Picture yourself in a grocery store: You see piles and piles of apples, all different varieties. About 95% of apples eaten in the U.S. are grown in the U.S.; the imports usually just plug a hole at the end of the growing season.

Now check out the pile of bananas. The first thing you notice is there’s usually just the one variety, the Cavendish. Every one of them has been grown, picked, washed, and boxed in another country and then shipped, still green, in a temperature-controlled environment. At their destination, they’re put in special ripening rooms that provide, among other amenities, the release of gases that trick the banana into thinking it’s still back home in the tropics. At a temperature of 64 degrees, a banana can ripen in as little as four days; at 58 degrees, it takes seven days.

Considering all this aftercare and the fact they’re all imported, you might expect a banana to be much more expensive than those very American apples. And yet they’re not: Bananas are typically less than half the price of apples. They’re actually among the cheapest fruits around. How can this be? How did an imported luxury item become a cheap American staple?

On this week’s episode of Freakonomics Radio, we explore the banana’s history, the deadly fungus that’s currently threatening it, and the fruit’s status as a symbol of commerce, political discord, and scientific controversy.

In 1876, the city of Philadelphia commemorated 100 years of U.S. independence with the Centennial Exposition, a big trade fair. In addition to the first public demonstration of Alexander Graham Bell’s telephone and an appearance by President Ulysses S. Grant, the fair boasted a horticultural exhibit with a banana plant.

Though the banana was one of the first fruits cultivated by humans, around 500 B.C., the Americas didn’t get it until much later. It’s not really possible to grow bananas in the United States, and sailing ships couldn’t travel fast enough to reliably keep the fruit from overripening, so the banana was still exotic to most Americans in 1876.

“In the first two-thirds or three-quarters of the 19th century, bananas might come in to an East Coast port on a sailing ship, and then they’d be sold at the port,” says Virginia Scott Jenkins, a cultural historian and the author of Bananas: An American History. “But they weren’t generally commercially available anywhere. They were a luxury item.”

By 1910, however, Americans were eating 40 million bunches a year, thanks to the advent of steamships and railroads that allowed for the bulk importation of bananas to the United States. By the 1920s, trains started getting mechanical refrigeration; in the 1930s came refrigerated trucks. This new technology had a huge impact on food distribution generally — it made possible the modern meat industry, for instance.

There are more than 1,000 banana varieties in the world, but the variety that Americans came to know and love early on was the Gros Michel, also known as “Big Mike.” But just as Americans were beginning their love affair with Big Mike, Panama disease struck. The disease — technically called Fusarium wilt — is caused by a fungus that infects the plant’s roots and eventually kills the whole plant. The fungus also leaves the soil unfit for future banana growth. By the 1950s, the disease was decimating Gros Michel production all over the world.

Growers tried to get ahead of the disease, moving to different countries and growing bananas there, but the disease couldn’t be outrun. The Gros Michel was doomed. The last Gros Michels in the United States were sold in 1965. In its place emerged the Cavendish, a variety that was not susceptible to Panama disease but, like the Gros Michel, was robust and reliable.

Well before the Cavendish emerged as a replacement for the Gros Michel, early U.S. banana companies made a strategic decision to transform the banana from a high-margin, low-quantity luxury product to a low-margin, high-volume staple. Banana companies were extraordinarily successful in executing this shift. Today, the European Union imports about six million tons of Cavendish bananas each year. That’s 110 bananas per person. The United States imports 130 bananas per person each year, and Canada beats both of them with 150.

Douglas Southgate is an economist and emeritus professor at The Ohio State University who studies bananas. He finds particularly instructive the story of Chiquita, which was founded in the 1800s and known for most of the 20th century as United Fruit Company. United Fruit had an enormous fleet of ships, second in the Western Hemisphere only to the U.S. Navy. The company’s fleet and innovations in refrigeration allowed it to import huge quantities of bananas from Central America to the United States.

“The major beneficiaries of this efficiency were, in fact, consumers,” Southgate says. “Prices were slashed, and within a few years, bananas were no longer a luxury item. They were instead a fruit of poor people. The first food that a lot of poor babies ate after weaning were mashed bananas in the days before canned baby food.”

United Fruit (and other companies) also engaged in some rather questionable practices in banana-growing countries.

“Foreign companies, led by United Fruit, were willing to make the investment to clear land, put in infrastructure, and so forth to start producing bananas on a massive scale for the U.S. market,” says Southgate, “but only if they were awarded vast tracts of land and largely exempted from taxation. So that gave them the dominant position. That’s what led to banana republics.”

“Banana republic,” before it was the name of a clothing store, meant something very different — essentially, a fragile country whose economy and often political leadership were propped up by an export crop. United Fruit tangled repeatedly with governments in various banana republics. Ultimately, the company ran afoul of the U.S. government as well, which accused United Fruit of monopolistic behavior.

In 1967, United Fruit agreed to reorganize and sell off some of its strategic assets. The next blow came from Ecuador. By the time major fruit companies turned their attention to Ecuador, most of its land was already owned by independent farmers, making the country less susceptible to political and economic exploitation.

“Here was this important source of supply that came online in a very big way, very quickly, after World War II, and it was a source of supply that was impossible for United Fruit to control,” says Southgate.

Today, no one company comes close to dominating the international banana trade like United Fruit once did. The three biggest banana companies — Dole, Del Monte, and United Fruit’s successor Chiquita — share around 40% of the global export market. As economists will tell you, competition helps keep prices down.

But there’s an even more powerful explanation for why bananas are so cheap: standardization. Andrew Biles, the former CEO of bananas and pineapples for Chiquita, says that companies today have perfected the science of growing Cavendish bananas.

“You know how that banana is going to function when it’s transported into refrigerated cargo,” says Biles. “You know how it’s going to perform in the ripening rooms in the country of destination, and you know how it’s going to perform and hold up on the retail shelf.”

It’s not just that nearly every banana grown for export is a Cavendish; it’s that every Cavendish banana is genetically the same as the next Cavendish. From a business perspective, that’s ideal — the ultimate in quality control. From an agricultural perspective, however, it’s a problem.

“There’s no diversity… each plant is the same,” says Biles. “Each plant has the same resistance to disease as it spreads.”

The strain of Panama disease that killed off the Gros Michel was known as TR1, or Tropical Race 1. In the 1990s, a strain called Tropical Race 4 emerged and started attacking Cavendish bananas. By 2000, it was clear that TR4 was going to be a big problem. As Biles tells it, TR4 started in Indonesia and has since spread to the Philippines. The industry is worried that Latin America will soon follow.

“If you look at the map,” says Biles, “it’s a disease that seems to be spreading west.”

Plant science has come a long way since the 1950s. Cavendish bananas, like the other kinds of bananas that people eat, have essentially been bred into a seedless, sterile condition. This makes the Cavendish hard to breed conventionally but a good candidate for genetic modification.

James Dale is a plant scientist at Queensland University of Technology in Brisbane, Australia. He also happens to be a banana specialist. When the magnitude of the TR4 threat became clear, Dale and his team set out to look for genes with resistance to TR4. One scientist came across a patch of wild banana plants in Malaysia that was growing successfully in an area that had been decimated by TR4. Dale and his team analyzed the DNA of the wild bananas and identified several genes they suspected were responsible for the resistance. They then inserted those genes into embryogenic cells and grew genetically modified Cavendish bananas.

“[E]ssentially, what we’ve done is, we’ve taken a gene from a wild banana that is resistant to Tropical Race 4, and we’ve taken that one banana gene and we’ve gone and put it into Cavendish,” explains Dale.

Dale and his team took their genetically modified Cavendish bananas to Humpty Doo, a small town in the Northern Territory of Australia that was once a fertile site for banana production, although TR4 had wiped out the Cavendish plants there. This made Humpty Doo the perfect place to hold the world’s first experiment to see whether genetically modified Cavendish bananas could survive Panama disease.

In 2012, Dale’s team began field trials, planting both genetically modified and non-genetically modified bananas in the Humpty Doo soil. Between two-thirds and 100% of the non-genetically modified bananas died or were infected within three years. In other words, Panama disease was still in the soil.

Among the six different lines of genetically modified Cavendish plants, however, several exhibited high levels of resistance, and one of them seemed to be completely immune to TR4. What’s more, researchers found that one specific gene of the resistant bananas called RGA 2 occurs in both wild bananas and Cavendish bananas but seems to work better in wild bananas.

“And so that’s actually really, really important because there’s a new technology known as gene editing. It’s different to gene modifications,” explains Dale. “Gene editing is where you can go into the DNA and just tweak genes that are already there.”

This type of gene editing is made possible by a tool known as CRISPR, or clustered regularly interspaced short palindromic repeats. (Freakonomics Radio spoke with one of CRISPR’s inventors, biochemist Jennifer Doudna, in 2017 for an episode called “Evolution, Accelerated.”)

Dale’s findings seemed to be great news for the banana industry. There were potentially two ways to save the Cavendish from Panama disease: using CRISPR to tweak its genetic code or introducing new, resistant genes from other bananas. The industry, however, is less than enthusiastic; Andrew Biles describes Dale’s genetically modified approach as “not so acceptable societally.” A sizable fraction of consumers in the U.S. and especially in Europe consider genetically modified crops to be risky despite assurances to the contrary from scientists.

Chiquita, according to Biles, believes the industry’s salvation instead lies in improved breeding techniques. But there’s a problem with this strategy: A breeding program — even a very good one — won’t produce Cavendish bananas; it will produce something very different. So for the billions of people who eat trillions of bananas, a great many of them Cavendish, how panicked should they be?

“[I]f you want to have Cavendish in 20 years’ time,” says James Dale, “they’re probably going to be genetically modified, or they’re probably going to be gene-edited.”

You can find the full Freakonomics Radio episode of “The Most Interesting Fruit in the World” at Freakonomics.com. You can also listen on Stitcher, Apple Podcasts, or any other podcast platform.