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 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. So, 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. Huzzah!

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 archaeologists 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 the 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. All these changes show us that corn as  we know it today would never have existed if people hadn’t started tinkering with it.

In fact, modern corn is completely  unable to reproduce without human help because it doesn't have a  mechanism for dispersing its seeds. So, thanks to the painstaking work  of these ancient agriculturalists, humanity got a new, hard-won cereal crop! But even after corn's human architects  had created a starchy, delicious grain, more work was necessary to make  it as nutritious as possible.

Because, remember -- corn was never the  best candidate for food in the first place. To this day, corn is among the  least nutritious staple crops. Although it contains many of the  nutrients we need, many of the nutrients aren't in a form that can be  absorbed by the human body.

But the pre-Colombian people of Mesoamerica  who cultivated corn also invented a process called nixtamalization, which  turned corn into more than just a side dish, and allowed it to be the basis  of millions of people’s diets. Nixtamalization involves cooking  and then steeping the corn kernels in an alkaline solution of water and wood ash. After the cooking process, the  kernels are washed multiple times to remove the outer shell of the kernels,  as well as excess alkaline solution.

The result is a slurry called nixtamal, which was ground into a soft dough that could be used to make things  like tortillas and tamales. And it turns out that treating  it with calcium hydroxide wasn’t just making it taste better. It was unlocking nutrients that would save lives.

See, nixtamalization solved a  lot of the nutritional problems with corn that we mentioned. It increases the dietary fiber, calcium, and  the bioavailability of iron in the grain, meaning how much of it you can actually absorb. But most importantly, it also increases  the bioavailability of niacin, also called vitamin B3.

Niacin is a coenzyme, which means it’s necessary for the functions of other enzymes in the body. It's instrumental in turning food into  energy, making fats and cholesterol, and creating and repairing DNA,  among other critical tasks. When Europeans came to Mesoamerica, they began eating corn, and brought  it back to Europe with them.

But when it became widely  eaten as a staple crop there, those growing and eating it  skipped the nixtamalization part. As a result, they came down  with a disease called pellagra, which is a nasty combo of diarrhea,  skin rashes, mouth sores and dementia. And the culprit was a lack of niacin.

Now, to be clear, it's perfectly fine to  eat corn that hasn’t been nixtamalized. We do it all the time. I mean, who doesn’t love corn on the cob?

Pellagra is only a concern if you aren’t  getting your niacin from any other parts of your diet, like, say, if you’re only  eating corn that wasn’t nixtamalized. Which means, if the  Mesoamericans who cultivated corn didn’t also invent nixtamalization, eating  mostly corn would have made them sick, so it never could have become  foundational to their diets. And in turn, it never would have  become such a big part of ours.

It was against all odds that corn  became edible, and then plentiful, and then yummy and nutritious. In that order. So, the next time you're enjoying a  taco, take a moment to think about the many coincidences that brought that corn  tortilla to your plate in the first place.

This video, and the fact that you may be  feeling a craving for tortilla chips right now, was made possible thanks to  our friends over at Patreon. Our patrons support the  work we do on this channel, and in exchange, they get  access to a bunch of perks. For example, access to our exclusive  discord, bloopers from our video shoots, and our behind the scenes podcast.

So, iIf that sounds like a good deal, you can head over to patreon.com/scishow  to sign up, or just to learn more. Thanks for watching! [♪ OUTRO]