AROUND 6200 years ago, farmers living on the eastern fringes of Europe, in what is now Ukraine, did something inexplicable. They left their neolithic villages and moved into a sparsely inhabited area of forest and steppe. There, in an area roughly the size of Belgium between the modern cities of Kiev and Odessa, they congregated at new settlements up to 20 times the size of their old ones.

This enigmatic culture, known as the Cucuteni-Trypillia, predates the earliest known cities in Mesopotamia, a civilisation that spanned part of the Middle East, and in China. It persisted for 800 years, but then, as mysteriously as it had begun, this experiment in civilisation failed. The inhabitants left the lightest of footprints in the landscape, and no human remains have been found. “Not a pinkie, not a tooth,” says palaeogeneticist Alexey Nikitin at Grand Valley State University in Michigan.

This puzzling lack of evidence has fuelled a lively debate about what Nikitin calls the “Dark Ages” of European prehistory. “You talk to five Trypillian archaeologists, you get five different opinions,” he says.

But the data gap hasn’t stifled interest – quite the opposite. Several projects in recent years have tried to make sense of the Trypillian proto-cities. Despite big disagreements, what is emerging is a picture of an early and unique attempt at urbanisation. It may be the key to understanding how modern Europe emerged from the Stone Age – and even throw new light on the emergence of human civilisation in general.

Uruk and Tell Brak, which arose in Mesopotamia early in the 4th millennium BC, are usually considered the world’s first cities. Their excavated remains point to an increased density of habitation and a novel, hierarchical social structure – two features that are considered integral to the definition of a city. The idea is that as human populations grew, strangers had to come together in a shared space and get along. “I think that was the real psychological threshold of urbanism,” says Monica Smith at the University of California, Los Angeles, an anthropologist and author of Cities: The first 6,000 years. But the Trypillian megasites don’t meet either of those criteria, so how should we make sense of them?

Ukrainian archaeologists have known about the megasites for more than a century, but systematic excavations didn’t get under way until after the second world war, and the sites only came to international attention a decade ago. Today, of the several thousand known Trypillian settlements, around 15 count as “mega” because they cover more than 1 square kilometre. The biggest, Taljanki, is over three times that size, making it slightly larger than London’s financial heart, the City, and bigger than Uruk throughout most of the 4th millennium BC.

Although sizable, the megasites weren’t densely populated. They were laid out concentrically, with houses made of wattle and daub lining ring roads circling a large central space. The biggest sites had several thousand houses and as many as 15,000 inhabitants – compared with no more than a few hundred people in a typical neolithic village. There is heated debate over numbers, though that, in part, is because it isn’t clear whether the sites were fully inhabited year round. This raises another question: what were these places for?

“The Trypillian megasites were very different from the first cities built centuries later”

Some take a traditional view. Archaeologist Mykhailo Videiko at Borys Grinchenko Kyiv University, Ukraine, thinks the megasites were simply a response to growing population pressure. The Trypillians’ move may have been facilitated by developments in technology, he says, notably the advent of sledges drawn by bulls or other animals. These made it possible to transport food and other resources over a dozen or more kilometres, from existing villages or outlying fields to the new sites. “There were no roads,” he says. “This was a landscape of forests and river valleys.”

Johannes Müller at Kiel University, Germany, views the megasites as essentially overgrown villages – an experiment, yes, but only in scale. The concentric design wasn’t new, he points out: “You see it from around 4800 BC, in older settlements with no more than 50 houses.” But John Chapman and Bisserka Gaydarska at Durham University, UK, couldn’t disagree more. “It’s like saying that an aircraft carrier is a very large yacht,” says Chapman.

For Chapman and Gaydarska, it really was an experiment in social organisation – and the appearance of the megasites reflects this ideological shift. Each was laid out in quarters that radiated from the centre roughly in the shape of pie slices, and further subdivided into neighbourhoods comprising a handful of houses. The overall layout seems to have been imposed from the start, though the quarters took on internal structure gradually, as people moved in. Often, neighbourhoods had their own assembly house, strategically placed on a ring road. A bigger one served each quarter, and there was one, very large meeting house for the site as a whole, near the centre and facing east. These structural subdivisions might have helped contain disputes, says Gaydarska, and the assembly houses could have been where decisions were made and communicated, at a time before writing was invented. “Trypillian sites were basically egalitarian,” says Chapman. “There’s very little evidence of prestige goods or elites.”

Why congregate?

These were cities, in other words, but of a very different kind from those conceived by the hierarchical, slave-owning societies of Mesopotamia a few centuries later. And that being the case, argue Gaydarska and Chapman, our definition of a city needs expanding.

Others don’t go quite as far. Smith calls the megasites “collective settlements”, and suggests we might think of them as immediate precursors of cities, where people who only knew the small-scale, egalitarian village life had their first taste of something bigger and more heterogeneous. “They could be capturing something of that transition,” she says. In fact, she thinks the megasites may have had something in common with Göbekli Tepe in modern Turkey, a building complex which is at least 10,000 years old and seems to have been a place where people congregated periodically to observe rituals. It might have been at such pilgrimage centres that the idea of unfamiliarity – of the need to tolerate and even trust strangers – was first sown, she says.

This is one of several hypotheses that Gaydarska and Chapman explore in a new book, Early Urbanism in Europe. Perhaps the megasites served a purely ritualistic purpose, being managed by a group of “guardians” who welcomed pilgrims over four or five months of the year – or maybe more intensively, over a single month, in the style of the Burning Man festival held annually in Nevada’s Black Rock desert. An alternative idea is that different clans took it in turns to govern, provisioning the site and leading visitors in rituals for a year, before another clan rotated in.

By contrast, Müller and his German colleagues believe the megasites were fully occupied all year round. The evidence is fiendishly difficult to interpret, partly because Trypillians periodically burned their houses down in a controlled way – possibly in a deconsecration rite when they moved out. At Nebelivka, where Chapman and Gaydarska work, for instance, two-thirds of the 1500 houses were torched over its 200 years of existence. Dating techniques don’t offer the precision needed to determine what proportion of the houses were inhabited contemporaneously before being burned. The ecological impact of activities at megasites was light, though, as is clear from detailed analyses of pollen, which can indicate cultivation and forest management, and charcoal in sediment cores taken from surrounding land. But whether that was because the sites were only occupied seasonally or because resources were brought in from elsewhere, is unknown.

There is another suggestion for why the megasites came to be: Trypillians congregated defensively against some external threat. Here again, the archaeologists disagree. Megasites are typically surrounded by a ditch. The one at Nebelivka is 5 kilometres in circumference. But at 1.5 metres wide and 0.8 metres deep, it would have been easy for an adult to jump, suggesting to the UK-based researchers that it wasn’t defensive. However, Videiko says the ditch once contained a palisade – an enclosure made of wooden stakes – that has long since rotted. Either way, there is also protection in numbers.

Nikitin also favours the defensive hypothesis. He and David Anthony, an anthropologist at Hartwick College in New York, see the emergence of the megasites as a response to broader regional conflicts. To the south, in what is now Romania and Bulgaria, were the heartlands of Europe’s oldest farming cultures. By 4600 BC, these Balkan communities had a flourishing copper industry and were fabulously rich. A gleaming symbol of their wealth is the spectacular, gold- and copper-filled grave of a high-status man discovered at a cemetery in Varna, Bulgaria. Then, around 4200 BC, those farming settlements were abandoned. Archaeologists have found signs of violence just before that happened. Nikitin and Anthony believe the survivors fled north to their distant relations the Trypillians, and that the megasites, which arose around the same time, were built to accommodate them. “I think these were refugee camps,” says Nikitin.

If there was a massacre, it isn’t clear who was responsible. Was it farmer-on-farmer violence, triggered or exacerbated by the impact of climate fluctuations on harvests? Or did nomads from the steppe to the north and east become aggressive when those farming communities went into decline – perhaps for the same reason – and their copper production dwindled? Finds of Balkan copper deep in the steppe indicate that the two groups had traded for several centuries by then. Although, analyses of individuals from Varna and other Balkan cemeteries suggest that, with rare exceptions, there was no interbreeding.

Whatever triggered the slaughter around 4200 BC, the Trypillian farmers further north seem to have been spared – at least to begin with. They continued to interact with nearby steppe people, as evidenced by a type of steppe pottery known as Cucuteni C that crops up in every layer at the megasites until their abandonment. “The Trypillians managed to work it out with the steppe,” says Nikitin. And yet they didn’t breed with their neighbours either. Nikitin’s team found s at a Trypillian site whose occupation overlaps with the megasite period. One reason, he suggests, was their radically different world views. Steppe people valued individual prowess – as demonstrated by their use of coveted Balkan copper to decorate the bodies of their dead chieftains – whereas the essence of Trypillian culture, with its concentric megasites and assembly houses, appears to have been egalitarianism.

Unsurprisingly, the refugee camp idea doesn’t appeal to everyone. “You can’t have a crisis for 800 years that people have not dealt with,” says Gaydarska. Others have wondered how relatively small bands of nomads, however warlike, could have destroyed the wealthy, densely populated Balkan farming settlements. Nikitin admits the idea has weak points, not least that building the megasites rapidly, to accommodate migrants, would have required an extraordinarily large investment of labour. Nevertheless, he suggests that it could explain the absence of human remains. “If these were temporary camps, the incomers probably didn’t stick around for long and did their dying someplace else,” he says.

Around 3400 BC, the megasites were abandoned in their turn – though the Trypillians went on, inhabiting smaller, more scattered sites. Anthony thinks that whatever peace the farmers had negotiated with steppe people broke down. Genetic analysis reveals that after the demise of the megasites, the two populations started interbreeding. A tantalising theory that Nikitin is exploring – in collaboration with David Reich’s ancient DNA lab at Harvard University – is that the offspring of that genetic mixing were the Yamnaya people. If so, we may need to rewrite the story of these herders, thought to have come from the steppe, who, starting around 5000 years ago, transformed Europe’s population genetically, linguistically and culturally. They have been portrayed as a murderous people, but, perhaps, being already part European farmer, they were able to complete this transformation peacefully. Though the question remains wide open, Nikitin says it is possible that the Yamnaya came after a violent period and ushered in a new ideology shaped by the steppe. “At the peak of this despair an idea formed, of a new world order,” he says.

Others think there is no need to invoke outside forces to explain the abandonment of the megasites. Müller, who has excavated principally at a megasite called Maidanetske, says that by 3700 BC, the assembly houses in its quarters and neighbourhoods had gone. Only the largest assembly house remained. “This shows, at least for me, that there was a kind of centralisation of decision-making processes going on,” he says. That might have been incompatible with social cohesion. Gaydarska and Chapman also think the problem was internal, noting that as Maidanetske grew, the central space – which could have served a critical function as a gathering place – was filled in. However, another possibility is that the megasites simply lost their prestige, they say. Perhaps, given enough exposure to steppe ideas through trade, the Trypillians began to question their own.

In a rare instance of unity, most Trypillian researchers agree that environmental depletion cannot be the reason they left. “It is quite clear that the carrying capacity of this area was never reached,” says Müller. They also reject an idea proposed in 2018 by microbiologist Nicolás Rascovan at the Pasteur Institute in Paris and his colleagues. Rascovan argued that plague got a foothold in the megasites, from where it spread north and west, eventually turning up in a Swedish cemetery around 2900 BC. Plague victims’ bones would have turned up, says Gaydarska. Moreover, the megasites had been gone for 500 years by then, which is too big a gap even for a relatively slow-moving disease like plague.

However it happened, by the time the Yamnaya appeared in Europe, what may have been the world’s first urban experiment was over. Far to the south and east, the cities of Egypt and Mesopotamia – built on a radically different model – were thriving, still several centuries off their peak. From then on, civilisation took a new path and the world never looked back.