H. naledi (Photo: John Hawks, Wits University)
Two years ago, a paleontologist sent two cavers to explore the Rising Star cave system, not far from Johannesburg, South Africa, and they discovered what turned out to be the largest trove of hominin fossils ever found. The 1,550 or so bone fragments belong to more than a dozen individuals—at least 15—of a new species of hominin, named Homo naledi, the scientists announced on Wednesday. And it looks as if these skeletons were placed purposefully in the cavern, in what could be called a burial ritual.
Often, hominin skeletons are discovered incomplete, and scientists are left to fill in the gaps. With this wealth of fossils, the new species is "already practically the best-known fossil member of our lineage," Lee Berger, the project's leader and a paleontologist at the University of Witwatersrand, in South Africa, said yesterday during a press conference.
The scientists that analyzed the fossils are confident that the individuals all belong to the same species, because of consistencies among bones. (The New Scientist notes a dissent, based on variations in the forehead slopes of the skulls.) But the collection of features that these hominins had is surprising. In some ways, they look more like apes and very early human ancestors. But in others, they are much closer to modern humans. The species had a small brain, slopping shoulders, long fingers and arms—but also long legs and feet that resemble ours. H. naledi would have stood about 5 feet tall and also seems to have used tools.
The bones were excavated by six women, recruited for both skill and size, who passed through a tiny shift to reach the chamber where the bones had been laying for, likely, hundreds of thousands—maybe millions—of years. (The fossils have not yet been dated, which has puzzled some of the team's colleagues.)
The bones were first discovered two years ago, when paleontologist Lee Berger asked two cavers to help him explore caves in South Africa that held the promise of possible hominin fossils. This one had been explored many times before, but one caver, by accident, discovered a skinny and previously unknown opening, when he put a foot in and found it went deeper than he expected, almost 40 feet long. When he made his way, through, he saw bones: the pictures he brought back to the surface included a hominin skull.
Ed Yong of the Atlanticwrites:
By the end of the week, the team had excavated more fossils than had ever been found in a South African site. Shortly thereafter, they exceeded the tally from all of southern Africa from the previous 90 years. It took months to process all the 1,550 or so fragments and assemble them into 15 skeletons—male and female, elderly and infant. As hominin fossils go, that’s a superlative haul, paralleled only by Spain’s Sima de los Huesos cave, a bonanza of Neanderthal remains.
One of the most intriguing questions about the skeletons is how they came to be in the cave. The scientists have found no evidence of other activity there, and Berger thinks the best explanation is that other H. naledi dropped these bodies down into the cavern. Only a very few species of hominins—us, Neanderthals, and Homo heidebergensis—are thought to have deliberately disposed of their dead.
This discovery has already added a remarkable entry into the history of humans and the hominins that developed before or alongside us. But this isn't the end of the story. Other scientists will debate the meaning of this find. But, also, there's likely more to be found in this one cavern, and Berger and his colleagues plan to keep digging.
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