Diving for the Bones of the Ice Age

Cave divers carefully maneuver the giant ground sloth's pelvis through Hoyo Negro. Photo Credit: Sam Meacham, CINDAQ F or thousands of years, the massive pelvis lay undisturbed at the bottom of the watery black pit. Approximately four feet across and weighing an estimated 80 pounds, it had once belonged to a giant ground sloth, an elephant-sized animal that roamed the ancient Americas alongside the saber-tooth cat and the woolly mammoth. Sometime during its life, the sloth lumbered into a labyrinth cave system and wandered until it encountered the subterranean pit known today as Hoyo Negro , or "Black Hole." Blind in the darkness, the sloth took a fatal step over the edge of the pit and plummeted nearly 100 feet. The impact would have killed it instantly. These days, Hoyo Negro is a morbid treasure trove for paleontologists: a collection of partially fossilized, Ice Age-era skeletons belonging to saber-tooth cats, several species of ground sloths, an extinct species of bear and Naia, a young woman who lived and died approximately 13,000 years ago. Dominique Rissolo, a research scientist and archaeologist with UC San Diego's Qualcomm Institute (QI), and colleagues have studied their bones for the past eight years to learn more about the region's history.