Back in the late 1970s, the city planners of Karatsu, a fishing community on the northern coast of Kyushu, decided to build a new road. This provided a rare opportunity for local archaeologists. Seizing the chance to burrow with abandon in the densely developed region, they established a dig and began to search for pollen and seeds from ancient plants (among other buried treasures).

One day, they mixed a scoop of soil with water to separate out the pollen, and something unexpected floated to the top: a handful of tiny black discs. It turned out to be carbonized millennia-old rice that would soon lead them to the oldest paddy fields ever discovered in Japan.

"Reporters were calling around the clock," recalls Ryuuta Tajima, who was a young researcher at what came to be known as the Nabatake Ruins, and who today directs the Matsurokan Museum built on the site in Saga Prefecture.