The idea of a “folk wandering” was once a well accepted idea in history, in particular for the phase of the Late Roman Empire, and the subsequent fall of the Western Empire. It’s a rather simple concept: the collapse of the Pax Romana occurred simultaneous with a mass ethnic reordering of Europe, primarily via the migration of Germanic peoples across its frontiers and beyond. The most extreme depictions of this can be found in the works of the British cleric Gildas: German hordes literally drove the British into the sea, until they only retained their redoubts around the “Celtic Fringe.”
This was an extreme understanding of the dynamics of post-Roman Europe. It was, and has been, succeeded by another extreme model: that the ethnic change in the post-Roman world was more illusion than substance, a manner of shifting nomenclature, than lineage. For example, I have commonly read in this literature that the Germanic tribes which crystallized as “federates” to the Romans, or on occasion as antagonists (or vassals to hostile powers such as the Huns) were ad hoc collections of mercenaries who created an identity de novo. In some cases it is posited that masses of Romans simply assimilated to the identity of a small cadre of warriors whose demographic impact was trivial. This is the scenario that is posited for the transformation of Celtic Britain into Germanic England. But let’s shift away from that extreme case, and look at another one: the 5th and early 6th century kingdom of the Vandals in Norh Africa.
What does this have to do with genetics? Easy. A few years ago the historian Peter Heather came out with a book, Empires and Barbarians, where he attempted to resurrect the idea of a folk wandering. Instead of the idea of post-Roman Europe being dominated by the rapid emergence of ethnic identities from a small platoon of warriors, he posits that there were general transfers of the freeborn caste of whole Germanic tribes across Northern Europe. The women and children moved with the men. Heather’s thesis is more modest than that of Gildas. He does not suggest there was total, or even wholesale, replacement. Rather, the Franks, Visigoths, Anglo-Saxons, etc., were not rapid social constructions on a chaotic cultural landscape, but peoples which were organic developments out of a broader Germanic cultural milieu who were transplanted in toto across the post-Roman world. The kludge of a dual monarchy in the case of the king of the Vandals and Alans does not make much sense if ethnic identity was so fluid as to be purely instrumental in a proximate sense. Rather, even in extremis the Alans insisted upon retaining their identity as a people in the face of the more practical option of total assimilation into the Vandal horde. If ethnic identities are purely ephemeral labels given to political coalitions of mercenaries this behavior makes no sense. On the other hand if these identities carry with them the weight of history, of cultural memory, then these actions and baroque compromises are rendered understandable.
The Vandal kingdom of North Africa in some ways is probably the most least plausible case for a folk wandering, in that the wandering was quite extensive, and the Vandal kingdom seems to have been the least culturally robust its long term impact (suggesting perhaps a superficiality of their hegemony). And I have read scholarly literature which does argue that the concept of “Vandal” and “Alan” were simply constructs, which post-Roman elites easily took upon when the circumstances suited them. There is something to the idea that individuals can acculturate, but I think what the idea of radical social constructionism in post-Roman Europe misses is that you need a culture to assimilate to, and that culture can only exist in the first place due to a critical mass. Could a small number of German and Iranian warriors, without any women or other elements of their freeborn population replicate their tribal culture over thousands of miles? I think not. Single elements of culture are replicable, but whole cultural systems often exhibit more integrity and contingency than is obvious from the outside.
To explore the possibility of Germanic ancestry in North Africa I decided to use the Henn et al. data set. I merged it with the Utah white sample from the HapMap. I then had 188,000 markers. My goal was to find runs where Southern and Northern Europeans were distinct. Below are two sets of runs where Northern and Southern Europeans were distinct. The first are supervised, and the second unsupervised.
I don’t really see any good evidence of the impact of specifically a German element in this. The Vandals seem to fail the test of long term demographic impact in these samples. To really explore this issue I’d have to look at the ancestry at the chromosomal level, and look for matching haplotypes and segments identical-by-descent. Perhaps I will in the future.
Image credit: Wikipedia