New study clarifies nature of genetic admixture in South Africa’s Afrikaner population
By Primarashni Gower
A collaboration between researchers from the University of Pretoria (UP) and Uppsala University in Sweden has found some unexpected patterns of genetic admixture in South Africa’s Afrikaner (white and Afrikaans-speaking) population.
The results of the study, titled Patterns of African and Asian admixture in the Afrikaner population of South Africa, were published earlier this year in the respected scientific journal BMC Biology. This research forms part of work by Professor Jaco Greeff, of UP’s Faculty of Natural and Agricultural Sciences, on the genetic heritage of Afrikaners and Professor Carina Schlebusch and Professor Mattias Jakobsson (both from Uppsala University) on the history of human populations in general. These studies show how humans have moved and admixed over time, and that migration, mobility and admixture should be seen as a hallmark of our species rather than a new phenomenon.
Genealogies and private DNA tests show that modern Afrikaners’ DNA reflects past admixture between European immigrants, slaves arriving from Africa and Asia, and local Khoe-San. In a study that is almost four times larger than similar studies, the researchers genotyped 77 Afrikaners at five million places in their genomes and found that, on average, 4.7% of their DNA has a non-European origin. Despite this small fraction, the vast majority of the sampled individuals, 76 of 77 (98.7%), had non-European admixture.
The non-European component is comprised of Khoe-San (1.3%), Asian (2.6%) and African (excluding Khoe-San; 0.8%) contributions. Further analyses showed some surprises: First, the small Khoe-San signal is a very common signal among Afrikaners and was present in 74 of the 77 men, even though only one marriage between a European and a Khoe-San was recorded at the Cape. This discrepancy can only be explained if there was gene flow between frontier farmers, “trekboere” (nomadic farmers), and Khoe-San women.
Second, despite being founded by a fairly small number of immigrants, Afrikaners have a similar degree of inbreeding to other Europeans. This can be explained by the variety of origins of European immigrants together with admixture with non-European groups.
The study also confirmed some historical observations. First, Afrikaners show West African ancestry rather than links to South African Bantu-speakers. This signal most likely stems from two slave ships from West Africa that arrived in 1658. Second, it confirms that European men preferred slaves from India for formal and informal relationships, since Asia contributed most of the non-European admixture. There is evidence that certain genetic variants were favoured by selection, for example several genes associated with diet, possibly indicating adaptation to modified or novel food sources.
This scientific paper is available here.