Kansas, a landlocked American state more than 1,700 km from the sea, is not the most obvious place to find a font of knowledge on sushi, Japan's most iconic food. But Eric Rath teaches Japanese cultural history at the University of Kansas and his new book "Oishii: The History of Sushi" ( oishii is Japanese for "delicious") is an enticing title for one of the first substantial books written in English on the history of sushi.

Rath starts by asking "What is sushi?" It is a good question, as most of us have our own idea or images of sushi. But it turns out to be deceptively difficult to define, and the author doesn't answer directly. Instead, he looks at two Chinese characters for sushi found in ancient Chinese dictionaries. The first character, in a reference dating back to the third century BC, defines sushi as "fish preserved in salt" while the second says that sushi is a "pickled food fermented in salt and rice." In modern Japan both characters are used interchangeably.

Japanese dictionaries, meanwhile, say that sushi is a Japanese food made with two components: shari (sour flavored rice) and neta (a topping, often fish but sometimes vegetables, eggs or meat). But the answer doesn't lie here. After an extensive exploration of the origins of sushi Rath comes up with a surprising revelation, at least for less well-informed sushi fans. Sushi, he says, originated not in Japan but somewhere in the rice-growing regions of Southeast Asia as a way of preserving fish. Exactly when sushi arrived in Japan remains unclear, although there are historical records showing that the Japanese were making it by the ninth century.

"Oishii" is not a cookbook, but Rath includes a number of historical recipes showing how sushi might have been made in earlier times. Today's funazushi (carp sushi) is often cited as the nearest thing to the so-called original narezushi (mature fermented sushi). Funazushi is a regional delicacy of the district around the Lake Biwa, Japan's largest freshwater lake, in Shiga Prefecture. It is made with crucian carp ( funa ) from the lake, which is salted to remove moisture before being packed in a wooden pickling barrel in cooked rice with a heavy stone weight on top.

The rice is there to feed natural bacteria that convert rice starch into glucose and create lactic acid to ferment the fish. Fermentation can take three months, six months or even three years. At the end the fish looks, smells and tastes nothing like the sushi you find in London or New York, or in Tokyo for that matter. The strong-smelling fish is cut crosswise into thin slices and served with separately cooked rice, because the rice used for pickling has dissolved and drained away in the long fermentation process.

Top: Blowfish and other types of sushi are displayed at a market in Shimonoseki, Japan, in February 2020. (Reuters). Bottom: Funazushi (carp sushi) is often cited as the nearest thing to the so-called original narezushi (mature fermented sushi). (Courtesy of Reaktion Books)

During the Japanese medieval period, between the late 12th and 16th centuries, sushi transitioned from a pickled fish into a rice dish called namanarezushi (fresh matured sushi). In the context of sushi's long and intriguing history, the appearance of namanarezushi was revolutionary, because both fish and rice were eaten before they were fully fermented and were ready in weeks instead of months or years.

Had the author highlighted the newly emerging samurai culture and the warrior way of life, we would have a better grasp of the significance of namanarezushi. In particular, frugality was one of the samurai virtues, rice was precious and waste was discouraged. Samurai sword skills permeated down to specialist knife masters, who carved and presented fish or game birds in a highly formalized artistic manner as sashimi at banquets. The knife ceremony, reminiscent of Japanese Noh theater performances, can be seen on YouTube.

Wrangling a tuna at Tokyo's Tsukiji fish market. (Courtesy of Reaktion Books)

Opening chapter three, the author declares that Japan's Edo period (1603-1867) was "a golden age for sushi innovation." Many new styles of sushi were developed, including, most significantly, hayazushi (fast sushi).

Here, Rath might have given more attention to the centrality of rice. The powerful and highly organized Tokugawa shogunate in Edo, now called Tokyo, placed farmers second in the social class hierarchy after samurai and ordered them to boost production of rice, which became an important alternative currency. The country's economy revolved around rice, with every feudal lord's wealth measured by the annual rice production of his dominion, which was taxed accordingly. Japanese like to say that the imperative to rice cultivation helped to forge the nation's hardworking character.

Increased rice production led indirectly to the birth of hayazushi because rice-based ingredients such as rice vinegar, sake and sake lees became widely available. As its name implies, hayazushi is quick to make. Instead of waiting for lactic-acid fermentation, rice vinegar or sake lees was added to rice, speeding production and leading to the invention of new styles such as makizushi (rolled sushi) and inarizushi (stuffed sushi in deep-fried tofu pouches). But the most dramatic new invention was nigirizushi , a hand-formed sushi also known as Edomaezushi , (Edo-style sushi).

An illustrated assortment of Meiji-period sushi. (Courtesy of Reaktion Books)

Credit for inventing (or perhaps just popularizing) nigirizushi is given to Hanaya Yohei, who discarded the box used to shape sushi, instead pressing a slice of fish from Edo Bay directly onto small mounds of vinegar-seasoned rice. Nigirizushi quickly became a favorite late-night snack, a 19th-century fast food for Edo's male population that was eaten at street stands.

The story of sushi after the beginning of Japan's Meiji period in 1868 changes not so much in recipes but in the way sushi evolved from a quintessential late-night street snack to a luxury restaurant food. Nigirizushi and makizushi became the most recognized styles of sushi nationwide after World War II. Sushi making became professionalized, and at the same time, the introduction of conveyor-belt sushi made sushi cheaper and more widely accessible. The dish's popularity reached far beyond the shores of Japan. In 2007, Tokyo's Sukiyabashi Jiro restaurant became the first sushi restaurant to receive three stars from the France-based Michelin group.

In examining the current state of sushi as a global cuisine, the author analyzes its impact on the health of both humankind and the planet. In the process, he raises many uncomfortable questions, especially on the sustainability of fishing and even suggests using some apps that tell you how a fish has been caught.

Top: The introduction of conveyor-belt sushi made sushi cheaper and more widely accessible. (Reuters) Bottom: Then-Japanese Prime Minister Shinzo Abe, third from right, and then-U.S. President Barack Obama, second from right, meet in 2014 for a "sushi summit" at Tokyo's Sukiyabashi Jiro, the first sushi restaurant to receive three Michelin stars. (Courtesy of Reaktion Books)

In the concluding chapter, he looks at the future of this remarkable cuisine that has evolved from an ancient preserved fish technique to a popular late-night street snack in the Edo period, and through to a contemporary global cuisine that comes in many different styles. Sushi, like any cuisine, is not static and will continue evolving, he argues. In a final message, he notes that if we hope to continue to enjoy sushi, it is important that we make our choices mindfully.

"Oishii" is extensively and well researched, using numerous sources from both historical and current data, and brims with fascinating and often amusing anecdotes told in a nonacademic, light writing style. If you crave the lesser-known, intriguing details of sushi's history, then this is a book that will feed your hungry mind.

"Oishii: The History of Sushi," by Erik Rath (Reaktion Books, 2021)

Kimiko Barber is a London-based author of cookbooks including "Sushi: Taste and Technique" (with Hiroki Tamemura), and essays on Japanese culture and food.