Researchers in South Africa discovered extensive remains of a previously unknown humanlike species in a subterranean boneyard, highlighting an early offshoot of humankind and raising questions about the origins of ritual burial and self-awareness, the scientists said Thursday.
So far, the researchers have extracted 1,550 bone fragments belonging to about 15 individuals in what is likely the largest single discovery of early human remains in Africa. Thousands more bone fragments, from bodies stacked on top of each other, are still entombed in an inner chamber of the Rising Star cave system 30 miles from Johannesburg, they said.
“These are pretty cool and pretty strange,” said Rick Potts, director of the Human Origins Program at the Smithsonian National Museum of Natural History, who wasn’t involved in the project.
But no one knows yet just how old these remains may be. Conventional dating techniques so far haven’t worked.
“We understand that we are looking at something extraordinary,” said Lee R. Berger, a paleoanthropologist at the University of Witwatersrand in Johannesburg who led an international team of 60 scientists and cavers. Dr. Berger and his colleagues announced the discovery of Homo naledi, as they named the new species, at a news conference on Thursday. Naledi means “star” in Sesotho, a local South African language.
They published their findings in the online journal eLife and in National Geographic, which helped fund the project.
Heightening the mystery, nobody knows how these creatures found their way through a lightless maze of narrow fissures into the cave’s inner sanctum 100 yards underground. The scientists found bones of males, females, children and infants scattered on the cave floor or embedded in its soft clay. There is no sign that they were dragged by predators, washed in by floods, or deposited in some fatal mishap. In fact, there is little evidence that any other life form ever reached the chamber.
“We can exclude the easy explanations,” said John Hawks, a paleoanthropologist at the University of Wisconsin in Madison, a senior member of the project. “What we end up with is that they must have been putting bodies in there.”
If so, it raises the possibility that these creatures exhibited a reverence for their dead by giving remains ritual treatment and burial, which generally is considered a sign of self-awareness unique to humans and humanity’s closest relatives, the Neanderthals.
“It is another species—not human—yet it appears to be practicing a behavior that until this moment people thought was not only unique to us but perhaps identified us: the ritualized disposal of our dead,” Dr. Berger said.
Several independent experts in human origins said there was no direct evidence to support that speculation. “I don’t think Sherlock Holmes would conclude this was deliberate burial,” said Bernard Wood, a paleoanthropologist at George Washington University. “If it was, then everything we think we know about the evolution of human cognition is in the toilet.”
South Africa’s Rising Star cave system, where the bones were discovered, is located near a World Heritage Site called the Cradle of Humankind where many fossils of human predecessors have been found. It has long been a popular spelunking spot for amateur cavers, some of whom may have trampled the bones.
Not until 2013 did scientists learn of the fossil trove in the underground labyrinth.
In life, these creatures were long-legged, lightweight and lithe, standing a little over five feet tall, the scientists concluded. They had surprisingly modern hands and feet, yet a primitive flattened pelvis and a tiny brain barely one third that of a modern human. All in all, they seemed designed for striding with a modern gait and, possessing unusually long curved fingers, perhaps adapted for rock climbing as well, the scientists said.
“We had a combination of features that we had never seen in a single species before,” said Caroline VanSickle, a biological anthropologist at the University of Wisconsin who helped analyze the bones. “It is just so weird.”
Most likely, the bones don’t belong to a direct human ancestor, but represent one of nature’s early experiments in the human form, experts said.
Several disputed the claim that the fossils belong to a new species. Jeffrey Schwartz, a paleo-anatomist at the University of Pittsburgh, said the remains are probably a mix of early human varieties, including a primitive species called Homo erectus that has been known for more than a century.
“A new species name is not adequately warranted for the Rising Star fossils,” said Tim D. White, an anthropologist at the University of California, Berkeley.
Ian Tattersall, a paleoanthropologist at the American Museum of Natural History in New York who wasn’t part of the research group, called it “an amazing assemblage of fossils that should keep paleontologists buzzing for a long time.”