South African paleoanthropologist and National Geographic explorer Lee Berger described finding sooty walls, charcoal shards, burnt antelope bones and rocks arranged like hearths in the Rising Star cave system, where nine years earlier the team discovered the bones of a new member of the human family, homo naledi.
The control of fire is considered a crucial milestone in human evolution, as it provides light for navigation in dark places, enables nocturnal activity, and leads to the cooking of food and the subsequent increase in body mass. However, when exactly the breakthrough occurred has been one of the most controversial questions in all of paleoanthropology.
“We are probably looking at the culture of another species,” said Berger, who eschewed scientific convention by reporting the discoveries not in a peer-reviewed journal, but in a press release and a Carnegie Science lecture at the Martin Luther Institute. King Jr. Memorial Library in Washington on Thursday. In an interview with The Washington Post, Berger, a professor at the University of the Witwatersrand in Johannesburg, said the formal documents are being reviewed, adding: “There are a number of important discoveries coming over the next month.”
He stressed that his team’s discoveries this summer answer a critical question posed when they announced the initial find of 1,500 fossil bones: How did this ancient species find its way into a cave system some 100 to 130 feet underground, a place that is devilishly difficult? to reach and, in his words, “horribly dangerous”?
The research team now believes that H. naledi used small fires in chambers throughout the cave system to light its way. Berger based the claim in part on his personal journey through the narrow passages of the cave, which required him to lose 55 pounds.
Furthermore, he argued that the use of fire by a human relative with a brain slightly larger than a large orange alters the traditional story of our development. For years, experts portrayed evolution as “a ladder” that moved upward toward species with larger brains and greater intelligence, while leaving species with smaller brains to perish.
But evidence has been accumulating that the process may have been more complicated than previously thought, a view that would be bolstered if, in fact, this smaller-brained early contemporary Homo sapiens he was far enough along to use fire.
Berger’s lecture, accompanied by photographs of the cave but not by carbon dating and other traditional scientific methods, drew criticism, as did some of his earlier claims about H. naledi fossils.
“There is a long history of claims about the use of fire in South African caves,” said Tim D. White, director of the Center for Human Evolution Research at the University of California at Berkeley, who has been critical of Berger. “Any claim about the presence of controlled fire will be met with a fair amount of skepticism if it is a press release rather than data.”
Previous reports of humanity’s early use of fire, even those accompanied by scientific evidence, have been controversial. In 2012, archaeologists using advanced technology reported “unequivocal evidence in the form of burned bones and ash plant remains that burning events occurred in Wonderwerk Cave” in South Africa approximately 1 million years ago. Critics disputed that age estimate, and scientists revised the date to at least 900,000 years after using a complex technique called cosmogenic nuclide dating.
White said rigorous studies need to date both the fire evidence and the H. naledi bones if Berger’s team wants to show that they both come from the same period. Other studies should show not only the presence of fire, but its controlled use. The tests should establish that the material believed to be soot is actually soot and not discoloration caused by chemicals or other factors.
Berger acknowledged that one of the biggest challenges he and his colleagues will face will be dating the materials they have found. So far, they have said that the bones of H. naledi date to between 230,000 and 330,000 years ago, though Berger stressed that those dates should not be seen as the first or last occurrence of the species.
White seemed more skeptical about the lack of stone tools found in the caves. He said archaeologists would expect to find thousands of stone tools in a place where human relatives used fire for lighting and cooking.
“I will tell you that at this point there are no stone tools that we have found in the presence of a hearth,” Berger said in the interview. “That’s kind of weird.” Nonetheless, he told the audience at the Carnegie Science conference: “Fires don’t start spontaneously 250 meters down in a damp cave, and animals don’t walk into fires and get burned.”
He said stone tools have been found in the general landscape outside the caves. He also rejected criticism that what the team found does not constitute proof of an ancient home.
“We found dozens of homes, not just one,” Berger said when asked about the evidence during the interview. “It’s 100 percent. No doubt. … We are now entering a phase where this goes from just being bones to a rich understanding of the environment in which they lived.”
Berger was previously met with controversy during the initial announcement of the discovery of H. naledi, when he suggested that these ancient relatives were deliberately using the caves as a place to lay their dead. Despite the debate, Berger repeated the claim at various points during the conference, acknowledging that “it was perhaps not very well received by most of the academy.”
Other researchers said that while much testing remains to be done, the latest findings at Rising Star are impressive.
“I think it’s fantastic. It seems very convincing,” said Richard W. Wrangham, professor of biological anthropology at Harvard University and author of the 2009 book “On Fire: How Cooking Made Us Human.”
“Of course it’s fascinating because of the small and generally mysterious nature of these people.”
Wrangham said that when the discovery of H. naledi was announced, he was discussing the dark caves where the bones were found with one of Berger’s colleagues, commenting, “Surely this must mean they had light.”
However, Wrangham said he remained puzzled on one issue: “How did you deal with the smoke? Was there a draft that blew smoke out of the cave?
Wrangham said he is willing to take Berger at his word on the use of fire, based on preliminary evidence. However, he said the strongest evidence for early fire control comes from an archaeological site in Israel called Gesher Benot Ya’akov, where experts say early human relatives used fire to cooking fish about 780,000 years ago.
During the conference, Berger also shared vivid descriptions of some of the 50 H. naledi individuals the team found.
He described the fossil bones of a hand “folded in a death grip”; the skull of a child found sitting on top of a shelf in the rock; and the skeleton of another child hidden in a hole in one of the chambers. The dramatic images required an equally dramatic journey through a cleft in the dolomite that narrows to just seven inches and requires extreme contortion of an explorer’s body.
“You’re basically kissing the ground,” said Keneiloe Molopyane, a 35-year-old researcher at the South African university’s Center for the Exploration of Deep Human Voyage. The explorers, he continued, emerge on a dangerous ridge some 65 feet above the cave floor. Inside, it’s pitch black, with “bats buzzing by you on either side. If you fall, you belong in the cave.
The payoff, however, is a feeling that Molopyane remembered vividly from his first descent into the cave system: “Oh, God. I am the first person to see these remains in I don’t know how many thousands of years, and now I am touching them.”
Berger said that approximately 150 scientists from around the world are participating in the effort to excavate, date and study the remains and artifacts found in the Rising Star cave system.
Asked to speculate on the interactions and potential conflicts that may have taken place between H. naledi and H. sapiens, Berger replied: “Everything you just asked, within the next 36 months, we’ll have answers.”
