It's an idea that could transform our understanding of how humans went from small bands of hunter-gatherers to farmers and urbanites. Until recently, anthropologists believed cities and farms emerged about 9,000 years ago in the Mediterranean and Middle East. But now a team of interdisciplinary researchers has gathered evidence showing how civilization as we know it may have emerged at the equator, in tropical forests. Not only that, but people began altering their environments for food and shelter about 30,000 years earlier than we thought.

For centuries, archaeologists believed that ancient people couldn't live in tropical jungles. The environment was simply too harsh and challenging, they thought. As a result, scientists simply didn't look for clues of ancient civilizations in the tropics. Instead, they turned their attention to the Middle East, where we have ample evidence that hunter-gatherers settled down in farming villages 9,000 years ago during a period dubbed the "Neolithic revolution." Eventually, these farmers' offspring built the ziggurats of Mesopotamia and the great pyramids of Egypt. It seemed certain that city life came from these places and spread from there around the world.

But now that story seems increasingly uncertain. In an article published in Nature Plants, Max Planck Institute archaeologist Patrick Roberts and his colleagues explain that cities and farms are far older than we think. Using techniques ranging from genetic sampling of forest ecosystems and isotope analysis of human teeth, to soil analysis and lidar, the researchers have found ample evidence that people at the equator were actively changing the natural world to make it more human-centric.

It all started about 45,000 years ago. At that point, people began burning down vegetation to make room for plant resources and homes. Over millennia, the simple practice of burning back forest evolved. People mixed specialized soils for growing plants; they drained swamps for agriculture; they domesticated animals like chickens; and they farmed yam, taro, sweet potato, chili pepper, black pepper, mango, and bananas.

École française d'Extrême-Orient archaeologist Damian Evans, a co-author on the Nature paper, said that it wasn't until a recent conference brought international researchers together that they realized they'd discovered a global pattern. Very similar evidence for ancient farming could be seen in equatorial Africa, South Asia, and Southeast Asia. Much later, people began building "garden cities" in these same regions, where they lived in low-density neighborhoods surrounded by cultivated land.

Evans, Roberts, and their colleagues aren't just raising questions about where cities originated. More importantly, Roberts told Ars via email, they are challenging the idea of a "Neolithic revolution" in which the shift to city life happened in just a few hundred years. In the tropics, there was no bright line between a nomadic existence and agricultural life. When humans first arrived in South Asia, Southeast Asia, and Melanesia, they spent millennia adapting to the tropics, eventually "shaping environments to meet their own needs," he said. "So rather than huge leaps, what we see is a continuation of this local knowledge and adaptation in these regions through time."

There is also evidence that, as soon as humans reached South America , they took up residence in the Amazon and began farming. Often these ancient farms evolved into highly-developed networks of cities like those of the Maya.

Do these discoveries mean that everything we knew about urban development in the Middle East is wrong? No, says Roberts. Anthropologists are simply realizing that early cities took extremely diverse forms. "Clearly, urbanism is different in different parts of the world, and we need to be more flexible in how we define this," he explained. He continued:

The tropics demonstrate that where we draw the lines of agriculture and urbanism can be very difficult to determine. Humans were clearly modifying environments and moving even small animals around as early as 20,000 years ago in Melanesia, they were performing the extensive drainage of landscapes at Kuk Swamp to farm yams [and] bananas... From a Middle East/European perspective, there has always been a revolutionary difference ("Neolithic revolution") between hunter gatherers and farmers, [but] the tropics belie this somewhat.

There are also lessons that contemporary city dwellers can learn from the ancient metropolises of the global south. Put simply, these ancient settlements are a proof of concept, demonstrating that people can live sustainably for thousands of years in fragile environments. In the tropics, our ancestors did it by living in low-density communities, with local farms feeding neighborhoods and families. Instead of widespread slash-and-burn agriculture, there was a patchwork of cleared areas at the edges of forests.

Roberts said troubles in these areas arose relatively recently, when "colonial, industrial societies" came from outside the tropics and tried "to practice monoculture, pastoralism, and urbanism within them." This led to "unsustainable landscape modification and environmental destruction," he said. "The classic example of this is palm oil monoculture in Southeast Asia, which is basically destroying this region's rainforest as a result of a lack of genetic diversity, landscape instability, and the spread of fire across large swaths of these areas."

The ancient settlements of the tropics are also a reminder that Homo sapiens is an incredibly adaptive, flexible species, said Roberts. That's why we can "occupy every environment on the planet, through periods of dramatic climate change, and became the last remaining hominin." In other words, our ingenious, sustainable farms and cities may have been what saved us from the fate of the Neanderthals.

Nature Plants, 2017. DOI: 10.1038/nplants.2017.93 (About DOIs).