Altaicization and De-Altaicization of Japonic and Koreanic

This article discusses 40 grammatical features in Japonic and Koreanic in relation to their neighbouring languages in Northeast Asia. The data comprise 66 modern language varieties of 13 different linguistic affinities, and 12 historical languages (including Old and Middle Japanese and Old and Middle Korean). The results generated from a computational phylogenetic tool show a significant distance in the typological profiles of three main clades: Northeast Asian, Japonic-Koreanic, and Sinitic spheres. Typologically, the Japonic and Koreanic languages form a common grammatical type by sharing up to 26/40 features. By tracing their attestation in the historical languages we can see that the converged grammars are likely to be results of typological Altaicization and de-Altaicization. The combination of linguistic and historical evidence points to a chronology in which Japonic and Koreanic had mutually converged by Altaicization and de-Altaicization, respectively, during the 1st millennium BC and AD before eventually diverging in the 2nd millennium AD.