「古日本語」のルーツは

　偏堡文化　→　ムムン文化　→　弥生文化

で決着ついてる


"An archaeological explanation for the diffusion theory of the Japonic and Koreanic Languages" Miyamoto, Kazuo (Kyushu University)
「原日本語・原韓国語伝播説を考古学的に考える」 宮本一夫 (九州大学)

Table 1. Cultural change in the four stages of agricultural development in Northeast Asia
https://image.prntscr.com/image/zSriyVD1TsSC9enXk3lB-A.png


Stage 1 (c.3300 BC)
　Crop: millet (雑穀)
　Tools: Stone mortar and pestle, hoe (石臼, すりこ, くわ) [from NW KorPen to KorPen, sRFE]
　Culture: Chulmun (櫛目文土器文化) [from Middle western KorPen to Southern KorPen] (西朝鮮〜南朝鮮)
　Replacing: Early Neolithic Korea
　Society: Horticulture

Stage 2 (c.2400 BC)
　Crop: wet-rice (水稲)
　Tools: pol. stone axe, adze, reaper (磨製石斧, 鍬, 穂摘み具) [from Shandong P. to Liaodong P.]
　Culture: Pianpu (偏堡文化) [from Eastern Liaoxi district to Liaodong] (東遼西〜遼東)
　Replacing: Wujiacun culture
　Society: Millet farmer

Stage 3 (c.1500 BC)
　Crop: irrig. wet-rice, millet, wheat (灌漑水稲, 雑穀, 麦)
　Tools: pol. stone axe, adze, reaper (磨製石斧, 鍬, 穂摘み具) [from Shandong P. to Liaodong P. >KorPen]
　Culture: Mumun (ムムン文化) [from Liaodong to Southern KorPen] (遼東〜南朝鮮)
　Replacing: Final Neolithic Korea
　Society: Rice farmer and rise of chiefs

Stage 4 (8c BC)
　Crop: irrig. wet-rice (灌漑水稲)
　Tools: pol. stone adze, reaper (磨製石鍬, 穂摘み具) [from Southern KorPen to N. Kyushu]
　Culture: Yayoi (弥生文化) [from Southern KorPen to Northern Kyushu] (南朝鮮〜北九州)
　Replacing: Jomon
　Society: Rice farmer