History of Click-Speaking Populations of Africa Inferred from mtDNA and Y Chromosome Genetic Variation

TLDR

The history of Africa’s click‑speaking peoples is poorly understood; previous genetic work shows the Hadza of eastern Africa are as distantly related to southern African click speakers as most other African groups, and the Sandawe—also in eastern Africa—are the only other Khoisan‑classified population, yet linguistic evidence for a link between Hadza and Sandawe remains disputed. We analyzed mtDNA and Y‑chromosome variation in the Sandawe, Hadza, and nearby Tanzanian populations. The data reveal that the Sandawe and southern African click speakers share rare mtDNA and Y‑chromosome haplogroups, indicating a common ancestry older than 35,000 years, while the Hadza and Sandawe share ancestry older than 15,000 years, suggesting that by the spread of agriculture and pastoralism the click‑speaking groups were already isolated and consistent with deep linguistic divergence.

Abstract

Little is known about the history of click-speaking populations in Africa. Prior genetic studies revealed that the click-speaking Hadza of eastern Africa are as distantly related to click speakers of southern Africa as are most other African populations. The Sandawe, who currently live within 150 km of the Hadza, are the only other population in eastern Africa whose language has been classified as part of the Khoisan language family. Linguists disagree on whether there is any detectable relationship between the Hadza and Sandawe click languages. We characterized both mtDNA and Y chromosome variation of the Sandawe, Hadza, and neighboring Tanzanian populations. New genetic data show that the Sandawe and southern African click speakers share rare mtDNA and Y chromosome haplogroups; however, common ancestry of the 2 populations dates back >35,000 years. These data also indicate that common ancestry of the Hadza and Sandawe populations dates back >15,000 years. These findings suggest that at the time of the spread of agriculture and pastoralism, the click-speaking populations were already isolated from one another and are consistent with relatively deep linguistic divergence among the respective click languages.