Measurements taken on skeletal remains in cemeteries in southwestern Germany indicate that the average height for men was about five feet eight inches, for women about five feet four inches, statures well above those of late medieval and early modern times. Measurements taken on skeletons in other regions are comparable. In Denmark, for example, the average height for men was about five feet nine inches-just above those for southwestern Germany-and for women about five feet four inches. These average heights were not achieved again until the twentieth century. Compared with earlier and later populations in the same regions, these average measurements show that most people had adequate nutrition during most of their lives and their living conditions were generally good
This is in line with the charts I posted below. With the introduction of the three-field system, mouldboard plow and horse collar northwest Europe, in particular the regions of northern France, the Low Countries and the Rhineland, surpassed the Mediterranean as the population center of the continent (at least its western half). During the expansionary phase, i.e., 500-800, the span covered by Barbarians to Angels, the Malthusian pressures would have been relatively modest. The screws would have been tightened up to the medieval demographic peak before 1300.
In any case, remember my focus on morbidity vs. mortality? It might be apropos in this case. The uncertainty and political instabilities due to the collapse of the Pax Romana could plausibly have increased mortality as peasants were exposed to the erratic depredations of barbarian warrior bands. But as depopulation occurred, in part because of withdrawal from the frontiers in places like Gaul (France) an western Germany of most farmers, those who opted to remain and take on the risks would be relieved of some Malthusian pressures. I think the chart of European heights does point to this as well, you can discern a slight upward trend after the Black Death due to a radical population reduction. I’ve reedited one of the charts for clarity:
As for Barbarians to Angels, the author doesn’t really make me reconsider. I’ve talked about my skepticism of the idea of revisionism in regards to the decline of Rome. The author argues that technological advances occurred during the Dark Ages, and that many cities remained active nodes in trade networks. But the author’s treatment is highly qualitative where he had concrete examples of how complex society persisted after the collapse of the Pax Romana, and he repeatedly scolds the readers to not judge Dark Age societies by modern standards which would tend to align more with the priorities of Roman civilization (e.g., reading, writing, arithmetic, public architecture, basically what we might term civilization). If the author wants to strip the term “civilization” of any normative biases brought to bear due to the prejudice of moderns, the argument is won, amassing a large collection of ornate weapons with which one might be buried is just as Cultured as writing letters to your friends laced with literary references. A good cup of mead is at the same level as a Falernian.