How one of Earth’s worst volcanic disasters affected societies in prehistoric Japan

A new international study led by Lund University examines what happened to population levels after the Kikai-Akahoya volcanic eruption in prehistoric Japan. The results paint a more complex picture than what had previously been believed. The paper is published in the journal Science Advances.

The Kikai-Akahoya eruption took place in Japan some 7,300 years ago. At the time, Jomon foraging communities lived in Japan, surviving as hunter-gatherers.

“This eruption must have been devastating, exploding out of the seabed with little warning. It battered the Japanese islands with powerful earthquakes and enormous tsunamis, and then blanketed the landscape with meters of volcanic ash,” explains senior author Peter Jordan, professor of archaeology at Lund University.

The consequences of the eruption have been widely debated by archaeologists for decades. Some argue that it was an ‘apocalypse’ in which all human life abruptly ended closest to the epicenter, while others have started to argue for the survival of local populations, even in areas quite close to the eruption.

The research team found that both these versions—total collapse or continuity—were too simplistic.

On the one hand, populations did decline, as ecosystems suffered and areas became uninhabitable. On the other hand, the researchers found evidence that humans were resourceful in the face of dire circumstances. In some cases, the population increased in the period after the eruption.

“The disaster caused major loss of life. However, survivors migrated, forged new social relations, innovated new kinds of economy, and appear to have found creative ways to exist and later thrive in the new post-disaster conditions,” says lead author Enrico Crema, professor at Cambridge University.

According to Jordan, the research demonstrates how unpredictable and complex the aftermath of a major disaster can be.

“This study helps in creating a deeper understanding of the contingent ways in which cultures and societies cope with sudden shocks and catastrophes. Even in the most impossible situations, survivors and communities have choices, however limited: they need to act and make decisions, they need to adjust, collaborate and find new connections and social networks,” he concludes.

Population patterns identified by the study

Jomon forager populations were already in decline in southern Kyushu long before the eruption, and so the disaster hit a region that was already sparsely populated and only being visited by highly mobile groups.

Populations were growing in northern Kyushu and this population growth trend continued right through the disaster and its aftermath, despite the massive and enduring damage to ecosystems. The authors suggest this resilient growth trend may be the result of ‘refugees’ moving out of the worst-hit areas immediately after the disaster.

Inland survivors appear to have moved away and clustered along northern coastlines, where marine ecosystems quickly recovered. Population growth may have been accelerated by new kinds of adaptation focusing on exploiting the abundant resources of the sea.

The more distant areas of Japan had experienced population growth prior to the eruption, but saw demographic stagnation or even decline after the disaster. These far-reaching effects have never been identified before, and may be linked to short-term climate change triggered by the eruption, or to catastrophic tooth attrition among the deer and boar that the Jomon relied on for their food supplies (possibly a consequence of the animals grazing in ash-covered landscapes), or to a suite of other volcanic impacts on human health and well-being.

Who’s behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries.

Full profile →

Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

Full profile →