Why is Hmong-Mien not generally accepted as part of the Sino-Tibetan language family?

The classification of Hmong-Mien languages as part of the Sino-Tibetan family is not widely accepted by linguists outside of China because it lacks support from the standard methodology of comparative linguistics.12

While some scholars have proposed this connection, the evidence does not meet the rigorous requirements for demonstrating a genetic relationship. Key reasons for this rejection include:12

• Lack of Basic Vocabulary Correspondence: The determination of genetic affiliation relies on identifying recurrent sound correspondences in basic vocabulary. Studies have failed to find such evidence linking Hmong-Mien to Chinese.1
• Influence of Borrowing: Hmong-Mien languages contain a massive number of Chinese loanwords, which can create a false appearance of relatedness.1
• Typological Similarities: Similarities in grammar, word structure, and phonological systems—such as monosyllabicity and tone usage—are attributed to long-term contact, widespread bilingualism, and the significant influence of Chinese in the region, rather than a shared ancestral origin.134

Until researchers can effectively separate these layers of Chinese borrowings from the native Hmong-Mien vocabulary, the most prudent scholarly position is to treat Hmong-Mien as an independent language family.1