Anthropologists from Brazil and the US have uncovered Amazonian settlements in Brazil dating from about 1250 to 1650, before European colonists came in. The findings, reported in the journal Science, show that these towns were more developed than previously thought, making up actual networks of walled towns and smaller villages, each organized around a central plaza.

The urban communities were discovered at the headwaters of the Xingu River, in an area previously buried beneath the dense foliage in what is now Xingu National Park. This means that the Amazon rainforest, previously thought of as pristine, was actually heavily influenced by human activities.

The team was led by anthropologist Michael Heckenberger of the University of Florida, whose team collaborated tightly with the local Kuikuro people in the Brazilian state of Mato Grosso. They went to uncover 28 towns, villages and hamlets that may have supported as many as 50,000 people within roughly 7,700 square miles of forest. Each road was pointing north-east to south-west in order to keep with the mid-year summer solstice. Researchers also found a series of dams and artificial ponds which the dwellers used for fish farming.

The researchers also discovered signs of farming, wetland management and fish farms in the ancient settlements that are now almost completely covered by rainforest. The remains are hardly visible, but they could be identified by members of the Kuikuro tribe, who apparently are the direct descendants of those ancient tribes. The scientists used both satellite imagery and GPS navigation in order to uncover the towns, which used to be surrounded by large walls, similar to the ones encountered in medieval European and ancient Greek towns.

The tribes living in the newly found settlements, which date back to before the first Europeans arrived in the Upper Xingu region of the Brazilian Amazon in the 15th Century, don’t seem to be as sophisticated as well-known cultures like the Maya to the north, but still, their culture was much more complex that anthropologists had believed.

Heckenberger and his colleagues first announced the discovery of the settlements in a 2003 Science paper.