Sincerely not my ideal of research on population genetics but this new paper still offers some stuff to chew on:
Priya Moorjani et al. The History of African Gene Flow into Southern Europeans, Levantines, and Jews. PLoS Genetics, 2011. Open access.
An important bias is the lack of other West Asian or North African references. The paper deals with Europeans, Jews and Palestinians (with emphasis in the comparison with the Yoruba outgroup YRI) and that’s about it (we also find Turks in the supplements). This has interest, of course, but also has huge limitations.
Specially problematic, considering that the paper tries to study an apparent African component in West Eurasian populations, is the lack of North African references.
The authors fail to see it but for me it is transparent that what they identify as “African admixture” is nothing but North African admixture, surely related to the expansion of Y-DNA E1b (though not strictly so). The origin of this lineage is surely in NE Africa, around modern Sudan, and arrived to West Asia and Europe surely by two main routes:
- Via West Asia and Greece and then with the Neolithic flows.
- Via West Iberia and then through the Atlantic (mostly) with Dolmenic Megalithism.
In order to illustrate my point, I shall borrow here an image from a previously discussed paper:
|The YRI component vanishes when Iberians and NW Africans are directly compared|
The authors also pretend to be able to pinpoint the approximate age of such alleged (and ill understood to them) “admixture” but their dates make no sense whatsoever. At least not for me. So I’ll ignore that part.
We lack of a good source population: HapMap Yorubas YRI can only be a proxy outgroup and the various Palestinian groups can only be an already much admixed proxy. But estimating from several sources (including this PCA, from this earlier entry) I believe that the “YRI admixture” approximates 1/3 of the true admixture with the original Low Sudanese or Upper Egyptian main true source (?) of West Eurasian Africanness.
So all the results should be multiplied by three to estimate the apportion of “Nubian” input. A “Nubian” true original population is anyhow an approximation, because in the Iberian case most of the Africanness is in fact of Moroccan or otherwise NW African origin, with no immediate ties with Sudan (E1b1b1b1-M81).
If so, I estimate, based on table 2 (and multiplying by three), that there is roughly the following fractions of Nubianness:
- Palestinians c. 30%
- Portuguese c. 6% (notice that the actual amount of North African component in West Iberia is more like 9%, so we are underestimating here the real “Moroccanness” by 50% – this is probably because Moroccans are quite less Yoruba-like than Nubians)
- South Italians c. 5%
- Spain c. 3% (4.5% is probably more realistic for “Moroccanness”)
- Sardinians and North Italians c. 0.6%
- Ashkenazi Jews c. 8%
- Other Jews c. 12%
Whiter than thou…
And that would be what I’d have to say on this only somewhat interesting paper but I happened to dig into some of the supplementary material and I’d say that fig. S1 has some interest.
Of course it has some interest for those who enjoy racialist (tending to racist) comparisons. The lack of other outgroups like East or South Asians, allows for a very black and white (literally) reading of this material. That’s why the title of this section, because in most racialist forums there is not going to be a blacker than you argument, certainly not involving European populations.
Interestingly there are very few populations whiter than HapMap’s CEU sample. As you may know this strange sample that pretends to represent Europeanness in so many simplified genetic studies is made up of Caucasoid people from Utah (USA): it’s not even a true European sample. However it seems representative enough for English-plus (most white Utahns claim English or, some, Danish ancestry, according to US census data).
Following fig. S1, most populations are actually blacker than CEU, so to say, i.e. they tend towards YRI at least slightly more than CEU. I could only spot two exceptions: Orcadians and Basques. So we can well say that CEU are, at least in contrast to Africa, a paradigm of Europeanness (after Orcadians and Basques) – however no judgment can be made in relation to other outgroups (from Asia) based on this paper’s data.
Some significant structure within Europe
An interesting element in this supplemental fig. S1 is the second (vertical) dimension. In most tripartite comparisons between CEU, YRI and another European population, CEU and the other Europeans overlap in the second dimension, which only reflects diversity within Yorubas themselves. I understand that if Yorubas are more internally diverse than these two European populations, the potential structure between NW Europeans (CEU) and the compared third population is not-significant, trivial, irrelevant.
This is the case for: Swedes, Irish, Germans, German-Swiss, Belgians, Scots, Orcadians, Dutch, French-Swiss, French (two different samples), Polish, Austrians, Hungarians, Czechs, one of the two Russian samples (POPRES), Spaniards, Portuguese, Bosnians, Croatians, Romanians, Greeks, one of the two Italian samples (CEPH-HGDP), Tuscans, Italian-Swiss. This was also the case for Turks (not technically European) but not for any of the other West Asian (Palestinian) samples nor the Ashkenazi Jewish one (which is the most Europanized of all Jewish subgroups).
Among Europeans, a number of populations show more structure in comparison to CEU (and hence the majority of Europeans) than Yorubas show among themselves, defining a second dimension in intra-European terms. These “outlier” European populations are:
- Russians CEPH-HGDP (which I believe are from the Far North and have probably a strong Finnic component)
- Italians POPRES (which are partly from the South – North Italians alone did not contrast much with CEU)
In addition all the Palestinian groups (“Palestinian”, “Druze”, “Bedouin”) also show such contrast with CEU, as do Ashkenazi Jews but not Turks.
Follow the four relevant eigenvector graphs:
|Comparison with Basques|
|Comparison with POPRES Italians|
|Comparison with Sardinians|
|Comparison with CEPH-HGDP Russians|