Beginning about the fourth century B.C., Jomon culture was gradually replaced by the more advanced Yayoi culture, which takes its name from the site in Tokyo where pottery of this period was first discovered in 1884. The new culture first appeared in western Japan and then spread east and north to Honshu. While some aspects of Yayoi society evolved from the Jomon, more important to its development was the technique of wet-rice cultivation, which is thought to have been introduced to Japan from Korea and southeastern China sometime between 1000 B.C. and the first century A.D. In keeping with an agrarian lifestyle, the people of the Yayoi culture lived in permanently settled communities, made up of thatched houses clustered into villages.
In striking contrast to Jomon pottery, Yayoi vessels have clean, functional shapes. Nonetheless, the technical process of pottery making remained essentially the same, and in all likelihood women using the coil method continued to be the primary producers. Two technical differences, however, are significant: the fine clay surfaces of Yayoi vessels were smoothed, and clay slip was sometimes applied over the body to make it less porous. Many Yayoi vessels resemble pots found in Korea, and some scholars have proposed that the Yayoi style originated in that land, arriving first in northern Kyushu and gradually spreading northeastward. Nevertheless, some pieces clearly show the influence of Jomon ceramics, leading others to speculate that Yayoi wares were the product of an indigenous evolution from the less elaborate Jomon wares of northern Kyushu.
Metallurgy was also introduced from the Asian mainland during this time. Bronze and iron were used to make weapons, armor, tools, and ritual implements such as bells (dotaku). The latter were frequently decorated with hatched lines, triangles, spirals, and geometric patterns, although representations of domesticated animals and scenes of daily life appear on some examples.
A class society began to emerge during the Yayoi period. Over time, the Yayoi people grouped themselves into clan-nations, which by the first century numbered more than a hundred. Throughout the second and third centuries, the clans fought among themselves until the Yamato clan gained dominance in the fifth century.