Deconstructing Jaco: Genetic Heritage of an Afrikaner
J. M. Greeff∗
Department of Genetics, University of Pretoria, Pretoria 0002, South Africa
Summary
It is often assumed that Afrikaners stem from a small number of Dutch immigrants. As a result they should be genetically homogeneous, show founder effects and be rather inbred. By disentangling my own South African pedigree, that is on average 12 generations deep, I try to quantify the genetic heritage of an Afrikaner.
As much as 6% of my genes have been contributed by slaves from Africa, Madagascar and India, and a woman from China. This figure compares well to other genetic and genealogical estimates. Seventy three percent of my lineages coalesce into common founders, and I am related in excess of 10 times to 20 founder ancestors (30 times to Willem Schalk van der Merwe). Significant founder effects are thus possible. The overrepresentation of certain founder ancestors is in part explained by the fact that they had more children. This is remarkable given that they lived more than 300 years (or 12 generations) ago. DECONSTRUCT, a new program for pedigree analysis, identified 125 common ancestors in my pedigree. However, these common ancestors are so distant from myself, paths of between 16 and 25 steps in length, that my inbreeding coefficient is not unusually high (f ≈ 0.0019).
......
Given that genealogists could show that as much as 7% of Afrikaner genetic heritage is not of European descent (Heese, 1971), I find it curious that a system such as apartheid worked in South Africa. Seven percent is not a trivial amount, and is equivalent to having slightly more than a great-great-grandparent who was non-European. Since most of this non-European genetic heritage came into the Afrikaner population via female slaves, one would expect that as much as 14% of Afrikaner mitochondrial DNA is not even European. This female bias influx stems from the fact that emigrants were predominantly male, resulting in a male biased sex ratio of adults (Gouws, 1981).
Similarly, genetic studies also give support for this mixed racial ancestry. Working with a number of blood group gene frequencies, Botha & Pritchard (1972) estimated that between 6–7% admixture between western European and slaves from Africa and the East, and/or Khoikhoi, would be required to explain the allele frequencies. Nurse et al. (1985) listed a number of alleles typical to the Khoisan and Bantu-speaking peoples that are found in low frequencies in Afrikaners (ABO system: Abantu; glucose-6-phosphate dehydrogenase: GdA− and GdA; Rhesus: R◦ ; Haemoglobin C).
......
Even though my pedigree is 17% incomplete, the accumulation curves suggest that as few as 7 more founder ancestors remain to be discovered. This is due to the substantial ancestor loss to which I will return below. It does mean that what I have calculated here with regards to my composition is unlikely to change substantially as additional lineages are completed.
The fact that my average lineage, including myself, is almost 12 generations long and that the average gene in me is now spending almost its 11th generation on this continent show that, although there are some founder ancestors that immigrated here more recently, most contributions stem from the early immigrants. One may thus expect a fairly close agreement between my composition and the average Afrikaner as calculated by Heese (1971).
Considering the nationalities of contributors I contain 12% more French genetic heritage than Heese’s calculations (Table 3). This increase is balanced by an 8% loss from German, a 3% loss from other European, and a 1% loss from non-European genetic heritage. The fact that most non-European genetic heritage came into the Afrikaner population via German immigrants (Heese, 2005) probably explains the drop in non-European genetic heritage. However, my high relatedness to the more recent immigrant, Rosalyn van Macao, who contributed 25% of my non-European genetic heritage, ‘reconciled’ this mismatch between my data and that of Heese’s (1971).
It is not clear if my higher estimate of French contribution is because of a systematic mistake in Heese’s (1970) estimate, or if it is because of a quirkiness in my own ancestry. It seemed to be the case that when a lineage hit the French Huguenots it stayed in this group. It will be interesting to compare the degree of inbreeding of the early generations of Huguenots to the other early immigrants. In the light of the calculations of Heyer et al. (2005) there is an interesting possibility that the cultural inheritance of fitness may have led to a systematic bias in Afrikaners, since Huguenots tended to be more educated and trained than German emigrants who tended to be soldiers. We are currently investigating this hypothesis.
It is unclear how the 2% contribution by women known only as van die Kaap should be allocated. At least one of them, Maria Bastiaans van die Kaap, carried an M mtDNA haplotype, which suggests an Asian and possibly Indian ancestry (Maca-Meyer et al. 2001). Although more slaves came to the Cape from Madagascar than from Guinea, Guinea contributed almost 5 times more to my gene pool than Madagascar. This is through the fertile contributions of a woman known as Lijsbeth Sanders van die Kaap. From her social associations it is believed that she was from Guinea (Hattingh, 1980). Of the slaves, however, a large number of women from India contributed to my genes.
My estimate of 6% non-European genetic contribution is in close agreement with genealogical (Heese, 1971) and genetic (Botha & Pritchard, 1972) estimates. I am not aware that this estimate has been validated for any other Afrikaner individual, but it will be interesting if this can be confirmed for more Afrikaners. Presently, most white and black South Africans are equally incredulous at the prospect that Afrikaners have such a rich genetic heritage. Hopefully, with time all South Africans will celebrate the fact that Afrikaners are, and continue to be, a proudly south African concoction.
Southern Africa
Reply With Quote
Originally Posted by Soten
Bookmarks