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Fulani

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Genseric

Genseric

Sara Tishkoff and company are leveraging their massive African data set again, with a paper out which surveys the diverse landscape of lactase persistence genetics across continent, Genetic Origins of Lactase Persistence and the Spread of Pastoralism in Africa. Many of the results were well known or could have been anticipated, selection for the trait in Africa, or even the fact that lactase persistence in the Khoikhoi derive from East Africa. So let me quote at length one section which I think is rather notable: In fact, the T-13910 variant in the Mozabite from Algeria occurred on the same haplotype background as observed in Middle Eastern populations, whereas the Fulani from Cameroon and the Bulala from Chad shared the same haplotype background with Europeans. The Fulani also shared a distinct T-13910 haplotype background with the Arabic Baggara. These patterns suggest that the distribution of observed haplotype variation might be due to gene flow that occurred over time from outside and within Africa possibly during key historical events, such as the settlement of the Roman Empire in parts of northern Africa and the expansion of the Arabs prior to and during the Ottoman empire within the last 2,000 years.67 These inferred migration events are also consistent with studies based on mtDNA, Y chromosome, and autosomal genetic variation.

The T-13910 variant is the one that is very widespread in Western Eurasia, from Northern Europe, all the way to Northwest India. Earlier analysis had suggested hat the Fulani people of the western Sahel carried the the European and South-Central Asia mutation for lactase persistence, as opposed to the ones more common in Eastern Africa or the Middle East. This was curious, but not totally incomprehensible in light of the fact that it seems that populations such as the Tuareg mediated gene flow across the Sahara, and the Berber polities extended to the northern Sahel. What is surprising is that upon closer inspection the flanking regions around T-13910 in the Fulani, but not the Mozabite Berbers, exhibit a signature which indicates a European origin. The Mozabite Berbers are a rather isolated group, probably representative of genetic variation in large part before the settlement of non-Berber populations along the coastal zone in antiquity. So it would not surprise me if T-13910 haplotypes in much of Morocco and Algeria are of the European, and not the Mozabite, flavor. But that still prompts the question, why are there two variants in the Maghreb when they are functionally the same?

A plausible model is that the European haplotype came along with the Vandals, a Germanic barbarian tribe with origins in southern Scandinavia and northern Germany which conquered North Africa in the early 5th century A.D. Of course the allele could have arrived in the centuries of earlier Roman rule, but the T-13910 mutation is generally found in low frequencies in Mediterranean populations like Italians. In contrast it is well over 50% among Northern Europeans. It is fashionable in studies of Late Antiquity to assume that the Vandals, and their Alan confederates, were ad hoc social constructs which somehow congealed out of the political compost heap of the late Roman Empire. An alternative view, championed by Peter Heather (see Empires and Barbarians), is that groups such as the Vandals were a genuine volk engaged in wholesale migration. The idea that the Vandals were social constructs of some sort, and of trivial numbers, suggests that they made only a marginal impact and disappeared in totality after the conquest by the Byzantines in the 6th century of the Maghreb. But the presence of these distinctive genetic markers indicates that the Vandal numbers may have been substantial enough to allow for the transfer of the T-13910 allele to the Berber tribes which assimilated the the rural estates they still held.

Much of this is speculation of course. We’ll know the truth of the matter when someone does extensive resequencing of the whole region of LCT in a variety of populations. At that point presumably one might be able to discern if the Fulani allele is closely related to German ones in particular. The point is that these sorts of bizarre scenarios which are more in keeping with late 19th and early 20th century adventure fiction might actually be closer to much of history than we would have thought.

Note: I should add that Greg Cochran speculated in this direction a few years ago.

 
• Category: Science • Tags: Fulani 
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After the second Henn et al. paper I did download the data. Unfortunately there are only 62,000 SNPs intersecting with the HGDP. This is somewhat marginal for fine-grained ADMIXTURE analyses, though sufficient for PCA from what I recall. That being said, the intersection with the HapMap data sets runs from ~190,000 SNPs, to the full 250,000 SNPs (this makes sense since the Henn et al. #2 data set has some HapMap populations in it). So I’ve been experimenting a fair amount in the past few days, and I thought I would post on one issue which was clear in the original paper, but which I have replicated.


The Fulani (Fula) people of the western Sahel seem to have a relatively old West Eurasian component which has distinct affinities with the “Maghrebi” element discerned by Henn et al. In fact, the non-Sub-Saharan African ancestry of the Fulani is almost exclusively of this origin. To me this serves as a peculiar mirror of what you see in the Cushitic and Ethiopian Semitic peoples of the far east of the Sahel-Sudan latitudinal region. These populations also seem to be compounds of a Sub-Saharan Africa element with a West Eurasian one, but in their case the admixture is almost exclusively from a Southwest Eurasian (Arabian) component. Geographically these two symmetric admixture events make sense, but the exclusivity is still a bit surprising. Additionally, in both the case of the Fulani and the Ethiopian and Cushitic groups the admixture is widely distributed and even enough to imply that they are old events. I also assumed this because in some admixture runs a “pure” Fulani cluster partitions out, which is not unexpected for stabilized hybrid populations (all human populations are stabilized hybrids if you go back far enough).

To give you a flavor of what I’m talking about here are some screen shots of a run which is currently going. It has 180,000 markers. I removed Tunisians and many African populations from the Henn et al. data set, and included in the Utah whites from the HapMap. The individual plots show the ancestral proportions for each Fulani in the data set:

So what can we see here? First, let’s reiterate something: as in the case of the populations of the Horn of Africa the West Eurasian element in the Fulani is difficult to find in “pure” form in the populations from which it putatively derived. What does that imply? I think that that means that the Fulani have an origin in relatively recent historic time, on the order of 2,000, not 10,000, years. That is because I am skeptical that the Fulani would be able to maintain genetic distinctiveness for ~10,000 years from other populations around them. In contrast, the last 2,000 years have seen the rise of various cultural institutions, from trans-Saharan nomadism to Islam, which might slow down admixture sufficiently to maintain the differences between the Fulani and their neighbors. It also implies to me that the non-Maghrebi “Near Eastern” element which Henn et al. discerned is relatively a recent phenomenon in northwest Africa, else the Fulani should also carry it. How recent? Probably from Classical Antiquity down to the Muslim period. Observe that many North Africa groups have a red “European” element. This may be from Near Eastern populations, but I suspect that the fraction here is just too high to be explained by that. Also, you can see above that some groups in Morocco have nearly as much of this as Egyptians, but far less of the more genuine Near Eastern components.

In all likelihood the West Eurasian component came to the Fulani via the Tuareg or a related or antecedent population. So if you typed the Tuareg you would probably get a better sense of the “pure” “Maghrebi” genetic profile. These genetic results also can serve as fodder to understanding the ethnogenesis of the landscape of the Sahel. In the map above it is interesting to observe that the Hausa speak an Afro-Asiatic language, even though their West Eurasian component is far lower than the Fulani, who speak Niger-Congo dialects. What gives? I suspect that the difference here is that the Hausa are a case of elite emulation of a cultural complex which was much more integrated and elaborated by the time it arrived on the West African scene. This explains how there could be language shift, while in the case of the Fulani there was none. Another hypothesis is that Afro-Asiatic derives from Sub-Saharan Africa itself, and the Chadic (Hausa) group are basal to the phylogeny. I’ll let readers explore the implications of that. A final aspect, I put the quotations in the title because perhaps the Berber dialects spread via elite emulation, and the original Maghrebi ancestors of the Fulani spoke a different language, which has been lost? As they say, for every answer there bloom a thousand questions….

Image credit: Wikipedia, Wikipedia.

(Republished from Discover/GNXP by permission of author or representative)
 
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Razib Khan
About Razib Khan

"I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. If you want to know more, see the links at http://www.razib.com"