When exploratory divers discovered the underwater Mexican cave site known as Hoyo Negro, the conditions of the cave were so pristine and stable, says archaeologist Dominique Rissolo, “it looked like no one had ever exhaled a breath there.”
But there was evidence that at least one person had been inside the cave before the divers: A Paleoamerican girl nicknamed Naia, who had fallen to her death while presumably collecting water from the cave during the late Pleistocene era, between 13,000 and 12,000 years ago. The divers found her skeleton, as well as the remains of several Ice Age animals, on the cave floor. According to Rissolo and project co-director, James Chatters, it was like the La Brea tar pits without the tar.
This remarkable discovery represents the first and only example of human remains found in direct association with extinct megafauna in the Americas, says Rissolo, who is a visiting scholar at UC San Diego from the Waitt Institute and a research associate at the Scripps Institution of Oceanography. The remains of two gomphotheras (extinct elephant-like creatures), two Shasta ground sloths, a pair of saber-toothed cats and numerous other animals were also found with Naia in the underwater pit, which measures 200 feet in diameter and is located in the far Southeast of the country, on the Yucután Peninsula.
Computer science Ph.D. student Vid Petrovic – a member of the Center’s Integrative Graduate Education and Research Traineeship (IGERT) program in cultural heritage diagnostics – is using photos taken by the scientific dive team to create 3D structure-from-motion (SfM) models of the cave site, and he has used the same technique to recreate Naia’s mandible.
SfM is an imaging technique that, in this case, uses two-dimensional photographs taken underwater at the cave site. Petrovic tracks and aligns features in the photos (such as corner points) to ‘stitch together’ and reconstruct the objects digitally in 3D.
Rissolo says that given the proper lighting, camera set-up and protocols, SfM is a relatively straightforward and cost-effective imaging and visualization method, especially for documenting archaeological sites that are not easily accessible or are threatened with destruction, either natural or human-derived.