A publication of the Archaeological Institute of America
The emergence of Japan's massive keyhole tombs, called kofun, may have been much earlier than previously believed, according to the findings of dendrochronologist Takumi Mitsutani of the Nara National Cultural Properties Research Institute, who has established chronologies for cedar and cypress trees back to the first millennium B.C. Archaeologists had previously dated the beginning of state formation, marked by the appearance of kofun, to the late third or early fourth centuries A.D., based on stylistic dating of mirrors imported from Han and Three Kingdoms-era China discovered in the tombs. By dating wood from a well shaft and a building pillar belonging to the Yayoi period, immediately preceding the appearance of kofun, Mitsutani has established that a pottery style associated with the wood is 100 years older than once thought. Most Japanese archaeologists have accepted this change for the Yayoi, and are assessing the amount of chronological revision needed for the emergence of kofun.
Chinese historical records report diplomatic exchanges in the mid-third century with a Japanese kingdom named "Yamatai," said to have held suzerainty over 30 other polities. Opinion has long divided over whether this kingdom was located in northern Kyushu, the most advanced region during much of the Yayoi period, or in the central Yamato region in Nara, where the earliest kofun are found. If the date for the emergence of kofun is moved back to the mid-third century or earlier, the likelihood that the Chinese were dealing with envoys from Yamato becomes stronger.