1,100-year-old 'altar of skulls' found in Mexico cave

The grisly discovery of about 150 human skulls in a cave in Chiapas, Mexico, initially led local police to think they had come across a crime scene when they first inspected the site in 2012. Now, it's clear that these victims didn't die recently; the skulls are pre-Hispanic and date from around A.D. 900 to 1200, and are most likely the victims of sacrificial rituals, new research finds. 

Following the discovery, the bones were removed from the cave and taken to the state capital of Tuxtla Gutiérrez, where a joint operation between the police and the National Institute of Anthropology and History (INAH) began investigating the gruesome find. 

The bones were discovered near the town of Frontera Comalapa in an area that is reportedly notorious for "violence and immigrant trafficking," according to the Associated Press. On top of that, it wasn't immediately clear that the human remains belonged to pre-Hispanic individuals, as piles of skulls from centuries-old Indigenous sites often have bashed-in skulls and are found in ceremonial plazas.

Related: 16th-century ritual sacrifice, cannibalism and bloody slaughter revealed in Mexican city

But after analyzing the remains, INAH researchers determined that the bones were over 1,000 years old. The remains are mostly of adult women, with the exception of skeletal remains of three infants. None of the skulls had teeth, the archaeologists reported.

The remains suggest that a tzompantli, or "altar of skulls," once existed in the cave, Javier Montes de Paz, a physical anthropologist at the INAH who helped determine the age of the bones, said in a translated statement. This is due to the fact that the remains are mostly skulls or fragments of skulls, and that no complete skeleton was found.

Tzompantli were racks constructed out of wood on which the Aztecs and other Mesoamerican cultures would display the skulls of sacrificial victims, according to The Guardian. The Mesoamerican scholar Juanita Garciagodoy, who taught in the department of Spanish at Macalester College in St. Paul, Minnesota when she wrote the book "Digging the Days of the Dead: A Reading of Mexico's Dia de Muertos" (Colorado University Press, 1998), wrote that "the detached heads of the sacrificial victims were pierced through the temples and slipped onto poles like beads on an abacus." Traces of aligned wooden sticks were reportedly found alongside the skulls, providing further evidence of a tzompantli, a record raised by the Chiapas State Attorney General's Office during the initial 2012 discovery noted, the statement said.

This is not the first time a tzompantli may have been uncovered in Chiapas. In the 1980s, in Banquetas Cave, 124 skulls — all missing their teeth — were uncovered, according to the statement. Similarly, in 1993 during the discovery of the Devil's Tapesco Cave, five skulls  were found that thought to have been placed on a wooden tapesco (a kind of grid).

Montes de Paz emphasized the need to continue archaeological research in the area and stated that if individuals were to uncover sites that could be of interest  they should contact the authorities or the INAH immediately.

Originally published on Live Science.