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've been one of the plants we domesticated for food,

much less one of the top 10 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.

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.

9,000 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.

And 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 it in the first place, and it had nothing to do with the kernels.

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 over winters on the ground for months,

which is very useful for the plant, but not for whoever's trying to eat it.

Ancient cultivators most likely began selecting seeds of Teosinte with the softest glume.

And these days, that 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 (the) 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 a 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've become foundational to their diets, and, in turn, it never would've 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, just take a moment to think about the many coincidences that brought that corn tortilla to your plate in the first place.

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