How Corn Began

 About 17 years ago, I wrote a series of articles on the history of corn for the Ontario Farmer. With its permission, I plan to reproduce several of them, with minor revision, on this blog site. A couple of the original columns feature historical information already available on the site and so won’t be reproduced here. Future columns will be mainly about corn in Ontario and adjacent parts of North America in years following settlement by immigrant farmers. However, the first is a brief overview of corn’s origins. More information is available in the references listed at the end of the article.

Maize-teosinte

Teosinte ear (Zea mays ssp mexicana) on the left, maize ear on the right, and ear of their F1 hybrid in the center (photo by John Doebley, University of Wisconsin)

The real gold discovered by Columbus in 1492 in the New World was a plant that Caribbean Indians called “Mahiz.” Maize seeds were brought back to Spain, planted and the new crop spread quickly.  Within a generation, it covered much of southern Europe and parts of Africa.  Soon after, it reached India, China and Southeast Asia.

The high, yield and ability of maize/corn to produce several hundred seeds per seed planted – far greater than with Old World grains – made it popular.

Corn flourished, though details were rarely recorded.  Indeed, seventeenth-century botanists identified Turkey or Africa as its place of origin. “Turkish wheat” or “Guinea wheat” were common names. Some writers linked corn to Biblical scriptures, proclaiming a Mediterranean origin.

A treasured book of mine, “Le Maïs ou Blé de Turquie,” first published in Bordeaux France in 1785, debates whether the source was Old World or New. With time, the evidence became clearer: It was the New World, specifically Mexico, where corn began.

The story begins with arrival of humans in Mexico sometime before 10,000 BC.  The first people in Mexico, as in most of the Americas, were big game hunters. But as human populations grew and large animals became scarce or extinct (mammoths, indigenous horses), people in Mexico became more dependent on wild plants for food. With time, they selected preferred plant types and eventually learned about planting.

Beans, squash and gourds were among the first “farmed” crops.  They also ate grass seeds such as Setaria (foxtail). Eventually they tried teosinte.

Teosinte is a grassy weed growing in certain semi-arid valleys of Mexico and northern Guatemala.  Teosinte plants exist as both annuals and perennials and look like well-tillered corn, with male flowers at the top and female flowers in leaf axils.

The seed and ear structures, however, are very unlike corn. Seeds are encased in hard shells – a bit like buckwheat – and grow in a single spike that shatters at maturity. There are many spikes per leaf axillary node.

Because of the different seed structure, many scientists rejected teosinte as the parent for corn when this was first proposed sometime before 1900. Some still argue that the true ancestor is a now-extinct plant, and that teosinte is only a relative.

But the case for teosinte is strong.  Corn and teosinte have the same chromosome number, they cross easily, and resulting seeds are fertile.  Genetic studies have shown that the key differences between teosinte and corn involve only about five major genes.

Teosinte seed casings must be removed and/or softened before eating. Some researchers suggest that early diners popped the seeds by heating – like popcorn.  Perhaps seed casings were removed using grinding stones. Or teosinte seeds may have been softened in water and then eaten directly with hulls spit out after partial chewing (like sunflower seeds). Eventually someone found a mutant with no seed cases, or softer ones, and teosinte became a better food crop.

The difference between a single and multiply double kernel rows also involves mutant genes. One gene permitted teosinte kernels to grow in two alternating rows, somewhat like heads of rye or two-row barley.  Other mutations meant two-row teosinte became four-row corn – and later eight-row corn.  The latter is still grown in Mexico, known by names such as “Maiz de Ocho.” (The number of kernel rows is always even since two seeds develop at each node on the compressed “rachis” or cob in all types of corn except teosinte where only one kernel develops.  Modern Ontario hybrids usually have 14, 16, 18 or 20 kernel rows.)

Natural mutation and human selection changed teosinte/corn from having several spikes per axil to only one large ear.  However, the original teosinte trait still exists in modern corn.  If you examine an ear of corn at silking, you’ll find several tiny ears – each with its own minute kernel initials – in the axils of husk leaves.  If the main ear does not pollinate properly, the side ears will sometimes enlarge and produce silks.

The first archeological evidence of corn dates back 7000 years to Tehuacán caves near Mexico City containing cobs, about one inch long, which once bore 50-60 kernels in four or eight kernel rows per ear.  The initial steps in domestication likely occurred as much as 2000 years earlier.

Teosinte still crosses naturally with corn where teosinte grows wild near Mexican cornfields.  Cross pollination occurred regularly during early days of domestication, adding new genes to the corn genetic base.

A rapid expansion in corn ear size occurred about 1500-1000 BC.  Higher yields triggered a boom in human cultural development. Corn served as the base – both nutritional and religious – for several Mexican societies including the successive Olmec, Mayan, Toltec and Aztec civilizations between 1200 BC and the time of Spanish conquest. Corn also dominated life for the Incas in South America.

The first evidence of corn in the United States was found in caves in New Mexico, containing corn ear remnants from about 2500 BC.  Corn was grown extensively from 0 to 1400 AD throughout Arizona and New Mexico using sophisticated irrigation schemes. These major southwestern civilizations ended for unknown reasons about 200-400 years before the Spanish conquest, leaving only the building ruins that are so intriguing to tourists today.  However, some present-day Hopi, Navajo and other southwestern Indian communities still grow corn using traditional varieties. (Blue corn is popular.)

From Mexico and the southwestern United States, corn spread slowly north and east by various avenues including a dominant route along the Gulf coast to the Mississippi and thence north. Substantial settlements existed at various times up the Mississippi.

A spectacular site is the former city of Cahokia, near St. Louis, where up to 30,000 people lived before 1400 AD in a settlement extending over six square miles.  Imagine how much corn would have been required at an estimated per-capita annual consumption of 8.5 bushels!

Most native corn in the Mississippi valley and southeastern United States had soft, long, thin, indented white kernels, commonly called “gourdseed” corn by settlers. Ears were fat and squatty, often containing more than one thousand kernels in 16 to 36 kernel rows.

By contrast, the indigenous corn grown in Ontario, in New England, the northern Great Plains and in states bordering the Great Lakes, had round, yellow or white, flint kernels, generally with only eight or ten kernel rows on long, thin cobs.

U.S. east coast settlers grew both flint corn favoured by northern aboriginals and gourdseed varieties from the south.  Eventually the two were crossed to form the familiar dent corn that now dominates North American agriculture.

The plant now grown worldwide is known as “maiz” in Latin America, “maïs” in France and Germany, “blé d’inde” in Quebec, “maize” in most English-speaking countries and by many other names elsewhere – including “corn” in English-speaking Canada and the United States. The double name, “Indian corn,” once used widely to distinguish maize from old world corns such as wheat and rye is rarely used. (“Indian corn” now means only a particular type of multi-coloured flint.)

Corn has been called the New World’s greatest gift to humankind. Little did Christopher Columbus realize the real treasure he had encountered in the New World was the few corn ears he took back home.

Some readily accessible references on origins of corn:

Carroll, Sean B. 2010. Tracking the Ancestry of Corn Back 9,000 Years. New York Times. https://www.nytimes.com/2010/05/25/science/25creature.html

Doebley, John. 2004. The Genetics of Maize Evolution. Annual Review of Genetics. https://teosinte.wisc.edu/pdfs/DoebleyAnnRev2004.pdf

Edmeades, G.O.; Trevisan, W.; Prasanna, B.M.; Campos, H. 2017. Tropical maize (Zea mays L.). In: Campos, H.; Caligari, P.D.S. (eds). Genetic improvement of tropical crops. https://cgspace.cgiar.org/handle/10568/91727

Fedoroff, Nina. 2004. Ancestors of Science – Prehistoric GM Corn. Science. https://www.sciencemag.org/careers/2004/10/ancestors-science-prehistoric-gm-corn

Katz, Brigit. 2018. Rethinking the Corny History of Maize. Smithsonian Magazine. https://www.smithsonianmag.com/smart-news/rethinking-corny-history-maize-180971038/

National Geographic. 2009. Corn Domesticated From Mexican Wild Grass 8,700 Years Ago. https://blog.nationalgeographic.org/2009/03/23/corn-domesticated-from-mexican-wild-grass-8700-years-ago/

Comments are closed.