Yes I think about 1% of Afrikaner ancestry is probably Khoikhoi

As a follow-up to my previous two posts on Afrikaners, I wanted to reiterate something that I implied/said earlier: yes, I think about 1% of the ancestry of modern day Afrikaners derives from Khoisan pastoralists of the Cape who were resident there when the Europeans first arrived. These people are often called Khoikoi. Unlike the more famous Bushman the Khoikhoi were not hunter-gatherers. Rather, they herded cattle. Both archaeological and genetic evidence points to the fact that pastoralists arrived in southern Africa through the expansion of East African nomads, who had some Eurasian ancestry (ergo, Khoisan peoples have differing degrees of non-Khoisan African ancestry, as well as Eurasian ancestry).

Today there are no major Khoikhoi groups in South Africa that have not been extensively influenced by other populations (in Namibia the related Nama maintain tribal cohesion and continue the cultural tradition of Khoisan pastoralism). Where did the Khoikhoi go? Many died due to disease, and the privations of slavery. But, some were certainly absorbed into other populations. The Xhosa people have substantial Khoisan ancestry for example.

The plot to the left has various populations, including Dutch, whites from Utah, white South Africans, Nigerians, African Americans, Barbadians, and Bantu populations (click the image for a larger version). As well as Khoisan groups which are a combination of Nama and San Bushmen samples.

If you click the larger image you can see that the South African Bantus are shifted toward the Khoisan. The Kenyan Bantus are skewed in the direction of Eurasians…though only mildly so (no doubt due to Cushitic admixture).

The plot to the right (click to enlarge) is a zoom in. It is clear that the South African samples are very subtly shifted out of the normal Northern European cluster. If you look at the cline from the Nigerians running toward the Northern Europeans, the South African whites look to be perturbed from it. Notably, some of them are clearly shifted in the direction of the Khoisan.

Next, I ran Admixture analysis. I set the reference populations as Esan from Nigeria, Khoisan, and Dutch whites. You can see that African Americans exhibit a cline as you’d expect. A minority of their ancestry is Northern European. But mostly they are African, with the dark blue representing the Esan Nigerian reference population. This is as it should be; most of the slaves who came to America seem to have come from the Congo up the Africa coast all the way to Senegal.

The fraction of African ancestry in the South African samples is low. But observe that many of them have just as high a fraction of the red component, which comes from the Khoisan reference population. These ten mostly white South Africans average 1.4% Khoisan and 2.3% non-Khoisan African.

Finally, I decided to run Treemix and do a three population test.

With two migration edges the results make a lot of sense. The African Americans are placed next to the Nigerians, but there is a migration edge of some significance from the Northern Europeans. The South Africans are in a clade with the Dutch samples, with Utah whites being the outgroup. But, they have a migration edge from between the Esan from Nigeria and the Khoisan.  Recall that there was more Nigerian-like ancestry in the South African whites than Khoisan-like ancestry according to Admixture. The gene flow edge seems to be closer to the Esan by some margin.

Finally, I ran a three population test, which tests gene flow by placing an admixed population as an outgroup to source populations. Negative statistics indicate “complex population history” not accounted for by the tree.

Outgroup Pop 1 Pop 2 f3 Z score
Af_American Netherlands EsanNigeria -0.0103 -89.1922
Af_American UtahWhite EsanNigeria -0.0102 -88.7189
Af_American South_Africa EsanNigeria -0.0099 -87.1784
Af_American Netherlands Khoisan_SA -0.0034 -16.6754
Af_American Khoisan_SA UtahWhite -0.0033 -16.5408
Af_American South_Africa Khoisan_SA -0.0029 -14.6855
South_Africa Netherlands EsanNigeria -0.0015 -10.9174
South_Africa Netherlands Khoisan_SA -0.0015 -10.5677
South_Africa UtahWhite EsanNigeria -0.0014 -9.0416
South_Africa Khoisan_SA UtahWhite -0.0014 -8.7962
South_Africa Netherlands Af_American -0.0011 -10.0158
South_Africa Af_American UtahWhite -0.0010 -8.1132
UtahWhite Netherlands EsanNigeria -0.0001 -1.6344
UtahWhite Netherlands Khoisan_SA -0.0001 -1.6344

The bottom two results can be ignored. What you see is that African Americans have the most negative f3 values with the highest z-scores. There is a drop-off from the Nigerians to the Khoisan as one of the source populations because the Nigerians are a much better fit. The values for South Africans are much lower, which makes sense in light of their lower admixture proportion. But observe that the f3 statistic for using Esan vs. Khoisan is not that different. This suggests neither group is necessarily a better proxy for the other.

As for the ethnographic details of where this ancestry came from, I think it was the proto-Cape Coloured population.

2 thoughts on “Yes I think about 1% of Afrikaner ancestry is probably Khoikhoi

  1. I think it was the proto-Cape Coloured population.
    wouldn’t the presence of South Asian ancestry, the mtDNA / X / autosomal composition ratios, and the local ancestry all be important indicators of the timing of the admixture or admixtures?

    I couldn’t figure out how thoroughly the S Asian DNA has mixed in in the Colored population, but it is expected to date back to the 2nd half of XIX c. in the earliest? And (at least some) white S Africans are reported to have this component as well?

    The older is the main admixture event, the more bias towards local DNA on X and especially on mtDNA one would expect to see, given the sex-biased nature of the admixture? Just like in Argentina, with its waves of massive influx of European immigrants, the non-European DNA is almost completely relegated to mtDNA?

    And the local ancestry segments would not only have informative size distributions but also informative juxtapositions of contiguous Khoisan / other African / S Asian segments? Is there any way to analyze these patterns?

  2. And the local ancestry segments would not only have informative size distributions but also informative juxtapositions of contiguous Khoisan / other African / S Asian segments? Is there any way to analyze these patterns?

    yes.

    that would take longer than an hour or so analysis though (what you see above; i did some data cleaning etc. so just not letting admixture run etc.). my data is 200,000 snps, so probably could do some local ancestry deconvolution.

    that being said, i think we can be sure it’s in the 1650 to 1850 window, being generous. i don’t know that much about south african history, but probably before the great migration in the early 19th.

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