古代出雲（2）山陰の弥生遺跡と青銅器Ancient Izumo, Part 2: The Bronze Hoards of the San'in Region

Yesterday, in Part 1, I looked into ancient Izumo, centered on Izumo Taisha. Continuing, this time, to reveal the reality of the ancient San'in region (the Sea of Japan side of Shimane and Tottori), I introduce astonishing sites found in Shimane Prefecture near Izumo Taisha.

In 2000, when the pillar remains of an ancient high-rise shrine were found within the grounds of Izumo Taisha, the reality of ancient Japan, ignored as legend, rose rapidly to the surface. Around that time, astonishing discoveries came one after another from the hills surrounding Lake Shinji and Lake Jinzai in ancient Shimane, which were larger than they are now.

First, in a survey from 1997 to 2000, a Yayoi-period site with a triple moat was found on the summit of Tawayama, overlooking Lake Shinji on the Matsue side. The discovery came during a preliminary survey, when a plan to build a hospital nearby arose. What makes this site interesting is that in Yayoi moated settlements the houses are generally inside the moat, but here, for some reason, the houses were set outside it, an extremely unusual structure.

Westward from Tawayama into the mountains, finds that overturn ancient Japanese history followed one after another. The Yayoi-period Kojindani site, with 358 bronze swords, 16 bronze spears and 6 bronze bells, was found by chance in 1984 during farm road construction. The site was discovered in steep hill country.

Note here that the bronze swords, spears and bells of the Yayoi period were not used for fighting. They were bronzes used in ritual, and these objects are a main feature of the Yayoi period. The bronzes found at Kojindani shocked because the number buried in one place was the largest in the country. Until then the established view was that Shimane had few Yayoi remains and drew little interest, but this find demanded a rethinking of history.

Twelve years later, in 1996, the Kamo-Iwakura site, in a hill deep in a valley only 3.3 km in straight-line distance from Kojindani across the mountains, was found, again during farm road construction. Thirty-nine Yayoi bronze bells were unearthed together there, and this too drew attention as the largest number of bells buried in one place in the country.

Kojindani and Kamo-Iwakura lie on opposite sides of the mountains, but at this time an old Yayoi-period road running along the ridges between them was found. Interestingly, it was a mountain path the local people had used daily until the twentieth century, and no one knew it had been opened by the Yayoi people.

The bronzes found are Yayoi ritual objects made from an alloy of copper, tin, lead and so on. Interestingly, analysis of the lead in the bronzes excavated at these sites showed that the lead was not from Japan but from Korea and northern China. Moreover, though buried in the same place, some swords had lead from Korea and others lead from northern China. Where the copper was brought from is still unknown.

Bronze-making in the Yayoi period was extremely complex. The view is strong that bronzes made in Korea, mainly by way of China, were brought to Japan, but slight traces of bronze-making within Japan have been found. The bronzes of the region introduced here are numerous, and since an “x” mark is seen in common on the upper part of several, it is thought that a specialist group of makers existed somewhere in the area and that the “x” was stamped as proof of their manufacture. The base has not yet been found, but the possibility is high.

From these discoveries we can see that ancient Izumo (the land from today's Izumo City to Matsue City) had active relations not only with other lands of the Japanese archipelago but with neighbors such as Korea and China. In fact, when I asked a local person, I was told that in the settlement near the Kamo-Iwakura site, where the bells were found, there had been a legend since long ago that ancient treasure was buried. Until 1996 it was only a legend, but the bells were found in a remote spot in a valley beyond that settlement.

On a hill a little west of these sites, 27 tombs from the late Yayoi to the Kofun period were found, called the Nishidani tomb group. It had been known as a site since a large quantity of pottery was found in 1953, but no one thought that countless huge tombs existed. Surveys from 1983 to 2018 showed that tombs of a shape without precedent stood on the hilltop.

The shape is a rectangular tomb with projections at the four corners. This shape exists only in Izumo, and examination of the structure and finds shows that it was the tomb of a king who once ruled Izumo. It is, so to speak, the tomb of the royal house of Izumo.

Even listing the main examples shows that around the hills entered from Izumo Taisha, into the ancient lake, there are many Yayoi remains and sites, and traces appear of rule by a considerable power. But here is a puzzle. Because I have continued a journey exploring ancient Japanese history, I know that the Yayoi people basically lived settled lives of grain cultivation, so they tended to make their living on flat land, and a tendency to go deep into valleys has been entirely unknown in research so far.

Why, then, did only the Yayoi of the Izumo region bury ritual bronzes in the hills deep in the valleys? This time I also observed the movement of the sun at the sites, and the places do not seem related to east, where the sun rises, or west, where it sets. They seem rather to have been chosen carefully so that no one would find them. The key to this puzzle is not Japan but the philosophy of ancient China.

First, in the way the bells were buried at Kamo-Iwakura, strangely, all the bells were carefully lined up in one of two pits, and nothing was buried in the other. From this it has been pointed out that the people who buried these bells may have used the yin-yang thought of ancient China, a way of thinking different from Japan's own old thought. It should not be overlooked, too, that because the bells were buried deep in a valley, a link has been pointed out with the thought of Laozi, founder of Taoism, who was versed in yin-yang.

Laozi thought that there is a valley spirit in a valley, and taught the deep relation between life and valleys: “the valley is the source of the generation of all things and never runs dry.” No trace of valley worship is seen in the Jomon people before the Yayoi, and most Yayoi people did not have this tendency either.

Taking all this into account, it is possible that people with ties to China and Korea, who advanced by way of Izumo Taisha, the gateway into the inland San'in, brought the wisdom of ancient China to this land in a limited way, and that people of this region were influenced by it. Whether they came from across the sea, were local people influenced by a new philosophy, or a mixture of the two can be variously imagined, but nothing is known. From the finds, however, it appears that the Izumo side and the Matsue side had different ways in which cultures overlapped.

Beyond influence from ancient China and Korea, discoveries in San'in over the past thirty years have even made clear that the myths of the Kojiki and Nihon Shoki convey part of historical facts of ancient times.

What on earth happened in ancient Izumo?

Why did the Yayoi people of this region suddenly bury ritual bronzes in one place, and vanish abruptly when the Kofun period followed?

What holds the key to these mysterious questions is the remains of the ancient high-rise shrine of Izumo Taisha, which I mentioned last time, still undiscovered and sleeping underground. If it is found, the movement of unknown people who advanced by way of San'in to Nara (once called Yamato) will come into view. Then not just ancient Japanese history but the accepted account of the history of the emperors will be completely overturned.

My journey through ancient Japanese history will go on, and I will keep conveying to readers the romance of ancient Japan as it really was.