The Great Maya Aquifer

7 mins read

Exploring a hidden world beneath the Yucatán Peninsula

A photo of a diver underwater, illuminated by a shaft of light from above.
The Great Maya Aquifer project is dedicated to understanding and preserving the submerged world beneath the Yucatán Peninsula. Diving is an indispensable tool for their research and conservation work. [Image: Ricardo Castillo]

Southeast Mexico is rich in caves. This extraordinary underworld has influenced human activity for thousands of years. Now a project dedicated to understanding and preserving this realm is shedding new light on the archaeology of the Yucatán Peninsula, as Guillermo de Anda told Matthew Symonds.

The Spanish invaders of Mexico called them cenotes. This came from a mishearing of the Maya word tz’onot, which was used to describe great circular sinkholes that dropped down to inviting pools of freshwater. In a region where groundwater is scarce, these natural wells were a magnet for Maya settlements. As well as providing a vital source of drinking water, the cenotes were woven into Maya beliefs. A fine example comes from the sprawling city of Chichén Itzá, which was carefully positioned to benefit from nearby cenotes. One of them, the Sacred Cenote, was connected to the Great Plaza at the heart of the city by a ceremonial way. A 16th-century Franciscan bishop, Diego de Landa, recorded that a range of offerings were made there: ‘into this well they have had… the custom of throwing men alive as a sacrifice to the gods, in times of drought… They also threw into it a great many other things, like precious stones and things that they prized.’ Sure enough, investigation of the cenote in the 20th century revealed human remains, and a wealth of artefacts, including wooden idols, pottery, jade, and ornate gold discs.

A photo of the Sacred Cenote, with a group of researchers stood at the top of one side.
The research team of the Great Maya Aquifer project carries out archaeological prospecting using non-intrusive technology in the Sacred Cenote at Chichén Itzá, more than 50 years after the last exploration in this body of water was carried out by Román Piña Chan. [Image: Karla Ortega]

Cenotes are created when the ground surface collapses into underground cavities, exposing the water table below. While the size of these natural wells can be impressive, with the Sacred Cenote measuring about 60m in diameter, this pales by comparison with the wider expanse of caves lying beneath the Yucatán Peninsula. This natural network is still being explored and charted, so its full extent remains unknown. Even so, it is clear that the scale of this underground realm is nothing short of extraordinary. Recent work by the Great Maya Aquifer project has revealed that one cave system, known as the Sac Actun or White Cave, stretches for over 350km. This project is dedicated to learning more about all aspects of this breathtaking submerged world. While the water within it remains essential for the modern inhabitants of the Yucatán, these sunken passages also hold evidence for thousands of years of human activity in the area. The project’s work is revealing not only fascinating new glimpses of Maya life, but also the world inhabited by some of the earliest human occupants of what is now Mexico.

An underwater photo of a diver and the opening of a cenote with trees above, taken from below.
Seen from underwater, the cenotes resemble windows opening into the immensity of the Great Maya Aquifer. [Image: Pedro Almada]

Final frontier

‘I always say that this is the last frontier of exploration of pristine places left in the world, apart from the oceans,’ says Guillermo de Anda, director of the Great Maya Aquifer project. ‘That is one way of getting across how important this area is. It is an amazing experience to work there – completely magical – because it is like a planet within a planet. As much of the cave system is submerged, it is a place where you need special equipment, special training, and a special attitude to be able to explore it. In some ways it is like an astronaut going to outer space, but in our case we are charting an inner space. And it is an inner space that is so vast that there is still plenty underneath the ground waiting to be discovered and documented. Putting together everything that has been mapped so far gives us 1,650km of caves.’

‘People have been working on this for a long time. I started as a cave-diving apprentice 40 years ago. Back then, I don’t think anyone appreciated how big the network would turn out to be, that four decades later people would still be mapping and exploring it. Even after all of this time, the archaeological finds don’t cease to amaze us. One reason for this is because we find things that we don’t get on the surface. What I mean by that is the level of preservation is amazing. We have found textiles, wool, charcoal, and even human remains. Together, they have changed our perception of the archaeology of this area.’

An underwater photo of a diver swimming towards a flat surface with a human skull on.
A portion of a Maya skull is recorded by the Great Maya Aquifer project team in the depths of a cenote in Quintana Roo. [Image: Rodrigo Friscione]

The water that enchants modern visitors to the cenotes and was so important to Maya success is also a key reason why charting the caves is such a laborious process. Limited access points, the length of some cave systems, and the lack of natural light all make pushing the boundaries of knowledge in this environment a highly specialised pursuit, where safety is paramount. Given that the presence of water seems quintessential to both the beauty of the caves and the challenge they present for modern survey, it can be surprising to learn that they were not always submerged. On the contrary, the first human settlers in the region were greeted with a radically different underworld. Back then, towards the end of the last Ice Age, the caves were still dry. While this would have made interacting with them a very different experience, the subterranean labyrinth still had a powerful pull on human imagination and belief.

‘In one cave we were lucky enough to find what turned out to be the first of five skulls,’ says Guillermo. ‘The first time I saw the skull, I wondered what kind of animal it was from. Initially I thought it might be a big jaguar, or feline of some kind. When we got a photograph, I contacted my zooarchaeologist friend Chris Götz. I remember that I was back in my house that evening when he replied and said something like “This is not from Yucatán, this is a picture from somewhere else – you are trying to trick me!” So I said, “No, no, it was taken this morning”, but it was only when he saw another photograph with one of my colleagues diving close to the skull that he believed it was from Yucatán. And the reason why he suspected a trick, is because the skull was from a bear. Before we found it, we had no clue that bears existed nearby. You do get Pleistocene bears in north Mexico, but after that there appeared to be a gap as far as Belize. Now that gap seems to be filling in.’

A diver investigating a bear skull wedged between two rocks.
This Ice Age bear skull is among the most important findings made by Guillermo de Anda. It was found in a cenote in the Yucatán. [Image: Guillermo Pruneda]

‘Our five bear skulls belonged to two adults and three subadults, but one of the weird things was that there were no long bones associated with them. This led us to suppose that the bears didn’t die there accidentally. Instead, the heads – and only the heads – had been deliberately placed there. Unsurprisingly, this opened a huge line of research questions. Previously, only a few Pleistocene animals were known from the area. But now, thanks to projects like the Great Maya Aquifer project, we can say that there were gomphothere – an early relative of the elephant – and mammoth, as well as sabre-tooth tigers. We also have the remains of humans that were in the region 13,000 years ago, and maybe even earlier. That brings us back to the question of the bear skulls.’

‘I have always thought that in ancient cultures – and Mesoamerica is no exception – religion started in caves. Just look at places like Altamira, in Spain, with its amazing Palaeolithic art. That really looks like a ritualistic approach to caves. We can see signs that people believed these places had a magical and religious significance, and were powerful for that reason. Although we cannot yet prove it, my working theory is that early humans living in the Americas were worshipping in caves. If so, this is a historical process that we can trace through to the Maya – although I should stress that I am not saying the Maya can definitely be traced back directly to those first settlers. This is something that is still the subject of polemic debate! But I do believe that we can see evidence of a ritualistic mindset among those Ice Age humans interacting with the caves. Of course, they could find shelter there, so maybe they lived there for short periods of time, but we have not found much evidence for that, and the caves didn’t present very comfortable conditions. Instead, what we have seen so far seems a better fit with caves being viewed as marginal, magical places.’

It was at the end of the Ice Age, about 11,000 years ago, that the caves took what is now their familiar form. This was a time of rising sea level, but it was not only salt water that inundated the caves. Instead, increased rainfall seeped through the porous bedrock, draining into the expanse of natural underground passages. While this water does eventually make its way to the sea, the caves should not be seen as underground rivers. Instead, they are essentially gigantic cisterns that fill up during the rainy season. As a result, droughts were capable of producing severe fluctuations in the water level of these natural reservoirs.

An aerial view of the Sacred Cenote, surrounded by trees.
An aerial view of the Sacred Cenote in Chichén Itzá. It was connected to the Great Plaza by a causeway. [Image: Chris Millbern]

This is an extract of an article that appeared in CWA 114. Read on in the magazine (Click here to subscribe) or on our new website, The Past, which offers all of the magazine’s content digitally. At The Past you will be able to read each article in full as well as the content of our other magazines, Current ArchaeologyMinerva, and Military History Matters.

Leave a Reply

Your email address will not be published.