A large carnivore — most likely a hyena — ate an ancient human 500,000 years ago, according to the discovery of teeth marks on a thighbone found in a Moroccan cave.

Key points: First definitive evidence that animals ate ancient humans half a million years ago

First definitive evidence that animals ate ancient humans half a million years ago Ancient humans living at this time could use fire and tools to defend themselves

Ancient humans living at this time could use fire and tools to defend themselves Unclear if the animal killed the human or scavenged remains

The fossilised femur provides the first definitive evidence that carnivores ate early humans in North Africa during the Middle Pleistocene era.

Researchers found the adult-size bone in a vast cavity south west of Casablanca called the Thomas Quarry 1 Hominid Cave.

The cave is famous for its ancient human bones and stone tools believed to represent a population of Homo rhodesiensis, a type of early human.

Other fossils found inside the cave include bones from extinct species of bear, wildebeest, panthers and a giant baboon.

"The pattern of chewing on the bone indicates a hyena, or rather a cave hyena, which is a slightly larger species that doesn't exist anymore," said Professor Jean-Jacques Hublin, from the Max Planck Institute for Evolutionary Biology, Germany.

"If you compare large carnivores they have a different way of eating. The big cats, like lions or tigers, will eat the flesh and chew the extremities of the bones.

"Hyenas are much more capable of breaking and cracking large bones because they have very powerful mandibles and jaw muscles."

The bone showed distinct tooth-marks, and both ends were crushed and fractured.

The analysis, published in the latest edition of PLOS ONE, shows that much of the marrow remained intact, which suggested the hyena might have been interrupted.

Bone chewed soon after the human's death

Fossilised human bones showing carnivore teeth marks have been found in South Africa, Europe, and the Middle East, Professor Hublin said. These include bones found in hyena dens.

However, the bones found in those areas of the world were either much earlier, or much later — between 40,000 and 10,000 years ago, when carnivore hunting became widespread.

"We suspected humans would be prey in the Middle Pleistocene era, but we have very little evidence," he said.

"We are coming closer to when humans became humans as we know them now. They were better equipped to deal with carnivores. They could keep themselves safe by using fire and had much better weapons that could kill at a distance."

The analysis showed that the bone was chewed soon after the human's death.

"Of course, we can't tell if the human was killed by this carnivore, or if the hyena or something else took the limb into the den," Professor Hublin said.

"But, with the abundance of human fossils together with the remains of different types of animals like baboons and antelopes, this cautiously supports the hypothesis that humans at this time were a resource for large carnivores."

Humans were quite capable of being able to evict carnivores and take carcasses from them 500,000 years ago, while carnivores were coming after humans and eating their leftovers, he continued.

"We know this because there are carnivore teeth marks and human cut marks on the same animal bones from other sites."

