Afrikaner genetics shows how unique New England culture is

There’s a new paper in BMC Biology, Patterns of African and Asian admixture in the Afrikaner population of South Africa, which confirms some of what I found years ago with a much smaller data set, The Genetics Of Afrikaners (Again). The PCA above and Treemix to the right I generated from the data in the new paper.

Here are their results:

To investigate the genetic ancestry of the Afrikaner population today (11–13 generations after initial colonization), we genotyped approximately five million genome-wide markers in 77 Afrikaner individuals and compared their genotypes to populations across the world to determine parental source populations and admixture proportions. We found that the majority of Afrikaner ancestry (average 95.3%) came from European populations (specifically northwestern European populations), but that almost all Afrikaners had admixture from non-Europeans. The non-European admixture originated mostly from people who were brought to South Africa as slaves and, to a lesser extent, from local Khoe-San groups. Furthermore, despite a potentially small founding population, there is no sign of a recent bottleneck in the Afrikaner compared to other European populations. Admixture amongst diverse groups from Europe and elsewhere during early colonial times might have counterbalanced the effects of a small founding population.

Afrikaner ancestry is overwhelmingly Northern European. But as you see in the PCA above they are notably African and Asian shifted when compared to their potential ancestral populations (I used Dutch and German individuals above). For me this is the part that is important, if not surprising:

The individual with the most non-European admixture had 24.9% non-European admixture, and only a single Afrikaner individual (out of 77) had no evidence of non-European admixture…Amongst the 77 Afrikaners investigated, 6.5% had above 10% non-European admixture, 27.3% between 5 and 10%, 59.7% between 1 and 5% and 6.5% below 1%.

So about 87% of Afrikaners in their sample had between 1 to 10 percent non-European ancestry. As suggested by genealogical evidence, genetics indicates this is a relatively recent admixture, occurring during the 17th and 18th-century. The early decades of the Cape Colony. It’s a mix of diverse Asian and African components. In some ways, it seems that the non-European ancestry in modern Afrikaners is just the same phenomenon which gave rise to the Cape Coloured population, which is a mix of European, Asian (Indian and Austronesian) and African (Bantu and Khoisan).

Honestly, I think the individuals with more than 10% non-European ancestry, or 0% non-European ancestry, may have recent non-Afrikaner ancestry, and so are not representative (Hendrik Verweord was Dutch and immigrated to South Africa, so he would not have had non-European ancestry). Arguably, the fact that Afrikaners are only ~5% non-European is rather surprising in light of the conditions of the Cape Colony during its early years.

But, this result is more interesting in light of how it contrasts with another case. Also in the 17th-century, there emerged another European settler society on the edge of a vast ocean rooted in a deeply Calvinist faith. By this, I mean the colonies of New England. Though New England has been reshaped by later migrations, between 1640 and 1790 30,000 English settlers expanded and grew into a region with 750,000 Americans. In the early 19th-century, New England spilled out over much of the northern swath of the United States of America, in part due to the fact that the fertility of New Englanders was quite high (the early Mormons were fundamentally a New England-derived subculture).

And yet unlike the Afrikaners or the whites of Latin America, the scions of New England have no non-European ancestry. One might argue here that this is due to the lack of opportunity, as the number of slaves in New England was always very low, and there were no native peoples. King Philip’s War falsifies the latter contention. There were numerous native people. At least initially. But the New Englanders were very efficient and effective at marginalizing and exterminating the native peoples of the region. To a far greater extent than occurred in the South.

There was no New England “Trail of Tears,” because New Englanders eliminated most of the local tribes. There are even records New England militias in the 17th-century drowning native children in the Connecticut River as an ultimate solution (to the chagrin and concern of some ministers who wished these children to be baptized and raised as Christians).

Of course, another distinctive aspect of the New England settlement is that it was the transplantation of a whole English society, men and women, rather than simply men seeking fortune and opportunity. This sex balance from the beginning meant that there was no necessity of looking for partners in the local population, as often occurred in other colonial contexts.

The lack of any local imprint on New England’s genetics, in contrast with almost all other settler and colonial societies, is in keeping with the other peculiarities of the region’s cultures. By the latter portion of the 18th-century New England was unique because it was beginning to see itself as not just a complement of the metropole, but a potential rival.* A potential that would be realized with the intellectual (the emergence of Harvard) and economic (industrialization) developments of the 19th-century.

Today when talking to Patrick Wyman of Tides of History, I suggested that genetics can only be understood in a broader context, even if it is to answer specific questions. Though European settler societies are all predominantly European, both culturally and biologically, New England’s uniqueness genetically in having almost no native input reflects I think a broader cultural reality of the region’s history: it is peculiarly European without much synthesis with the local substrate.

* The South was a traditional commodity-exporting colony. The Mid-Atlantic, focused on New York City, was the center of mercantile activity that operated as a transaction hub of a global trade system.

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.

OutgroupPop 1Pop 2f3Z score
Af_AmericanNetherlandsEsanNigeria-0.0103-89.1922
Af_AmericanUtahWhiteEsanNigeria-0.0102-88.7189
Af_AmericanSouth_AfricaEsanNigeria-0.0099-87.1784
Af_AmericanNetherlandsKhoisan_SA-0.0034-16.6754
Af_AmericanKhoisan_SAUtahWhite-0.0033-16.5408
Af_AmericanSouth_AfricaKhoisan_SA-0.0029-14.6855
South_AfricaNetherlandsEsanNigeria-0.0015-10.9174
South_AfricaNetherlandsKhoisan_SA-0.0015-10.5677
South_AfricaUtahWhiteEsanNigeria-0.0014-9.0416
South_AfricaKhoisan_SAUtahWhite-0.0014-8.7962
South_AfricaNetherlandsAf_American-0.0011-10.0158
South_AfricaAf_AmericanUtahWhite-0.0010-8.1132
UtahWhiteNetherlandsEsanNigeria-0.0001-1.6344
UtahWhiteNetherlandsKhoisan_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.

No, Afrikaners do not have British or English ancestry

Update: Some people are taking this post as a criticism of 23andMe. Really it’s not. It’s just to point out that customers sometimes overinterpret the granularity of these regional tests. There just isn’t the power to discern between British and Dutch too well (there are other ways to do this genealogically….). And, it really matters in the case of Afrikaners since their Dutch (and German and French) national origins are well known.

kan

In my post below on the non-European ancestry of Afrikaners, several readers mentioned that friends of Afrikaner background were rather chagrined to have reported British ancestry from genetic tests. The cultural reason for this is well known: many Afrikaners exhibit hostility toward British imperialism due to the deprivation and death which was the consequence of their resistance to the expansion of the Empire during the Second Boer War. This is above and beyond the antipathy which was manifestly made obvious by the fact that with the transfer of the Cape Colony to the British in the early 19th century thousands of white farmers migrated into the hinterlands to escape the new power (in part to preserve their customs, such as slavery).

By the 20th century, this anti-British aspect of Boer identity manifested itself in pro-German sentiments, as can be seen in the film The Power of One.

But the reality is that it is strange for Afrikaners to have British ancestry. Yes, they are not exclusively Dutch, with substantial German and French (Huguenot) components in their background. And there has been some recent intermarriage with English speaking whites. But presumably that’s recent enough that people would know.

Rather, I think what is happening is that genetic tests do not have the power to distinguish well between English and Dutch ancestry. In fact, the minority ancestry from Anglo-Saxons in southeast Britain would have stronger affinities with the Dutch than most of the island.

To figure out what was going on I asked people on Twitter for 23andMe profiles. I got a response from someone whose results I posted above. This individual has Boer ancestry, mostly Dutch, going back to the late 17th century on his mother’s side and late 18th century on his father’s side. And you see 17% “British” ancestry. He also provided his wife’s 23andMe output. Her ancestry dates back to the late 17th century on both paternal and maternal sides, so it is not a surprise she has more non-European ancestry:

She is 18% British. In fact, the European ancestry fractions of both these individuals are rather similar when it comes to “French-German”, British, and Scandinavian. I suspect what we’re seeing here is what the algorithm pops out quanta wise for Dutch.

I took the South African individuals who had some non-European ancestry, and ran them on Admixture and projected a PCA with British and Dutch individuals. You can make your own judgment, but I think these are definitely people who are of mostly Dutch ancestry.

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The non-European ancestry of Afrikaners


A few years ago I got some South African genotypes. Some of the individuals were clearly African. A few mapped perfectly upon Northern Europeans. But many of the samples consistently were European but shifted toward non-European populations.

Based on history of the assimilation of slaves into the European population of Cape Colony in the 18th century, my assumption is that these individuals are Afrikaners.

Recently I realized that Brenna Henn had released some more Khoisan samples, so I decided to look at this question of admixture again. The two Khoisan populations are the Nama and the Khomani. I removed those with lots of Bantu and European admixture and combined them together into one population.

Running unsupervised Admixture shows how distinct the South African whites are.

The average Utah white in this sample (this population is a mix of British, German, and Scandinavian in ancestry) is 99% European modal cluster, and 1% South Asian. The average for the white South Africans in this data set is 94% European modal cluster. The residual is 1% East Asian (Dai modal), 1% Khosian, 1% non-Khoisan African, and 2% South Asian.

I ran Treemix a bunch of times, and every single plot came out like this when I ran it for three migrations:

 

The gene flow from the Utah whites to the Gujuratis is simply an artifact of the fact that the Gujurati sample is mixed caste, and some of the Brahmin or Lohannas have more “Ancestral North Indian.” The gene flow from the Europeans to the Khoisan is probably real, or, might be due to pastoralist admixture via East Africans. The last migration arrow goes from the African populations to the South African whites, with a shift toward the Khoisan.

I also ran a three population test where A is the outgroup, and B and C are a clade. A significantly negative f3-statistic indicates admixture in population A. The negative values are listed below:

ABCf3f3-errorZ-score
GujratiDaiUtahWhite-0.001217180.000140141-8.68539
South_AfricaEsanNigeriaUtahWhite-0.001277180.000147982-8.63059
South_AfricaKhoisan_SAUtahWhite-0.00129280.000151416-8.53802
GujratiSouth_AfricaDai-0.0007787910.000155656-5.00329
South_AfricaDaiUtahWhite-0.0005419740.000133262-4.06699
South_AfricaUtahWhiteGujrati-0.0001035818.46193e-05-1.22408

This aligns well with the Admixture results. Afrikaners have both African ancestries, and, Asian ancestry.

In James Michener’s The Covenant one of the plot lines alludes to mixed ancestry in one of the Afrikaner families. The results above suggest that mixed ancestry is very common, and perhaps ubiquitous, in this population. True, there are some Afrikaners such as Hendrik Verwoerd who migrated to South Africa from the Netherlands in the past century or so, but these are uncommon to my knowledge.