Yayoi (弥生時代) is an era in Japan from 300 BCE to CE 250. It is named after the section of Tōkyō where archaeological investigations uncovered its trace. Yayoi period is marked either by the start of the practice of growing rice in a paddy field or a new Yayoi style earthenware.
Following the Jōmon period, the Yayoi flourished between about 300 BCE and 250 CE from southern Kyūshū to northern Honshū. Modern discoveries believe that it started early as 900 BCE. Because of the seemingly abrupt and dramatic cultural change especially as it was considered a half millennium as shorter, it was once generally assumed that the Yayoi culture did not develop directly from the Jōmon, but that the Yayoi were a people who migrated from the Asian mainland. A recent discoveries like evidences of farming rice on a dry clop of land that predates a paddy field and the fact that the genetic makeup of Japanese rice is similar to that of sticky rice that came from Laos made the following theory mostly obsolete.
As Korea is the most accessible location, a theory publicized in early Meiji period in Japan argued that these immigrants were Korean most likely of the Goguryeo or the Baekje. This theory is confounded by the fact that there is no obvious similarity between the modern Korean and ancient Japanese languages and that it is unlikely that an upward of 4 million people which is needed to fill the population gap between Jōmon and Yayoi period, could have migrated in such a short time. On the other hand, grammatical structures are similar between the 2 languages, and some aspects of Japanese language closely resemble that of the Goguryeo. Historians such as Jared Diamond have theorized that the Yayoi may have been related to the Goguryeo or the Baekje, tribes that were eventually incorporated into the medieval Korean state. Information on the Goguryeo language is limited, but analysis by Christopher Beckwith and others appears to support a connection to ancient Japanese.
The current theory is that the Yayoi culture did emerge out of the Jōmon culture with only a limited immigration from Baekje upon its extinction. The practice of farming rice that was once believed to be passed on from China trespassing the Korean peninsula is instead recognized to have been passed from southern China by the way of Okinawa and passed onto southern Korea.
The earliest Yayoi people, themselves using chipped stone tools, appear to have started from northern Kyūshū and intermixed with the Jōmon. Although the pottery of the Yayoi was more technologically advanced--produced on a potter's wheel--it was more simply decorated than Jōmon ware. The Yayoi made bronze ceremonial nonfunctional bells, mirrors, and weapons and, by the 1st century CE, iron agricultural tools and weapons. As the population increased and society became more complex, they wove cloth, lived in permanent farming villages, constructed buildings of wood and stone, accumulated wealth through landownership and the storage of grain, and developed distinct social classes. Their irrigated, wet-rice culture was similar to that of central and south China, requiring heavy inputs of human labor, which led to the development and eventual growth of a highly sedentary, agrarian society. Unlike China, which had to undertake massive public works and water-control projects, leading to a highly centralized government, Japan had abundant water. In Japan, then, local political and social developments were relatively more important than the activities of the central authority and a stratified society.
The earliest written records about Japan are from Chinese sources from this period. Wa 倭 (the Japanese pronunciation of an early Chinese name for Japan) was first mentioned in 257. Early Chinese historians described Wa as a land of hundreds of scattered tribal communities, not the unified land with a 700-year tradition as laid out in the Nihongi, which puts the foundation of Japan at 660 BCE. 3rd century Chinese sources reported that the Wa people lived on raw vegetables, rice, and fish served on bamboo and wooden trays, had vassal-master relations, collected taxes, had provincial granaries and markets, clapped their hands in worship (something still done in Shintō shrines), had violent succession struggles, built earthen grave mounds, and observed mourning. Himiko, a female ruler of an early political federation known as Yamatai, flourished during the 3rd century. While Himiko reigned as spiritual leader, her younger brother carried out affairs of state, which included diplomatic relations with the court of the Chinese Kingdom of Wei (220-265 CE).
A recent study
A new study that used AMS method to analyze carbonized remain on potteries and wooden stakes discovered that these were dated back to 900-800 BCE, nearly 500 years earlier than previously believed. These artifacts came from the northern region of Kyūshū and to further confirm this finding, artifacts of the same time period from Korea and Tohoku's Jōmon earthware were compared with the same result. Another researcher used different artifacts from similar Yayoi period sites and found that these were dated back to 400-500 BCE.