Human language diversity and the acoustic adaptation hypthesis

Abstract

Bioacousticians have argued that the acoustic effects of differing ecological environments contribute to shaping the acoustic signals used by a variety of species, including within single widely-distributed species. Moreover, anthropogenic changes in soundscapes have also been shown to generate modifications to the spectral envelope of bird songs. Several studies posit that part of the variation in sound structure across spoken human languages could likewise reflect adaptation to the local ecological conditions of their use. Specifically, environments in which higher frequencies are less faithfully transmitted (such as denser vegetation or higher ambient temperatures) may favor greater use of sounds characterized by lower frequencies. Such languages are viewed as "more sonorous". This paper presents a preliminary test of this hypothesis. Data on segment inventories and syllable structure is taken from LAPSyD, a database on phonological patterns of a large worldwide sample of languages. Correlations are examined with measures of temperature, precipitation, vegetation, and geomorphology reflecting the mean values for the area in which each language is traditionally spoken. Major world languages, typically spoken across a range of environments, are excluded. The results show a significant relationship between the 'consonant-heaviness' of languages and the environmental factors considered, especially tree cover and precipitation.