A stolen skeleton, which was first discovered in an underwater Mexican cave in the 2010, may be one of the oldest-known human remains in the Americas, Ewen Callaway reports for Nature.
In a study published yesterday in the journal PLOS One, the archaeologists found that the skeleton, dubbed "Young Man of Chan Hol II," which was looted from an underwater cave on the Yucatán Peninsula in 2012, dates back more than 13,000 years, making it one of the oldest-known human remains on the continent. It joins the company of a more than 12,000-year-old skeleton found in a different Yucatán cave, as well as another skeleton found nearby, which dates back approximately 13,500 years, writes Callaway.
The underwater caves of the Yucatán Peninsula preserve some of the earliest years of human settlement in North America. “During the Late Pleistocene, these caves were dry. The first people to occupy what is now the Caribbean coast of Mexico wandered into these caves, where some ultimately met their demise," Waitt Institute archaeologist Dominique Rissolo told National Geographic's Fabio Esteban Amador in 2011. “As the last glacial maximum came to end, the melting of the polar ice caps and continental ice sheets raised sea levels worldwide. The caves of the Yucatan Peninsula filled with water and the First Americans were hidden for millennia — only to be discovered by underwater cave explorers."
In 2007, the aforementioned 12,000-year-old bones of a teenage girl were discovered in another Yucatán cave. Then, in 2010, another promising skeleton was discovered by divers in Chan Hol (meaning "little hole" in a Mayan language, referring to the small size of the opening to enter it). The divers posted about the thrilling discovery on social media around February 2012, Callaway reports. But when archaeologists arrived at the site the following month, they found that the social media posts had also attracted looters, who stole the skeleton from its millennia-old place of rest, as Frank Nowikowski of New Scientist reported at the time.
About 10 percent of the 80-percent-intact skeleton was left behind in the cave, likely because it was embedded into the rock and too difficult to extract by the looters, wrote paleontologist Sarah Gibson in a blog post for the PLOS Paleo Community.
Previous attempts to date these bones with conventional methods like carbon dating produced extremely inconsistent results, reports Andrew Masterson for Cosmos. This was due to a unique quirk of the cave in which the skeleton, which appeared to archaeologists to be from a young man, had resided since his death. The Chan Hol cave had regularly been flooded with both saltwater and freshwater since the man's death, leaching nearly all of the collagen from the bones that is vital for accurate carbon dating.
To get around this problem, the archaeologists turned to the rock that had nestled the skeleton, reports Sarah Sloat for Inverse. The researchers were able to extract samples of a stalagmite grown through the skeleton and from other nearby rocks and scrutinize the amount of isotopes of different elements in those samples. Studying those isotopes can tell researchers about the climate of the time when they were deposited onto the stalagmite, thus giving clues to when they began to be formed.
The scientists are now working to extract DNA from the remaining bones of the skeleton, Callaway reports, and despite five years passing since the theft, they are still holding out hope for the ancient remains' safe return.