Jomon People Who Crossed the Kuroshio Current to the Island

Obsidian on Hachijojima

Obsidian, also known as natural glass, was used as a material for knives, spearheads, arrowheads, and tools for tanning animal hides until the introduction of iron in the Yayoi period, because its edges are as sharp as blades. Obsidian is produced in places like Kozushima and Hakone, but not on Hachijojima. However, obsidian from Kozushima has been found among the stone tools at the Yubama and Kurawa Ruins. This indicates that there has been a close relationship with the northern Izu Islands and the mainland via the sea since ancient times.

How Did the Jomon People Cross the Kuroshio Current?

It is thought that the Jomon people traveled the seas of the Izu Islands from an early period. In an age without sailing ships or compasses, how did the Jomon people cross the Kuroshio Current in dugout canoes to reach Hachijojima?The flow of the main Kuroshio Current sometimes meanders greatly, bypassing the south of Hachijojima, such as when a cold water mass appears off the Izu Peninsula. It is believed that they traveled south along the Izu Islands, island-hopping, and crossed to the island during these brief, short-lived windows of opportunity. The Jomon people of Kurawa must have been a group with advanced dugout canoe handling skills, who could sense the complex currents and wind directions and skillfully take advantage of their chances.

Kuroshio Current Flow Patterns

The Kuroshio Current does not always follow the same path, but flows while changing in various ways. The blue line shows the original flow, but it meanders due to changes in weather conditions and other factors.