Archaeologists have discovered who actually built Colombia’s ancient canals

This ancient system is situated in the La Mohana region on Colombia’s Caribbean coast. It was first used as early as the last centuries BC, and some of its structures remained in use until around the 11th century.

The landscape here is regularly flooded, so rather than fighting the water, the ancient farmers had to learn to manage it.

They created a network of canals and raised sections of land above the surrounding terrain. On these raised areas, they could grow crops and build dwellings, whilst the canals helped to redistribute the water.

During the rainy season, the system took in vast volumes of water, whilst in drier months it allowed water to be stored for longer. The raised fields both protected crops from flooding and provided fertile soil.

The canals were probably also used for fishing.

Details

The area of the ancient field systems is estimated at approximately 500,000 hectares. This is around 1.2 million acres.

Given this scale, archaeologists long assumed that the construction required a large workforce and top-down organisation.

This gave rise to a picture that seemed logical at first glance: there must have been an influential elite or leaders who planned the work, allocated labour and supervised the construction.

Further support for this view came from the intricate gold artefacts and pottery found in the region, which were also linked to the development of a social hierarchy.

However, researchers from the University of Cambridge and their colleagues decided to test the key assumption — just how many people and how much time were actually required to build the canals.

Using satellite imagery, the scientists mapped in detail an area of around 500 hectares in the municipality of San Marcos.

There, they identified around 1,600 raised terraces and 63 settlement sites.

The researchers also measured the dimensions of the structures and calculated the volume of earth that the ancient builders had to move.

Initially, the difference in height between the top of the terraces and the bottom of the neighbouring canals was approximately 1.4 metres.

The team then developed a model that took into account the properties of the local soil, the tools available, the estimated population size and the scale of the work required.

According to the scientists’ calculations, the construction of a single complex of canals and raised fields could have taken less than two months.

For their calculations, they assumed a population of around 1,600 people in the studied area and a workforce of approximately 800 people. The authors consider this estimate to be quite conservative: men, women and, probably, children could have taken part in traditional agricultural work.

Even the heavy clay soil and the lack of metal spades did not make such a task unachievable.

The authors concluded that local families and neighbouring communities could well have organised the necessary work themselves during the dry season.

It is precisely this that challenges the previous interpretation.

The researchers do not claim that there were no leaders, influential families or social inequality at all in ancient La Mohana.

The study shows something else: the scale of the canals cannot be taken as proof that their construction was controlled by a centralised authority.

If the construction of a single system required several weeks of collaborative work, communities could organise the building themselves by pooling the efforts of families and neighbours.

According to the authors, the region’s ancient inhabitants may have employed a more horizontal model of cooperation than previous reconstructions had suggested.

Thus, the impressive infrastructure was not necessarily the result of orders from a ruler. It may have gradually emerged from a multitude of local projects.

Another important difference in the ancient system lay in the very attitude towards seasonal flooding.

Rather than attempting to completely block the flow of water, the inhabitants of La Mohana adapted the agricultural landscape to regular flooding.

Canals redirected the flow, whilst raised plots allowed them to remain above the water level.

The authors contrast this approach with certain modern methods based on the construction of dams and attempts to keep water out of agricultural areas.

For modern La Mohana, this issue is particularly relevant: the region faces both severe floods and droughts.

Ancient technology may still be useful today

The researchers believe that certain principles of the old system could be incorporated into modern water management.

Of particular importance is their conclusion regarding the potential for local organisation of the work. Communities may require state resources and funding, but this does not mean that every decision must necessarily be entirely planned and controlled by central authorities.

However, the ancient system cannot simply be copied and expected to yield the same results. Over the centuries, the climate, population, agriculture and the landscape itself have changed.

Archaeological evidence suggests an alternative principle: adapting to the natural flow of water, rather than attempting to halt it entirely.

Why this matters

The findings from La Mohana touch on a broader question in archaeology: do large ancient structures necessarily indicate the existence of powerful rulers?

New research shows that the answer is not always obvious.

Hundreds or thousands of families could have created impressive infrastructure through gradual collective effort, without the need to mobilise a huge workforce under a single centralised command.

This changes our understanding not only of ancient Colombia, but also of how archaeologists interpret large-scale structures in societies where there are no clear signs of a state.

Source

Study: J. Vieri et al. Collective labour and sustainability of pre-Hispanic field systems in La Mojana.

Journal: Communications Sustainability, 2026.