Whether intentional or not, the way large settlements were constructed in Southeastern Europe 6,000 years ago may have limited the spread of diseases.
A new study focusing on the early farmers of Europe raises an intriguing question: Why did people live in densely populated villages only to disperse over the centuries, eventually forming cities that would be abandoned? What was behind this phenomenon?
Archaeologists often attribute what we call urban collapse to factors such as climate change, population overload, social pressures, or a combination of these elements. However, scientists have introduced a new hypothesis into the discussion: disease. Living in close quarters with animals led to the transmission of infectious diseases from animals to humans. Outbreaks could cause densely populated settlements to be abandoned, at least until later generations figured out how to arrange their settlements to be more resilient against diseases.
Excavations at Çatalhöyük reveal how closely humans lived together before the settlement’s decline. (Photo: Mark Nesbitt/Wikimedia Commons).
The First Cities: Many People and Animals
Çatalhöyük, now located in Turkey, is the oldest known agricultural village in the world, dating back over 9,000 years. Thousands of people lived in mud-brick houses that were so closely packed that residents had to enter through a ladder via a rooftop hatch. They even buried chosen ancestors beneath the floors of their homes. Despite the ample space on the Anatolian Plateau, people continued to live in close quarters.
For centuries, the inhabitants of Çatalhöyük raised sheep and cattle, cultivated barley, and produced cheese. Sensuous paintings of bulls, dancing figures, and a volcanic eruption evoke their folk traditions. They kept their homes tidy and clean, sweeping floors and maintaining storage containers near the kitchen, located under the hatch to allow smoke from the oven to escape. Maintaining hygiene meant they would even plaster the interior walls of their homes multiple times a year.
These traditions came to an end around 6000 BCE, when Çatalhöyük was mysteriously abandoned. The population dispersed into smaller settlements in surrounding floodplains and beyond. Other large agricultural populations in the area also scattered, and nomadic cattle herding became more popular. For the populations that remained, the mud-brick homes were now isolated, in contrast to the concentrated homes of Çatalhöyük.
Was Disease a Factor in the Abandonment of Densely Populated Settlements Around 6000 BCE?
At Çatalhöyük, archaeologists found human bones mixed with livestock remains in burial mounds and refuse piles. The close quarters between people and animals may have led to zoonotic diseases at Çatalhöyük. Ancient DNA has identified tuberculosis (TB) from cattle in the area dating back to 8500 BCE and tuberculosis in the bones of infants shortly thereafter.
DNA from ancient human remains has identified salmonella dating back to 4500 BCE. Assuming that the transmissibility and virulence of Neolithic diseases increased over time, densely populated settlements like Çatalhöyük may have reached a tipping point where the impact of disease outweighed the benefits of living in close proximity.
By around 4000 BCE, large urban populations re-emerged in the large settlements of the ancient Trypillia culture near the western Black Sea. Thousands of people lived in large Trypillia settlements such as Nebelivka and Maidanetske, located in present-day Ukraine.
If disease was a factor in the dispersal of populations millennia ago, how could these large settlements exist?
Simulating Neighborhoods with Social Distancing
To model the spread of disease at Nebelivka, researchers had to make a few assumptions.
- First, they assumed that initial diseases spread through food, such as milk or meat.
- Second, they assumed that people visited neighboring homes in their neighborhood more frequently than homes outside their area.
Was this clustering of populations enough to prevent an outbreak? To test the impact of varying interaction rates, the researchers ran millions of simulations, first on a network representing clusters of residences. They then reran simulations on a virtual layout modeled after actual floor plans, where homes in each neighborhood had a higher chance of interacting.
Based on these simulations, the researchers found that if people visited other neighborhoods less frequently than they visited homes within their own neighborhood, the layout of the Nebelivka housing clusters would significantly reduce initial outbreaks of foodborne diseases. This makes sense as each neighborhood had its own gathering houses. Overall, the results suggest that the Trypillia layout may have allowed early farmers to live together in low-density urban populations during a time when zoonotic diseases were on the rise.
The residents of Nebelivka may not have needed to consciously plan their neighborhood layouts to help their population survive. However, they might have done so instinctively, as human nature tends to avoid signs of infectious disease. Just like at Çatalhöyük, residents kept their homes clean. Additionally, about two-thirds of the houses in Nebelivka were deliberately burned at various times. These periodic, intentional burnings may have been a pest control strategy.
Some initial diseases eventually evolved to spread through means other than contaminated food. For instance, tuberculosis became airborne at some point. When the bacteria causing the plague adapted to fleas, it could spread through rats, a species indifferent to neighborhood boundaries.
The world’s first cities, along with cities in China, Africa, and the Americas, are the foundations of civilization. It can be said that their shape and function were shaped by millennia of disease and human responses to it, stemming from the world’s first agricultural villages.
