This is the most secure vault  we have on the site.

Okay.

I'm excited to see  what's behind this vault.

Things that money can't buy.

It’s in your snacks and on your dinner plates.

It’s on your face and in your gas tank.

Say hello to our dear friend maize, known to many as corn.

It’s been around for a long time, but today one industrialized strain of corn is rapidly replacing  thousands of indigenous and local varieties.

So what does this transformation mean for our  food security… and our cultural heritage?

And why does this underground vault  filled with corn have a security system like Fort Knox?

I’m Shane Campbell-Staton, and this is Human Footprint.

Come with us.

In Maizajo, what we do every day is, we make tortillas.

Santiago and Dani love maize… almost as much as they love their corgis.

The key ingredient in a tortilla is maize.

But at Maizajo, it’s not just any maize.

So we have Michoacán, Puebla, really close to Oaxaca, y el Estado Mexico.

So the idea is to get back all these corns to the people.

Sourcing ancient varieties of maize from farmers  all over Mexico, Maizajo crafts their tortillas using a millennia-old process.

What this does, is it’s gonna modify the protein chains in corn.

Why?

Because  corn is not digestible for humans.

Same in and out, is what you’re saying?

Yeah.

Okay.

Let’s go to make some tortillas.

This whole corn process is  really related to family.

Yeah, we have gods of corn.

Centeotl  is the god of the corn.

The corn is very literally a reflection  of who the Mexican people are.

We are made of corn.

Over millennia and across the Americas,  people adopted corn and wove it into their cultures - creating thousands of unique varieties in the process.

Just outside of Mexico City, you can actually see all that diversity in one place.

Isn’t it cool?

This is the place to be.

Meet Sarah Hearne.

She’s a good baker, and an even better geneticist, working at one of the world's largest seed banks.

You have more security in here than I've  seen in any biological building I think I've ever been in.

It's like CDC level.

It is like going into a bank vault.

How many different varieties  of maize are in this room?

There are around 28 and a half  thousand different kinds of maize.

28 and a half thousand.

Of all of them, do you have a singular favorite?

I have favorite colors.

So I like the blue maizes and the pigmented maize.

Most of the corn  that you see in the shops is yellow or white.

This is like being in a candy store  for me.

They're like jelly beans.

Every different one is a flavor.

There's black corn, blue corn, red,  yellow, and white.

Small, medium, and large.

Experimentation by native peoples created tens of thousands of varieties of maize.

Each one adapted  to a specific time, place and purpose.

But in the last century, just a handful of  commercial varieties have come to dominate global corn production.

What happened?

Abeer, what's going on, man?

This is Abeer Saha, food historian  and open mic aficionado.

He studies the history of corn.

How did the rest of the world get cheated out  of all of the variety that I have here?

I think it was Robert Reed in the mid-19th  century.

He planted two kinds of corn through the magic of crossbreeding, what was  produced was Reed’s Yellow Dent.

Before Reed’s Yellow Dent, American farmers were  growing and selling hundreds of varieties of corn.

Then came the railroads.

Traders demanded  corn that was more uniform to streamline mass transportation and set global market prices.

Reed’s Yellow Dent became that standard.

At the 1893 Chicago World's Fair,  Reed’s Yellow Dent was recognized and given prizes and awards for its traits.

Later, in response to the Dust Bowl and The Great Depression, the federal government tried to  save farmers by subsidizing corn production.

In a historical heartbeat, this culture-sustaining  crop became a government-backed commodity.

Then came World War Two.

The war effort was not just about bombs and guns.

It was also about how to  feed people.

Farmers began automating and mechanizing their production processes.

After the war, companies that had grown rich making bombs, grew even richer when they realized  the same chemicals made powerful fertilizers.

Farmers began using fertilizers and pesticides,  and every farm started to look more like a factory.

Then the government begins to look  for ways to create outlets for this corn.

One of those outlets: meat.

Farmers since the 19th century thought of livestock as corn  that walks itself to market.

Corn became a staple in our livestock’s diet  and the meat industry exploded… but we were still producing more corn than we could possibly use.

We had to find another outlet.

And we did.

Somewhere close to 40% of most corn  now goes into ethanol production.

But meat and fuel are just the beginning.

Today, corn is in just about everything… And we keep finding new ways to use it, creating  a vicious cycle of demand and surplus.

The amount that humans consume, according to  some estimates, is probably less than 1% of all the corn produced in the United States.

Corn is not just a plant.

Corn is a kernel of human existence.

Tres tamales.

So, what does it matter if our way of life  depends on just a few varieties of maize?

One of the potential consequences of having  less diversity is you don't have as much room for maneuver in terms of adaptation.

Maize varieties don’t just differ in their taste and texture, but in their ability to survive  extreme conditions and new diseases.

Those differences are encoded in their DNA.

On a fast-changing planet, that genetic variation is like money in the bank.

With climate change, we have higher frequency of drought, higher frequency of heat stress.

I work at the interface between the collection that we've seen and the active breeding programs to identify characteristics that will help future-proof maize growth.

Sara is scouring the seed bank for genes hidden in ancient and seldom-grown maize  varieties, that can make commercial varieties   more productive and resilient.

For some, it makes the difference between having a harvest and food to eat versus having no food to eat.

I guess in that sense it really is a bank.

It's a bank.

It's a very important vault.

For Sarah, ensuring corn can meet the demands  of the present and the future means looking into its evolutionary history...

But that history is  built on our cultural connections to maize.

Salud.

Enjoy this Mexican Manhattan with corn whiskey.

Santiago used to work at this restaurant under his sensei, chef Gerardo Vasquez Lugo.

But now his  company Maizajo supplies the tortillas and masa for the restaurant’s unique dishes.

How did you two come to meet?

We had this event with the chef of this  restaurant, and we met there, and we clicked.

I get into her house the first  day.

I never… I never left.

You take one tortilla.

Put this roll made with beef stuffed  with guacamole.

Enjoy it like a taco.

Amazing.

Thank you.

Mm.

I’m trying real hard not to curse.

This is delicious.

These are our tortillas.

That’s a hell of a tortilla.

You were asking about where we can see corn around  the city.

We can see it in the fashion.

Representing, I like that.

Actual fashion.

Do you think something is being lost,  you know, as so much of the corn is being dominated by this one type of corn now?

When we first met, I asked Santiago what he wanted, and he told me that he wanted to change  the world.

And I told him that he was crazy - that how on earth was he going to do that?

And he told  me the thing is, I already did.

I make people turn around and see corn for what it is.

Sometimes, grandmothers come to Maizajo.

When they just get in, they smell the corn.

And they, the first thing they do… sometimes they cry.

We are not just talking about an  ingredient.

We're talking about culture.

We are talking about what we are.

That's beautiful.

That’s beautiful.

Thank him.

I want to cry.

Thanks for watching!

If you  want more Human Footprint, you can tune in to the full length  series on the PBS App or on your local PBS station.