During the Ice Age, the East China Sea was mostly dry land, so that Yonaguni was the southern end of a land bridge that connected it to Taiwan, Ryūkyū, Japan and Asia.
During the Ice Age, the East China Sea was a narrow bay opening to the ocean at today's Tokara Gap. Therefore, Yonaguni was the southern end of a land bridge that connected it to Taiwan, Ryūkyū, Japan and Asia.