MEXICO CITY -- Experts and cave divers in Mexico's Yucatan peninsula have found ocher mines that are some of the oldest on the continent, which could explain why ancient skeletons were found in the narrow, twisting labyrinths of now-submerged sinkhole caves.





The early miners apparently brought torches or firewood to light their work, and broke off pieces of stalagmites to pound out the ocher. They left smoke marks on the roof of the caves that are still visible today.

"While Naia added to the understanding of the ancestry, growth and development of these early Americans, little was known about why she and her contemporaries took the risk to enter the maze of caves," wrote researchers from the Research Center for the Aquifer System of Quintana Roo, known as CINDAQ for its initials in Spanish.

"There had been speculation about what would have driven them into places so complex and hazardous to navigate, such as temporary shelter, fresh water, or burial of human remains, but none of the previous speculation was well-supported by archeological evidence," they wrote.

"Now, for the first time we know why the people of this time would undertake the enormous risk and effort to explore these treacherous caves," said CINDAQ founder Sam Meacham. At least one reason, Meacham said, was to prospect and mine red ocher.

Roberto Junco Sanchez, the head of underwater archaeology for Mexico's National Institute of Anthropology and History, said the discovery means the caves were altered by humans at an early date. The early miners may have removed tons of ocher, which, when ground to a paste, can be used to colour hair, skin, rocks or hides in varying shades of red.

"Now we know that ancient humans did not risk entering this maze of caves just to get water or flee from predators, but that they also entered them to mine," Junco Sanchez said.




Red ocher mining "seems especially important during the first period of human colonization ... you find it on tools, floors, hunt sites," Pelton said. "It's a substance of great power ... everybody likes shiny red things."

"It gives them a reason" to go into the caves, Pelton said, adding: "Considering the massive scale of this mining, it's the first thing I would go for."

The caves provide a well-preserved environment and are where one of the oldest sets of human remains found in the Americas, a young woman nicknamed "Naia," was discovered in 2007.

Chatters said Naia "most likely died from a 30 metre (100 foot) fall from the dark cave tunnel" onto the floor of a chamber below.