What is the Altaic Hypothesis?

In historical linguistics, we group languages into families based on the belief that they all descended from a common ancestor, a “proto-language.” Think of the Romance languages—French, Spanish, Italian, and Romanian—all evolving from the Vulgar Latin spoken in the Roman Empire. The Altaic hypothesis proposes a similar, but much older and vaster, family.

In its broadest form, the “Macro-Altaic” theory claims that several major language groups form a single genetic unit. The core members are:

• The Turkic languages (Turkish, Azerbaijani, Uzbek, Kazakh, etc.)
• The Mongolic languages (Mongolian, Buryat, Kalmyk, etc.)
• The Tungusic languages (Manchu, Evenki, etc., spoken in Siberia and Northeast Asia)

The most controversial—and popular—version of the theory extends the family tree to also include:

• Korean
• Japanese (and the related Ryukyuan languages)

If true, this would mean that a speaker in Ankara and a speaker in Osaka are using languages that share a single, ancient grandmother tongue, dubbed Proto-Altaic, spoken thousands of years ago somewhere on the vast plains of Central or Northeast Asia.

The Case for a Family Reunion: Evidence for Altaic

Proponents of the Altaic hypothesis, often called “Altaicists”, point to a fascinating collection of shared features that are, at first glance, too numerous to be mere coincidence. The evidence generally falls into two categories.

Shared Grammar and Structure (Typology)

The most striking similarities aren’t in the words themselves, but in how the languages are built. They share a common “blueprint”:

• Agglutination: This is the “Lego brick” method of word-building. Instead of changing a word internally (like sing, sang, sung), these languages stack distinct suffixes onto a root word, each with a single, clear meaning. For example, in Turkish: ev (house) → ev-ler (houses) → ev-ler-im (my houses) → ev-ler-im-de (in my houses). This structure is a hallmark of all the proposed Altaic languages.
• Vowel Harmony: This is a rule where vowels within a word must belong to the same “class” (e.g., front vowels like e, i, ö, ü or back vowels like a, ı, o, u). If you add a suffix, its vowel changes to match the root word. In Turkish, the plural of ev (front vowel) is ev-ler, but the plural of kol (back vowel) is kol-lar. Vestiges of this system are found in Korean, Mongolian, and even Old Japanese.
• SOV Word Order: All these languages overwhelmingly prefer the Subject-Object-Verb word order. Instead of “The cat (S) ate (V) the fish (O)”, they would say “The cat (S) the fish (O) ate (V).”
• Other Features: They also lack grammatical gender (no he/she distinction in pronouns) and prepositions, using postpositions instead (e.g., saying “the house to” instead of “to the house”).

Seemingly Shared Vocabulary

Altaicists have compiled lists of hundreds of proposed cognates—words believed to have evolved from a single ancestral word. While many are debated, some are undeniably compelling. Consider these examples, traced back to a reconstructed Proto-Altaic form:

• For “stone”: Proto-Altaic *ti̯àlo -> Old Turkish taš, Mongolian čilaɣun, Korean tolh.
• For “sea” or “large river”: Proto-Altaic *müri -> Mongolian mörön (“river”), Korean mul (“water”), Old Japanese mi- (in mizu, “water”).
• For “I” / “me”: Proto-Altaic *bi -> Old Turkish bän, Mongolian bi.

When you see these patterns laid out, it’s easy to get excited. How could so many languages, spoken across millions of square kilometers, independently develop such a similar toolkit?

A Tale of Ancient Neighbors: The Case Against Altaic

For most of the 20th and 21st centuries, the mainstream view in linguistics has shifted dramatically against the Altaic hypothesis. Critics, sometimes called “anti-Altaicists”, argue that the similarities are not the result of a shared parentage, but of something else entirely: intense and prolonged contact.

The central counter-argument is the concept of a Sprachbund (German for “language league”). A Sprachbund is a group of languages that are not genetically related (or only distantly so) but have become structurally similar by borrowing features from each other over a long period. The peoples of the Eurasian steppe—Turks, Mongols, and Tungus—have been neighbors, allies, and enemies for millennia. They have traded, intermarried, and built empires together and on top of one another. In such a historical melting pot, it’s inevitable that they would borrow not just words, but even grammatical patterns.

With this in mind, critics dismantle the pro-Altaic evidence:

1. Typology is Not Genealogy: Shared structural features like agglutination and SOV word order are not proof of a genetic link. Many unrelated languages around the world have these features (like Basque in Spain or Quechua in South America). It’s like arguing two people must be siblings because they both have brown hair and brown eyes—it’s suggestive, but not definitive proof.
2. Loanwords, Not Cognates: Critics have painstakingly shown that many of the supposed “cognates” are actually ancient loanwords. Words related to horses, military organization, agriculture, and titles are easily borrowed between cultures in close contact. For example, the Mongolian word for “gold”, altan, is a loan from Old Turkic, altun. Without careful historical analysis, they could easily be mistaken for cognates.
3. Irregular Sound Correspondences: This is the most technical, and most damning, argument. To prove a language family, linguists must establish regular and systematic sound laws. For instance, Grimm’s Law shows that where Latin has a ‘p’ (e.g., pater), English and German will reliably have an ‘f’ (father, Vater). Critics argue that the sound laws proposed for Altaic are riddled with exceptions and special pleading. The correspondences often seem random, which is a hallmark of borrowing, not genetic descent.

The Current Verdict: A Dissolved Family?

Today, the overwhelming consensus among historical linguists is that the Macro-Altaic hypothesis, especially the version including Korean and Japanese, is not supported by the evidence. The similarities are considered a textbook case of a Sprachbund—a story of ancient neighbors, not a family tree.

The debate isn’t entirely dead. A smaller group of scholars continues to research the topic, refining sound laws and lexical lists. The “Micro-Altaic” hypothesis (just Turkic, Mongolic, and Tungusic) is still considered plausible by some, though even it is increasingly viewed as a Sprachbund.

The Altaic debate is a perfect example of the scientific method at work in linguistics. A bold hypothesis was proposed based on compelling data. But under decades of rigorous scrutiny, the data was reinterpreted, and an alternative explanation—the Sprachbund—was found to be a better fit. So while Turkish and Japanese may not be grandmother and grandchild, their shared features tell an equally fascinating story: a history of deep, prolonged contact and cultural exchange across the vast and dynamic continent of Asia.