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The ancestor of the Ryukyuan branch was dated to around the 9th century, which coincides with the first traces of cereal farming in Amami and Okinawa between the 8th and 10th centuries, suggestive of the Japonic population movements into the islands that would become contemporary Ryukyuan.

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The topology of Ryukyuan largely followed geography. A Northern Ryukuan clade emerged with clear Amami and Okinawa subgroups. Within Southern Ryukyuan, Miyako formed a clear subgroup, but a monophyletic Macro-Yaeyama did not emerge consistently due to uncertainties around Hateruma and Yonaguni.

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The ancestor of the contemporary Japanese lects was dated to the 12th century. This is puzzling given attested differences between the central and eastern varieties of Old Japanese (8th century). Later dialect levelling/replacement is one explanation, but further targeted work is needed.

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The topology of Japanese neatly unifies the East-West and center-periphery divisions recognised in traditional Japanese dialectology. The Tohoku lects split from the ancestor first; the Central Japanese clade diverged into “core” (the Kyoto-Nara area) and “peripheral” lects (including Kyushu).

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The Japanese-Ryukyuan split was dated at 500–400 BCE. This coincides with the influx of Bronze Age rice agriculturists during the Yayoi Period, supporting a language-with-farming dispersal. Thanks to the phonotactic data, we can report this with greater certainty than Lee and Hasegawa (2011).

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Our analyses strongly support a primary split between mainland Japanese and Ryukyuan, in line with traditional views in dialectology and work in (computational) historical linguistics, and contrasting with the (recently revived) proposal grouping the Kyushu and Ryukyu lects together.

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Inspired by Jayden Macklin-Cordes’ work, we combined lexical data with phonotactics to present an updated phylogeny for Japonic, which includes a more extensive sample of Ryukyuan lects than previous studies. We thank the Scandinavia-Japan Sasakawa Foundation for supporting this research.

New paper out in the Journal of Language Evolution, with @bonniemclean.bsky.social and Chieh-Hsi Wu: “Combined lexical and phonotactic data resolves uncertainties in the evolutionary diversification of the Japonic language family” doi.org/10.1093/jole...
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