Climate and currents shaped Japan’s hunter-gatherer cultures

New climate records from a peat bog show how two neighboring cultures responded differently to shifts in climate and ocean currents.

eos.org -- May 05
The island prefecture of Hokkaidō, Japan’s second-largest island, has a rich cultural history of hunter-gatherers both on land and at sea.

Over thousands of years through the Holocene and into the 19th century, the prevalence of these cultures across the island waxed and waned. Climate oscillations and changing seas were likely important factors in these cultural shifts, a new study shows.

Historically, Hokkaidō was home to two main types of subsistence cultures: land-based hunter-gatherers, such as the Zoku-Jomon and Satsumon peoples, and seafarers like the Okhotsk people. The Zoku-Jomon and Satsumon peoples gathered and likely managed millet, barley, and beans, whereas the Okhotsk primarily fished, hunted for marine mammals such as seals, and collected other marine foods. Each group is ancestral to the contemporary Ainu people.

Historical records and archaeological evidence of these three cultures span thousands of years, from 8,000 years before the present to the late 19th century, when modern lifestyles began to replace hunter-gatherer culture. Historians and scientists thought shifts in which cultures were dominant and where they were located could be related to climate, but evidence to robustly connect the dots was lacking.

In search of an answer, paleoclimatologists Masanobu Yamamoto and Osamu Seki, both of Hokkaidō University in Japan, turned to a bog on Rishiri Island, north of Hokkaidō, to test whether its deep peat deposits could hold clues to past climates. With students in tow, the two researchers extracted 5-meter bog cores comprising mostly peat moss commonly found in subpolar bogs worldwide. The researchers carbon-dated the core and analyzed the oxygen isotopic composition of cellulose in the peat moss and grasses as oxygen isotopes in plants are related to climatic factors like precipitation, humidity, and water source. ...continue reading