The Yayoi period (弥生時代, Yayoi jidai?) is an Iron Age era in the history of Japan traditionally dated 300 BC to AD 300. It is named after the neighborhood of Tokyo where archaeologists first uncovered artifacts and features from that era. Distinguishing characteristics of the Yayoi period include the appearance of new pottery styles and the start of an intensive rice agriculture in paddy fields. Techniques in metallurgy based on the use of bronze and iron were also introduced in this period. A hierarchical social class structure also emerged in this period. The Yayoi followed the Jōmon period (13,000–400 BC) and Yayoi culture flourished in a geographic area from southern Kyūshū to northern Honshū.
Yayoi people is loosely defined by new pottery cultures that emerged since 300BC, the problem left is to see, which mtdna is absent before 300 or 500BC, if none, yayoi people essentially shared the same mtdna with jomon and ainu. At least, the origin of yayoi is still not established historically, how can one say yayoi people genetically were absent from Japan before 300BC? Maybe they had been in Japan for some millania without distinguishing themself culturally. The cultural emergence of yayoi is not equal to physical emergence, the two may be several thousand years apart, and we can not be sure yet. After all the recent history of Yayoi is a new anthropological theory, not a recorded history, yayois genetic profile is to be misinterpreted by limited personal understanding of japanese history.