Five hundred thousand years ago a hyena was munching on the remains of one of our early human ancestors.

It was damaged, broken and had been chewed

More specifically, it was tucking into the thigh bone of an individual believed to belong to the prehistoric species Homo rhodesiensis, thought to be the common ancestor of both our species and the Neanderthals.

The human remains were found resting in a cave in the suburbs of what is now Casablanca in Morocco, an area known to be rich in fossils.

The femur bone was uncovered in a layer of sediment known to be half a million years old. It was unearthed in excavations in 1994 but only "rediscovered" over a decade later.

"It was damaged, broken and had been chewed," says Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. 

Such was the damage that it was not even immediately identified as an early human fossil. "On second look we saw it was a human femur," he says.

The team performed detailed analysis of the tooth marks – which were observed at both ends of the bone – to understand more about the fate of the early human it belonged to.

The dimensions of the tooth marks suggest they were made by a large carnivore.

Fossil evidence from the cave shows it was also a lair for extinct relatives of modern hyenas – although not at the same time that early humans occupied the cave. 

The presence of carnivore tooth-marks on human remains is not sufficient to demonstrate predation

"It looks like the cave has been used by humans and also carnivores, so there is a physical proximity between the two groups," says Hublin. 

Putting two and two together, it makes sense that an ancient hyena caused the damage, the team report in journal PLOS ONE

The exact form of the bone fractures is also most consistent with damage by a hyena, says lead author Camilla Daujeard from the National Museum of Natural History in Paris, France.

We do not know whether the early human was attacked and killed by hyenas acting as predators, or whether he/she died from other causes and was then picked over by scavenging hyenas.

There is poor evidence of direct confrontation, such as serious or lethal bone damage

"The presence of carnivore tooth-marks on human remains is not sufficient to demonstrate predation," says Daujeard. 

It was a surprising find, the researchers note, especially because so few hominin fossils show evidence of being gobbled up by large carnivores.

"Although competition was rough during the Middle Pleistocene, there is poor evidence of direct confrontation, such as serious or lethal bone damage," says Daujeard.

Hublin adds that humans were "rare animals on the landscape" at this time. "A hyena or [large] cat would have more chance to eat something else. This is true today but more true in Middle Pleistocene."

We know that H. rhodesiensis were sophisticated humans, already adept at using complex tools. They used heavy spears and hand axes to attack and kill animals of the Middle Pleistocene. Their prey almost certainly included carnivores like hyenas. 

What the new find suggests, says Daujeard, is that the very animals early humans feasted on were just as capable of hunting and killing the hominins.

Successfully exploiting such dangerous animals as a food source would have been a particularly good human survival strategy. By doing so, the humans were simultaneously providing a meal and removing a threat. 

Melissa Hogenboom is BBC Earth's feature writer. She is @melissasuzanneh on Twitter.

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