Underwater caves in Mexico’s Yucatán Peninsula have yielded evidence of a prehistoric ochre mine, in a discovery that could explain why the region’s earliest inhabitants ventured so deeply inside this treacherous cave system.
People living in the Yucatán Peninsula during the Pleistocene-Holocene transition (around 11,000 years ago) took part in subterranean ochre mining, according to new research published last week in Science Advances. Using stalactites as hammers, these resourceful Paleoindians chipped away at the limestone to gain access to the precious ochre, a natural earth pigment. This is the first discovery of a Paleolithic ochre mine in the Yucatán Peninsula or anywhere else in the Americas, according to the research.
Radiocarbon dating places the mine to between 12,000 and 10,000 years ago. Back then, the caves, located in what is now the Mexican state of Quintana Roo, were dry and farther inland. The caves became submerged around 8,000 to 7,000 years ago and are now only accessible to divers who enter through openings known as cenotes. In 2017, a local cave diving team contacted archaeologists after stumbling upon the site, called La Mina (meaning “the mine” in Spanish).
Red ochre—a mixture of iron oxide, sand, and clay—was a valuable resource during prehistoric times. As a pigment, ochre was used to make cave and rock paintings and for decorating bodies, but it served many other purposes as well.
The submerged caves in Quintana Roo have proven vital to archaeologists. These complex cave systems have yielded some of the oldest human fossils to be found anywhere in the Americas, including “Naia,” a skeleton dated to between 12,000 to 13,000 years old. In total, 10 human skeletons have been found in these submerged caves, including a 9,900-year-old skeleton described earlier this year.
The new research, co-authored by McMaster University geoarchaeologist Eduard Reinhardt, may explain the early fascination with these caves and why many Paleoindians dared to venture so deep inside.
Reinhardt, an expert cave diver, had to be careful while exploring the cave, as the narrowest areas are just 28 inches wide (70 cm). Incredibly, the Paleolithic ochre miners worked well into the cave’s dark zone, in some places as far as 2,130 feet (650 meters) from a natural light source.
The archaeologists discovered ochre extraction pits and hammering tools made from stalactites. They also found piles of rock, called cairns, which the miners used as navigational markers within the labyrinthine cave system. Analysis of charcoal found in fire pits shows it came from trees packed with resin, which would’ve been ideal for making torches.
The mine was active for 2,000 years, from about 12,000 to 10,000 years ago. This was likely an intergenerational activity, in which mining skills were passed down from generation to generation, according to the research.
The mine was eventually abandoned, some 2,000 years before the caves filled with water.
The purpose of the red ochre could not be discerned from the evidence. Sadly, the hot and humid conditions on the surface have wiped out much of the archaeological evidence. Evidence found elsewhere suggests a number of possibilities, however, including a ready-made paint, sunscreen, medicine, insect repellent (ochre contains arsenic), tanning hides, among other uses. The red ochre could have been used during funerals and rituals or applied as war paint.
“The sophistication and extent of the activities demonstrate a readiness to venture into the dark zones of the caves to prospect and collect what was evidently a highly valued mineral resource,” wrote the authors.