Science
Themba Hadebe / AP
Scientists say they have discovered a new member of the human family tree, revealed by a huge trove of bones in a barely accessible, pitch-dark chamber of a cave in South Africa.
The creature shows a surprising mix of humanlike and more primitive characteristics; some experts called it bizarre and weird.
And the discovery presents some key mysteries: How old are the bones? And how did they get into that chamber, reachable only by a complicated path that includes squeezing through passages as narrow as about 7½ inches?
The bones were found by a spelunker about 30 miles northwest of Johannesburg. The site has yielded some 1,550 specimens since its discovery in 2013. The fossils are from at least 15 individuals.
Researchers named the creature Homo naledi (nah-LEH-dee). That reflects the Homo genus, which includes modern people and our closest extinct relatives, and the word for “star” in Sesotho, a local language. The find was made in the Rising Star cave system.
The creature, which evidently walked upright, has a mix of traits. For example, the hands and feet look like Homo, but the shoulders and the small brain recall Homo's more apelike ancestors, the researchers said.
Lee Berger, an American professor at the University of the Witwatersrand in Johannesburg who led the work, said H. naledi's anatomy suggest that it arose at or near the root of the Homo group, which would make the species some 2.5 million to 2.8 million years old. The discovered bones may be younger, he said.
At a news conference Thursday in the Cradle of Humankind, a site near the town of Magaliesburg where the discovery was made, a partial skeleton was arranged in a glass-covered wooden case, along with fragments of small skulls, an almost complete jawbone with teeth and pieces of limbs, fingers and other bones.
The researchers also announced the discovery in the journal eLife. They said that they were unable to determine an age for the fossils because of unusual characteristics of the site but that they are still trying.
Berger said researchers are not claiming that H. naledi was a direct ancestor of modern-day people, and experts unconnected to the project said they believed it was not.
Rick Potts, the director of the human origins program at the Smithsonian Institution's Natural History Museum, who was not involved in the discovery, said that without an age, “there’s no way we can judge the evolutionary significance of this find.”
If the bones are about as old as the Homo group, that would mean that H. naledi is “a snapshot of … the evolutionary experimentation that was going on right around the origin” of Homo, he said. If they are significantly younger, then H. naledi retained the primitive body characteristics much longer than any other known creature or it re-evolved them, he said.
Eric Delson of Lehman College in New York, who also wasn’t involved with the work, said his guess is that H. naledi fits in a known group of early Homo creatures from about 2 million years ago.
Besides the age of the bones, another mystery is how they got into the difficult-to-reach area of the cave. The researchers said they suspect H. naledi may have repeatedly deposited their dead in the room or that it was a death trap for individuals who found their way in.
“This stuff is like a Sherlock Holmes mystery,” declared Bernard Wood of George Washington University in Washington, D.C., who was not involved in the study. Visitors to the cave must have created artificial light, such as a torch, he said. The people who did cave drawings in Europe had such technology, but nobody has suspected that creatures with such a small brain as H. naledi would have the mental ability for that, he said.
Potts said a deliberate disposal of dead bodies is a feasible explanation for the collection of bones, but he added it’s not clear who did the disposing. Maybe it was some human relative other than H. naledi, he said.
Not everybody agreed that the discovery revealed a new species. Tim White of the University of California at Berkeley called that claim questionable. “From what is presented here, [the fossils] belong to a primitive Homo erectus, a species named in the 1800s,” he said in an email.
The Associated Press
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