Archaeological site of Iwajuku

The Controversial Iwajuku Site and the Argument for the Japanese Paleolithic Period


It was once thought that the human habitation of the Japanese archipelago began during the Jōmon period (approximately between 13,000 and 500 BC) This view changed however, with the discovery of Paleolithic sites on the archipelago, which stretched the occupation of Japan by human beings as far back as 30,000 BC. One source even suggests that humans might have inhabited the Japanese islands as far back as 50,000 BC. The first of these Paleolithic sites that was rediscovered is a site known as Iwajuku.

The Discovery of Iwajuku

The study of the Japanese Paleolithic period is said to have only begun relatively recently. It was shortly after the end of the Second World War that the first Japanese Paleolithic site, Iwajuku, was discovered. Prior to this discovery, no Japanese Paleolithic sites had been known to exist. This site is located in Midori, which is situated in the Gunma Prefecture of Honshu’s Kantō region. It was in 1949 that Iwajuku was excavated by archaeologists, though some artifacts were said to have been found at that site three years before that.

Excavating Iwajuku.

Excavating Iwajuku. ( Kiryu International Exchange Association )

Tadahiro Aizawa

The man responsible for this discovery was Tadahiro Aizawa, an amateur archaeologist. Aizawa first found a small flake of obsidian by chance whilst passing along a narrow road in Iwajuku in 1946. He noticed that this flake, which was buried in a layer of red soil, resembled a stone tool known as a microlith, and decided to look for other stone tools or pottery fragments within the same area. Aizawa had expected to find pottery from the Jōmon period, as it was, at that time, the oldest known Japanese culture.

Photo of Tadahiro Aizawa.

Photo of Tadahiro Aizawa. ( Kiryu International Exchange Association )

The amateur archaeologist, however, did not find this. Instead, he found more and more stone tools. Furthermore, it was commonly believed that human beings did not inhabit Japan during the period when the layer of red soil was formed. Thus, Aizawa was greatly puzzled.   

In 1949, Aizawa decided to excavate the red soil layer in order to prove that the Japanese archipelago was already inhabited by humans when this layer was formed. In addition, Aizawa chose to seek the help of professionals in evaluating the site by visiting a professor at a university in Tokyo. Due to the prevailing thinking at that time (that Japan was not inhabited by humans prior to the Jōmon period), the professor was not convinced by Aizawa.

Statue of Tadahiro Aizawa. Photo by woles

Statue of Tadahiro Aizawa. Photo by woles (woles が撮影) ( Public domain )

Nevertheless, Aizawa did not give up, and made repeated visits, though to no avail. In the end, an archaeologist in Meiji University, who was impressed by Aizawa’s perseverance, decided to give him a chance by undertaking further investigations at Iwajuku.

Excavation Locations

Thus, it was decided that Iwajuku should be thoroughly investigated, so as to ascertain what was in the site. Three locations were chosen for the excavation, and were labelled as ‘A’, ‘B’, and ‘C’. From ‘A’, stone tools which were buried between two distinct layers of soil were discovered. This allowed the archaeologists involved to further break down the ‘Iwajuku Era’ into separate ages. ‘B’ was the place where Aizawa had first excavated, whilst the excavation of ‘C’ yielded many pottery fragments from the earliest Jōmon period in the black layer of soil above the red soil.

Although no stone tools were discovered in the red soil of this area, it proved that those from the red soil of ‘A’ and ‘B’ were from a culture that predated even the earliest known Jōmon culture.

An aerial view of the Iwajuku site.

An aerial view of the Iwajuku site. ( Kiryu International Exchange Association )

The discovery of Iwajuku was a major discovery that stimulated archaeological interest in Japan, as it proved that the human habitation of the country was much older than previously thought. In the years following the discovery of Iwajuku, many other ‘Iwajuku Era’ sites were discovered all over Japan.

It has been estimated that the total number of such sites excavated to date is over 3,000. It may be worth pointing out that, in the past, excavations would stop when the Jōmon cultural layer ended, due to the belief that there was nothing else that was archaeologically significant below them. Recent excavations, however, have confirmed that Paleolithic material has been found in many sites below layers containing artifacts from the Jōmon period.

Featured image: Archaeological site of Iwajuku. Photo source: Geocities

By Ḏḥwty


Bahn, P., 2014. The History of Archaeology: An Introduction. New York: Routledge.

Ikawa-Smith, F., 1978. The History of Early Palaeolithic Research in Japan. In: F. Ikawa-Smith, ed. Early Paleolithic in South and East Asia. The Hague: Mouton Publishers, pp. 247-286.

Imamura, K., 1996. Prehistoric Japan: New Perspectives on Insular East Asia. Honolulu: University of Hawai'i Press.

Kipfer, B. A., 2000. Encyclopedic Dictionary of Archaeology. New York: Springer.

Kiryu International Exchange Association, 2015. About the Iwajuku Archeological Site. [Online]
Available at:


Really fine post, I definitely adore this website, keep on it.

That sounds very plausible. Another interesting thing to consider is there were megalithic sites investigated by Graham Hancock. A lot of these were underwater. Any large buildings could be considered Neolithic or agricultural at the minimum.

Troy Mobley

Register to become part of our active community, get updates, receive a monthly newsletter, and enjoy the benefits and rewards of our member point system OR just post your comment below as a Guest.

Next article