In 2007 members of the Proyecto de Espeleología de Tulum (PET) discovered Hoyo Negro as part of a three-year concentrated effort to explore and map the underwater caves of the Ejido Jacinto Pat, located about 20km north of the City of Tulum. The team worked with land-owners to visit many remote cenotes and surveyed ~100,000 feet of passages.

During one of their expedition, while traversing 3000ft underwater from Cenote La Virgen, they entered a very large chamber. This space was so vast that their powerful light could not penetrate to the other side of the pit. They felt as if this void was absorbing all visible light, and decided to call their discovery “Black Hole”, which in their native Spanish language is Hoyo Negro. The Pit is 200 ft in diameter and it goes from 20 ft at the roof to about 190 ft at the bottom. There are no openings to the surface at the roof of this chamber.

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On the floor and walls of Hoyo Negro the divers discovered the remains of many animals from the Late Pleistocene period, most of which are now extinct. They are remarkable well-preserved - intact and unbroken except by their falls over 100 ft to the floor of the cave. Giant ground sloths, gomphotheres, saber-toothed cats, and bears, pumas, peccaries and many other animals entered the chamber at least 8000 years ago, tunnels leading into the pit were mostly dry. At that time the sea level was considerably lower (up to 300 ft) transforming these underwater passages into dry caves that animals could walk through in search for water or refuge.

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The remains of an adolescent girl were also found in close proximity to the bones of one the gomphotheres. She was a short and very slim individual who found her resting place as she became lost in the cave and eventually fell into Hoyo Negro. Scientific dating methods are being applied to determine if this girl could be one of the oldest Americans ever found on our continent.

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As required by Mexican law the team announced their discovery to INAH, Instituto Nacional de Antropología e Historia, and provided maps and photo-documentation of some of the animals and the human remains at the site. Since that time members of PET have centered their organization efforts, in collaboration with INAH, around protecting, documenting and understanding this unique and invaluable resource.