Proto-Japonic, the common ancestor of the Japanese and Ryukyuan languages, is thought to have been brought to Japan by settlers coming from the Korean peninsula sometime in the early- to mid-4th century BC (the Yayoi period), replacing the languages of the original Jōmon inhabitants,[4] including the ancestor of the modern Ainu language. Very little is known about the Japanese of this period. Because writing had yet to be introduced from China, there is no direct evidence, and anything that can be discerned about this period must be based on reconstructions of Old Japanese.