Classification of the Japonic languages
[1][2] 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.
[7][8] 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.
[10] Vovin (2015) shows evidence that the early Koreans borrowed words for rice cultivation from Peninsular Japonic.
[19] Chaubey and van Driem (2020) propose that the Japonic languages may have already been present in Japan during the early Jōmon period.
Japonic-speakers then expanded during the Yayoi period, assimilating the newcomers, adopting rice-agriculture, and fusing mainland Asian technologies with local traditions.
[citation needed] William George Aston suggested in 1879 in the Journal of the Royal Asiatic Society that Japanese is related to Korean.
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).
[1] 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.
[23] This theory has been criticized for serious methodological flaws, such as rejecting mainstream reconstructions of Chinese and Japanese, for less accepted alternatives.
Vovin also argues that the claimed cognates are nothing more than early loanwords from when Japonic was still spoken in southern Korea.
[8] Similarly Whitman (2012) concluded 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.
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.
[26] The hypothesis proposes that Japanese is a relative of the extinct languages spoken by the Buyeo-Goguryeo cultures of Korea, southern Manchuria, and Liaodong.
He postulates that the majority of the identified Goguryeo corpus, which includes all of the grammatical morphemes, is related to Japanese.
Such factors of typological divergence as Middle Mongolian's exhibition of gender agreement[citation needed] can be used to argue that a genetic relationship with Altaic is unlikely.
[33] The morphology of Proto-Japanese shows similarities with several languages in South East Asia and southern China.
[35] Itabashi (2011) claims that similarities in morphology, phonology and basic vocabulary point towards "a strong genealogical connection between Japanese and Austronesian".
[36] Paul K. Benedict (1992) suggests a genetic relation between Japanese and the Austro-Tai languages, which include Kra-Dai and Austronesian.
He notes that Benedict's idea of a relation between Japanese and Kra-Dai should not be rejected out of hand, but he considers the relationship between them not to be genetic, but rather a contact one.
