How does widespread bilingualism complicate the classification of Hmong-Mien languages?

Widespread bilingualism complicates the classification of Hmong-Mien languages by creating linguistic similarities that can be mistaken for genetic relationships. Because Hmong-Mien speakers have long been influenced by dominant Chinese populations, their languages have adopted a high number of Chinese loanwords and share certain typological features, such as word structure and phonological systems.12

While some scholars have used these shared characteristics to argue that Hmong-Mien belongs to the Sino-Tibetan family, many linguists outside China reject this theory. They argue that these similarities are not evidence of a common ancestry but are instead the result of long-term contact and widespread bilingualism in the region. Consequently, these external influences obscure the true linguistic history of the family, making it difficult to resolve its wider genetic connections until researchers can effectively separate native vocabulary from layers of Chinese borrowings.1