Investigating environmental effects on phonology using diachronic models

Area of Science:

• Linguistics
• Environmental Science
• Cultural Evolution

Background:

• Previous theories suggest environmental factors, like humidity, may influence linguistic features.
• Specifically, dry air was hypothesized to affect pitch control, impacting features like lexical tone.
• However, historical and geographic confounds have challenged these proposals.

Purpose of the Study:

• To rigorously test the theory that environmental humidity affects the emergence of linguistic features.
• To employ a causal inference approach to control for confounding variables in language evolution.
• To specifically examine the relationship between humidity and the development of lexical tone in the Bantu language family.

Main Methods:

• Utilized a causal path model to analyze linguistic and environmental data.
• Employed a geographic-phylogenetic tree to establish historical language locations and timelines.
• Integrated historical climate models to estimate past humidity levels for the studied regions.

Main Results:

• Found no statistical evidence to support the claim that humidity influences the emergence of lexical tone.
• The causal inference model controlled for linguistic inheritance and borrowing effects.
• The detailed analysis provided a robust test of the environmental theory of linguistic features.

Conclusions:

• The study refutes the hypothesis that environmental humidity drives the evolution of lexical tone.
• Causal inference methods offer a powerful framework for investigating complex claims in cultural evolution.
• Further research may explore other environmental factors or linguistic features.