Fossils of a newly discovered ancient species, named "Homo naledi", are pictured during their unveiling outside Johannesburg September 10, 2015. [Photo/Agencies]

OF TOOLS AND CHIMPS

He set aside another theory that they may have been hiding their dead deep underground, simply to keep off scavengers like the long-legged hyena.

"They are only selecting their own dead. If they were doing that they would put everything in it that would attract a predator or a scavenger," he said.

This is not the first time that the study of our relatives, extinct or living, has yielded evidence that humans do not have the monopoly on certain kinds of behaviour.

Jane Goodall in 1960 famously observed chimpanzees, our closest living relative, using grass stems for termite "fishing", the first recorded use of a crude tool by non-humans.

Homo naledi, discovered in the cave in September 2013, had a brain slightly larger than a chimpanzee's, but its age remains an enigma, said Berger.

This is because the specimens found were deliberately taken to the chamber, and so there are no rocks or sentiments under or overlaying them, he added.

There are also no fossils with them from other animals that could provide clues.

"But we can see from their physical morphology or appearance where their species originates in time. If our present understanding is correct, then that must be in excess of 2.5 million years," said Berger.

The surrounding area is a UN World Heritage site, named the "Cradle of Humankind" by the South African government because of its rich collection of hominin fossils.