When Fred Davos and Sam Meacham of the Quintana Roo Aquifer System Research Center (CINDAQ) ventured into La Mina—a submerged cave beneath Mexico’s Yucatán Peninsula—in spring 2017, they became the first humans to visit the site in some 10,000 years.
Among the most intriguing finds made during this history-making dive, writes Maya Wei-Haas for National Geographic, were hammers crafted out of broken stalagmites and stalactites, piles of rocks scattered on the ground like a trail of breadcrumbs, and a soot-coated ceiling. Combined with traces of a rich red pigment known as ocher, these remnants pointed toward the site’s identity as an 11,000-year-old mine.
“Across the world, archaeological evidence has shown that humans have been using ocher for hundreds of thousands of years,” Brandi MacDonald, an archaeological scientist at the University of Missouri and lead author of a new study on the discovery, tells Reuters’ Will Dunham. “Even Neanderthals used ocher.”
La Mina is nestled so deep in the Quintana Roo cave system that torches would have been ancient visitors’ only possible source of light. But these tools wouldn’t work today—between 7,000 and 8,000 years ago, rising sea levels flooded the coastal cave network, inadvertently creating a time capsule of prehistoric human activity. Now, a paper published in the journal Science Advances details the results of more than 100 dives conducted in the cave system.
These dives—totaling more than 600 hours—may shed light on the presence of human remains in the caverns. In 2007, researchers discovered the bones of a 12,500-year-old of a teenage girl nicknamed Naia in a cave near the one at the center of the study, but they were unable to determine why she had descended so deep within the subterranean network.
“What … were they going down there for?” says Roberto Junco, director of the Underwater Archaeology office of the National Institute of Anthropology and History (INAH), which regulates archaeology in Mexico, to National Geographic. “Now we have really, really strong evidence that at least one of the reasons ... was for the mining of ocher.”
In all, divers identified more than 350 pits used for extracting red ocher, reports Bruce Bower for Science News. Piles of stacked stones mark the path these ancient miners followed—and offer insights on their mining strategy: When a vein petered out, workers would simply move sideways in search of a fresh one.
“They understood ... some basic geological principles that weren’t really codified or formalized until the mid 1600s,” says study co-author Barry Rock, an environmental scientist at the University of New Hampshire, to National Geographic.
Rock led the analysis of charcoal found in the cave, showing that miners relied on high-resin woods that burned brightly for long stretches of time.
The researchers don’t offer an explanation for why the region’s ancient residents made the dangerous trek into the cave system. But humans have long revered red ocher, using the pigment in everything from cave paintings to mortuary rituals. Communities including the Himba in Namibia continue to use red ocher as a bug repellant and sunscreen today; the pigment is also useful for tanning hides.
“The love of shiny red things is a pretty universal human trait,” Spencer Pelton, an archaeologist at the University of Wyoming who wasn’t involved in the research, tells Michael Price of Science magazine. “ … It’s why we buy red sportscars.”
Holley Moyes, a Maya cave specialist at the University of California, Merced, who was not involved in the research, tells National Geographic that deep caves—viewed as an entrance to the underworld or a source of sacred water—were often sites of ritual importance for ancient Mesoamericans. Though the Maya settled the Yucatan thousands of years after La Mina was abandoned, ocher continued to feature in the culture’s rituals and art.
As Meacham tells Reuters, “It is pretty electrifying to be the first people to enter into an area that has not seen humans for thousands of years and to see what they left behind.”