How Farming Almost Destroyed Ancient Human Civilization

Roughly 9,000 years ago, humans had mastered farming to the point where food was plentiful. Then, abruptly, these proto-cities were abandoned for millennia.

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.

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.

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).

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.

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.

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.

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For years, opponents have argued that genetically engineered plants wreak havoc with human health and nature, and accuse plant biotech companies, such as Monsanto, of putting profits before people. On the other hand, agricultural biotech proponents argue that engineered crops enable farmers to grow at a time of global food shortages, insidious pests, weeds and extreme weather. "It's a complicated issue," says James E. McWilliams, author of American Pests and professor of history at Texas State University. Plant virologist Roger N. Beachy, president of the Donald Danforth Plant Center in St. Louis, Missouri, thinks that environmentalists and biotech experts can emerge from the cloud of controversy, find common ground, and move toward green goals together. So, whether transgenic crops make you think "yum-yum" or "no ma'am," McWilliams and Beachy share what's cooking:

1. Biofortified Soya Beans

What advantage did these few plants gain by evolving the ability to catch animals instead of just capturing the sun's energy? The elaborate structures necessary for killing bugs -- pools of nectar, bright colors, unusual shapes and digestive enzymes -- must be costly for the plant to make. Not so, says a new study, published in the American Journal of Botany, that examined Asian pitcher plants (pictured here), Venus flytraps, sundews and others.

2. Edible Cotton Seeds

By nature, cotton seeds are inedible because they contain gossypol, a component that keeps bugs away. In 2006, Texas A&M University and Cotton Inc. collaborated on research to produce genetically engineered seeds without the inedible part while keeping it in the plant for protection. The researchers made nutty-tasting meal from the seeds that could be used for flour, but the discovery has many regulatory and logistic hurdles to clear before it could be a reality in cotton-growing areas.

3. Jatropha

Food or energy? With gas prices soaring, biofuel advocates find themselves going toe-to-toe with farmers. Jatropha is an inedible plant whose seeds produce a liquid like palm oil that could be used for biofuel. Earlier this year the plant caused political tension in India, where tribal communities accused the government of destroying their native crops to plant jatropha for fuel needs. Plant breeding and genetic engineering will result in high-yielding jatropha that will increase overall production and potentially reduce the hectares needed; Roger Beachy says jatropha and other oil-producing, non-food plants also have the potential to produce bioplastics that can degrade in landfills.

4. Golden Rice

More than 120 million children globally don't get enough vitamin A and as a result are at risk for blindness. Back in the 1990s, a scientific team at the Swiss Federal Institute of Technology by Ingo Potrykis and collaborators at Syngenta Company discovered that adding several key genes from flowering plants to rice could dramatically increase the amount of beta carotene, a molecular that human beings can convert to Vitamin A. Even though the research ran into intellectual property rights problems, a public-private partnership between the inventors and agrichemical company Syngenta allowed the research to continue. Golden rice was successfully field-tested in Louisiana four years ago, but the inventors blame bureaucratic measures for slowing its adoption abroad.

5. Flood-Resistant Rice

Husband and wife team Pamela Ronald and Raoul Adamchak bridge the biotech-environmental divide in their book Tomorrow's Table, arguing that genetic-engineering and organic farming can be blended. Ronald, a professor of plant pathology at University of California-Davis, has been working with David Mackill of the International Rice Research Institute in the Philippines on genetically-modified rice that can withstand flooding. If field trials are successful, the rice could be available as early as next year.

6. Sugar Beets

For something that's so sweet, the debate over this crop has been rather bitter. Last year the New York Times chronicled sugar beet farmers' woes as they battled weeds to harvest the beets that provide around half the nation's sugar. They eagerly awaited Monsanto's Roundup Ready beets to produce higher yields and pay less for herbicide and workers to weed the fields. Environmentalists, meanwhile, raised alarm over the problem of weeds that are resistant to Roundup herbicide, cross-pollination with organic crops, and a group of advocates sued the U.S. Department of Agriculture over the matter. The beets became available to farmers earlier this year.

7. Yeast

Admittedly, this isn't a crop, but it will likely be cultivated like one. The London Times recently reported that a biotechnology company in San Francisco called LS9 had genetically modified industrial yeast to munch on plant sugars and excrete crude oil. No, really. The company plans to feed the yeast agricultural waste, although they haven't quite scaled up the operation up beyond the beaker level. And there's no word yet on whether they will be able to engineer some bugs to eat up all the carbon dioxide from combustion.

8. Cassava

This starchy, potato-like root is an essential plant for millions of people around the world, especially in Africa. This staple lacks a range of vitamins that are crucial to development and its cultivation can be adversely affected by drought. BioCassava Plus is a group of scientists led by Ohio State University Professor Richard Sayre and financed with a grant from the Bill and Melinda Gates Foundation. Currently they're working on a virus-resistant cassava that contains a day's worth of vitamins, proteins, and minerals. They plan to field test it in two African countries within the next two years.

9. Papaya

Plant pathologist Dennis Gonsalves has been involved in papaya research for 30 years. It's not a stretch to say that papayas might have been wiped out entirely had it not been for his work. A virus was rapidly eating up the orange-yellow tropical fruit when Gonsalves, then at Cornell University, and fellow researchers engineered the SunUp papaya strain. Earlier this year, the University of Hawaii-Menoa led a group of 85 scientists to decode the SunUp papaya's genome -- the first fruit species sequenced. They'd like to use that information to strengthen the fruit's resistance to pests so farmers can cut back on the chemicals.

10. Castor Beans

"Plants make so many things," Roger Beachy says. He points to the castor plant, whose beans make versatile oil that can be used in a wide range of products, from jet engine lubricant to shampoo. The castor bean also contains a deadly toxin called ricin that has no antidote, which explains why the crop isn't very popular to grow. Two researchers at the U.S. Department of Agriculture became the first in the world to genetically engineer castor plants, blocking ricin production as well as intense allergens that the plants make. In addition, the USDA researchers would like to genetically engineer the plant to produce castor oil epoxy, which could replace toxic solvents in paints.