According to Mark J. Hudson, in Ruins of Identity, University of Hawaii Press, 1999, the Japanese islands were settled by populations from Southeast Asia and/or South China during the Pleistocene (epoch before the Holocene). They were the ancestors of the Jomon who occupied the islands from the beginning of the Holocene (approximately 11,500 years before present) until the end of the Jomon period. The Yayoi period began in 300 BCE. with the influx of Northeast Asian people who spread through the islands from Kyushu to Tohoku during the next six hundred years until the Kofun period began in 300 CE.
There was a single parent Jomon language, Proto-Japanese, which existed before the texts of the 8th century (Kojiki and Nihon Shoki) . Hudson reserves the term Japanese to refer to the population beginning in the Yayoi period that was the admixture of the indigenous Jomon with the Continental immigrants.
He points out that “the most noticeable things… is the comparative lack of linguistic variation in Ainu, Japanese, and Ryukyuan. Many Japanese linguists assume that Japanese has a long history stretching back into the Jomon period for 10,000 years or more, e.g., Sakiyama 1969, 169.” This quote is from Hudson, p 92, and the italics are Hudson’s.
The Northern Kyushu dialect should be the oldest, based on the movement of the immigrating people. However, there is the lack of variations as mentioned above. There is a “relative uniformity of dialects,” p 96, considering the 10,000 years of history.
Commentary by WositeWorld
WoshiteWorld has been providing information about the Wosite language of the Jomon period. Wosite corresponds to Hudson’s “Proto-Japanese.” Hudson has emphasized the uniformity of dialects through the Japanese islands. That phenomenon may be due, whether in part or in large measure, to the efforts of the Hutakami who unified the Wosite language and the population as they created the kuni called Yamato. See Awanouta and other posts about kuni-umi.