Map showing the language majority areas (LMAs) of each SEB group. The centroid of each of the regions is indicated using a black dot. The three sampling sites are shown in coloured circles; Soweto in blue, Dikgale in orange and Agincourt in yellow.Sengupta, D., Choudhury, A., Fortes-Lima, C. et al./ Nature Comm. 12, 2080 (Apr. 2021)
South Eastern-Bantu (SEB) speaking groups are too different to be treated as a single genetic unit, a study by researchers from Wits University, in South Africa, has shown. The findings were based on analysis of the genetic data of more than 5,000 participants speaking eight different southern African languages.
Over 80% (40 million) of South Africans speak one of the nine SEB family languages (among them isiZulu, isiXhosa and Sesotho) as their first language. Despite clear linguistic differences, the SEB are often treated as a single group in genetic studies.
“One of the key observations was the surprisingly high variation in frequencies of some of the genetic variants that are known to either predispose to or protect from diseases such as diabetes and hypertension, between these groups”, says Dhriti Sengupta, a lead author based at the Sydney Brenner Institute for Molecular Bioscience.
Sengupta explains that a variant that is protective against sleeping sickness varied by four-fold among two of the groups. “Therefore, unless these genetic differences are considered and accounted for, we might end up with erroneous or incorrect inferences about disease risk,” she adds.
The study also reveals the different linguistic groups have a distinctive history over the last millennium, probably associated with their migration into and within the country, settlement, and interactions with indigenous Khoi and San communities.
Although this research was focused only on South African populations, such fine-scale genetic differences might be common across Africa. Sengupta says that more nuanced studies could generate a baseline data that could inform precision medicine treatment initiatives.
