South African paleoanthropologist and National Geographic explorer Lee Berger described the discovery of soot-covered walls, fragments of charcoal, burnt antelope bones and stones arranged as hearths in the Rising Star cave system, where nine years earlier the team had excavated the bones of exposed a new member of the Rising Star caves. human family, Homo naledi.
Control of fire is considered a critical milestone in human evolution, as it provides light to navigate dark places, allows activity at night and leads to the cooking of food, and a subsequent increase in body weight. When exactly the breakthrough happened, however, is one of the most contentious questions in all of paleoanthropology.
“We’re probably looking at the culture of a different species,” said Berger, who departed from 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 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 formal papers are being reviewed, adding, “There will be a series of important discoveries in the coming month.”
He stressed that his team’s discoveries this summer answer a critical question that arose when they announced the first trove of 1,500 fossil bones: How did this ancient species find its way into a cave system about 30 to 40 meters below ground, a place devilishly difficult? reach and, in his words, “terribly dangerous”?
The research team now believes that H. naledi used small fires in chambers throughout the cave system to light their way. Berger based the claim in part on his personal journey through the cave’s narrow passages, which required him to shed 55 pounds.
In addition, he argued that the use of fire by a human relative with a brain slightly larger than a large orange distorts the traditional narrative of our development. For years, experts have portrayed evolution as “a ladder” that kept climbing toward species with bigger brains and greater intelligence, while species with smaller brains perished.
But there’s mounting evidence that the process may have been messier than thought, a view that would be strengthened if this smaller-brained contemporary from the early 1900s did indeed homo sapiens was advanced enough to use fire.
Berger’s talk, accompanied by photographs from the cave but not carbon dating and other traditional scientific methods, drew criticism, as did some of his earlier claims about the 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 Human Evolution Research Center at the University of California at Berkeley, who has been a critic of Berger’s in the past. “Any claim about the presence of controlled fire will be met with some skepticism if it comes through a press release rather than data.”
Previous reports of humanity’s early use of fire, even those accompanied by scientific evidence, have proved controversial. In 2012, archaeologists using advanced technology reported “unequivocal evidence in the form of burnt bones and ashes of plant remains that burning events occurred in Wonderwerk Cave” in South Africa about 1 million years ago. Critics questioned that age estimate, and scientists revised the date to at least 900,000 years old after using a complex technique called cosmogenic nuclide dating.
White said rigorous studies would need to date both the fire evidence and the H. naledi bones if Berger’s team wants to show that both are from the same time period. Other studies must demonstrate not only the presence of fire, but also its controlled use. Testing should show that the material believed to be carbon black is actually carbon black and is not discolored by chemicals or other factors.
Berger acknowledged that one of the biggest challenges for him and his colleagues will be dating the materials found. So far, they’ve said the H. naledi bones date to between 230,000 and 330,000 years ago, though Berger stressed that those dates shouldn’t be viewed as the first or last appearances of the species.
White seemed very skeptical about the lack of stone tools in the caves. He said archaeologists would expect to find thousands of stone tools at a site where human relatives used fire for light and cooking.
“I will tell you at this stage that there are no stone tools that we have found in the presence of a hearth,” Berger said in the interview. “That’s a weird thing.” Nevertheless, he told the audience at the Carnegie Science talk, “Fires don’t spontaneously start 800 feet in a wet cave, and animals don’t just wander into the fire and burn.”
He said stone tools have been found in the general landscape outside the caves. He also countered criticism that what the team found is not evidence of an ancient hearth.
“We found dozens of hearths, not just one,” Berger said when asked about the evidence during the interview. “It’s 100 percent. There’s no question. … We are now entering a phase where this is moving from just bones to a rich understanding of the environment they lived in.
Berger previously met with controversy during the initial announcement of the H. naledi discovery, 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 several points during the lecture, acknowledging that it “may not have been very well received by most of the academy”.
Other researchers said that while much testing remains to be done, the latest finds at Rising Star are impressive.
“I love it. It looks very convincing,” said Richard W. Wrangham, a professor of biological anthropology at Harvard University and author of the 2009 book “Catching Fire: How Cooking Made Us Human.”
“Of course it’s fascinating because of the petite and generally mysterious nature of these people.”
Wrangham said that when the discovery of H. naledi was announced, he discussed the dark caves where the bones were found with one of Berger’s colleagues, noting, “Surely this must mean they had light.”
However, Wrangham said he remained puzzled by one issue: “How did they take the smoke?” Was there a draft that drew smoke from the cave?
Wrangham said he is willing to take Berger at his word about the use of fire, based on the initial evidence. However, he said the strongest evidence for early control of fire comes from an archaeological site in Israel called Gesher Benot Ya’aqov, where experts say early human relatives used fire to cook fish about 780,000 years ago.
During the talk, Berger also shared vivid descriptions of some of the 50 H. naledi individuals the team found.
He described the fossilized bones of a hand “curled in a death grip”; the skull of a child sitting atop a plank in the rock; and another child’s skeleton, tucked away in a niche in one of the rooms. The dramatic images required an equally dramatic journey through a fissure in the dolomite that narrows to just seven centimeters and requires extreme twisting of an explorer’s body.
“You’re basically kissing the ground,” said Keneiloe Molopyane, a 35-year-old researcher at South African University’s Center for the Exploration of the Deep Human Journey. Explorers, she continued, emerge at a perilous ridge about 20 meters above the cave floor. It’s pitch dark inside, with ‘bats whizzing past you on either side. If you fall, you belong to the cave.”
The reward, however, is a feeling that Molopyane vividly remembered from her first descent into the cave system: “Oh, God. I am the first person to see these remains in thousands of years, I don’t know how many, and now I am touching them.”
Berger said about 150 scientists 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 possible conflicts that may have occurred between H. naledi and H. sapiens, Berger replied, “Everything you just asked, within the next 36 months we will have answers.”