History of the Ryukyu Islands  This article is about the history of the Ryukyu Islands southwest of the main islands of Japan. The name "Ryūkyū" originates from Chinese writings. The earliest references to "Ryūkyū" write the name as 琉虬 and 流求 () in the Chinese history "Book of Sui" in 607. It is a descriptive name, meaning "glazed horn-dragon". The origin of the term "Okinawa" remains unclear, although "Okinawa" (Okinawan: Uchinaa) as a term was used in Okinawa. There was also a divine woman named "Uchinaa" in the book "Omoro Sōshi", a compilation of ancient poems and songs from Okinawa Island. This suggests the presence of a divine place named Okinawa. The Chinese monk Jianzhen, who traveled to Japan in the mid-8th century CE to promote Buddhism, wrote "Okinawa" as 阿児奈波 (). The Japanese map series Ryukyu Kuniezu labeled the island as in 1644. The current Chinese characters (kanji) for Okinawa (沖縄) were first written in the 1702 version of Ryukyu Kuniezu. The ancestry of the modern-day Ryukyuan people is disputed. One theory claims that the earliest inhabitants of these islands crossed a prehistoric land bridge from modern-day China, with later additions of Austronesians, Micronesians, and Japanese merging with the population. The time when human beings appeared in Okinawa remains unknown. The earliest human bones were those of Yamashita Cave Man, about 32 000 years ago, followed by Pinza-Abu Cave Man, Miyakojima, about 26 000 years ago and Minatogawa Man, about 18 000 years ago. They probably came through China and were once considered to be the direct ancestors of those living in Okinawa. No stone tools were discovered with them. For the following 12 000 years, no trace of archaeological sites was discovered after the Minatogawa man site. Okinawa midden culture or shell heap culture is divided into the early shell heap period corresponding to the Jōmon period of Japan and the latter shell heap period corresponding to the Yayoi period of Japan. However, the use of Jōmon and Yayoi of Japan is questionable in Okinawa. In the former, it was a hunter-gatherer society, with wave-like opening Jōmon pottery.