London survivors of the Black Death were healthier than their ancestors before the plague devastated the city. The reasons remain unclear and may be revealing about the long term effects of other disasters.
Dr Sharon De Witte of University of Southern Carolina examined skeletons from 200 years either side of the Black Death's arrival in 1347. She says, “Given that the mortality associated with the Black Death was extraordinarily high and selective, the medieval epidemic might have powerfully shaped patterns of health and demography in the surviving population, producing a post-Black Death population that differed in many significant ways, at least over the short term, from the population that existed just before the epidemic.”
In PLoS ONE De Witte reveals that prior to the disaster 30% of those buried in London cemeteries were aged 10-20, and almost 35% were between 20and 40. Afterward these figures dropped to 23 and 20% respectively. On the other hand, the proportion having survived past 70 rose from less than 10% to more than 25% (see graph below).
A disease that carries off the most vulnerable members of society might be expected to improve the average health, simply by removing the sickest members of the population. To the extent that this frailty is heredity the effect may be transferred to subsequent generations. However, De Witte notes that wages rose with the labor shortages and says further work is required to see which was the more important factor. Migration also increased after the plague and De Witte also raises the possibility that those arriving from the country were healthier than their city cousins.
De Witte notes, “The results of this study are particularly striking given that the Black Death was just the first outbreak of medieval plague, and the period after the epidemic was characterized by repeated crisis mortality resulting in particular from repeated outbreaks of plague. These subsequent outbreaks of medieval plague might have prevented population recovery following the Black Death.”
In the immediate aftermath of the plague transport networks broke down and some villages starved, particularly if there were not enough people to bring in harvests. However, it has also been claimed Ithat Europe was overpopulated in the lead up to the epidemic relative to what the technology of the day could win from the soil. If so, the loss of so many hungry mouths would have left more for the survivors once a measure of normality was restored.
De Witte found no significant difference in birth rates or infant mortality before and after the plague.
As a sample of only 600 bodies from once city the work is not necessarily indicative of the situation worldwide during the era, but matches studies of records from England and Spain, although these documents were skewed towards adult men in general and often towards the wealthy as well.