QUOTE (PingLing @ Oct 26 2009, 07:21 AM)

Jomon - Ainu or/and aborigines from Taiwan and Ryukyu (Malay?). I am not really sure about Jomon people.
Some believe that Jomon was comprised of early Austronesian speakers. Others think that they were mixed with "northern Australoids." In either case, it is likely that they were an early proto-population that spread across the world tens of thousands of years ago, and became "trapped" on the Japanese islands when the sea levels rose. It is also likely that they were not homogeneous.
QUOTE
Yayoi - Korean and Chinese
Current research indicates that the Yayoi expansion started even earlier than previously thought - ie in 800 BC, well before there was a common "Korean" or "Chinese" identity. Thus, the immigrants/invaders would not have considered themselves "Korean" or "Chinese," but would've instead identified with the particular ethnic landscape of East Asia around 800 BC. At that time, the Western Zhou Dynasty maintained feudal overlordship in China, but the so-called "Yi" and "Man" were still active players. Meanwhile, Manchuria and the Korean peninsula was populated by various tribes which left no written records, and are so difficult to assess.
It is believed that the early Japanese had no written records. Consequently, it is unlikely that they were related to the Chinese aristocracy, which by 800 BC had already developed writing. If this group had immigrated to Japan to any large extent, they would've brought writing with them and we would've had continuous records, in all likelihood, from 800 BC onwards. But we don't, and so just as in the case of Manchuria and Korea, it is unlikely that the Chinese aristocracy, from either the Shang, the Zhou, or the early Warring States were present.
But what about non-aristocratic immigrants from China? This is plausible, as Japanese archaeologists have discovered archaeological and anthropological similarities between coastal sites in China and early Japan, and we also see that the majority of O3 haplogroups in Japan are O3a5, which is associated specifically with Sino-Tibetan populations. These could've been carried over to Japan by early proto-Chinese groups like the "Yi" and "Man," who were spread across the Chinese coast during the Zhou period, or later Chinese groups, ie merchants (later migrations are not contradictory as Japan adopted Chinese writing at some point in time).
Either way, they were joined by large groups of immigrants from early Manchuria and Korea, who came to Japan in waves starting from the early Yayoi period. These people would've brought agricultural techniques, largely known across in Asia by that time, and such technologies as bronze. Since Manchuria and Korea did not appear to have its own writing system in 800 BC, the lack of written records in early Japan is concordant with such an expansion. These people would've met with earlier Jomon natives, and either mixed with and/or displaced them (mixed is currently the more accepted theory).