Key questions have yet to be answered

THE scale of the Rising Star find is massive. It represents one of the largest single fossil finds across the globe, and the biggest in Africa.

With 1 550 specimens collected, the team has recovered the remains of at least 15 individuals — and more are likely to follow. This abundance stands in sharp contrast to the research findings drawn from single celebrity fossils such as Mrs Ples, Lucy, or Little Foot.

But while everyone agrees on the scale of the find, not everyone agrees on researcher Lee Berger’s interpretation of it. For starters, the lack of an age estimate has sparked debate.

Chris Stringer of the Natural History Museum in London told eLife: “[Dating] could have been achieved directly via radio-carbon dating . . . or indirectly based on ancient DNA samples. Tests on even small fragments of bone and tooth enamel could have narrowed down the possible age range and at least ruled out either a very ancient or very young age.”

Berger and his team say the remains are difficult to age be- cause there were no fossils of other species with them, and neither were there clues from rock sediments.

“We have tried three approaches that have failed to give dates for the actual fossils, and are working on further attempts,” Berger said. “We only want to publish age limits when we are absolutely sure.”

Curtis Marean, a palaeoanthropologist at Arizona State University, said it was “absolutely essential” that the re- mains be dated. “For example, if they date to the last 300 000 years, then it is plausible that early modern humans killed them and stashed them in the cave as part of a ritual,” he told sciencemag.org.

Berger argues that there is a clear suggestion that Homo naledi individuals entered the cave on purpose to deposit bodies.

“There is no evidence of any water or mud flowing . . . with enough force to transport bod- ies. There is no evidence of predators having been involved, nor acts of cannibalism, nor trauma resulting from a fall.”

He said the bodies were “probably deposited over a period of time”, and entered the chamber using the same entrance as today.

Berger’s claims that Homo naledi is a new species has also been questioned.

Christoph Zollikofer, an anthropologist at the University of Zurich, told The Guardian: “The few ‘ unique’ features that potentially define the new species need further scrutiny, as they may represent individual variation, or variation at the population level.”

Tim White, a fossil expert at the University of California, Berkeley, said it seemed that the fossils belonged to primitive members of Homo erectus, a species named in the 1800s.

But Berger argues that the unusual combination of characteristics in the Homo naledi bones is unlike anything seen in any other early hominin species. “It represents something entirely new to science.”