As we’ve seen, the evidence – largely archaeological evidence, by the by (Liebeschuetz thus fits with many other historians in the “decline and fall” counter-reformation in relying heavily on archaeological data) – suggests that urban centers declined markedly beginning in the fourth century, with that decline accelerating as the empire crumbled. That of course raises the fairly obvious question: where did all of the people go? One possible theory is that the population mostly ruralized, moving out of the city and into the countryside. That might even suggest a positive change, if one accepts the view that ancient cities were mostly “consumer” cities which didn’t produce much value but instead survived off of taxes and rents extracted from the countryside. In that view, the decline of cities could simply be a product of the collapse of systems of exploitation as the political order which maintained them weakened.

It’s a plausible theory and the only problem with it is that it doesn’t appear to have actually happened.

Here the key archaeological method is what is called “field survey“. While readers are probably more familiar with the intensive excavation work done at famous sites like Pompeii or Vindolanda, one tool archaeologists have to study the past is to survey large areas, sometimes by air, sometimes by on foot, sometimes with ground penetrating radar, in an effort to map out larger scale settlement patterns in the past than would be possible by labor-intensive single-site excavation work. Dateable remains (pottery most often) allow for archaeologists to get a rough sense of the dates in which sites were inhabited and in some cases building remains and the like can give some sense of what kind of settlement was present. The “error-bars” on some of this data can of course be large, but they offer a tool for tracking long-term changes in land use patterns. On the flip side, these sorts of studies really become valuable only when you have a lot of them to create a robust data-set over a fairly large area that lets you adjust for purely local patterns and distortions. Fortunately in much of the former Western Roman Empire and especially in Roman Italy (where these studies are very important for the study of Roman demography and agriculture) we’ve hit the tipping point where there is enough archaeological data to begin reaching for conclusions.

Now there is an immediate difficulty with using this kind of evidence, which is that for reasons we’ll get to in a moment (though they are reasons that tend to also be bad for the “change and continuity” argument), we have a major confounding variable here: site visibility. Our ability to see a site, archaeologically, is heavily dependent on factors like building material and the quantity of imperishable goods (especially pottery) that people are using. For reasons we’ll get to, compared to, say, second century AD communities, sixth century AD communities tended to build their buildings in far more perishable (and thus less visible) materials (like wood) and also tended to use a lot less imperishable household goods. Consequently, it is substantially harder to see a sixth century village than it is to see a second century villa.

Nevertheless, the decline is so marked and so consistent as to strongly suggest there is something real here. R.P. Duncan Jones (in “Economic Change and the Transition to Late Antiquity” in Swain and Edwards (eds) Approaching Late Antiquity (2006)) assembles some of the site data from around the empire; there is unsurprisingly a lot of regional variation (with some regions, like Syria, actually moving against trend), but in the western Empire (except N. Africa; decline there comes later) the trend is fairly clear, with site numbers declining (often drastically by half or more) beginning in the late third or fourth centuries. Bryan Ward-Perkins in The Fall of Rome notes a field study outside of Rome in which the number of sites declines by three quarters. Site data accumulated like this isn’t often very chronologically precise, so we’re dealing with centuries, not decades, but the clear trend suggests rural population decline, not an urban population ruralizing. To be visible to us in this way, the decline must have been quite severe.

To give a sense of the scale of the decline, here is an abbreviated version of a chart from Bruce Friar’s “Demography” chapter in the second edition of the Cambridge Ancient History, which breaks down the estimated population of the Roman Empire by region and adds the dates when each of those regions got back to their Roman-era population:

Chart from Frier, “Demography” CAH2 XI (2000), 814. Some of these figures would likely see some revision today, mostly downward revisions of growth combined with upward revisions in population reflecting a somewhat (but generally not massively) higher estimated pre-Roman population.
Note that the decline in the East was, as noted last time, both later and generally slower. The reason for the later times to reattain Roman population here in many cases is that the major medieval Islamic population centers were further East (e.g. Baghdad under the Abbasids) placing them outside the traditional bounds of the Roman Empire, but also that the Roman East was much more urbanized and densely populated compared to its land area than the Roman West in the second century (or at any time during the Roman Period) so the “population to attain” bar on the East was much higher. After all, the cities of places like Syria or Egypt were in many cases centuries or even millennia old when the Romans showed up.

Now the long times there to regain the Roman population can be a bit deceiving (and are very approximate). For reasons we’ll get into shortly, population growth from 600 to 900 or so in Europe was very low, so the issue here isn’t that the decline was so steep that it took many centuries to recover from, but rather that the decline was from a high population equilibrium to a low population equilibrium, both of which were, under their own conditions, stable (if that is confusing, don’t worry, we’ll delve more into it in a moment). Second, the apparent gap between places that “caught up” before 1300 and those that “caught up” after it is smaller than it looks, because of course the mid-1300s represent a massive population discontinuity over the entire broader Mediterranean world due to the Black Death such that a lot of those places “catching up” in the 1200s probably fell behind again due to the plague and then caught up again in the 1400s or early 1500s.

But this now raises two related questions: first, why did population decline so sharply and second, what was the impact on quality of life that resulted? The old answer to the first question was of course “the barbarians killed everyone” but as we’ve seen, while the fifth century was a violent time, the violent discontinuities were not that extreme. Surely the violence of the period has something to do with some of this declining population, but as noted, the underlying population (with their language and religion) didn’t much change (and the raw number of “barbarians” coming over the frontier was, in demographic terms, fairly small). Most of those Roman cities decayed, rather than being burned. But if the “barbarians” didn’t kill everyone, what did and why did that somehow have a negative impact on the survivors? The answers to these two questions are actually linked in that they depend on the same evidence, so that is where we will go next.

Bret Devereaux, “Collections: Rome: Decline and Fall? Part III: Things”, A Collection of Unmitigated Pedantry, 2022-02-11.