Evolution of Lexical Morphology in Old Japanese Sources and Evolutionary Psychology of Language Yekaterina Shmaevskaia Independent Scholar Astana, Kazakhstan Key words: adjectival morphology; prototypical meaning; evolutionary psychology of Japanese language; Thesis for discussion: ✔ Taking the view that race and language are separate concepts, a dozen of papers proposed that the Japanese language arrived in the Japanese archipelago in the Yayoi Period. The evidence is drawn from both archaeology and anthropology, and demonstrates that the bearers of Yayoi culture had a radically different culture from the Jomon, thus making likely the introduction of a new language unrelated to the language(s) of Jomon period. ✔ Japonic was the language of the Yayoi culture. Archaeological research research has long ago established an extremely fitting framework for the above conclusions. In this framework, the insular expansion of Japonic is connected with the Yayoi culture. ✔ Data from Old Japanese sources is quite transparent in demonstrating that “… the system of verb-like inflection in Western Old Japanese was still in the process of establishing itself, and that originally pre-Old Japanese adjectives behaved quite similar to adjectives in Turkic, Mongolic, and Tungusic, that is they were nominals rather than verbs” (Vovin 2020, 429). Corpora help in understanding that from the semantical point of view “...meaning of these words did not stay the same over time – the limits of their change are extended. The same word can be divided into several homonyms, and when analyzing its semantics, each meaning acts like a set of components” (Syromyatnikov 1972, 67).