Migration and Interaction in a Contact Zone: mtDNA Variation among Bantu-Speakers in Southern Africa

Abstract

Bantu speech communities expanded over large parts of sub-Saharan Africa within the last 4000–5000 years, reaching different parts of southern Africa 1200–2000 years ago. The Bantu languages subdivide in several major branches, with languages belonging to the Eastern and Western Bantu branches spreading over large parts of Central, Eastern, and Southern Africa. There is still debate whether this linguistic divide is correlated with a genetic distinction between Eastern and Western Bantu speakers. During their expansion, Bantu speakers would have come into contact with diverse local populations, such as the Khoisan hunter-gatherers and pastoralists of southern Africa, with whom they may have intermarried. In this study, we analyze complete mtDNA genome sequences from over 900 Bantu-speaking individuals from Angola, Zambia, Namibia, and Botswana to investigate the demographic processes at play during the last stages of the Bantu expansion. Our results show that most of these Bantu-speaking populations are genetically very homogenous, with no genetic division between speakers of Eastern and Western Bantu languages. Most of the mtDNA diversity in our dataset is due to different degrees of admixture with autochthonous populations. Only the pastoralist Himba and Herero stand out due to high frequencies of particular L3f and L3d lineages; the latter are also found in the neighboring Damara, who speak a Khoisan language and were foragers and small-stock herders. In contrast, the close cultural and linguistic relatives of the Herero and Himba, the Kuvale, are genetically similar to other Bantu-speakers. Nevertheless, as demonstrated by resampling tests, the genetic divergence of Herero, Himba, and Kuvale is compatible with a common shared ancestry with high levels of drift, while the similarity of the Herero, Himba, and Damara probably reflects admixture, as also suggested by linguistic analyses.

The role of matrilineality in shaping patterns of Y chromosome and mtDNA sequence variation in southwestern Angola

“…Secondly, the levels of intrapopulation diversity in the Bantu-speaking peoples from the Namib were found to be consistently higher for mtDNA than for the NRY, reflecting the marked association between the Bantu expansion and the relatively young NRY E1b1a1a1 haplogroup, which has no parallel in mtDNA 25,39 . In contrast, the !Xun have a more diverse NRY haplogroup composition, combining deeply rooted lineages and .…”

Prehistoric Bantu-Khoisan language contact

“…In contrast, the neighboring southwest Zambian Bantu-speaking groups carry an average of only 3 % of L0d/L0k lineages (Fig. 2), with the exception of the Shanjo, who do not speak a click language but have 16% L0d/L0k (Table 2) (Barbieri et al, 2013a;Barbieri et al, 2014b). Neither the Fwe nor the Mbukushu carry any Y-chromosomal lineages of autochthonous origin (Table 2).…”

“…In southern Africa, most Khoisan-speaking populations are characterized by high frequencies of specific mtDNA and Y-chromosome haplogroups, which are otherwise found only in populations that are very likely to have been in intimate contact with Khoisan-speaking groups (Wood et al, 2005;Behar et al, 2008;Soodyall et al, 2008;Barbieri et al, 2013b;Barbieri et al, 2014a;Barbieri et al, 2014b). The mtDNA haplogroups that are characteristic of Khoisanspeaking populations are labelled L0d and L0k, the Y-chromosomal ones are A2, A3b1, and B2b.…”

“…We therefore suggest that the evidence for paralexification and language manipulation through spread of clicks to Bantu words might indicate that "speakers of swb languages once valued Khoisan origins and positively identified with these" (Gunnink et al, 2015: 220). Unfortunately, we can assess this statement only for the Fwe of southwestern Zambia and the Mbukushu of southwestern Zambia and northeastern Namibia, for whom molecular anthropological data are available (Barbieri et al, 2013a;Barbieri et al, 2014b). As shown in Table 2, the mtDNA analyses provide evidence for considerable levels of autochthonous gene flow in the maternal line into the Fwe (where haplogroups L0d and L0k are present at~24 % frequency) as well as into the Mbukushu (15% L0d and L0k).…”

Ancient DNA comes of age

“…Already a substantial body of DNA knowledge for living Khoesan peoples is available, [3][4][5] which gives us a tremendous capability for comparison. The race is on to extend this work back in time through ancient DNA.…”