Lee Berger put his ad up on Facebook on October 7th, 2013. He needed diggers for an exciting expedition. They had to have experience in palaeontology or archaeology, and they had to be willing to drop everything and fly to South Africa within the month. “The catch is this—the person must be skinny and preferably small,” he wrote. “They must not be claustrophobic, they must be fit, they should have some caving experience, climbing experience would be a bonus.
“I thought maybe there were three or four people in the world who would fit that criteria,” Berger recalls. “Within a few days, I had 60 applicants, all qualified. I picked six.” They were all women and all skinny—fortunately so, given what happened next. Berger, a palaeoanthropologist at the University of the Witwatersrand, sent them into the Rising Star Cave, and asked them to squeeze themselves through a long vertical chute, which narrowed to a gap just 18 centimeters wide.
That gap was all that separated them from the bones of a new species of ancient human, or hominin, which the team named Homo naledi after a local word for “star.” We don’t know when it lived, or how it was related to us. But we do know that it was a creature with a baffling mosaic of features, some of which were remarkably similar to modern humans, and others of which were more ape-like in character.
This we know because the six women who entered the cave excavated one of the richest collections of hominin fossils ever discovered—some 1,550 fossil fragments, belonging to at least 15 individual skeletons. To find one complete skeleton of a new hominin would be hitting the paleoanthropological jackpot. To find 15, and perhaps more, is like nuking the jackpot from orbit.
The early hominins included the australopiths, with their sturdy builds, long arms, short legs, and small brains. A couple of million years ago, they were joined by the first members of our genus Homo, with their longer legs, stiffer walking feet, more dextrous fingers, and much larger brains. And some curious species harbor traits that are typical of both lineages
In 2008, Berger found one such mosaic in South Africa’s Malapa cave: a new hominin called Australopithecus sediba. He spent the next five years studying it. The project became so all-encompassing that in 2013, Berger, an explorer at heart, realized that he had stopped exploring. To rectify that, he enlisted two cavers, Rick Hunter and Steve Tucker, to explore other South African caves that might yield important fossils. The Rising Star Cave was one of them.
When the duo entered it in October 2013, they weren’t expecting much. Cavers had thoroughly explored the system for some 50 years, and the chances of finding anything new were low. Tucker did so by accident. During a rest, he wedged himself in a crevice—and found that his feet didn’t touch the bottom. The crevice, it turned out, led to an absurdly narrow shaft, which descended for 12 meters before opening into a chamber. When Tucker dropped into it, he found bones. He took out his Go-Pro and snapped some shots.