The Yersinia pestis bacterium that caused the Black Death was, in 2015, shown to be at least 5,000 years old. That is, it became prevalent at the beginning of the Bronze Age, around 3000 BCE, a time of increased urbanization, intensified agricultural production, and long-distance trade.
Fragile Ecosystems of Early Cities
Early cities—ancient and medieval—provided the perfect conditions for breeding and fostering pathogens. In Mesopotamia and elsewhere, they were ‘multispecies resettlement camps’, in the words of anthropologist James C. Scott. Walled to protect human inhabitants from other urban competitors and resource-hungry nomadic peoples, these cities were heavily dependent on the intensive overcultivation of their hinterlands. Legions of mostly unfree agricultural laborers, therefore, came into closer and more sustained contact with waterfowl, insects, and animals that harbored diseases.
The Epic of Gilgamesh, our oldest written narrative of this era, lauds the hero’s home city, Uruk, as divided into three parts: densely populated neighborhoods, clay-pits for the manufacture of more buildings, and folds for livestock intermingled with gardens and orchards for withstanding times of siege: perfect petri dish conditions for zoonotic diseases.
The very fact that none of these very early cities survived for more than a few decades is a testament to their fragile, virulent ecosystems.
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First Documented Account of an Epidemic
The onset of both pandemics and more localized epidemics, therefore, was and is inevitable. Moreover, these outbreaks always have a tendency to further weaken already fragile socioeconomic hierarchies.
The first documented account of an epidemic, in the year 430 BCE, also documents this societal breakdown. It comes from the Athenian exile-turned-pundit Thucydides, who wrote his history of the wars between Athens and Sparta after he was banished from his polis.
In the soaring funeral speech given by the Athenian general Pericles—and reported by Thucydides—during the winter before this epidemic broke out, Pericles praised the institutions of democracy in his polis and eulogized the young men who had died in the name of its values.
However, no sooner had the sound of Pericles’s soaring oratory died away, the policies and stratagems that had led to the war caused the outbreak of a plague that killed an estimated 75 to 100,000 people in the city over a three-year period—that is, at least half of the entire population of Athens.
A Misguided Decision in Athens
Sadly, this population had just recently increased because, at Pericles’s behest, families and agricultural laborers living in the surrounding region of Attica had been told to abandon their farms and crops to the Spartans, to avoid stretching the resources of Athens’s citizen-militia.
As a result, tens of thousands of now-impoverished refugees moved within the walls of Athens with their livestock, camping out in its narrow streets and marketplaces. Thanks to Athens’s formidable navy, Pericles had reasoned, the entire population could survive on supplies shipped into the port a Piraeus.
Some of the more than 30 pathogens, that have since been identified as causing the plague in Athens, came in with these overseas supplies, while others had just come in from the countryside. The result was probably typhoid, combined with viral hemorrhagic fever from person-to-person contact and certainly exacerbated by malnutrition and overcrowding.
Moreover, Pericles’s strategy of relying on imports from Athens’s overseas colonies and allies turned out to be unsustainable as those colonies were laid waste and the Spartans themselves acquired a navy and blockaded the port. Athens was starved into submission and surrendered its empire, its walls, and its democracy in 404 BCE.
Sequencing of Yersinia Pestis Genome
That is our first narrative of an epidemic. What about the first global pandemic? Our knowledge of this medieval plague has been utterly transformed in just the past decade, and much of that research was published in the inaugural double issue of The Medieval Globe.
The research was catalyzed by the discovery of one of London’s massive cemeteries for Black Death victims, which was then excavated by a team of historians and bio-archaeologists. In 2011, thanks to recent scientific advances, they were able to extract ancient DNA from the teeth of those victims.
This led, in turn, to the sequencing of the Yersinia pestis genome, in 2013, which revealed its morphology over time—including the mutation which caused the plague outbreak during the reign of the Roman Emperor Justinian, who himself contracted and survived it in the 540s, as well as the many near-simultaneous mutations—the polytomy or big bang, which catalyzed the Black Death, seven or eight centuries later.
Where Did Yersinia Pestis Come From?
These discoveries also enabled researchers to hone in on Yersinia pestis’s homeland and the conditions under which it can lie dormant or be revived. A few years ago, its epicenter was thought to be the Qinghai-Tibet Plateau in what is now northwestern China, where many DNA samples were found. However, the pathogen has now been located as emerging and incubating further north, in probably what is known as Kyrgyzstan.
That said, a historian of middle-period China, Robert Hymes, has presented convincing evidence that the Black Death’s ‘super-spreader’ phase did begin in China, and at least 100 years earlier than in Europe or Africa—meaning that the Black Death does not date to the 1340s, but to the early 13th or even late 12th century in Asia.
Common Questions about the Cause for the Outbreak of Black Death
The Epic of Gilgamesh lauds the hero’s home city, Uruk, as divided into three parts: densely populated neighborhoods, clay-pits for the manufacture of more buildings, and folds for livestock intermingled with gardens and orchards for withstanding times of siege.
At Athenian general Pericles’s behest, families and agricultural laborers living in the surrounding region of Attica had been told to abandon their farms and crops to the Spartans, to avoid stretching the resources of Athens’s citizen-militia. As a result, tens of thousands of impoverished refugees had moved within the walls of Athens with their livestock.
The excavation of one of London’s massive cemeteries for Black Death victims helped historians and bio-archaeologists extract ancient DNA from the teeth of the victims. This led, in turn, to the sequencing of the Yersinia pestis genome, which revealed its morphology over time.