouped in 5 racial complexes were identified. Subsequent work has refined this characterization to at least 42 races in 3 great racial complexes. Mexican and international organizations have expended major effort to preserve this rich genetic treasury against the genetic erosion caused by 1) decreased maize cultivation associated with Mexico's rapidly industrializing economy, and 2) the introduction of hybrid cultivars. The world's major collections of Mexican maize germplasm are maintained by the International Center for Maize and Wheat Improvement (CIMMYT, El Bataan, Edo. de México), the Mexican National Institute for Agricultural, Forestry and Livestock Research (INIFAP), and the United States Department of Agriculture's North Central Regional Plant Introduction Station (Ames, Iowa).

Maize is the domesticated form of a strain of teosinte [Zea mays ssp. parviglumis], a wild grass occurring naturally in isolated patches currently restricted to elevations between 400 - 1700 meters in the Mexican western Sierra Madre (Michoacan and Jalisco). Both social and plant scientists regard maize agriculture as a prime example of the coevolution of a plant and its domesticators: as the plant and human society evolved, they each exerted strong influence on one another. The Mexican anthropologist and maize historian Arturo Warman has referred to maize as a thoroughly cultural artifact, in that it is truly a human invention, a species that does not exist naturally in the wild and can only survive if sown and protected by humans. Likewise, the domestication and improvement of maize is strongly correlated with the development of cultural complexity and rise of the high civilizations of prehispanic Mesoamerica.

The domestication of teosinte predates the historical Mesoamerican period, with most extant oral traditions alluding to this cultural milestone in highly encoded mythical tales and folklore. Lacking a reliable historical record, the issue of maize origins has long been a controversial ethnobotanical problem. Recently, a number of new techniques have been applied to this question. These methods include, in addition to traditional archeological excavation, numerical taxonomy (cladistics), analysis of chromosome and allozyme homologies, and accelerated mass spectrometry dating techniques. Application of these procedures has permitted scientists to narrow the general date and location of teosinte's domestication to 4 - 3,000 B.C. in Michoacan's Balsas river drainage. However, there is still uncertainty regarding whether this momentous achievement was, in the words of Hugh Iltis, "a process or an event."

In pursuit of evidence for Mesoamerican agricultural origins, archeologists Richard McNeish and Kent Flannery led various interdisciplinary teams in excavating a number of highland arid caves throughout the central Mexican plateaus. From the 1940s to the 60s, these researchers documented the transition from hunter-gatherer lifestyle to that of early agriculturists occurring during the 4th and 3d millennia B. C. in the present-day states of Tamaulipas, Puebla and Oaxaca (these dates are those assigned by current researchers, and are more recent than originally estimated by McNeish and Flannery, who were limited by the dating methods available to them). The picture that emerged was of small migratory bands following the seasonal patterns of plants and animals, subsisting on antelope, deer, rabbits and similar small prey, gathering piñon nuts, hackberry and other species, and experimenting with parched grains and cereal meal.

The first cereal domesticated by early Mesoamericans was evidently not maize, but Setaria geniculata, a relative of today’s grain millets. However, by 2,700 B. C. maize had been introduced from Michoacan to Puebla’s Tehuacan valley, the residents of the Coxcatlan caves in the southern fringes of the valley were utilizing a small-eared pop maize (6-9 kernels per cob), and had innovated the process for grinding maize grain with stone mortars and baking flat bread. Over a period of 2,000 years the residents of Coxcatlan and of Guila Náquitz, Oaxaca, gradually began to depend more on their cultivars and less on their hunting and foraging. Indicators of social stratification and complexity, such as irrigation works and the manufacture of pottery, textiles and woven products, increased. By 1,400 B. C. maize cultivation had reached both Mexican coasts, and the cultural takeoff of peoples in the central highlands, southern gulf coast and Chiapas/Guatemala lowlands was underway.

It is instructive to compare the history of teosinte’s domestication as deciphered by contemporary scientists with oral traditions surviving among native Mesoamerican peoples. In the most common Mesoamerican myth of maize origins a fox follows an ant and discovers a stash of maize enclosed within a large mountain or boulder, partakes of the grain, and later betrays in his flatulence that he has found a wondrous new food. In most accounts the maize trapped within the mountain or boulder is initially accessible to small animals but not to humans, and is eventually released to humans by divine intervention. One interpretation of this is that it is cultural memory of a time when the foliage or grain produced by the ancestor of maize was edible only by animals and not humans. Or this may refer to a sudden set of mutations that instantaneously "liberated" maize.

In these stories, the maize-liberating deity blasts open the mountain encasing maize with a thunderbolt. This explains why maize grain occurs in various colors ranging from black (scorched from having been on the exterior of the stash) through red to blue, yellow, and finally pure white (maize that was at the center of the stash and therefore protected from the bolts of thunder).

There are stories that deal more directly with maize origins. Significantly, the best examples of these are the creation myths that lay down the structure and meaning of the universe. A good source of such traditions are the Mayan peoples, who maintain the most ancient and continuous cultural relationship with maize among extant aboriginal peoples of Mesoamerica, and for whom, according to Freidel and Schele, the major constellation visible in the heart of the night sky is in fact a sacred maize plant about which the universe is ordered.

J. E. S. Thompson collected a large number of Maya maize/creation myths and provided a useful comparative analysis. An important theme is that found among the Mam, Quiché and Cakchiquel peoples, who believe that in ancient times there was no maize, but people fed on the roots of a plant called "mother maize, " txetxina, which had a large root and a single stalk. This observation may be of relevance in dealing with the riddle of what aspect of ancestral teosinte attracted the attention of its domesticators as a food source. These traditions tell how people "discovered" maize by noting the presence of grain in dung of the uech wildcat. Thompson reports that when asked directly where maize originated, most informants in Maya land point to the northern boundaries of their territory.

Maya creation myths tell of three gradual improvements of creation. First, men were made of mud, followed by wood and corn dough successively, with maize dough proving to be the ideal human flesh. This idea is further developed in the much later creation myths of the Aztecs of central Mexico, which tell of the present world having been created after a succession of four previous eras, or "suns."

In the accounts of the distinct eras of creation that we have from both Maya and Aztecs, the idea permeates that the creation was persistently improved with each successive era. The myths explain how various beings and features of the world came to be. So, in the First Sun, imperfect giants (they were foragers, not agriculturists, and they were too large for the dimensions of the world) were devoured, save for those who themselves became jaguars. In similar fashion, throughout each of the eras of creation the earth was gradually populated by different organisms. In the Maya account, the failed organisms of the first creation were fashioned from clay and became birds and deer. In the second era humans were fashioned from wood, but it was not until the third attempt (the Fourth Sun for the Aztecs) that the gods made maize dough and mixed it with their own blood to produce present day humans, literally "maize people," the best possible beings. The Nahuatl word for maize dough is in fact "our flesh" (toneuhcayotl).

In like fashion, the food that human beings consumed improved during each iteration of creation. In the First Sun, those beings who did not sow or till ate acorns and fruits. In the Second Sun humans progressed to pine nuts. In the Third Sun it was millet. In the Fourth Sun it was teocentli or cencocopi, suggestively also known as "Madre de Maíz" (Mother of Corn) in some parts of rural Mexico. The very name teocentli is of interest because its literal meaning is "great grain" or "divine grain," revealing that the fruit of the immediate ancestor of maize was known and recognized by maize peoples as a grain. Finally, during the Fifth Sun the food provided by the gods was centli, modern cultivated maize. It was integral to the beliefs of the Mesoamericans that not only had the creation been improved at each step, but also its beings, plants and foods, so that present day humans, "Maize People," were the best possible creature, and maize the best possible food.

Mesoamerican agricultural systems evolved over a period of approximately 4,500 years prior to arrival of the Spaniards in the early 16th century. While such systems were highly variable, they were unequivocally centered on the culture of maize. In general, aboriginal production systems featured intensive plant polycultures in small plot settings. Species such as beans, peppers, cucurbits, tomatoes, amaranth and an assortment of greens shared the same production field with maize. Specific agroecological management techniques were related to local climatic, topographic and cultural features. In arid zones irrigation by diversion of spring and river water, as well as the use of artificial water catchments, was common. On hill slopes terraces were employed. In forest zones agroforestry systems were practiced that simulated or fit with natural successional stages. In humid zones techniques such as raised-bed agriculture, field drainage and the "chinampa" system (artificial islands built up from lake-bottom silt) were devised. All labor was provided by humans (no draft animals were available,) implements consisted of fire-hardened wooden digging sticks and hoes, and few animal domesticates existed (turkeys and a species of edible dog were notable exceptions.)

In general, land tenure systems were communal, with rights to parcels of land earned and maintained by working a given parcel and maintaining good social standing. When the Spaniards arrived in the central Valley of Mexico, land was measured by a unit (quahuitl) equivalent to 2.5 linear meters which was squared to express area (6.25 m2). Aboriginal records of parcels cultivated by individual family heads have survived, and these show that land was officially registered by area as well as soil type. Analyses by Barbara Williams of prehispanic codices show that a typical family unit of 6 individuals might cultivate 1.8 ha of land spread across 4 different parcels of varying soil quality, and that this land could produce an excess of 17% maize grain above the annual dietary needs of the family. This excess production was the family's buffer against poor production seasons, or a potential commodity for sale or barter. It clearly signified an economy beyond subsistence. In addition to each family's communal land, most heads of household contributed a minimal number of labor hours annually to maize production on parcels that supplied the needs of theocratic lords.

The conquering Spaniards introduced new agricultural techniques and species into Mesoamerica, just as they also introduced Mesoamerican species to Europe. Among practices introduced by the Spaniards were: extensive plantation agriculture, extensive livestock raising (hogs, cattle, sheep), monoculture, plowing, broadcast seeding and lumbering, in addition to a number of new plant species (e.g., sugarcane, wheat, olive trees.) Many Mesoamerican crops were introduced into Europe as novelties and curiosities, but maize spread quickly wherever Spaniards traveled, in large part because of its broad adaptability and high productivity. Though Spaniards themselves tended to regard maize as an inferior grain that produced coarse food stuffs best suited for animal consumption, many peoples contacted by the Spaniards (and Portuguese) in their expanding global trade routes quickly adopted it as a source of human food. In such a way maize quickly penetrated Africa, India and China during the 16th century. A Chinese drawing of an apical-eared maize has been dated to 1597.

The Spanish conquest strongly impacted the social and agricultural systems of Mesoamerica. Initially, the ratio of Spaniards to aborigines in the region was small, and the Spanish population was focused on extracting mineral wealth for transport to Spain. This allowed for parallel economies to develop, where native production systems coexisted with those of the conquerors. Wheat, leavened breads, pork, mutton and Mediterranean fruits were produced and consumed by the Spaniards, while the natives continued to produce maize and beans in traditional ways. However, the interaction of the parallel economies was detrimental to the native Mesoamericans in that they were the primary source of forced labor for the Spanish mining industry, and increasingly for their agricultural enterprises. A number of legal structures were successively put in place by Spanish authorities to sanction the appropriation of native labor and property.

Several additional trends aggravated the precarious position of the native population. First, colonial Spaniards appropriated prime agricultural land surrounding major settlements for the production of their own introduced food crops, relegating the natives to marginal areas. The forced labor demands of the Spaniards during the early colonial period, as well as a series of epidemics, severely reduced the native population, impacting both general labor availability as well as the ability of the natives to produce enough to pay tributes, tithes and feed themselves. As the mining boom subsided in the 1580s and Spanish colonists looked for substitutes to generate capital they increasingly turned to agriculture. The form of agriculture they adopted was extensive (plantation agriculture, grazing), and by a number of devices (e.g., "congregations") they displaced natives and their agricultural systems into remote, mountainous hinterlands and other undesirable locations. The cumulative effect of these trends was to debase the aboriginal population and force its retrenchment to a sordid subsistence lifestyle. Economic depression in Spain during this time fueled an immigrant wave to Mexico (New Spain), and paired with the decimation of the native population the ratio of Spaniards to aboriginals increased dramatically. A famous estimate by Cook and Borah places the native population of Mexico at 1.4 million in 1595, compared with 25.2 million in 1518, when the Spanish arrived. Together with its cultivators, maize became a subsistence crop, identified with the poor and dispossessed (both rural and urban,) and used by the Spaniards primarily to feed their livestock.

During the colonial period Spain played an important part in the evolution of mercantile economies into global capitalist economies. The wealth Spaniards generated by extracting labor, land, agricultural produce and minerals from New Spain was cycled through an expanding trade web that embraced Asia, America, Africa and Asia. However, the boom and bust cycles characteristic of incipient capitalism raged throughout New Spain, with a disproportionally negative effect on the poor. Between 1560 and 1578 the "official" price of maize grain increased by more than 400%. In an attempt to stabilize prices colonial authorities devised a number of mechanisms, including requirement of payment of tributes in maize grain, in order to stimulate supply, but ultimately resulting in the creation of an "official granary" (alhóndiga) in Mexico City. This was intended to buffer large fluctuations in supply and demand by becoming the central depository for all grain to be sold, and by selling this grain at controlled prices. By eliminating intermediaries and speculation the alhóndiga was meant to eliminate fraud and sudden swings in prices. However, in order to work the official granary needed to pay top prices during scarcity and then sell the grain below market price. This operating deficit was made up by a royal subsidy. Though the scheme tended to work, it was opposed by large land owners.

By 1630 Spanish grain producers had taken over commercial production of the crop. The Indian population producing maize for their own subsistence had become irrelevant to the growing national economy. While the export of colonial commodities (minerals, furs) to the Spanish motherland was subject to unpredictable market turns, and the local market for wheat was relatively fixed by the number of Spaniards in the population of New Spain, the growing populace composed of castas (racially mixed) represented a sure market for the capitalist enterprise of maize grain production. Within the span of a century following the conquest the Spanish economy had successfully appropriated the best agricultural land and produce of Mesoamerica. However, as Enrique Florescano has observed:

Florescano argues that such centrifugal forces contributed to the dissolution of the Spanish colony in New Spain. During the intervening century between independence (1821) and the revolution of 1910 the dynamics of concentration of wealth in the class of large landholders at the expense of the forced labor of the underclass scarcely seemed to be altered by the fact that Spain was no longer colonial master. Though large-scale landholding was eventually outlawed, and the rights of Indian peasants to communal landholding were officially recognized, it was not until the land reform programs of the 1930s that serious efforts were enacted to empower the peasantry. However, the land expropriations of Lázaro Cárdenas that intended to redistribute land to the dispossessed, made up in large part by the native population, had but a fleeting effect.

With few exceptions the best agricultural land in Mexico is devoted to crops other than maize, which is viewed by an increasingly urban population as food of the poor. The top income category of Mexicans obtains less than 13% of its dietary protein from the traditional maize and bean diet, whereas 84 percent of the protein consumed by those at the lowest income level comes from this source. Steve Sanderson has calculated that though 59% of total cultivated area in Mexico is devoted to maize, this is more reflective of the number of subsistence farms than it is of actual maize productivity. This is shown by the fact that the importance of the crop is inversely proportional to farm size. While 85% of peasant cultivators grow maize, they typically do so in plots of 3 ha, or less, under limiting rainfed conditions. Such farmers typically have limited access to the technical or economic assistance that is readily available to large-scale agricultural entrepreneurs. Furthermore, the feasibility of providing effective technical assistance to such farmers is diminished by their limiting ecological and climatic situations. The small plots, marginal lands, and highly variable environments in which peasant farmers produce do not lend themselves to the economies of scale that make intensive hybrid maize production feasible.

Sanderson estimates that Mexican maize cultivation has grown neither in extension nor productivity since the 1950s. Though yields have increased from 0.7 tons/ha in 1950 to 2 tons/ha at present, these gains represent increased productivity of large-scale farms located in federal irrigation districts, having access to credit, hybrid seed and synthetic fertilizers. While Mexico was self-sufficient in Maize for a brief period prior to 1960, since that time per capita production has fallen to the current level of 105 kg annually. Maize imports have risen steadily from 0 in 1960 to the current level of 5 million tons annually.

Through successive policies such as the Sistema Alimentario Mexicano and PROCAMPO the Mexican government has attempted to simultaneously support the peasantry and urban wage earners by setting minimum prices to farmers and subsidizing the price of tortillas to consumers. The government's most recent policy has been to abandon such tactics in favor of free market economics. Reversing the long-term official recognition of communal land ownership for the peasantry, the government amended the constitution to allow for private ownership of communal land. The effect of this move will be to once again allow large-scale landholding, which the government, and external providers of credit, believe will favor the economies of scale necessary to make intensive, industrial agricultural systems profitable. If the policy produces the results envisioned by its drafters, free market dynamics will create economic opportunities for peasants who will be displaced from their land. By comparative advantage, national maize production will decline and a greater proportion of the national maize needs will be met by importing from major producing nations such as the United States (yellow maize for animal feed) and South Africa (white maize for human consumption.)

A fundamental value transmitted and preserved through thousands of years among all maize-based groups with links to the pre-Columbian past is a deep reverence for maize as the source of life. Among Mesoamerican natives this belief is expressed even today in words very similar to those collected by Friar Sahagún from an Aztec informant of the 16th century:

This reverence, embodied in the cult of maize deities in the prehispanic past, and of agricultural patron saints in the present, reflects the central role of maize in Mesoamerican material subsistence and culture. Most Mexican meals are founded upon maize in one form or another, and would be incomplete or inconceivable without the traditional flat bread known as the tortilla. Current annual per capita consumption of tortillas in Mexico is about 186 kilograms, or 0.5 kilogram per day, and in rural areas it is estimated that tortillas provide about 70% of all caloric intake.

Although maize can supply the minimum daily caloric requirement for humans, alone this grain is a poor source of the essential amino acids lysine and tryptophan. A diet in which maize predominates can lead to serious deficiency diseases such as pellagra and kwashiorkor. The traditional Mexican diet based on maize as a staple avoids such health consequences by two means: 1) complementarity with Phaseolus bean, also an essential component of the traditional diet (together these two products provide an amino acid profile similar to that of milk), and 2) pre-processing of maize grain in an alkali bath, resulting in greater availability of niacin that is otherwise bound and unavailable. It is thought that this alkali treatment was originally devised to separate the fruit case (pericarp) of maize kernels from the endosperm to produce hominy, a step preceding grinding, with the original alkali being wood ashes or slaked lime.

Although tortilla manufacture has been mechanized, the process remains essentially the same as originally prescribed by early Mesoamericans. Mexican Spanish abounds with native words intimately related to the processing of maize for production of tortillas (e.g., tequisquite, nejayote, nixtamal, metate, testal, comal, tenate), not to mention the names of the various food products that can be produced from basic corn dough (e.g., tamal, pozole, tlacoyo). A 1996 report in the Wall Street Journal indicated that the world market for tortillas is worth about $5 billion U. S. According to this report, even though Mexicans consume about 10 times as many tortillas per capita as U. S. consumers, the Mexican tortilla market is still dominated by small "tortillerias." In Mexico, packaged tortillas account for only 5 percent of sales. However, large flour-producing industries, such as Maseca and Bimbo, are predicting that "the end of tortilla subsidies in Mexico will transform the Mexican market, giving an advantage to U.S.-style marketing of plastic-bagged tortillas in supermarkets."

Adoption of the North American Free Trade Agreement (NAFTA, 1 January 1994) will have a marked effect on Mexican maize production, in that traditional government subsidies designed to support cheap tortillas will be gradually reduced until they are completely eliminated in, or before, the year 2009. It is expected that the quantity of maize produced within Mexico will decrease, with Mexican agriculture specializing more in the production of tropical species and vegetable crops with export value. This will threaten the viability of maize land races that until now have been preserved in vivo and in situ by Mexican peasants. Beadle estimated that at the time of Spanish contact, between 200 - 300 land races of maize were cultivated in Mexico, compared with 42 land races currently. In addition, reduction of internal maize production will affect the diet of rural and urban Mexican residents alike because maize products based on white floury maizes will be replaced by those produced with imported yellow dent grain, or expensive imported white flour maizes, and may be priced beyond the reach of the poor.

The phased transition to market-based pricing of maize grain built into NAFTA was allowed specifically to prevent the large-scale social destabilization that would almost certainly result from a sudden rise in the price of this important staple, and to allow for the purported build-up of wealth that will result from free-market policies, and which will allow Mexicans to afford costlier foods. Important social upheavals have resulted from lack of physical and economic access to maize throughout Mesoamerican and Mexican history.

In the year 1450 a series of five consecutive years of crop failures struck the valley of Mexico (disease, frosts and drought). According to Aztec chronicles, epidemics broke out when people began consuming inedible plants. Children were sold into slavery in exchange for maize. Royal reserves helped feed the population of 200,000, but lasted only for the first year of the disaster. Some students of Aztec history speculate that this event spurred the conquering expansion of the empire, under the emperor Motecuhzoma Ilhuicaminatl, in search of more land to ensure a more stable food supply. The petlacalco, or royal reserve, was thence stocked with a 20 year supply of maize. By the time of the conquest, the amount of grain extracted from tributaries each year by Tenochtitlan was enough to feed 50,000 people, a potent effect of maize crop failure, inflicted upon many people across a broad geographic range.

Enrique Florescano documented a series of social and economic crises in colonial Mexico that he showed were directly tied to the rise of maize prices, and which he argues were an important contributor to the political instability that, among other effects, resulted in the revolutionary war against Spain in 1810. Whether the current perturbations of trends in maize production and prices will have similar effects on contemporary Mexican society, or whether the free-market strategies of the present Mexican administrations will successfully allay such catastrophic consequences, remains to be seen. Also in the balance is the possibility that current economic and agricultural policies that reduce traditional maize production in Mexico may decimate the genetic treasury that is the Mexican maize germplasm pool, an important and recurrent contributor to the key hybrid germplasm of the U. S. maize belt. Whatever the final outcome, it is clear that rarely in the history of human societies have the fates of a plant and a people been so intimately intertwined.