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As technology advances and research is expanded, new discoveries can influence and change previous ones through evidence previously undiscovered. Corn, one of earth’s most vital and popular crops, remained largely a mystery, the origin story of a crop thousands of years old in the making. Through scientific breakthroughs in genetics, botany, and biology, the curious case of corn begins to be uncovered. Its story originates in Mexico at an estimated 6000 to 9000 years ago, when native agriculturalists recognised the potential teosinte had and decided to culture it. Thousands of years later, through careful selection, the grassy weed known as teosinte had evolved into many branching species, each unique both in morphology and purpose.
Teosinte is a wild weed, found growing on the hills of southern Mexico, Honduras, and Nicaragua. It is a small, grass-like plant, belonging to the family Poaecae- one of the most abundant and widespread of earth’s unique flora, able to habituate even the most extreme conditions on all of earth’s seven continents. The family Poaecae is one of the many families of agricultural crops now cultured today, producing wheat, oats, sugarcane, and sorghum. Teosinte was most likely chosen as a crop to be cultivated due to it easily being found in the fields of Mexico, as well as the its abundant variation. In a study done by Avinash Karn, a PhD biologist who has worked at Cornell University and the University of Missouri regarding the genetics of Teosinte Alleles for Kernel Composition Traits in maize, a chart is shown with the range of different contents in a grain of teosinte. The ranges from the 255 chosen seeds have large differences, showing the genetic diversity in teosinte. Teosinte was most likely chosen by natives to also be used as grain for feeding livestock, something we still do with teosinte today, as it has a high starch and protein content. Teosinte is also known to have “a high resistance to both viral and fungal diseases of corn” (Teosinte), as well as a tooth-crackingly hard shell that protects it from hungry birds and pests.
In the late 1930s, colleagues Paul Mangelsdorf, A Harvard professor of economic botany, and Robert Reeves, a professor of cytotaxonomy and cytogenetics at the Texan Agricultural Experiment Station, proposed the Tripartite Hypothesis, a hypothesis that stated that domesticated maize was derived from an extinct wild maize. They suggested that teosinte was a hybrid of corn and Tripsacum. Although Mangelsdorf and Reeves were able to prove their hypothesis right by producing Tripsacum and Ze Mays hybrids in abundance, they found that that many “aborted” at an early stage, and “few reached maturity” and were “capable of germination” (The Origin of Maize, 305). In 1939, George Beadle, an American geneticist who shares a Nobel prise in physiology or medicine, a member of the National Academy of Sciences, argued against the Tripartite Hypothesis in an article in the Scientific American, the oldest American science magazine and winner of 2011 National Magazine Award for General Excellence, instead proposing the idea that maize is simply a domesticated form of teosinte brought into existence “through selective breeding by the ancient Indian agriculturalists of Central America” (The Ancestry of corn, 112). Using Mangelsdorf and Reeves’s data, he argued that “their 4 factors might just as well correspond to 4 major genes, each of which controlled a single trait that differentiated teosinte from maize"(Tracking Footprints of Maize Domestication, para. 9). He argued that even though the hybridisation between maize and tripsacum was possible, too few were capable of reproduction and would be close to impossible to re-create in nature. In later studies, it was discovered that most Zea species and subspecies have ten chromosomes, while most Tripsacum species have 18 or 36. Both teosinte and maize have ten chromosomes, making it possible for them to crossbreed and go on to reproduce naturally without a genetic decline. Teosinte and Maize are only slightly different genetically, but over a short period of time evolved vastly different morphologies through mutations that were selected by natives.
There are six main types of corn- flint, flour, dent, pop, sweet, and waxy. Within these six types, there are hundreds of variations, made of hybrids or selectively isolated plants. Flint corn has a hard exterior, and is similar to popcorn. Another type of corn is sweet corn, a type of corn high in fibre and sugar. Sweet corn is naturally sweet, as the sweet flavour within the corn comes from the natural sugars within the plant. When picked at the right time, the sugar in the corn is at its peak, having not had enough time to turn to starch.
However, according to Iowa Agriculture Literacy, a non-profit organisation that serves to educate people on agriculture and farming, that even though Iowa is America’s top producer for corn, “less than 1% of the corn grown in Iowa is sweet corn” (Sweet Corn Science, 2016). Today’s most commonly grown crop in America is Yellow dent corn, according to Terry Danyard, the early president of both the Canadian Renewable Fuels Association and OCPA (Ontario Corn Producers Association), who writes, “at least 99% of North American grain corn is yellow – indeed, almost always yellow dent corn” (Danyard, 2020). Corn is an incredibly versatile crop, easily able to adapt and moulded into products, yellow dent corn especially. In 1920-1930, farmers hybridised new crops, able to be planted closer together and increasing the amount of corn able to be produced within an acre. Because yellow dent corn must share similar characteristics to be called yellow dent corn and fulfil the purpose it was bred for, it is easy to infer that all yellow dent corn is genetically similar, and is what one would call a monoculture. A single disease could wipe the entire corn species out, as since there is little to no genetic variation within the crops, survival of the fittest would not take place as they are all the same. Yellow dent corn is not the most popular kind of corn to the people, but it is the most used type of corn in the industry according to the Washington post, which writes that “Less than 10 percent of the corn used in the United States is directly ingested by humans. The bulk is either turned into ethanol, for use as fuel, or fed to the hundreds of millions of animals we raise” (How corn made its way, 2019).
Corn is a plant with a rich history in science and agriculture. As more and more corn is grown and hybridized, it is possible that new types of corn might spring up and others fade out of existence. Corn is one of the world’s most successful crops, and has been a fascinating topic for biologists and botanists to study alike. The study of corn has helped numerous scientists in hypothesises and studies, as well as furthered research on the topic of seletive breeding and genetics. The dangers of corn as a monoculture crop are evident, but corn has a lot of exellent uses as well and should not be discredited.