Food and pathogen adaptations in the Angolan Namib desert: Tracing the spread of lactase persistence and human African trypanosomiasis resistance into southwestern Africa.

OBJECTIVES: We investigated the frequency distribution and haplotype diversity of human African trypanosomiasis (HAT) resistance and lactase persistence (LP) variants in populations from the Angolan Namib to trace the spread of these genetic adaptations into southwestern Africa.

MATERIALS AND METHODS: We resequenced two fragments of the LCT enhancer and the APOL1 gene and genotyped flanking short tandem repeat loci in six groups with different subsistence traditions living in the Angolan Namib, and in a comparative dataset including other populations from Africa and Europe. LP in the Angolan Namib is represented by the -14010*C allele, which is associated with a predominant haplotype that is shared with other southern and eastern African populations. While LP was found to be more frequent in foragers than in pastoralists, the frequencies of the two APOL1 variants associated with HAT-resistance (G1 and G2) did not differ between the two groups. The G1 allele is mostly associated with a single widespread haplotype. The G2 allele is linked to several haplotypes that are molecularly related to haplotypes found in other African Bantu-speaking populations. The putatively archaic G3 variant displayed more intra-allelic diversity in Africa than in Europe.

DISCUSSION: The LP adaptation was carried to southern Africa by non-Bantu speaking pastoralists from eastern Africa, but an obvious link between its presence in southern Angola and groups speaking languages of the Khoe-Kwadi family, as previously found in other areas, could not be confirmed. The presence of APOL1 variants G1 and G2 is linked to the Bantu expansions. Our results suggest that the G3 variant was retained in modern humans by incomplete lineage sorting.