Bones in South African cave reveal new human relative
A new member of the human family tree has been discovered in South Africa, according to scientists.
The creature, found among a huge trove of bones in a barely accessible cave, shows a surprising mix of human-like and more primitive characteristics.
And The discovery presents some key mysteries including the age of the bones and how they got into the chamber, which is only reachable by a complicated pathway that includes squeezing through passages as narrow as about 7-and-a-half inches.
The site, about 30 miles north-west of Johannesburg, has yielded some 1,550 specimens since its discovery in 2013. The fossils represent at least 15 individuals.
Researchers named the creature Homo naledi. That reflects the "Homo" evolutionary group, which includes modern people and our closest extinct relatives, and the word for "star" in a local language. The find was made in the Rising Star cave system.
The creature, which evidently walked upright, represents a mix of traits. For example, the hands and feet look like Homo, but the shoulders and the small brain resemble Homo's more ape-like ancestors, the researchers said.
Lee Berger, a professor at the University of the Witwatersrand in Johannesburg who led the work, said naledi's anatomy suggests 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 themselves may be younger, he said.
The researchers announced the discovery in the journal eLife and at a news conference in the Cradle of Humankind, a site near the village of Magaliesburg. They said they were unable to determine an age for the fossils because of unusual characteristics of the site.
Professor Berger said researchers are not claiming that neledi was a direct ancestor of modern-day people, and experts unconnected to the project said they believed it was not.
Rick Potts, director of the human origins programme at the Smithsonian Institution's Natural History Museum, 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 argue that 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, it either shows the naledi retained the primitive body characteristics much longer than any other known creature, or that it re-evolved them, he said.
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 the naledi may have repeatedly deposited their dead in the room, but alternatively it may have been a death trap for individuals that found their own way in.