New ancient DNA research has identified the bacterium Yersinia pestis, which causes the deadly and epidemic illness known as plague, in Chalcolithic and Bronze Age Central Eurasia, from Altai to Poland and the Caucasus.
S. Rasmussen, M.E. Alentoft et al., Early Divergent Strains of Yersinia pestis in Eurasia 5,000 Years Ago. Cell 2015. Open access → LINK [doi:http://dx.doi.org/10.1016/j.cell.2015.10.009]
The bacteria Yersinia pestis is the etiological agent of plague and has caused human pandemics with millions of deaths in historic times. How and when it originated remains contentious. Here, we report the oldest direct evidence of Yersinia pestis identified by ancient DNA in human teeth from Asia and Europe dating from 2,800 to 5,000 years ago. By sequencing the genomes, we find that these ancient plague strains are basal to all known Yersinia pestis. We find the origins of the Yersinia pestis lineage to be at least two times older than previous estimates. We also identify a temporal sequence of genetic changes that lead to increased virulence and the emergence of the bubonic plague. Our results show that plague infection was endemic in the human populations of Eurasia at least 3,000 years before any historical recordings of pandemics.
The bacterium was yet unable to cause the bubonic form of the plague and could not spread by means of fleas either. Instead it probably caused pneumonic and spticemic plague and was propagated by coughing and sneezing, much like the flu.
In spite of the hype, the prevalence of the plague was low: only 7 out of 101 samples tested positive for the bacterium, ranging from c. 2800 BCE (Altai) to c. 1000 BCE (Southern Azerbaijan, Iran). A 7% prevalence is still significant but it's also obvious that 93% of the people in the period studied did not die from the plague, so let's not exaggerate, alright?
The exaggeration is already seeded in the study with passages as this one:
These early plagues may have been responsible for the suggested population declines in the late 4th millennium BC and the early 3rd millennium BC (Hinz et al., 2012, Shennan et al., 2013).
Neither of the referenced studies (see here and here) deals with Eastern Europe, West Asia or Central Asia, and the analyzed dates only slightly overlap with the period in which Y. pestis is found, so I fail to see the logic. It is true that there could be a coincidence in the case of Little Poland, where both Y. pestis and a demographic decline are apparent c. 2000 BCE but in all other cases it really needs a good deal of imagination to make any association.
In any case, it is clear that even the most virulent plague ever known, the Black Death, only managed to make a dent in the European demography and its consequences were not those of demographic re-expansion of the less affected populations (Polish, Basques) but a double socio-economic transition in two phases:
- The lack of manpower in the decades after the Black Death allowed the lower classes to renegotiate their situation in various ways. It was the period in which the feudal system was most dramatically eroded, with peasants gaining control on their farmed lands and lords losing large shares of their exploitative profits, while being forced to compete against each other for whom offered best working conditions to the now scarce farmers, who, legally or not, migrated from the worst places to the ones offering better conditions.
- A reaction by profit-jealous landlords that largely replaced farming by husbandry, which requires less manpower. A well known case were the English enclosures, which would, slowly but steadily, set the foundations of Capitalism.
This is explained by historian, actor and director Terry Jones in the following video:
So the consequences and context of these epidemics must be considered adequately and not distorted nor simplified unduly in the line of the infamous Guns, Germs and Steel book, which greatly exaggerates the consequences of natural epidemics and is one of the favorite books of Eurocentric reactionaries with a distorted and overly simplistic view of things. One of the "virtues" of the epidemic hype is that it somehow absolves the winners from their historical crimes, blaming them on nature almost alone: instead of genocide, they use these deformations of reality to blame the mass destruction of whole nations and populations, be them Neanderthals or Native Americans, on "natural causes".
Instead I wonder about the real demographic impact, not yet well assessed, of the epidemics, and also about the real socio-economic consequences of such demographic declines. Of course, they could have allowed for localized migrations in the aftermath of the epidemics (or whatever other causes of demographic declines) but they should also have favored at least short-term renegotiations of the social order in favor of the suddenly scarce working classes (farmers). This "upward mobility" and partial "leveling" of what was already in many cases a feudal-like caste society should have dramatic effects in the constitution of the nations of the Bronze Age, regardless of later re-adjustments and expansions, which one can imagine as an imperfectly cyclical process.