Roughly 9,000 years ago, humans had mastered farming to the point where food was plentiful. Populations boomed, and people began moving into large settlements full of thousands of people. And then, abruptly, these proto-cities were abandoned for millennia. It's one of the greatest mysteries of early human civilization.


The dawn of the age of agriculture falls during the "Neolithic," also known as the late stone age. At that time, about 12,000 years ago, people had already developed incredibly sophisticated stone tools, weapons, and clay vessels for cooking and storage. And when they found seeds that grew into particularly delicious plants, they took them along on their treks, planting them in river valleys on their route, so that they would have a tasty harvest the following year. Once these informal farms had gotten a little bigger, it started to seem less advantageous to keep roaming when there was so much food in one place. In the Levant area along the eastern Mediterranean, nomadic groups who had once lived by hunting and gathering began settling down in small villages for part of the year.


Chart from Michael E. Smith, et. al., in the International Journal of Urban and Regional Research

Families made their semi-permanent homes by digging shallow, round pits for the floor, lining it with smooth stones, and constructing domed walls out of mud and grass. They stored grain in similar structures, in bins that they placed on elevated floors made from wooden beams balanced on rocks. If water leaked in and flooded the granary, their food stores would stay dry. Soon, these wandering people began living in villages for whole seasons, and finally they settled down for good.

The Rise and Fall of the Mega-Village

As people accumulated more food stores, women began giving birth to more children. Nomadic groups of 20 or 30 people became villages of 200. And some of those villages, like Çatalhöyük in the region today known as central Turkey, grew to a few thousand people.


It's hard to say what, exactly, Çatalhöyük was. Was it a city or just some kind of bizarre, outsized village? We know it lasted for millennia, with thousands of people living there continuously from about 7500 BCE to 5700 BCE. Perhaps we might say that was the closest thing to a city in the Neolithic, since hundreds more people lived there than in typical villages nearby. But it had none of the features we associate with the grand, walled cities that emerged thousands of years later in Africa, Asia and the Middle East.


Image of Çatalhöyük by Dan Lewandowski. It's important to remember that in real life, probably many of these buildings would have been broken down and abandoned, used as trash heaps.

There were no palaces, no massive ziggurats or pyramids dedicated to the gods, and no signs of class distinction. Every family had a small, slightly rectangular one-room home with a hearth. Each home was roughly the same size. Streets didn't exist in Çatalhöyük — homes were erected next to each other, honeycomb-style, and people just walked over each other's roofs to get home through doors in their ceilings. Though there was art, there was no writing. And there was little in the way of specialized labor. Unlike in ancient Uruk or Mohenjo-Daro, there were no cottage industries in bead-making or weapons production. Families lived by hunting, but mostly by keeping farms and small herds of animals like goats in the nearby hills.


Maybe Çatalhöyük didn't look much like cities as we know them, but it and other mega-sites were the most developed forms of settlement anywhere in the world at that time. They were the urban developments of their age, sheltering huge populations and fostering technological progress like cooking with dairy and making fired pottery (both were major high tech inventions in the Neolithic).


Here's where things get weird. In the mid-5000s BCE, Çatalhöyük was suddenly abandoned. The same thing happened to several other outsized village-cities in the Levant. Their populations drained away, and people returned to small village life for thousands of years. Below, you can see a graph showing how the size of settlements dropped dramatically about 7,000 years ago (5000 BCE).


Graph via Ian Kuijt, in Journal of Anthropological Archaeology

Even more mysterious is the fact that we see a similar pattern — intensification of farming, booming population, growing settlements, and abandonment — elsewhere in the world. Farming came later to Western Europe and England, so we see this cycle starting roughly 5,000 years ago (around 3,000 BCE) in many European regions and in England.


What happened?

The Trouble with Settling Down

Settled life may have meant more food and less hiking around, but it wasn't easy. Once there's a large population dependent on a few local food sources, humans become vulnerable in ways that we never were as hunter-gatherers on the road all the time. A season of bad weather can wreck the entire food supply. And it's not easy to hike to another place when you've got a population of 1,000 people or more, who are accustomed to settled life.


In the Levant, climate change seems to be an obvious culprit in the dissolution of mega-sites. Çatalhöyük was once surrounded by gushing rivers; today they have run dry. As Harvard paleontologist Ofer Bar Josef has argued for most of his career, it seems certain that favorable climate conditions allowed agriculture to flourish in the Levant. But in the late Neolithic, the weather cooled down and dried out. A place like Çatalhöyük could no longer sustain itself on locally-grown crops and famine may have become a major issue. Scattering into smaller villages gave people a chance to have the comforts of settled life without depending on massive crop yields to feed everyone.

But archaeologists who study the population drops in Europe suggest another explanation. University College London archaeologist Stephen Shennan and his team found that there was no correlation between climate shifts and population drops in Europe. They suggest that what appears to be abandonment of megasites may actually be population drops due to disease. One of the major downsides to life in a large settlement is that diseases spread like wildfire — especially given that sanitation was minimal. Mostly, people dumped their trash right next to their homes.


Still, there are plenty of cities that have endured plagues and famines in the past several thousand years — and then rose again. Why did people abandon the proto-city designs of large Neolithic settlements, never to build them again?

Agriculture is often dubbed the "neolithic revolution," so University of Notre Dame anthropologist Ian Kuijt dubs these collapses "failure of the neolithic experiment." He describes the expansion and abandonment of a mega-village called Basta, located in what is now Jordan. Like Çatalhöyük, Basta grew larger than other villages around it. To cope with growing populations, the people of Basta invented two-story architecture, and began sub-dividing their living spaces into smaller and smaller rooms. Many homes contained specialized areas for living and for food storage.


Image via Kuijt

But Kuijt doesn't believe people abandoned Basta because its population outstripped its resources. Instead, its population outstripped its belief systems.


Old Beliefs and New Technologies

The problem is that people in Neolithic mega-villages had inherited a system of social organization and spirituality from their nomadic forebears. Because nomadic life requires everyone in the group to share resources to survive, these groups would develop rituals and customs that reinforced a very flat social structure. Certainly there would be families that had more prominent positions in a hunter-gatherer group or small village, but if they ever started hoarding resources too much that would be bad for the entire group. So people would strongly discourage each other from ostentatious displays of social differences.


You can see this set of beliefs reflected in the built environment of Çatalhöyük, where everyone's house is roughly the same size. Some houses have a lot more stuff in them — more pieces of art, or more ritual objects — but as I said earlier, nobody is living in the Neolithic equivalent of a mansion.

All of this works nicely in a small community, where you know all of your neighbors and only share with people whose lives are bound to yours (even if you don't like them very much). But once you have a thousand people living together, it's harder to have a flat social structure. People need local representatives to stand in for them, and perhaps even a system of writing to keep track of everyone and what they own. Some people start to do specialized tasks, and social differentiation begins.


But the ideology of these Neolithic people in mega-villages, Kuijt speculates, may have treated any kind of social differentiation as taboo. As soon as somebody took enough power to be a representative or proto-politician, other people would rail against them. He believes that major conflicts may have grown out of this tension between a belief in flat social organization and the need to create social hierarchies in larger societies. It's an intriguing hypothesis, especially when you consider that when cities re-emerge in the 4,000s BCE, they have rigid social hierarchies with kings, shamans, and slaves. Plus, they have writing, which is primarily used to tally up who lives where and owns what.


An artist's reconstruction of the ancient city of Uruk, with its monumental structures making social differentiation visible in its architecture.

It's possible that the mega-village model of life wasn't sustainable because it was propped up by belief systems that could only exist in small communities where everybody shared resources. That would explain why people abandoned these sites for smaller villages that never grew beyond about 200 people.


In a sense, agriculture was a technology that came before human civilization was ready. It gave humans the means to grow into large settlements and proto-cities. But we'd spent tens of thousands of years as nomads before that, and weren't yet ready to abandon our ancient beliefs that no family should ever accumulate more than its neighbors. As a result, our earliest experiment with urbanism ended in failure. When the going got rough, with bad harvests and disease, humans preferred to abandon their nascent urban creations because we had not yet developed a social structure that would allow us to cope with the difficulties of city life.

It was a near miss. We almost didn't have the world of cities that we have today. If we hadn't come to terms with the agricultural revolution, it's possible that humans would never have been able to sustain communities larger than a village.


Annalee Newitz is the editor-in-chief of io9. She's the author of Scatter, Adapt and Remember: How Humans Will Survive a Mass Extinction. Follow her on Twitter, or email her.