Abstract
Some Bantu languages spoken in southwestern Zambia and neighboring regions of Botswana, Namibia, and Angola are characterized by the presence of click consonants, whereas their closest linguistic relatives lack such clicks. As clicks are a typical feature not of the Bantu language family, but of Khoisan languages, it is highly probable that the Bantu languages in question borrowed the clicks from Khoisan languages. In this paper, we combine complete mitochondrial genome sequences from a representative sample of populations from the Western Province of Zambia speaking Bantu languages with and without clicks, with fine-scaled analyses of Y-chromosomal single nucleotide polymorphisms and short tandem repeats to investigate the prehistoric contact that led to this borrowing of click consonants. Our results reveal complex population-specific histories, with female-biased admixture from Khoisan-speaking groups associated with the incorporation of click sounds in one Bantu-speaking population, while concomitant levels of potential Khoisan admixture did not result in sound change in another. Furthermore, the lack of sequence sharing between the Bantu-speaking groups from southwestern Zambia investigated here and extant Khoisan populations provides an indication that there must have been genetic substructure in the Khoisan-speaking indigenous groups of southern Africa that did not survive until the present or has been substantially reduced.
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Acknowledgements
We are grateful to all sample donors for their participation in this study. We thank Mark Stoneking for helpful comments, the Livingstone Museum, Cesare de Filippo, Terry Nyambe, Ellen Gunnarsdóttir, and Mark Stoneking for help with sample collection, Antje Müller for help in the lab, Serena Tucci for help with sequence alignment, and Cesare de Filippo for organizing sample information, extracting DNA, writing R scripts and commenting on the analysis. This research was supported by the Max Planck Society and the Belgian Science Policy; CB was supported by a grant from the Deutsche Forschungsgemeinschaft (to BP).
Author contributions
KB and BP conceived the study, AB prepared the sequencing libraries, and CB performed phylogenetic analyses. The paper was written by BP and CB with detailed input from KB.
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Supplementary Information accompanies the paper on European Journal of Human Genetics website
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Barbieri, C., Butthof, A., Bostoen, K. et al. Genetic perspectives on the origin of clicks in Bantu languages from southwestern Zambia. Eur J Hum Genet 21, 430–436 (2013). https://doi.org/10.1038/ejhg.2012.192
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DOI: https://doi.org/10.1038/ejhg.2012.192
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