Areal patterns in the vowel systems of the Macro-Sudan Belt

Abstract

This paper investigates the areal distribution of vowel systems in the Macro-Sudan Belt, an area encompassing most of the western and central parts of northern Sub-Saharan Africa. We report on a survey of 681 language varieties with entries coded for two phonological features: advanced tongue root (ATR) harmony and the presence of interior vowels (i.e. non-peripheral vowels [⋯]). Our results show that the presence of ATR harmony in the Macro-Sudan Belt is limited to three geographically unconnected zones: an Atlantic zone, a West African zone, and an East African zone. Between the West and East African ATR Zones is a genetically heterogeneous region where ATR harmony is systematically absent: we term this the Central African ATR-deficient zone. Our results show that in this same Central African zone, phonemic and allophonic interior vowels are disproportionately prevalent. Based on this distribution, we highlight two issues. First, ATR and interiority have an antagonistic relationship and do not commonly co-occur within vowel systems; this finding is supported through statistical tests. Second, our survey supports the existence of the Macro-Sudan Belt, but the discontinuous distribution of ATR harmony and its systematic absence in Central Africa challenges the proposal that this area represents the 'hotbed' of the Macro-Sudan Belt.