Possible causes of good net nutrition during the Middle Ages

At the outset, it is useful to consider why average heights were surprisingly large during the Middle Ages. One might debate the representativeness of the results, something that is useful more generally of findings so at odds with preconceptions.

According to the data at hand, northern European heights did not consistently exceed those of 800—1300 until the early twentieth century. One important factor in this remarkable pattern may have been climate. Agriculture during the period from about AD 900—1300 benefited from what climate historians call the ‘Medieval Warm Period.' Based on ice cores, tree rings, and other sources, climate historians believe that temperatures during this era were as much as 2—3°C warmer than a few centuries later, and 0.7—1.0°C above the twentieth-century averages (see Fagan 2000). At the beginning of this era, the Vikings settled in Iceland and later in Greenland. This temperature change may not appear to be significant, but it was enough to extend the growing season by 3—4 weeks in many settled regions of northern Europe. The weather was sufficiently warm that commercial vineyards were viable 300—500 km north of their range in the twentieth century. Moreover, it allowed cultivation of previously unavailable land at higher elevations. Therefore, a population that was probably smaller relative to later eras, quite possibly had a portfolio of better land from which to choose in producing crops. A result would have been

more agricultural output (at the same or less work effort) compared with the centuries immediately following the Middle Ages.

It is well known that economic isolation, in the form of little trade beyond local interaction, also characterized life during the Middle Ages, at least relative to later centuries when regional commodity markets developed significantly. Anthropometric historians have noted the benefits to health and average heights of geographic isolation, low population density, or lack of commercial development for outlying areas within Sweden, Austria Hungary, Japan, Ireland, and the United States (Margo and Steckel 1982, 1992; Sandberg and Steckel 1987; Komlos 1989; Shay 1994; Nicholas and Steckel 1997; Cuff 1998). The protective effect of isolation, in the era before effective public health, probably operated through insulation from communicable diseases. In this regard, it is notable that the bubonic plague made its dramatic appearance in the significant revival of trade during the late Middle Ages.

Urban areas were bad for health, as established from their high mortality rates and the small statures of those who resided in such places for a significant portion of their childhood growing years. To my knowledge, this demographic phenomenon was found in all areas of the world until the late nineteenth or early twentieth centuries, when public health measures and improvements in personal hygiene significantly reduced exposure to pathogens. Moderately large cities were absent from northern Europe until the late Middle Ages (for discussions of urban growth see de Vries 1984; Hohenberg and Lees 1985). As late as the end of the thirteenth century, significant urbanization was confined mainly to southern Europe, in northern Italian towns such as Milan, Florence, Venice, and Genoa, each of which probably exceeded 100,000 in population. At this time, Paris was the only city in northern Europe that may have fallen into this category. The southern Low Countries were moderately urbanized by the late Middle Ages (the fourteenth century), but the largest city Ghent, probably had no more than 50,000 inhabitants, while London and Cologne held fewer than 40,000 people at this time. Therefore, the overwhelmingly rural distribution of the population was an asset for health.

4.3