i know from what i've studied, i believe the oldest known skeleton found in japan was believed to be at least 400,000 years old. there's a popular idea that because the japanese are much taller than their asian neighbors, there might have been some siberian influence, maybe even european at some point. correct me if im wrong, but the Ainu, being the indegnious class of japan shared alot of characteristics that weren't "typical asian." i also read in another book that some types of tools were excavated in northern honshu that didn't appear to be japanese at all, but norse. with language, the same can be considered of the entire world. it changes with times, based on legitamacy in religion, leadership, ect. not to mention being modified over such a long period of time. its my opinion that it did derive from korean and chinese influence, maybe brought with the first buddists. and eventually added on to. mexican spanish is another great example. spaniards taught the aztrecs their language for trade and missionary purpose but today its more or so a refined mexi-spainish-aztec language. adhering to their own culture and grammar.