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Homo naledi
This Homo naledi skull is part of a fossil skeleton dubbed “Neo.” (Wits University Photo / John Hawks)

The paleontologists who discovered a previously unknown line of human ancestors in South Africa say that they’ve found more fossils — and that the species, known as Homo naledi, could have lived alongside our own species 250,000 years ago.

The newly disclosed finds from the Rising Star Cave system could reignite the debate over the tangled roots of humanity’s family tree.

Fifty-two scientists from 35 organizations around the world, including University of Washington anthropologist Elen Feuerriegel, were part of the team behind the Rising Star research

In one of the papers published today by the journal eLife, the scientists set the age of the first Homo nadeli fossils they found at between 236,000 and 335,000 years ago, based on radioisotope dating, electron spin resonance dating and an analysis of the flowstone overlying the fossils.

That’s a much younger age than had been expected, and the findings suggest that Homo nadeli may have been contemporaneous with the earliest representatives of our own species, Homo sapiens. If the findings hold true, that could affect how paleontologists view the emergence of behaviors ranging from tool-making to funerary rites.

“We can no longer assume that we know which species made which tools, or even assume that it was modern humans that were the innovators of some of these critical technological and behavioral breakthroughs in the archaeological record of Africa,” the research team’s leader, Lee Berger of South Africa’s University of the Witwatersrand, said in a news release.

“If there is one other species out there that shared the world with ‘modern humans’ in Africa, it is very likely there are others,” Berger said. “We just need to find them.”

Berger and his colleagues discuss the characteristics of Homo naledi in a second paper in eLife. And in a third paper, the researchers report finding still more fossils in a different part of the Rising Star Cave system, dubbed the Lesedi Chamber.

The Lesedi fossils include bones from a child and the partial skeleton of an adult male with a well-preserved skull. The adult skeleton was given the nickname “Neo” — which was inspired not by Keanu Reeves’ character in “The Matrix,” but by the word for “a gift” in the Sesotho language.

“The skeleton of Neo is one of the most complete ever discovered, and technically even more complete than the famous Lucy fossil, given the preservation of the skull and mandible,” Berger said.

Based on the skeleton, the researchers concluded that Homo naledi had a smaller brain and more primitive features than Homo sapiens, but shared some characteristics with our species.

The fact that more remains were found deep in a different chamber lends weight to the controversial claim that groups of Homo naledi, like Homo sapiens, cached their dead in dark, remote places, said study co-author John Hawks, a paleoanthropologist at the University of Wisconsin at Madison.

“What are the odds of a second, almost identical occurrence happening by chance?” he said.

The odds that such a claim will be instantly and universally accepted are small. In his tweeted commentary, Chris Stringer of London’s Natural History Museum says such complex behavior is “unlikely for a creature with a brain size close to that of a gorilla.”

“Perhaps further exploration will reveal other, closer entrances or sinkholes which were temporarily open, through which the remains could have been introduced by accidental or natural processes?” he wrote.

Despite their differences, there’s at least one thing that skeptics and proponents of the newly reported find are virtually certain to agree on: The tale of human origins is far from finished.

Fossils from the Lesedi Chamber as well as from the original Rising Star Expedition will be put on public display starting May 25 at Maropeng, the official visitor center for the Cradle of Humankind World Heritage Site in South Africa. 

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