Unraveling the influence of essential climatic factors on the number of tones through an extensive database of languages in China

Abstract Recent research has provided supportive evidence for the role of humidity in the evolution of tones. However, there remain numerous challenges in delving deeper into the intricate relationship between the tone system and climatic factors: precisely tracking and identifying potentially relevant climate factors at appropriate temporal and spatial scales, while effectively controlling the potential interference caused by geographical proximity and language inheritance. Based on a substantial database of 1,525 language varieties in China and 41 years of monthly climate data, this study has delved into the correlation between multiple climate factors and number of tones, examined the mediating role of voice quality in this process, and further analyzed the interrelationship between climate factors and pitch variations. The findings reveal that climate factors influencing voice quality and the number of tones are diverse, with specific humidity, precipitation, and average temperature playing pivotal roles. After controlling the influence of language inheritance and geographical proximity, the chain of climate → voice quality → number of tones remains significant in China. Specifically, people living in a humid and warm environment tend to exhibit better voice quality. Meanwhile, regions with higher specific humidity and precipitation tend to have a richer and more diverse range of tone types. These findings enrich the theoretical framework of the interaction between language and the environment and provide robust empirical support for understanding the natural mechanisms of language evolution.