The Tonal Comparative Method: Tracing Sound Change in Lexical Tone

The Comparative Method is a primary tool of historical linguists that traditionally focuses on segmental evidence. Lexical tone has been used as an example of where the method is not applicable. Using data from hundreds of Tai doculects, this paper models extending the logic of the Comparative Method to lexical tone. Insights from computational phylogenetics assist in distinguishing shared innovation from shared retention and parallel innovation in tonal sound change. This approach represents an increase in rigor in the study of Tai language history, and serves as a model for studying sound change in lexical tone languages more generally.