The History of Corn

Humans can't get enough corn. It's in most items on grocery store shelves, from chips to breakfast cereals to beverages and even baby formula. Corn makes up around 20% of all the nutrition for all humans worldwide. Which makes it all the more surprising that corn basically shouldn't be edible at all.

Of course, it's a completely legit human food now, but, to get there, corn has had to come a long way.

There are a whole host of reasons why corn never should have been one of the plants we domesticated for food, much less one of the top ten staple crops on our plates.

This is the unlikely story of an unassuming grass that became one of the heavy hitters of the human diet.

[INTRO]

The evolution of corn, also called maize in some parts of the world, is sort of a rags-to-riches story of the food world. Nine thousand years ago, there was no corn as we know it. The closest thing was a grass called teosinte that grew in modern day southern Mexico. Teosinte produces cobs that are only about a sixth of the size of a modern ear of corn, with between 5 and 12 kernels per ear that break apart easily, as opposed to modern corn's hundreds of kernels on a sturdy cob. Those kernels were puny, tough, and literally indigestible, so the people who encountered teosinte wouldn't have bothered with the kernels at all. Because it's an annual grass that looks exactly nothing like modern corn, for a very long time scientists were flummoxed about where teosinte fit in corn's family tree, and if it did at all. The debates over corn's true ancestry became so contentious that it became known as the corn wars. And that battle raged for nearly half a century, until additional genetic evidence showed once and for all that teosinte alone was the ancestor of modern corn. And thus, a corn truce was called and there was peace in the land.

It's likely that teosinte was first cultivated by humans around the Balsas River Valley of southern Mexico about 9,000 years ago. The teosinte plant's stalks contain a sweet juice, kind of like sugar cane. And archeologists think that the stalks were the only reason Mesoamericans even cultivated teosinte in the first place, and it had nothing to do with the kernels. The Mesoamerican people would either chew on the stalks or juice them to ferment the sweet liquid into alcohol, because that's also a thing humans like to do with plants that contain sugary liquids. Genetic studies have provided evidence that corn came directly from teosinte, but it's less clear how the focus of cultivating the plant changed from stalk to kernel. What we do know is that it likely took just a few genetic changes to transform the hard-shelled teosinte seeds into something that could nourish a civilization. Over time, the nomadic people who cultivated teosinte started selecting the characteristics of the plants they liked best. Eventually, they set their sights on making the kernels as tender and plentiful as possible. Each teosinte kernel is covered in a rock hard shell called glume that renders it basically inedible to humans. The glume on the kernels of teosinte keeps the seed intact as it travels through an animal's digestive system or overwinters on the ground for months. Very useful for the plant, but not whoever's trying to eat it. Ancient cultivators most likely began selecting seeds of teosinte with the softest glume. These days, the glume is the part of the corn on the cob that gets stuck between your teeth. Another big step in making corn out of teosinte involved boosting the starch content in the kernels. Corn is about 73% starch by weight, which is much higher than teosinte's kernels, and it's what makes corn a great source of fast calories. Scientists still don't know a lot about early cultivation of corn. They're still investigating how corn developed multiple rows of kernels per ear, and that solid cob you can really grab onto, among other things.