Striking Genetic Diversity Among Populations of West Africa Uncovers the Mystery of a Language Isolate

Abstract

The past decade has witnessed great progress in our understanding of the relationship between languages and genes. However, the linguistic-genetic patterns of language isolates and their speakers are not completely understood. The Bandiagara Escarpment in Central-Eastern Mali is a hub to diverse languages, cultures and life subsistence patterns, and a mysterious language isolate called “Bangime”. Here, we investigate genome-wide data of populations from Central-Eastern Mali to reveal the genetic structure of its diverse linguistic groups and help solve the mystery of language isolate Bangime and its speakers “the Bangande”. We show that the Bangande population is also a genetic isolate, with a mean time of divergence from surrounding populations estimated at 9,900 (CI 8,726-10,838) years ago. These findings support the scenario that the Bangande represent the region’s past linguistic and genetic diversity prior to the Dogon Expansion. Moreover, our study reports limited signals of admixture in the Dogon, Bozo, and Songhai of Kikara, suggesting that the cliff dwellings may have acted as a long-term barrier to gene flow. In contrast, we reveal admixture signals in the nomadic Fulani and the Songhai of Hombori, which we interpret in the context of gene-culture interactions for the Fulani. Finally, with simulation modeling, we show that the previous interpretations of the Dogon population structure are probably an artifact of the model-based genetic clustering.

Keywords: Central-Eastern Mali, Bandiagara Escarpment, genetic-linguistic relationships, Bangime, Dogon, language isolate, Dogon Expansion, Mande, divergence time