By Susan Cosier
A city, as defined by Australian archaeologist Vere Gordon Childe in the 1950s, is a densely populated settlement. It has monumental buildings. Its people create art and writing and use money and taxes. They trade across long distances, create surplus goods, and exist in a complex social hierarchy.
Every urban centre, whether it existed 9,000 years ago or thrives today, has its own unique history, writes Annalee Newitz, a science, technology, and culture journalist, in Four Lost Cities: A Secret History of the Urban Age. Yet no matter why they form or how they flourish, all cities experience the same fate: They perish.
"It's terrifying to realise that most of humanity lives in places that are destined to die," Newitz writes. Some archaeologists claimed to have found so-called lost cities covered in sand or vines, a fate ripe for adventure stories and mythology. Those places, however, were more often simply abandoned: "The myth of the lost city obscures the reality of how people destroy their civilisations."
The four ancient cities Newitz focuses on "shared a common point of failure," they write. "Each suffered from prolonged periods of political instability coupled with environmental crisis." Each one also offers lessons about how to live with other people, how to exist within the natural world, and how to adapt to shifting political landscapes and environmental conditions.
Newitz spotlights four places built up and deserted on different continents over millennia. They couple historical descriptions with firsthand accounts from each of these locales, often highlighting the work of anthropologists and archaeologists conducting cutting-edge research into how these ancient societies grew and withered.
Descendants of nomadic tribes lived from about 7100 to 5700 BC in central Turkey's ÃatalhÃ¶yÃ¼k, one of the world's first cities. Described by some archaeologists as a collection of villages, the city bustled with activity before succumbing to flooding and rising frustrations between neighbours. Entrepreneurs from a number of social classes thrived for centuries in the Roman city of Pompeii before Mount Vesuvius buried it in volcanic ash in 79 AD. Cambodia's Angkor (roughly 800 to 1431 AD), once the capital of the Khmer Empire, relied on a massive network of canals and retention ponds built by indentured servants or slaves before eventually dissolving due to conflicts with an indebted workforce and failed infrastructure. And along the Mississippi River's floodplains, the city of Cahokia (approximately 1050 to 1350 AD) attracted people from all over the region who gathered for religious and cultural ceremonies, its population possibly dispersing as leaders became more authoritarian and a changing climate may have caused drought and famine.
Newitz tells fascinating stories about the people in these metropolises and how researchers came to understand how they lived their lives. Many of the discoveries are not just a result of traditional archaeological investigations, but also of new technologies and analytical methods.
Female figurines that archaeologists continue to unearth in ÃatalhÃ¶yÃ¼k, for example, illustrate a belief system that appears to have spread across the region, and evidence of fires set over time helps demonstrate how the city changed over its nearly 1,500-year history. In Pompeii, researchers are using "big data" " the aggregation of many smaller datasets into a larger collection " to build a more complete picture of everyday life there.
"It's terrifying to realise that most of humanity lives in places that are destined to die," Newitz writes.
Data-driven archaeology makes use of everything from markings on rock to inscriptions on paper. Analysis of wear on street stones and curbs in Pompeii can yield a wealth of information: Grooves made by thousands of vehicles moving through the streets, for example, indicate standardised spaces between carriage wheels. Cutouts on high curbs that kept pedestrians from stepping in sewage flowing through the streets show that Romans likely drove on the right side of the road. Sarah Levin-Richardson, an archaeologist at the University of Washington in Seattle, studied pornographic graffiti in Pompeii and found that a lot of it was written by women who took pride in their trade as former slaves turned sex workers.
"In a sense, data archaeology represents the democratisation of history," writes Newitz. "It's about looking at what the masses did, and trying to reconnect their social and even psychological lives."
In Angkor, archaeologists employ lidar, a technique that uses lasers to map geographic forms hidden in the earth. Data technology is used there, too, to analyse the lists of labourers, the majority of whom, it turns out, were women.
In Cahokia, archaeologists used magnetometers " instruments used to detect variations in the Earth's magnetic field " for "sniffing out buried structures because they can detect anomalies that can represent disturbed earth, burned objects, and metals several feet beneath the surface," Newitz explains, helping them to better understand the mounds that once stood there.
Whenever researchers uncover something new about these cities " whether it is deeper insights into Roman sexuality in Pompeii or human sacrifice in Cahokia " their revelations are inevitably coloured by what our current societies deem acceptable, says Newitz. Penis carvings, thought to bring good luck, are still kept in a "Secret Cabinet" section of the Naples Museum, though shopkeepers displayed them prominently in ancient Pompeii.
Newitz also examines how our ideas about the demise of urban places have evolved. In scientific circles, the idea that civilisations fall solely because of human interaction with the environment was waning before Jared Diamond reinvigorated the theory with his 2004 book Collapse: How Societies Choose to Fail or Succeed. "Diamond is right to highlight environment as a contributing factor in urban dissolution, but that's only part of the story," Newitz says. "Abandonment is most importantly a political process."
City leaders or royalty often want to invest in "beautiful spectacles," says Newitz, rather than the things people need to prosper, like functioning infrastructure and safe marketplaces. Without those things, cities are often more vulnerable to environmental catastrophes which can lead to political unrest when homes flood or crops shrivel.
Diamond also argued that a city's culture dies when the settlement vanishes, but Newitz cites scholars who say instead that people who migrated out of ancient cities typically brought their values, art, and technology with them and assimilated them into their new homes.
In the case of Pompeii, for example, those who survived the volcanic eruption often moved to other cities colonised by Romans. The former residents of Cahokia may have spread and formed smaller communities across the Midwest and formed smaller communities. Osage oral histories, writes Newitz, explain how migrating people stopped in Cahokia for centuries before continuing west. "Today, the Osage are one of many tribes whose culture and ideals were shaped by the people who abandoned Cahokia," they say.
"Metropolitan areas expand and contract with waves of immigration over time," Newitz writes. "When a city's population breaks apart into smaller villages, that isn't a failure. It's simply a transformation, often based on sound survival strategies. The culture of that city lives on in the traditions of people whose ancestors lived there, many of whom will go on to build new cities in its image."
Even though they may not last forever, successful cities need certain things to flourish: resilient infrastructure, areas accessible to the public, domestic places for everyone, social mobility, and leaders who respect the city's labourers. In the end, Newitz concludes, "This is not such a tall order, especially when you consider that thousands of years ago, our ancestors managed to maintain healthy cities for centuries at a time."
Susan Cosier is a Chicago-based writer who covers science and the environment. Her work has appeared in Scientific American, Science, The New York Times for Kids, The Guardian, and Audubon, among other publications.