A new study of a cave used by prehistoric people in southern Spain has uncovered a mystifying set of practices involving possible cannibalism and the manipulation of dead bodies.

Scientists have studied the Cueva de los Marmoles (Marble Cave) since 1934, but the most recent effort by researchers from the University of Bern and the Universidad de Córdoba is the first comprehensive study of the human remains there. The analysis relies on 411 bone fragments collected from the site, along with 47 attached teeth and 10 loose ones. The pieces – including a “skull cup” forming the upper part of the cranium – raise as many questions as they answer.

Many of the skull and long bones were fractured while the bones were still fresh, perhaps to allow the surviving people of the group to extract the nutritious marrow. That being said, the team didn’t find overwhelming evidence that the prehistoric people – who hailed from 3,000 years to 6,000 years ago – practiced more extensive cannibalism.

How Did Prehistoric People Use Their Dead?

Scientists have found such evidence at caves in Southern Spain but not at Cueva de los Marmoles. The bones lacked the extensive cut marks associated with slicing the meat off a corpse. As members of the Bronze and Stone ages, the prehistoric people would have had access to stone or metal tools. But the study found cutting marks on only 11 of the bones studied.

In an attempt to explain these results, the paper cites a 2015 investigation of the Scaloria Cave in Southern Italy, where researchers uncovered plentiful fresh bone breakages and fewer cuts to bones. That study proposed that the prehistoric people had gathered dead body parts from outside the cave, cut some tissue off the bones and then broke them.

These early morticians had dropped them in the cave, but why inter the dead in such dim places?

“Caves are frozen in time, lacking those phenomena usually marking the passing of time,” the new paper says. “The silence and subterranean position of caves would only add to their liminal connotation.”

Read More: A Stone Age Village Buried a Mysterious Girl with Fine Jewelry Befitting Ancient Egypt

History of Looting

Unfortunately, not all past explorers of Cueva be los Marmoles have been as interested in the cultural significance of its chambers.

In decades gone by, many amateur archaeologists and outright looters lifted artifacts from the caves, including ceramics, ornaments and stone tools. Many of those ended up in private collections and later in the Municipal Historical Museum of Priego of Córdoba.

This likely resulted in changes to the human remains, says the paper, which sets forth an anthropological record of those left.

Further study could reveal yet more about the site’s practices, it says, and whatever “symbolic purposes” they may have served.

Read More: Raiding Graves — Not to Rob But to Remember