El Mirador Cave in northern Spain.

The likely scene of human cannibalism some 5,600 years ago.

Researchers found bones from at least 11 people at the site in the Sierra de Atapuerca.

Researchers analyzed 650 fragments, belonging to children, adolescents and adults.

Many showed clear signs of posthumous processing.

The study, published in Scientific Reports, found 239 remains with modifications made after death.

More than 220 bones showed signs of burning.

Sixty-nine of those also had butchery marks.

Researchers found slicing, scraping, and chopping, likely linked to skinning and flesh removal.

“Cut marks are produced when a tool, a sharp-edged instrument used to cut meat, comes into direct contact with the bone and leaves those traces,” says Dr. Palmira Saladié, the lead author of the study.

“Carnivore bites or other marks produced by natural processes have different shapes at the microscopic level. To the naked eye, we often can’t distinguish them, but under the microscope, they can be clearly differentiated.”

Some bones may even show signs of human tooth marks.

“We also identified human bites on the bones,” Saladié said. “There is no doubt, no uncertainty, that these humans were consumed by other humans.”

None of the trauma appears to have happened before death.

The team says the injuries are consistent with butchering, not violence or ritual trophy-taking.

“Along with the cut marks, we have found other evidence,” Saladié adds. “Signs of cremation, indications that the bones were boiled or cooked, and intensive fracturing, both of skulls to extract the brain and limb bones to consume the bone marrow.”

They believe the cannibalism was extensive.

“They ate the brain. They ate the bone marrow. They ate the red meat and gnawed on the fingers, toes and ribs,” she says.

“We don’t know if they ate the internal organs. There are no signs, but we know they were removed from the body. Probably they were considered a delicacy. But that’s more of an opinion than evidence.”

The researchers suggest the remains may be evidence of a single act of conflict-related cannibalism, possibly tied to deeper social tensions in Neolithic life.

Isotope analysis shows the individuals were locals.

The bones were found mixed with remains from a later burial.

Cannibalism in the Iberian Peninsula has been documented as far back as one million years.

But researchers say direct evidence like this is rare and often hard to interpret.

For Saladié, the findings should be handled with care when thinking about modern humans.

“It teaches us that humans have been violent since the beginning,” she says. "We shouldn’t take violence as something that defines our essence as a justification for violence in the modern world. Nothing could be further from the truth, in my view."