Diachronic hierarchies of Tai tonal development

Abstract

This paper discusses the diachronic processes of tonal development of Tai languages. Tonogenesis is treated as the very first step of the arising of tones in proto-Tai. After tone arose, two groups of proto-initials (voiceless-voiced) conditioned primary tonal splits whereas splits conditioned by other pharyngeal features, such as aspiration and preglottalization represent stages of secondary development. Some secondary tonal split patterns result in three-way register splits. However, the bearing capacity of the tone numbers in a language often cause the third register to merge into one of the other two to make two-way register splits always be the mainstream.