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August 15, 2017

Roman cultural history has almost no demographic imprint

Filed under: ancient Population Genetics,History,Mary Beard,Roman History — Razib Khan @ 9:48 am

Several friends have asked that I weigh in the recent dust-up between Nassim Nicholas Taleb and Mary Beard. I haven’t for a few reasons. First, I can’t really be bothered to go incognito and see every detail of Taleb’s argument, as he has me blocked on Twitter (he called me a fucking idiot or something at some point). Second, the passion around this topic has little to due with genetics or ancient history from what I can see, two topics which I am actually interested in. Rather, it’s more about contemporary geopolitics. This is interesting too, and I have opinions on that, but I try really hard to keep history and politics in separate silos unless I am explicit about the connections and relevance. That’s because I don’t see classical history as simply something instrumentally important for modern times, but interesting in and of itself (the same goes for population genetics).

And for what it’s worth, Mary Beard says the same in her conclusion to SPQR. The ancients were ancients. Let them be what they were.

That being said, as someone with knowledge sets in ancient history and historical population genetics, I will make a few statements and let others interpret them however they wish (to be frank, I’m not going to cede ground to any of the experts I’ve seen who hae spoken on the intersection of these two knowledge sets, so I figured it was time to put something somewhere beside Twitter).

* The prior probability that a Roman officer of the period in Britain would have visible black African ancestry (as seems clear by the cartoon, though no one has asked the cartoonists what their intent was) probability seems rather low. But it is non-zero, because a small minority of Roman subjects and citizens would have been defined as black by their physical appearance if they were alive today (they are mentioned passingly in the literature and texts from the period). Including in Britain.

* The probability conditional that he was based on an officer in Britain who was a native of Tidis is low, but higher. Several historians have pointed out in defense of the cartoon’s plausibility that there were many North Africans in Roman service, as well as prominent North Africans in Roman history (to name three of note, Septimius Severus, Tertullian, and St. Augustine). Whole tribes of what we’d today term Berbers enrolled in the Roman military a federates.

There are several separate issues to note. First, of the many North African genotypes I’ve seen detectable Sub-Saharan ancestry is found in almost all of them. But, many (most?) North Africans do not look visibly of Sub-Saharan African ancestry (see list of heads of states of Algeria). Second, both historical and genetic evidence indicates that this admixture from Sub-Saharan Africa is overwhelmingly (though not exclusively) from the period after Islam and the rise of a much bigger trans-Saharan trade (see Genomic Ancestry of North Africans Supports Back-to-Africa Migrations). Modern North Africa does have a large population today of people who are black or of obvious part-black ancestry, but this is due to the slave trade under Islam, and not antiquity.

* As evidence of the lack of non-European ancestry the paper The fine-scale genetic structure of the British population has been submitted. This is a great paper with best-of-breed methods and a massive data set of native English, with regional data. How do we resolve textual and archaeological evidence of people born outside of Britain during the Roman period in Britain with their lack of long-term genetic footprint among native modern Britains?

These sorts of questions need to be integrated in a broader context of the demography and genetics of antiquity that we have. On the whole looking at papers on modern and ancient DNA I am surprised by the lack of perturbation on the genetic structure attributable to the Roman period across Western Eurasia. I will offer two likely reasons that are related.

First, Classical civilization was an urban one, and the textual evidence we have is going to be highly skewed culturally in terms of our perception. The Roman world was predominantly written in cultured Latin and Greek (from what I have read the early translations of the Bible are indicative of a more pedestrian background of Christians due to the class markers of their lexical choices and idioms). But it was not necessarily spoken in cultured Latin and Greek across vast swaths of its territory. Even in St. Augustine’s time Punic was still spoken the North Africa countryside, while the persistence and resurgence of Basque and Berber, and perhaps Brythonic Celtic in Britain, attest to vast reservoirs of people who were under the Roman peace, but not of it (also, the persistence of Albanian from a native Illyrian substrate). Because of the resources historians have on hand, text, there is going to be a major lacunae in our understanding and perception of the past. We hear the urban elites speaking to us. Not the rural majority.

Second, Classical civilization was an urban one, and this might have a major impact on the demographic consequences of migration. At any given size the effective breeding population is smaller than the census population, and the breeding population may not be representative of the overall population in terms of their genetic character. More specifically, it seems highly possible that the cosmopolitan urban Roman cities were massive demographic sinks. Rome before the Gothic Wars wars was a massive city, not too far on the path of decline from its early imperial peak. But by the year 600 it had decreased its population to the point that vast swaths of the city were abandoned. Where did these people go? No doubt some of the elites scattered. Cassiodorus simply moved when barbarism came to his front step. But this was less possible for the urban proletariat. There is strong evidence that slaves in the ancient world were not replacing themselves reproductively due to brutality under which they lived. Some of the same was likely true of the urban proletariat.

* There is a difference between the inheritance pattern of culture and genes. In The Geography of Recent Genetic Ancestry across Europe this passage has always stuck out for me: “There is relatively little common ancestry shared between the Italian peninsula and other locations, and what there is seems to derive mostly from longer ago than 2,500 ya…The rate of genetic common ancestry between pairs of Italian individuals seems to have been fairly constant for the past 2,500 years, which combined with significant structure within Italy suggests a constant exchange of migrants between coherent subpopulations.”

The straightforward conclusion from this is that the Latinization of the Italian tribes and Magna Graecia occurred with no great demographic transformation. Modern Italy has within it the ghost of tribes long gone. This is notable because if you read the historical records of the Roman period you see evidence of trade, transport, and migration. But the genetic data would not lead you to this conclusion outside of Sicily and a few parts of Southern Italy.*

Above I have presented my reasoning for why this might be. But I think what it tells us that genetic data can informs us when there is a demographic turnover, and therefore a cultural turnover, but it will miss cultural turnovers which don’t have demographic impacts. These are many. To give a few examples, the rise of Islam in South Asia and Southeast Asia, the Latinization of the Western Mediterranean, the de-Latinization of Britain after the withdrawal of Roman legion and before the mass arrival of Saxons, and arrival of Buddhism in East Asia. All these are massive historical and cultural events, but they would not be visible in the genetic record.

If you want to learn about Roman history there are many books you could read. But I do recommend you try Bryan Ward-Perkins’ The Fall of Rome: And the End of Civilization. It’s a nice materialist take, and I think it gets to the underlying dynamics of institutional fragility of ancient civilization which was so easily wiped away by barbarism.

Addendum: The migration of the Slavs, Anglo-Saxons, and the Islamic Empires, all seem to differ from antiquity in having a major demographic impact. Why? I the case of massive institutional collapse, as in the first two cases, very old dynamics of inter-group competition arise, and famine probably does the rest of the trick. For Islam, it was a genuinely cosmopolitan civilization, with a more complex gradation between free and slave than in antiquity. Though it was quite brutal, African and Turkish slaves became free, and their genetic impact can be seen throughout the Islamic world.

* Like Spain, a substantial proportion of the Sicilian gene flow exchanged is almost certainly due to the Islamic period. There are segments of North African and Sub-Saharan ancestry in Sicilians, albeit to a smaller extent than in Spain (in keeping with the shorter time period as part of the Islamic world).

January 2, 2013

When Rome fell civilization did decline

Filed under: Antiquity,History,Late Antiquity,Roman History — Razib Khan @ 9:37 pm

Before the Holidays I mentioned that I was rereading Bryan Ward-Perkins’ The Fall of Rome: And the End of Civilization. Why do I hold this book in such high esteem? Because of figures such as the one to the left. Granted, this chart is not from The Fall of Rome, but that book has an extensive bibliography which drew me to research on long term trends in pollutant concentrations. What you see illustrated are variations in the concentration of lead in ice cores from Greenland. Why is lead so important? Because it is a noxious byproduct in various primitive metallurgical processes. The basic thesis that Ward-Perkins fleshes out in great detail in The Fall of Rome is that the material basis of European life suffered a sharp regression after the collapse of the Roman Empire. In short the fall of Rome was the end of civilization, and what came after was coarser and more elementary in character. This may seem “common sense,” but it is actually a matter of some dispute and debate in the academy.

When discussing this issue there are two primary objections which always seem to come to the fore. First, after the de facto collapse of the West Roman imperium in the first half of the 5th century there were other societies of importance and grandness on the historical stage (see The Inheritance of Rome, When Baghdad Ruled the Muslim World, and China’s Cosmopolitan Empire). Far to the east of faded Rome Tang China’s glory waxed in the nadir of the European regression between 600 and 750. More well known to Westerners, the same period saw the apogee of Arab Islamic civilization. But the data above indicate that the industrial production of these two polities did not match that of the period around the peak of the Roman Empire. I refer here to period, because of course the Roman Empire flourished at the same time as Han China, and Sassanian Persia. The collapse of the 5th century was not a collapse of civilization as such, but of the western terminus of the oikoumene. And this decline was not compensated for by greater vigor in the Islamic center, or Chinese east.

Marcus Aurelius, 2nd century

A materialist perspective has the elegant attribute that it is less malleable in the hands of those with stylistic polish and the will and skill to engage in selective massaging of sources. I can assert plausibly I think that that the classical civilization which produced Thucydides, and later Polybius, Tacitus, and Ammianus Marcellinus, was superior in the fineness of its high culture than that in which Jordanes or the Venerable Bede flourished. But if an individual is clever, erudite, and set in their proposition, it will be impossible to definitively refute someone who holds that 8th century Anglo-Saxon England was no less cultured than 5th century Athens or 2nd century Rome. And if the exposition of the counter-intuitive position is placed in the hands of a cunning sophist, and the one who endorses common sense is plain and less learned, then the battle is already lost before it is begun. Terms like “superior” and “cultured” are slippery, and the whole enterprise of grading societies is held in bad odor in our age. A barrage of facts curated with intent to support a preposterous thesis can overwhelm simple sincerity. But the quantitative consequences of material production are not as contextualized or easily problematized. It is simply fact that proto-industrial production in the post-Roman world had regressed, and with it an array of material comforts and minor luxuries vanish from the record or become very rare. The dull can defeat the sly simply by pointing to the angle of the line on a chart.

A broader and more fundamental issue is that one must question how one judges the rise and fall of civilizations and society. From an orthodox Muslim or Christian perspective the collapse of Rome in the 5th century was an unfortunate incident, but ultimately secondary to the reality that the western half of the civilized world was to soon to be permeated by the presuppositions of their respective religious creeds. St. Augustine’s The City of God is only the most extended and thorough of many contemporaneous Christian apologetics which purport to explain the peculiarity of the collapse of the civilized (i.e., Roman) world just as the old pagan high traditions were finally superseded by Christianity. This is why I say that I find The Fall of Rome persuasive for partially normative considerations. Though I am willing to grant the superiority for various reasons of Christianity or Islam over the animistic primal religion of Republican Rome, or the Mystery Cults of the High Empire, I weight the extinction of industrial production of pottery and the reversion to localized barter economies as of greater consequence. Matter is more critical necessary precondition for civilization than mind. I doubt that Tacitus was anymore brilliant than Bede, but the former shone with more absolute greatness of the cultural capital which he could mine and leverage. The withering of the Christian church in the Balkans and England is a testament to the fact that higher religion themselves are preconditioned on a minimal level of social complexity and organization. It seems likely that by the 5th century Christianity succeeded in spite of the collapse of the West Roman Empire, not because of it. Rather than being a minor problem of history, the disturbance of the Roman order was a disaster for institutional Christianity, from which it only slowly recovered, still maintaining its original Roman outlines despite the Germanic interlude.

There are often debates as to whether fields like anthropology or history are humanities or social sciences. The truth is almost certainly both. In many ways I find archaeologists, particularly those of prehistory, theory-poor. Rather, what theory they attach to their wealth of material remains seems to be imbibed from the spirit of the times. Before World War II they were keen to illustrate the congruence of their material results with a migrationist narrative, while after World War II they rejected such models. But though archaeology can often tell us little directly in and of itself about the creators of a material culture, the flux of that material culture can tell us a great deal about aspects of that given society’s material workings. Technology is predicated on basic laws of nature, and those laws of nature produce constraints in the possibilities. Though it is possible in theory that Europeans between 500 and 1000 AD developed complex social systems which were also more ecologically friendly than those of antiquity (so as to generate less pollution in the material record), a more parsimonious explanation seems to me to be that in fact those societies were simpler, and that the order and institutions necessary for large scale proto-industrial production which had evolved organically from 1st millennium BC down to the Roman era had disappeared. This is simply not a matter of discourse, dialogue, debate, or contexualization. It is.

February 2, 2011

Empires and Barbarians: The Fall of Rome and the Birth of Europe

Link to review: Say it with me: Völkerwanderung

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