In the news: Yonaguni Monument — natural wonder, or man-made mystery?

Photo by Luke Short

Kevin Short / Special to The Daily Yomiuri

I’m a sucker for ancient mysteries. I’ll sit glued to the TV for hours watching shows debating the location of Atlantis, the true age of the Sphinx or the origin of the huge statues on Easter Island.
Japan also has its share of ancient mysteries. Small but well-preserved stone circles have been found at various sites, and Kuromanta, a low conical hill in Akita Prefecture, is believed by some scholars to be a stepped pyramid covered with earth.

Japan’s world-class ancient mystery, however, lies way to the south. Just off the shore of tiny Yonagunijima island in the southernmost part of Okinawa Prefecture lies an incredible landscape: Rising from depths of 25 meters almost to the surface is an immense structure of fine sandstone. Nearly 250 meters long and 100 meters wide, the structure is cut into series of flat, level terraces, connected by steps with perfect right-angle walls and corners.

Local professional scuba diver Kihachiro Aratake first spotted this marvel in 1986, while searching for good spots to take his scuba diving tours. His immediate impression was that the structure was just too neat and sharp-angled to be the result of natural erosion. To him it looked more like ancient ruins, like those found at Machu Picchu, Peru.

In the 20 years since Aratake’s discovery, the Yonaguni Monument has become the center of an international controversy. Marine geologist Prof. Masaaki Kimura of Ryukyu University has spent more than a decade conducting scientific investigations in and around the site. His conclusions: The monument is a ceremonial center built on land by an ancient civilization, probably at the very tail end of the last glacial period about 10,000 years ago. Later, as the global climate warmed, melting ice caused the seas to rise, covering the monument.

Stalagmite caves, which can form only on land, have been found on the Ryukyu Islands seabed at depths equal to or greater than the base of the monument. This vindicates Kimura’s assessment that the monument would have been on dry land about 10,000 years ago. Some scholars, however, believe that the entire structure is not man-made at all, but simply the result of natural forces.

Had the Yonaguni Monument been, like Machu Picchu or the Egyptian pyramids, built of stone blocks that had been cut and fitted neatly in place, there would be no controversy surrounding its origins. The problem, however, is that all the neat steps and terraces appear to have been chiseled right out of the actual bedrock. Opponents of the man-made theory point out that fine sandstone tends to split open along flat fracture planes, and that the powerful currents off the coast of Yonagunijima island could have sculpted the monument after the rocks had sunk beneath the waves.

Archeology and anthropology also have their say in the debate. National Geographic’s amazing Genographic Project, which is using genetic mutations in Y-chromosomes and mitochondrial DNA to trace the movements of early modern humans across the globe, has identified a unique genetic mutation marker called M-174. This Y-chromosome mutation is one of the oldest. The people (Haplogroup-D) who carry it trekked from northern Africa along the coastlines of south and southeast Asia, then up the Ryukyu Islands to Japan. Even today, many Japanese men still carry this marker.

Skeletal remains of these early migrants have already been discovered in the Ryukyu Islands. The oldest of these has been dated to 32,000 years ago. Kimura’s time frame of 10,000 years ago thus presents no problem in terms of people being present in the Ryukyu Islands.

The issue, however, is that monumental architecture is normally associated only with economies based on intensive agriculture. In Japan, slash and burn dry-field farming is now documented to be at least as old as the middle Jomon Period (ca 10,000 B.C.-ca 300 B.C.), about 6,000 years ago, and settled villages in southern Kyushu have been dated to over 9,000 years ago.

Still, this Jomon agriculture is thought to have been small-scale, and only supplemental to the mainstay hunting, fishing and gathering economy. It was only at the very latest stages of the Jomon Period and beginning of the Yayoi Period (ca 300 B.C.-ca A.D. 300), no more than 3,000 years ago, that intensive cultivation of rice in irrigated paddies was introduced to Japan.

Even so, many of the structures associated with the Yonaguni Monument–two immense monoliths standing on edge side by side; a road at the base swept clear of all debris; round holes that may have held wooden pillars; a nearby rock carved into what from some angles resembles a human face–are cited as proof of a human hand in the making. In addition, rocks in the vicinity of the monument have been incised with lines that resemble primitive pictorial writing, and some human-made stone tools have been recovered from the area.

Taken together, all this evidence seems overwhelmingly in favor of the ancient undersea palace theory. Graham Hancock, famous explorer and author of such bestsellers as Fingerprints of the Gods, is convinced that this is the case, and uses the Yonaguni Monument as a lynchpin of his arguments that a sophisticated civilization existed more than 10,000 years ago, but that its monuments and cities have been inundated by the rising seas.

Critics, however, point out that taken one at a time, each supposed proof remains circumstantial and subject to doubt or at least closer scrutiny. No absolute irrefutable evidence of human work, such as fitted stone blocks or a burial chamber within the structure, has been located to date.

The Yonaguni Monument is a breathtakingly beautiful undersea landscape, and Yonagunijima island is a great scuba and ecotourism destination. As to the origin of the monument, my only advice is to go and see it, then decide for yourself!