Prehistoric people in Spain may have made tools from human bones

Prehistoric farmers and herders in southern Spain buried their dead in a large cave – but may have later cut them up to make tools and possibly eat their bone marrow.

Since 1934, scientists, amateur archaeologists and even tomb raiders have been exploring human skeletal remains left in a Granada cave, called Cueva de los Marmoles.

Within the 2500-square-metre cave – which has harboured multiple generations of bodies across three millennia – people have previously found a carefully carved human skull cup, a well-crafted tibia tool and dozens of other bone fragments. New evidence suggests that some remains may have been intentionally broken and scraped up to a year after the individuals died.

The findings indicate that people may have been manipulating the deceased’s bones, after the cadavers had decayed slowly for some time in the cave’s cool, humid environment, says researcher Marco Milella at the University of Bern in Switzerland.

Milella, his co-lead researcher Rafael Martínez Sánchez at the University of Córdoba, Spain, and their colleagues went to the cave to collect further artefacts and investigate them using modern methods, such as advanced carbon dating, and hi-tech microscopic and scanning equipment.

They examined 411 bone fragments and 57 teeth that were unearthed in various zones of the cave, some of which they borrowed from a museum. They found that the remains were from at least a dozen human adults and children living in prehistoric agricultural societies. The findings suggest that people used the cave as a burial site during three distinct periods: 3900 to 3750 BC, 2600 to 2300 BC and 1400 to 1200 BC.

The team also found that while 3 per cent of the fragments had been gnawed by animals, nearly a third had been intentionally broken or cut with human tools. These fractures, scrapes and slices occurred when the bones were still “fresh” – probably up to a year after death, according to the researchers.

But the bones show no signs of having been forcefully separated from muscles or tendons. “This suggests that the human remains were already partially decomposed when manipulated, but with the bone still being relatively elastic,” says Milella. “This, in turn, points to action not performed shortly after the death of the individuals, but at least some months after death.”

Notable specimens include a skull – probably from a middle-aged man – that had been scraped with stone tools and fashioned into a bowl or cup, and a teenager’s shinbone that had been broken, polished and rounded into a sort of spatula, possibly for scraping other materials, such as leather. Several long bones had also been fractured and their insides scraped out, suggesting the marrow had been extracted for consumption, or possibly as part of a cultural practice of “cleaning the remains”, says Milella.

Lacking any evidence of violence, the remains are probably not the result of power struggles between different populations, he says. His team is planning to carry out DNA research that will compare the relationships among the individuals buried in the cave.