For traditionalists in 19th-century Japan, a new sushi place was a sign the neighborhood was going to hell. In 1852 one writer grumped about the proliferation of sushi stalls in booming industrial Tokyo. The McDonald's of their day, the stalls offered hungry factory workers a quick, cheap meal of fish and sweetened, vinegared rice. If the fish wasn't top of the line, well, a splash of soy sauce and a dab of spicy wasabi perked up a serving of fish gizzards nicely, with some antimicrobial benefits to boot.

Today that writer's spiritual descendants dwell on food chat boards like Chowhound, where calling a new Japanese place "inauthentic" or deriding it as "strip mall" or "food court" quality is the kiss of death. When we think of high-end, "authentic" sushi today, we envision rich, fatty slices of smooth tuna and creamy salmon arranged on a pristine plate—the height of elegant Japanese cuisine. But sushi wasn't always elegant, and salmon and tuna are relatively recent additions to the menu. In that sense, sushi's appearance in food courts worldwide is more a return to the dish's common roots than a betrayal of authenticity. Sushi has always been in flux, with new ingredients and techniques added as convenience demanded. Globalization has sped up that process exponentially, bringing novelty to an old food and bringing traditional food to new places. The story of sushi is the story of globalization writ small—very small, on tiny slivers of raw fish.

As Sasha Issenberg tells it in The Sushi Economy: Globalization and the Making of a Modern Delicacy (Gotham), sushi began in the fourth century B.C. as a preservation method for whitefish. Packing the fish in layers of rice helped it keep longer and lent both the fish and the rice intriguing new flavors. By the early 19th century, techniques had changed. The rice was flavored with vinegar and the fish with soy, and sushi could be created in seconds, without the long wait for fermentation.

The taste for richer fish such as tuna arrived with American troops after World War II, who introduced enthusiastic red meat eating to a previously ascetic people. The most prized sushi today is fatty tuna from the belly of the fish, or toro. But before Americans started ordering nigiri—raw fish laid on balls of rice—most traditional sushi chefs looked down on tuna with the same disdain a French chef has for fat-free mayonnaise.

Likewise, the American concept of tuna—the white, flaky stuff in cans—had no place for the rich, red flesh of the 600-pound creatures being caught in the cold water of the Atlantic. The huge tuna that now spark intense bidding wars at Japan's Tsukiji seafood market were used primarily to make cat food.

Everything changed in the early 1970s. Akira Okazaki was trying to solve a classic business dilemma for his company, Japan Airlines. His planes were flying to America loaded down with electronics but coming home empty. What could he use to fill them? The tuna craze was already under way as postwar tastes evolved and bank accounts grew, and a few exploratory trips revealed an oversupply of tuna in America's waters.

After many trials and tribulations—it isn't easy to rush enormous, delicate, expensive fish halfway across the world—the first important auction of Canadian bluefin tuna was held at Tsukiji market on August 14, 1972. This day was henceforth known as "the day of the flying fish." Two summers later, more than 90 percent of outgoing cargo on Japan Airlines flights from Canada was Tokyo-bound bluefin. Japan Airlines had "invented the modern tuna economy," writes Issenberg. "Sushi started as a form of preservation," he says, "but it [become] precisely the opposite: a way of using the infrastructure of modernity to chaperone a delicate dish around the world."

By the time Richard Nixon was resigning, tuna swimming through the Atlantic on Monday could find themselves part of a businessman's lunch in Tokyo on Thursday. At the height of Japan's economic bubble, bluefin was fetching $36 a pound at auction.

Trevor Corson sees serendipity in the global economy in The Zen of Fish (HarperCollins): "The Japanese have a nickname for bluefin—shibi. It means 'four days.' In the age before refrigeration, when someone caught a bluefin, he buried it in the ground for four days before eating it." Now that time is spent traveling, but the result is the same: a great lunch.

Fish weren't the only things moving rapidly around the world in the name of nigiri. Sushi chefs were also becoming more mobile, eager to escape the oppressive, decade-long apprenticeship a sushi education in Japan required.

Corson's book follows the education of novice American sushi chefs at the California Sushi Academy in Hermosa Beach. In additional to traditional nigiri, the students learn to make things like the very Americanized inside-out crunchy shrimp roll, from a chef who sighs that "anything oily or greasy—that's all Western influence." But from time to time, a Japanese tourist comes in and orders one.

As sushi migrated, its ingredients changed yet again. It's no accident that avocado joined the cuisine in the 1960s, when Los Angeles chefs started using it to mimic the taste of soft fatty tuna for their homesick Japanese customers. Tuna was by then a staple of the cuisine, much in demand among the burgeoning crowd of educated diners. Today avocado rolls are considered "starter sushi" for timid Americans, but they're popular in Tokyo too.

The greatest success story of the California style is a poster boy for globalization. Nobu Matsuhisa—Japanese by way of Lima, Buenos Aires, and Anchorage—brought "new style" sushi to America's food elite in his eponymous restaurant chain, and his clever use of local ingredients has reverberated around the world and back to sushi's birthplace.

In some cases, the global sushi economy has preserved uniquely Japanese traditions better than an unchanged, pristine provincial cuisine ever could: Men whose great-grandfathers made samurai swords now make the perfect long knives used to carve precious tuna at Tokyo's Tsukiji market, where subtle, intricate auctions are run on less computing power than the average Japanese teenager's cell phone. Without a global shipping system and global demand, the markets would disappear.

Chowhounders who fret about lost authenticity or lament the commercialization of cuisine should think again. There is no such thing as authentic sushi, and there never has been. There was no moment when sushi was purely traditional. And tuna and avocado rolls taste a heck of lot better than a cask of semi-rotten whitefish packed with rice.

Katherine Mangu-Ward is a Reason associate editor.