I am currently reading Peter Heather’s Empires and Barbarians: The Fall of Rome and the Birth of Europe. This is a substantially more hefty volume in terms of density than The Fall of the Roman Empire: A New History of Rome and the Barbarians . It is also somewhat of a page turner. One aspect of Heather’s argument so far is his attempt to navigate a path between the historically tinged fantasy of what its critics label the “Grand Narrative” of mass migration of barbarian tribes such as the Goths, Vandals and Saxons during the 4th to 6th centuries, dominant before World War II, and its post-World World II counterpoint. As a reaction against this idea archaeologists have taken to a model of pots-not-people, whereby cultural forms flow between populations, and identities are fluid and often created de novo. This model would suggest that only a tiny core cadre of “German” “barbarians” (and yes, often in this area of scholarship the most banal terms are problematized and placed in quotations!) entered the Roman Empire, and the development of a Frankish ruling class in the former Gaul, for example, was a process whereby Romans assimilated to the Germanic identity (with the shift from togas to trousers being the most widespread obvious illustration of Germanization of norms). I believe that liberally applied this model is fantasy as well. Being a weblog where genetics is important, my skepticism of both extreme scenarios is rooted in new scientific data.

There are cases, such as the Etruscans, where the migration is clear from the genetics, both human and their domesticates. The peopling of Europe after the last Ice Age is now very much an open question. The likelihood that the present population of India is the product of an ancient hybridization event between an European-like population and an indigenous group with more affinity with eastern, than western, Eurasian groups, is now a rather peculiar prehistoric conundrum. It also seems likely that the spread of rice farming in Japan was concomitant with the expansion of a Korea-derived group, the Yayoi, at the expense of the ancient Jomon people. And yet there are plenty of inverse cases. The spread of Latinate languages and Romanitas did not seem to perturb the basic patterns of genetic relationship among the peoples of Europe. The emergence of the Magyar nation on the plains of Roman Pannonia seems to have involved mostly the Magyarization of the local population. In contrast, the Bulgars were totally absorbed by their Slavic subjects culturally, leaving only their name. The spread of the Arabic language and culture was predominantly one of memes, not genes (clearly evident in the current dynamic of Arabization in parts of the Maghreb).

And yet you will note that there is a slight difference between the few examples I’ve cited: population replacement seems to have occurred in the more antique cases, rather than the more recent ones. This would naturally bias the perspectives of historians, who have much more data on more recent events (no offense, but archaeologists seem to be able to say whatever they want!). The Etruscan language itself is known only from fragments, while the happenings in prehistoric Europe and India can only be inferred very indirectly. I now offer a modest hypothesis for the distinction, why in some cases is it just the “pots” which move (Arabs), and in other cases it is the people who move (the Japanese). In cases of population replacement there is often a shift in mode of production. In cases where there is the diffusion of culture it is often a system or set of ideas which rent-seeking elites can exploit to maintain their position, or perpetuate it, flow across space. Islam was not only a potent ideology which bound the tribes of Arabia together so that they could engage in collective action, local elites across the new Muslim-dominated world found it a congenial international system whereby they could integrate themselves into a civilization of elite peers, as well as justify their god-given position at the apex of the status hierarchy (granted, many had this in the form of Christianity or Zoroastrianism, but once the old top dogs were overthrown the benefit of these systems was considerably less). The spread of Yayoi culture in Japan involved a shift from more extensive, toward more intensive, forms of agriculture. Their population base was greater, and the domains of the Jomon were left “underexploited” from the perspective of the more productive mode of agriculture which the Yayoi were engaged in. It need not be an issue of mass slaughter or extermination, a high endogenous rate of natural increase as well as disease, combined with assimilation and co-option of local elites, could result in the swallowing up of a population engaged in a less intensive mode of production. This sort of hybrid aspect of cultural and genetic expansion, whereby the local substrate is assimilated and synthesized with the expanding ethnic group, seems to be a good fit to the pattern that we see among the Han of China.

But shifts from modes of production exhibit some level of discontinuity, insofar as there are diminishing returns once all the land appropriate for that mode of production has been taken over. Farmers who are expanding into land held by hunter-gatherers or those practicing less intensive forms of agriculture can have enormous rates of natural increase because they’re not bound by Malthusian constraints. This is evident in the United States, until the late 20th century the majority of the ancestry of the white population of the republic descended from those who were counted in the 1790 census. The reason had to do with the extremely high birthrates among white Americans. When regions such as New England were “filled up,” they pushed out to the “frontier,” to northern Ohio, then to the Upper Midwest, and finally the Pacific Northwest. And in the process there was a radical change in the genetic variation of North America, as the indigenous populations died from disease, were numerically overwhelmed, or genetically absorbed. This is an extreme case scenario, but I think it illustrates what occurs when modes of production collide, so to speak. The pattern in Latin America was somewhat different, though an amalgamated Mestizo population did emerge over time, there was not the wholesale demographic replacement in many regions. And I believe that the reason is that the Iberians did not bring a superior mode of production, rather, the large local population base engaged in agriculture presented an opportunity for rent-seekers to place themselves atop the status hierarchy. Sometimes this involved intermarriage with local elites, as was the case in Peru where the nobility of the Inca intermarried with the Spanish conquistadors for the first few generations (the whiteness of the Peruvian elite despite the fact that the old families have Inca ancestry is simply due to dilution as successive generations of lower Spanish nobility set off to the New World and married into Creole families).

By the Roman period I believe that much of the core Old World was “filled up” in terms of intensive agricultural production. So most, though not all, of the changes in ethnicity or identity are biased toward elite emulation and novel identity formation. The Turks did not bring an innovative new economic system whereby they replaced the Greek and Armenian peasantry in Anatolia, rather, on the contrary peculiarities in the Turkish Ottoman system of rule produced a situation where the old families were usually replaced in positions of power by converts from the Christian groups who assimilated to a Turkish identity. When the economic arrangements reach stasis and the population is at Malthusian equilibrium change is a matter of shifting identities and affinities of the rent-seekers. When radically new economic systems emerge, opportunities for disparate population growth present themselves. Ergo, England went from being demographically dwarfed by France in the 17th century, to surpassing it in population in the 19th. England was of course the first nation to break into a new mode of production since the agricultural revolution.

Credit: Thanks to Michael Vassar for triggering this line of reasoning after a conversation we had about the Neolithic revolution.