Ancient skeleton found in underwater cave reveals DNA of earliest Americans

by Mary Caperton Morton
Friday, May 16, 2014

Between 13,000 and 12,000 years ago, a teenage girl entered a cave, likely searching for water, and fell to her death into a pit, which would later fill with glacial meltwater at the end of the last Ice Age. The pit, called Hoyo Negro, Spanish for “Black Hole,” part of the San Actun cave system beneath Mexico’s Eastern Yucatán Peninsula, has now yielded one of the oldest human skeletons ever found in North America.

Genetic analysis of mitochondrial DNA extracted from a molar revealed that the prehistoric girl bears genetic markers common to modern Native Americans, according to the researchers behind a new study in Science detailing the skeleton. The find lends support to the theory that the earliest Americans and modern Native Americans share a single ancestral population, which expanded out of Asia between 26,000 and 18,000 years ago crossing over Beringia, the landmass that once connected Asia and North America.

A variety of extinct animals also found in the pit, including giant ground sloths and an elephant-like creature called a gomphothere, which went extinct around 13,000 years ago, helped to constrain the age of the skeleton. Because it had been underwater for so long, the bones contained little of the collagen protein needed for radiocarbon dating, so the team, led by James Chatters of Applied Paleoscience, based in Bothell, Wash., turned to uranium-thorium dating of the calcite encrusting her bones to narrow the age range.

The near-complete human skeleton — dubbed Naia, meaning “water nymph” in Greek — was discovered in 2007 at the bottom of the pit, 40 meters below sea level. “Research in flooded caves is much like space exploration, with divers similar to astronauts reporting back to ‘mission control’ — a much larger scientific team at the surface,” said author and diver Patricia Beddows of Northwestern University, in a statement.

The project was led by the Mexico’s National Institute of Anthropology and History and supported by the National Geographic Society.

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