Environmental conditions do not predict diversification rates in the Bantu languages

Area of Science:

• Linguistics
• Ecology
• Evolutionary Biology

Background:

• Global language diversity often correlates with ecosystem productivity.
• This correlation is hypothesized to stem from social network size, which may increase in harsh climates, reducing language divergence.
• The study questions whether this pattern is solely synchronic or also has a diachronic relationship.

Purpose of the Study:

• To investigate the quantifiable relationship between environmental conditions and language diversification over time.
• To test whether local environmental factors influence linguistic diversification rates.
• To explore the role of geographic isolation versus environmental factors in language evolution.

Main Methods:

• Utilized a spatio-temporal phylogeny of the Bantu language family to estimate local diversification rates.
• Compared diversification rates with spatially-explicit reconstructions of palaeoclimate and palaeovegetation variables.
• Employed regression analysis to assess the statistical significance of environmental influences.

Main Results:

• No statistically significant relationship was found between climatic or ecological variables and linguistic diversification over time.
• A strong positive correlation was observed between pairwise linguistic and geographic distances within the Bantu languages.
• Geographic isolation, driven by rapid expansion, appears to be a more dominant factor than local environmental influences.

Conclusions:

• Environmental factors do not significantly drive language diversification over time in the studied Bantu language family.
• The rapid expansion and subsequent isolation of language groups play a more significant role in linguistic divergence.
• The findings suggest that historical processes like expansion and isolation can overshadow environmental influences on language evolution.