Where did Japanese dogs come from?

The Japanese Archipelago is now isolated from the Asian Continent by the Sea of Japan. But, how did ancient people come to Japan and how did animals including dogs do as well?

After the earth went into the last glacial stage about 110,000 years ago, it had experienced warm periods and cold periods alternatively, with the temperature gradually decreased. When the temperature reached the lowest about 20,000 years ago, seawater was fixed to the land in the form of snow or ice and wide areas of the Antarctica, Greenland, the North American Continent and the Eurasian Continent were covered with thick ice floor with the decreased sea level by 120m. As the result, Japanese Archipelago and the Asian Continent were almost connected. Although it is considered that the gaps of Tsushima Strait and the Tsugaru Strait might not be filled completely but the distances might be much smaller than now, or some ice might fill the gaps.

Japanese Archipelago about 20,000 years ago
■ The part considered to be land about 20,000 years ago
■ Current landform
Reprinted from Newton 1996-2, ©Newton Press

It is considered that ancient people came from the Korean peninsula, Siberia and Sakhalin to Japan via a land bridge* formed in a glacial age. Then, how and where did the ancestors of Japanese dogs live? Were they already in Japan? Or, did they come to Japan with ancient people coming from the continent? These questions have not been answered yet. However, it was confirmed that breeding dogs already started about 11,000 years ago in the early Jomon Period.

*Land bridge: Newly appeared land because of the lowered sea level

Dogs in the Jomon Period

Hunters and hunting dogs: Niigata Prefectural History Museum

The Jomon Period started about 12,000 years ago after the late Paleolithic Age and ended 2,500 years ago, when people used stone tools and earthenware for hunting and collecting food. Dogs being bred by humans and working for them in this time period are called Jomon dogs, which are the ancestors of modern Japanese dogs.

Judging from the bones unearthed in some relics, the dog at that time is considered small like a Shiba Inu today. The skull tells that the face is rather flat, and the stop is shallow. In addition, as the zygomatic arche is rather small, and the width of the face seems a little smaller than that of the Shiba Inu. So that, the looks of Jomon dogs might be quite different from those of Shiba Inu.

Skull of modern Shiba Inu (male)

Skull of Jomon dog
Sanganji Shell Mound (Late Jomon Period):
National History and Folklore Museum

For example, compared with the skull of a wolf, the face line of a Jomon dog is similar to that of wolf. The head of Jomon dogs is considered similar to those of wild animals of dog family.

Skull of wolf: National Science Museum

It is considered that as dogs started living close to humans, the way of obtaining food changed, and their mouse became shorter, accordingly.

The excessive bone mass due to the shorter mouth made the frontal bone higher and the stop deeper, and because of the wider zygomatic arch, the head became rounder. This is obviously observed in modern dogs improved by humans.

Living conditions can change the shape of the head, so that it is natural to think that a long period of more than 10,000 years had gradually altered the skull of Jomon dogs.

About 2,300 years ago, so-called Yayoi people, who started a farming culture, came from the Asian Continent to Japan with dogs. Those dogs were larger than Jomon dogs and their withers heights were similar to those of modern medium-size Japanese dogs. In addition, their stops were deeper. These dogs and Jomon dogs are considered to have crossed to leave their descendants.

Changes in the shape of the skull:
Niigata Prefectural History Museum
Upper left: Jomon dog　Upper right: Yayoi dog
Bottom left: Dog in the Medieval Period
Bottom right: Modern Shiba dog

As time had passed, interchange with people of the Asian Continent started, which might influence Japanese dogs. During a long period of time, those dogs had developed into ones recognized as Japanese dogs in the Meiji Era and later on.

Japanese dogs have straight ears

Dog-shaped clay product (Karumai ruins in Iwate Prefecture):
Niigata Prefectural History Museum

Tapered bamboo-like straight and slightly forward-bending ears are characteristics of Japanese dogs. Although there are many kinds of dogs in the world, artificially improved dogs have big ears or lop ears. Why do Japanese dogs have straight ears without exception? The picture shows a dog-shape clay product in the late Jomon Period. The tail is up, and the ears are straight. This shows the ears of Japanese dogs have been straight from the ancient times.

Pedigree pie of kinds and DNA of dogs
Reprinted from ©Newton 2018-7, Newton Press
Notes：This illustration is a simplified version of Figure 1 of a research paper（Heidi G. Parker et al., https://doi.org/10.1016/j.celrep.2017.03.079）in an academic journal “Cell Reports” in 2017. The linkage between the kinds of dogs and the names of families is based on this research paper as well.
①European mastiff ②Alpine ③Drover ④UK rural ⑤Continental herder ⑥Pointer setter ⑦Retriever ⑧Spaniel ⑨Scent hound ⑩Mediterranean ⑪New world ⑫Terrier ⑬pinscher ⑭American toy ⑮American terrier ⑯Poodle ⑰Hungarian ⑱Toy spitz ⑲Small spitz ⑳Schnauzer ㉑Nordic spitz ㉒Asian toy ㉓Asian spitz ㉔Basenji ㉕Wolf

All wild animals of dog family including small-size bat-eared fox (Otocyon megalotis) and large-size wolf have straight ears, a long head and a straight lower jaw with the teeth in a line. Japanese dogs also have triangular straight ears, a projecting mouth and rather triangular eyes, which are very similar to those of wild dog family animals. This is the reason why Japanese dogs are regarded as “primitive dogs”.

In 2017, a research on DNA of 161 kinds of dogs was reported. The results are shown in the figure.

In the report, among Japanese dogs, so-called Asian Spitz family such as Shiba Inu and Akita Inu are determined to be closer kinds to wolf.

Japanese dogs have double hair-coat

Molting

Wild animals of dog family living in the area at a north latitude higher than 30°or on highlands have double hair-coat consisting of surface hairs and woolly hairs. When a season changes, and molting starts, dogs look like wearing rags. We know how it happens when we see such a scene in a zoo, outdoors or in nature observation TV programs.

This kind of molting is also common among Japanese dogs, seen every year because the hair-coat of Japanese dogs is also double-type, which is the same as that of wild animals of dog family. They cope with hot and cold weathers by adjusting the amount of hairs.

The weather was once colder on the earth. For example, in Kanto and Tohoku regions, the climate was the same as that of Hokkaido now, which was proven geologically. To bear cold weather, Japanese dogs have had to have double hairs.

Hair coat is an essential index to determine the quality of Japanese dogs. Quality hair coat shows the functions and the beauty of the species.

Penciling and thumb mark
Left: Shikoku Inu♂ / Right: Eurasian wolf♂

The color of hairs is an important element as well as the quality. The colors of Japanese dogs are "goma (mixture of red, black and white)", red, black, white and striped. Regarding dogs other than Kai Ken, red hairs (reddish brown is expressed as red by Nihon Ken Hozonkai), which are the base, are mixed with some black hairs sparsely, so that the color of a hair-coat is determined by the darkness of the basic red hairs and the amount of black hairs.

The back sides of the limbs, mouth, ears, tail, etc. are very tint colors closer to white, which is called "urajiro".

As the pictures show, black "penciling", seen in the fingers of the four limbs, and also black "thumb mark", seen on the front side of the forefeet, are their characteristics. In addition, dark brown or black hairs are mixed with the base hairs at the base and tip of the tail, which is another characteristic. The mark on the forefeet is often seen in black and goma-color dogs while dark brown or black hairs in the tail are seen in all red, goma-color and black hair dogs. This local change in hair color can be seen in many wild animals of dog family.

Dark-color hairs at the base and tip of the tail
Left: Shikoku Inu♀ / Right: Eurasian wolf♂

Japanese dogs now still have the characteristics which are common with wild animals of dog family such as wolf, regarding the quality and color of hairs.