Beneath the Yucatan Peninsula lies an underwater world of tunnels, caves, wells and cenotes so labyrinthine that diving into their secrets is a risky operation, even for a veteran diver. However, there was a time when complexes like the Sac Actun, the largest underwater cave in the world, with its more than 374 kilometers long, were at sea level. 

Sam Meacham and Fred Devos, two veteran explorers from the Quintana Roo Aquifer System Research Center (CINDAQ), have been mapping this oceanic underworld for years. Three years ago, they decided to go down a little further and into rarely explored tunnels until they discovered something that left them totally perplexed. It was recently published in the journal Science Advances.

During a colossal expedition, 100 dives and some 600 hours of work, the CINDAQ explorers, together with submarine speleologist Eduard Reinhardt, collected samples from an ochre mine where miners from an 8,000 year-old pre-Mayan civilization worked tirelessly. This makes it the oldest archaeological record of human activity in the entire Western Hemisphere.  

Its name, Red Mine, has to do with the coloring of the ochre mineral, which is formed by hydrated iron oxide and was used during prehistoric times to make cave paintings, but also color objects in funeral rites and even to protect against insects. 

The 900-metre-long ochre mine is the oldest archaeological record of human activity in the entire Western Hemisphere.  

The most fascinating aspect of the discovery is its excellent state of conservation, since divers even found the tools with which the miners extracted the ochre, the piles of stones they used to mark the path into and out of the cave, and even soot marks from former bonfires with which they lit up when when entering the 900-meter mining complex. It's a fossilized instant 12,000 years ago from the mining life in the oldest mine in the Americas that magically emerges for study.

According to Reinhardt, a diver and professor of Geography and Earth Sciences at McMaster University, "these underwater caves are a time capsule," since "most of the evidence of ancient surface mining has been altered through natural and human processes," obscuring the record. The explorer also pointed out that working in the ochre caves required a lot of experience so "we know that it was a very valuable mineral for the first peoples of the Americas."

Meanwhile, forensic anthropologist, archaeologist and paleontologist James Chatter, explained the working process of these paleoindigenous people. 

"The miners first had to make transport bags or baskets for the ochre they planned to extract. Then they had to supply the mine with enough torchwood to illuminate themselves during the time they intended to work. We can imagine how some workers kept the fires burning while others worked in teams to break and lift rocks and expose the pigment. Just imagine the scene. The flickering light of the torches amidst deep shadows illuminating the red-stained hands of the miners as they pounded the ground with stalagmite hammers and lit the way for those who dragged ochre bags for hundreds of meters through the tunnels into the daylight," he said.

This is not the first time that ancient remains of human presence have been found in the Yucatan's subsoil. In 2014, INAH divers found the remains of a woman who lived more than 12,000 years ago and who they called Naia.