The once-popular theory attributing these similarities to a common ancestry has long been rejected by most comparative linguists in favor of language contact, although it continues to be supported by a small but stable scholarly minority.

[13] Lanhai Wei and Hui Li reconstruct the name of the Xiōngnú ruling house as PT *Alayundluğ /alajuntˈluγ/ 'piebald horse clan.

The earliest Para-Mongolic text is the Memorial for Yelü Yanning, written in the Khitan large script and dated to 986 AD.

Japanese is first attested in the form of names contained in a few short inscriptions in Classical Chinese from the 5th century AD, such as found on the Inariyama Sword.

[18]: 126–127  The name "Altaic" referred to the Altai Mountains in East-Central Asia, which are approximately the center of the geographic range of the three main families.

Even linguists who accept the basic Altaic family, such as Sergei Starostin, completely discard the inclusion of the "Uralic" branch.

Decades later, in his 1952 book, Ramstedt rejected the Ural–Altaic hypothesis but again included Korean in Altaic, an inclusion followed by most leading Altaicists (supporters of the theory) to date.

[26] His book contained the first comprehensive attempt to identify regular correspondences among the sound systems within the Altaic language families.

In 1960, Nicholas Poppe published what was in effect a heavily revised version of Ramstedt's volume on phonology[27][28] that has since set the standard in Altaic studies.

In 1990, Unger, emphasizing the need to establish language relationships rigorously "from the bottom up," advocated comparing Tungusic with the common ancestor of Korean and Japanese before seeking connections with Turkic or Mongolic.

A group of those proto-Altaic ("Transeurasian") speakers would have migrated south into the modern Liaoning province, where they would have been mostly assimilated by an agricultural community with an Austronesian-like language.

"[33] In 1962, John C. Street proposed an alternative classification, with Turkic-Mongolic-Tungusic in one grouping and Korean-Japanese-Ainu in another, joined in what he designated as the "North Asiatic" family.

Starting in the late 1950s, some linguists became increasingly critical of even the minimal Altaic family hypothesis, disputing the alleged evidence of genetic connection between Turkic, Mongolic and Tungusic languages.

They claimed that the words and features shared by Turkic, Mongolic, and Tungusic languages were for the most part borrowings and that the rest could be attributed to chance resemblances.

[43] In 1991 and again in 1996, Roy Miller defended the Altaic hypothesis and claimed that the criticisms of Clauson and Doerfer apply exclusively to the lexical correspondences, whereas the most pressing evidence for the theory is the similarities in verbal morphology.

[45] In 2003, Starostin, Anna Dybo and Oleg Mudrak published the Etymological Dictionary of the Altaic Languages, which expanded the 1991 lexical lists and added other phonological and grammatical arguments.

Robbeets and Johanson gave as their reasoning for the new term: 1) to avoid confusion between the different uses of Altaic as to which group of languages is included, 2) to reduce the counterproductive polarization between "Pro-Altaists" and "Anti-Altaists"; 3) to broaden the applicability of the term because the suffix -ic implies affinity while -an leaves room for an areal hypothesis; and 4) to eliminate the reference to the Altai mountains as a potential homeland.

The original arguments for grouping the "micro-Altaic" languages within a Uralo-Altaic family were based on such shared features as vowel harmony and agglutination.

[16] The Etymological Dictionary by Starostin and others (2003) proposes a set of sound change laws that would explain the evolution from Proto-Altaic to the descendant languages.

[55] Their results include the following phylogenetic tree:[56] Japonic Koreanic Tungusic Mongolic Turkic Martine Robbeets et al. (2021) argues that early Transeurasian speakers were originally agriculturalists in Northeastern Asia, only becoming pastoralists later on.

While acknowledging that prehistoric contacts are a plausible alternative explanation for the positive results, they deem such a scenario less likely for the lexical matches between Turkic and Japonic languages, which are better explained by genealogical relationship because of the substantial geographical distances involved.

[39][40][41] Those critics also argued that the words and features shared by Turkic, Mongolic, and Tungusic languages were for the most part borrowings and that the rest could be attributed to chance resemblances.

[62][63] Chaubey and van Driem propose that the dispersal of ancient Altaic language communities is reflected by the early Holocene dissemination of haplogroup C2 (M217): "If the paternal lineage C2 (M217) is correlated with Altaic linguistic affinity, as appears to be the case for Turkic, Mongolic and Tungusic, then Japanese is no Father Tongue, and neither is Korean.

Yet this molecular marker may still be a tracer for the introduction of Altaic language to the archipelago, where the paternal lineage has persisted, albeit in a frequency of just 6%.

"[65] Juha Janhunen hypothesized that the ancestral languages of Turkic, Mongolic, Tungusic, Korean, and Japanese were spoken in a relatively small area comprising present-day North Korea, Southern Manchuria, and Southeastern Mongolia.