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Worshipped for centuries in Japan as a divine messenger and protector of farmland, the Japanese wolf disappeared from the archipelago in the early 20th century after its population was decimated by disease and humans hunting them down in the name of defending livestock.

Its tragic fate, however, along with the lingering mystery over its true identity and even reports of modern-day sightings, has kept the beast alive in the minds of many. Now, a new study says the legendary animal may offer the key to understanding the origins of man’s best friend.

The Japanese wolf (Canis lupus hodophilax) is the closest relative to the ancestors of dogs, more so than any other gray wolf population, according to Yohey Terai, an evolutionary biologist at the Graduate University for Advanced Studies in Kanagawa Prefecture who led the research.

Studies so far have indicated that dogs and Eurasian wolves are both likely to have diverged from a common wolf ancestor, a process that took place 20,000 to 40,000 years ago. But there has been much debate over when and where this happened, partly because the original gray wolf population is thought to have vanished.

Many regions in Eurasia have been proposed as candidates for the origin of dogs, including the the Middle East, Central Asia, Europe and the southern part of East Asia, but discussions on the origin, or origins, as well as the timing of domestication, continues.

“Our research allows us to hypothesize that dog lineages diverged from wolves in East Asia,” Terai said during an interview Wednesday. More specifically, the extinct population of the gray wolf from which dogs are suspected to have been domesticated is closely related to the ancestor of the Japanese wolf and is likely to have inhabited East Asia, according to the study released last week, which is yet to be peer reviewed.

A stuffed specimen of the Japanese wolf at the National Museum of Nature and Science in Tokyo | ALEX K.T. MARTIN
A stuffed specimen of the Japanese wolf at the National Museum of Nature and Science in Tokyo | ALEX K.T. MARTIN

Terai, however, is careful to add that this doesn’t necessarily mean that dogs were domesticated in East Asia. “They could have dispersed elsewhere before having a relationship with humans — that’s something we cannot know from the genome data, and something that will require archaeological evidence.”

In their research, Terai and his team extracted and sequenced the whole genomes of nine Japanese wolves from the 19th to 20th century and 11 Japanese dogs including the shiba and Akita. They then compared their sequences with a wide range of canids from around the world including modern dogs, dingoes, coyotes and a variety of wolves. They found that the Japanese wolf was a unique subspecies of the gray wolf and genetically distinct from both modern and ancient gray wolves.

But when Terai and his colleagues built evolutionary trees, they discovered that the Japanese wolf was in fact the closest to dogs among wolves, and that they essentially had a “sister group relationship,” or were each other’s closest relatives.

The genetic affinity was especially evident among eastern dogs, including canines such as the dingo and the New Guinea singing dog, as well as modern Japanese breeds. In contrast, dogs of West Eurasian lineage, in particular dogs from Africa, showed little affinity to Japanese wolves.

Moreover, genomes show that the ancestor of the Japanese wolf interbred with the ancestor of eastern dogs at least 10,000 years ago after the West and East Eurasian lineages of dogs split, and that Japanese wolf ancestry has been inherited by many modern dogs — even western lineages through historical admixtures with their eastern counterparts.

As a result, up to 5.5% of modern dog genomes throughout East Eurasia are derived from Japanese wolf ancestry, the study says.

“The genome of the Japanese wolf hadn’t been accurately analyzed to date,” said Takefumi Kikusui, a professor at Azabu University’s School of Veterinary Medicine and an expert on dogs who was not involved in the research.

“But results indicating that the Japanese wolf is the closest relative to the primitive dog and that its genome is found in existing dogs will have great significance for future research on the evolution of dogs and their domestication.”

Considered one of the smallest wolves in the world, the Japanese wolf was once endemic to the islands of Honshu, Shikoku and Kyushu. It was venerated in various parts of the country, serving as a source of myths and folklore passed down for generations in rural communities.

The last known specimen of the animal was purchased by American explorer Malcolm Playfair Anderson in 1905 in Nara Prefecture and now rests at the Natural History Museum in London. Today, there are museums in both Japan and Europe that store specimens of the creature, from which Terai and his colleagues gathered the DNA samples from.

Among them are those preserved at the Naturalis Biodiversity Center in Leiden, the Netherlands, that have long been a source of zoological confusion.

Philipp Franz von Siebold's mounted specimen of the Japanese wolf, or yamainu, stored at the Naturalis Biodiversity Center in Leiden in the Netherlands | COURTESY OF NATURALIS BIODIVERSITY CENTER
Philipp Franz von Siebold’s mounted specimen of the Japanese wolf, or yamainu, stored at the Naturalis Biodiversity Center in Leiden in the Netherlands | COURTESY OF NATURALIS BIODIVERSITY CENTER

The riddle traces its roots to 1826, when German botanist and physician Philipp Franz von Siebold, a resident doctor on the island of Dejima, a Dutch outpost in Nagasaki Prefecture, bought two canines at Tennoji Temple in Osaka. He described one as an “ōkami” (“wolf”) and the other as a “yamainu” (“mountain dog”).

These specimens were eventually lumped together after being sent to Leiden, along with another full skeleton of a dog-like animal. They are collectively considered the Japanese wolf’s type specimen, or specimen originally used to name a species or subspecies.

Based on Siebold’s descriptions, however, researchers have debated whether there were two distinct animals called ōkami and yamainu in Japan, or whether they are one and the same. This was because these terms were often used interchangeably in pre-modern Japan along with other variations, and it wasn’t until the early 20th century that the creature was taxonomically classified as nihon ōkami, or Japanese wolf.

Terai and his team’s research offers an answer to this puzzle. While specimen “b,” the one Siebold described as a wolf, showed the same ancestry pattern as other Japanese wolves, specimen “c,” the mountain dog, contained 39% of the genome of a shiba.

“Specimen c is likely to be a hybrid between a female Japanese wolf and a male Japanese dog,” Terai says.

With his study suggesting that dogs may have diverged from its wolf ancestor in East Asia, Terai is keen on analyzing ancient bone samples from the region.

“Some may be closer to the Japanese wolf, others to dogs. And if they are discovered from archaeological sites, it could indicate that they were kept by humans,” he says.

“That could offer us clues to the origins of dogs and their domestication.”

Chichibu, a mountain-ringed region on the northwestern edge of Saitama Prefecture, is known for its long history of wolf worship. | OSCAR BOYD
Chichibu, a mountain-ringed region on the northwestern edge of Saitama Prefecture, is known for its long history of wolf worship. | OSCAR BOYD

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