The classification of the Japonic languages and their external relations is unclear. Linguists traditionally consider the Japonic languages to belong to an independent family; indeed, until the classification of Ryukyuan and eventually Hachijō as separate languages within a Japonic family rather than as dialects of Japanese, Japanese was considered a language isolate.
Among more distant connections, the possibility of a genetic relationship to language families like Austronesian or Kra–Dai is discussed. A relation between Japonic and Koreanic is also considered plausible by some linguists, while others reject this idea. Independent of the question of a Japonic–Koreanic connection, both the Japonic and Koreanic languages are sometimes included in the now largely discredited Altaic family."While 'Altaic' is repeated in encyclopedias and handbooks most specialists in these languages no longer believe that the three traditional supposed Altaic groups, Turkic, Mongolian and Tungusic, are related." Lyle Campbell & Mauricio J. Mixco, A Glossary of Historical Linguistics (2007, University of Utah Press), pg. 7."When cognates proved not to be valid, Altaic was abandoned, and the received view now is that Turkic, Mongolian, and Tungusic are unrelated." Johanna Nichols, Linguistic Diversity in Space and Time (1992, Chicago), pg. 4."Careful examination indicates that the established families, Turkic, Mongolian, and Tungusic, form a linguistic area (called Altaic)...Sufficient criteria have not been given that would justify talking of a genetic relationship here." R.M.W. Dixon, The Rise and Fall of Languages (1997, Cambridge), pg. 32."...[T]his selection of features does not provide good evidence for common descent....we can observe convergence rather than divergence between Turkic and Mongolic languages--a pattern than is easily explainable by borrowing and diffusion rather than common descent," Asya Pereltsvaig, Languages of the World, An Introduction (2012, Cambridge). This source has a good discussion of the Altaic hypothesis on pp. 211-216.
Primary language family The currently most supported view is that the Japonic languages are their own primary language family, consisting of Japanese and the Ryukyuan languages. The Hachijō language is sometimes classified as a third branch of the Japonic language family, but it is otherwise seen to be a very divergent dialect of Eastern Japanese.Thomas Pellard. The comparative study of the Japonic languages. Approaches to endangered languages in Japan and Northeast Asia: Description, documentation and revitalization, National Institute for Japanese Language and Linguistics, Aug 2018, Tachikawa, Japan. ffhal-01856152
It has been suggested that the linguistic homeland of Japonic may be located somewhere in southern, south-eastern, or eastern China prior to a hypothetical migration of proto-Japanese to the Korean Peninsula and the Japanese archipelago.RECONSTRUCTING THE LANGUAGE MAP OF PREHISTORICAL NORTHEAST ASIA - Juha Janhunen Studia Orientalia 108 (2010) Miyamoto suggests a homeland further north, around modern day Liaoning.Archaeological Explanation for the Diffusion Theory of the Japonic and Koreanic Languages - MIYAMOTO Kazuo Koreanic speakers, then established in Manchuria, expanded southward to the Korean peninsula, displacing Japonic speakers that had been living there and causing the Yayoi migrations into Japan.
It is believed that rice farming spread to Japan from the Yangtze River Delta to the Shandong peninsula, then to the Liaodong peninsula, and finally to the Korean peninsula, from where it was directly introduced to the Japanese archipelago. One hypothesis proposes that Japonic originated in Shandong and was transmitted to Japan by migrating rice farmers following this route, crossing the Bohai sea to Liaodong.
Vovin suggests that Japonic languages were spoken in parts of Korea, especially southern Korea, and were then replaced and assimilated by proto-Korean speakers. Similarly, Whitman (2012) suggests that Japonic is not related to Korean but that Japonic was present on the Korean peninsula during the Mumun pottery period (Yayoi people). According to him, Japonic arrived in the Korean peninsula around 1500 BC and was brought to the Japanese archipelago by the Yayoi at around 950 BC. In this scenario, the language family associated with both Mumun and Yayoi culture is Japonic. Koreanic arrived later from Manchuria to the Korean peninsula at around 300 BC and coexisted with the descendants of the Japonic Mumun cultivators (or assimilated them). Both had influence on each other and a later founder effect diminished the internal variety of both language families.
Most linguists today see the Japonic languages as their own distinct family, not related to Korean, but acknowledge an influence from other language families (and vice versa). Vovin (2015) shows evidence that the early Koreans borrowed words for rice cultivation from Peninsular Japonic. According to him, the middle Korean word psʌr (rice) is loaned from Peninsular Japonic *wasar.
Juha Janhunen (2003) proposed that the Japonic languages originated on the coast of the Shandong Peninsula, and that they originally had similar typological characteristics to the Sinitic languages before they acquired Altaic typological features through contact with the Koreanic languages on the Korean Peninsula.
The linguists Yurayong and Szeto in 2020 analyzed the stages of convergence between Japonic and other languages. They concluded that "our results indirectly speak in favour of a "Paleo-Asiatic" origin of the Japonic languages".
Chaubey and van Driem (2020) propose that the Japonic languages may have already been present in Japan during the early Jōmon period. They suggest that the Japonic languages were already present within the Japanese archipelago and coastal Korea, before the Yayoi period, and can be linked to one of the Jōmon populations of southwestern Japan, rather than the later Yayoi or Kofun period rice-agriculturalists. Japonic-speakers then expanded during the Yayoi period, assimilating the newcomers, adopting rice-agriculture, and fusing mainland Asian technologies with local traditions.
Possible external relations
Japonic-Koreanic theory There is disagreement over the protohistorical or historical period during which this expansion occurs, ranging from the Korean Bronze Age period to the Three Kingdoms of Korea period. As there is disagreement among experts when the expansion of Koreanic languages started, there is room for interpretation on the proto-historical and historical extent of the Japonic language presence in the central and southern Korean peninsula.
Similarities between Japanese and Koreanic languages
History Japanese and Korean languages also share some typological similarities, such as an agglutinative morphology, a subject–object–verb (SOV) normal word order, important systems of honorifics (however, the two languages' systems of honorifics are different in form and usage; see Japanese honorifics and Korean honorifics), besides a few lexical resemblances. Factors like these led some historical linguists to suggest a genetic relationship between the two languages.
William George Aston suggested in 1879 in the Journal of the Royal Asiatic Society that Japanese is related to Korean. A relationship between Japanese and Korean was endorsed by the Japanese scholar Shōsaburō Kanazawa in 1910. Other scholars took this position in the twentieth century (Poppe 1965:137). Substantial arguments in favor of a Japanese–Korean relationship were presented by Samuel E. Martin, a leading specialist in Japanese and Korean, in 1966 and in subsequent publications (e.g. Martin 1990). Linguists who advocate this position include John Whitman (1985) and Barbara E. Riley (2004), and Sergei Starostin with his lexicostatistical research, The Altaic Problem and the Origins of the Japanese Language (Moscow, 1991). A Japanese–Korean connection does not necessarily exclude a Japanese–Koguryo or an Altaic relationship.
Evidence After filtering out early loanwords, following a procedure suggested in 2010 by Alexander Vovin, Whitman (2012) tries to isolate potential cognates substantially more rigorously than in older literature, including his own works, affirming a relationship between Japonic and Korean, but he stresses that it is relatively distant.
Similarly, a 2016 paper proposing a common lineage between Korean and Japanese claims to trace around 500 core words that show a common origin, including several numerals such as 5 and 10.
Martine Robbeets and Remco Bouckaert from the Max Planck Institute for the Science of Human History used in 2018 for the first time a Bayesian phylogenetic inference analysis about "Transeurasian". Their study resulted in a "high probability" for a "Koreano-Japonic" group, but has not gained acceptance among mainstream linguists.
Criticism Many variants of this theory have been criticized for serious methodological flaws, such as rejecting mainstream reconstructions of Chinese and Japanese for less accepted alternatives. Other critics, like Alexander Vovin and Toh Soo Hee, argued that the connections between Japanese and Goguryeo are due to earlier Japonic languages that were present in parts of Korea, and that the Goguryeo language was closer to Sillan, and by extension, Korean.Toh Soo-Hee (2005). "About Early Paekche Language Mistaken as Being Koguryo Language". Journal of Inner and East Asian Studies. 2(2): 10–31. Further studies (2019) deny and criticize a relation between Korean and Japanese. Vovin also argues that the claimed cognates are nothing more than early loanwords from when Japonic was still spoken in southern Korea.
Similarly, Whitman (2011) concludes that the proto-Koreans arrived in the southern part of the Korean Peninsula at around 300 BC and coexist with the native descendants of the Japonic Mumun rice-cultivators (or assimilated them). Both had influence on each other, and a later founder effect diminished the internal variety of both language families, making them more similar. Thus Whitman sees a possible relation between Japonic and Koreanic as unlikely.
The idea of a Japanese–Korean relationship overlaps the extended form of the Altaic hypothesis (see below), but not all scholars who argue for one also argue for the other. For example, Samuel Martin, who was a major advocate of a Japanese–Korean relationship, only provided cautious support to the inclusion of these languages in Altaic, and Talat Tekin, an Altaicist, includes Korean, but not Japanese, in Altaic (Georg et al. 1999:72, 74).
Possible connection between Japonic and Koguryoic The Japanese–Koguryoic proposal dates back to Shinmura Izuru's (1916) observation that the attested Goguryeo numerals—3, 5, 7, and 10—are very similar to Japanese. The hypothesis proposes that Japanese is a relative of the extinct languages spoken by the Buyeo-Goguryeo cultures of Korea, southern Manchuria, and Liaodong. The best attested of these is the language of Goguryeo, with the more poorly attested Koguryoic languages of Baekje and Buyeo believed to also be related.
A monograph by Christopher Beckwith (2004) has established about 140 lexical items in the Goguryeo corpus. They mostly occur in place-name collocations, many of which may include grammatical morphemes (including cognates of the Japanese genitive marker no and the Japanese adjective-attributive morpheme -sa) and a few of which may show syntactical relationships. He postulates that the majority of the identified Goguryeo corpus, which includes all of the grammatical morphemes, is related to Japanese. Beckwith was later criticized for using flawed methods to create a relationship between the two languages that results in evidence that isn't accurate.
Altaic theory