Naledi brings a sizeable clan to the party, writes Sarah Wild, who investigates from the site.
Johannesburg - In the dark and humid Dinaledi Chamber at the Cradle of Humankind, dozens – possibly hundreds – of fossils are still undisturbed. This week, National Geographic explorer-in-residence and Wits University professor Lee Berger announced the discovery of 15 individuals, which his team of international scientists claim is a new species, Homo naledi, that were deposited in this site, intentionally by their kin.
H naledi is a “mosaic” of modern and ancient features: a skull big enough to fit a small brain, much smaller than ours; human-like feet and lower legs that could have been able to walk long distances; and wrists and hands that could belong to a tiny human but with elongated, strong fingers, adapted for climbing.
Its rounded shoulders and flat pelvis are more characteristic of Australopithecus, an extinct hominin species which has been found in southern Africa, but standing at about 1.45m, H. naledi would have dwarfed its distant hominin relation.
Most of the Dinaledi Chamber (“chamber of many stars” in Sotho) remains unexcavated, and this – according to international scientists – along with the lack of date-stamp attached to the specimens – creates suspicion about the conclusions draw by the team and expedition, which were funded by National Geographic, Wits University and the National Research Foundation.
The discovery of 1 550 fossil fragments, which make up the 15 H. naledi specimens, were collected during two painstaking expeditions in November 2013 and March 2014 by a team of six women who were slight enough to traverse the treacherous crawl, and climb and drop into the chamber, which is located 30m below the surface.
The women had to squeeze through the “Superman Crawl”, which is less than a school ruler high, before climbing 15m up the “Dragon’s Back” and then inching down a 11m chute.
“This is more fossils than have been found (in Africa) in 90 years,” said Berger, who discovered the Australopithecus sediba fossils in 2008. “How do you study that in a field that was designed to study part of a mandible?”
But it’s possible that many of the scientific community’s questions about the find would be answered if there was more data.
Prof Tim White, an American palaeoscientist at the University of California, Berkeley, and a critic of Berger’s work, says that the Rising Star team’s conclusions are “speculation”.
The area excavated in the chamber is “a test pit, really, measuring only 80x80x20-25cm”. “Most of the bones are still buried in the cave.”
The aspect of this find that has caught public imagination is the suggestion that this was a burial site, and implies a level of cognition that would reduce the behavioural distance between H. naledi and modern humans.
Burying our dead is a distinctly human trait.
The fact that, so far, the researchers have only discovered H. naledi remains in the chamber – along with some rat teeth and a few bird bones – adds weight to the idea of bodies being intentionally stored in the chamber.
“The Dinaledi Chamber is unusual because of the large number of fossils discovered so close together in a single chamber, and that the bodies had not been damaged by scavengers or predators,” the international author team writes in the open access journal eLife. “It also appears that the bodies were intact when they arrived in the chamber, and then started to decompose.”
The other possibility is that a mass-death event resulted in the cavern being filled with the remains of individuals.
Asked whether he thought that Dinaledi was a burial site, the University of Zurich’s Christoph Zollikofer said: “If you advance the idea of a burial site, this has so many implications and is so specific. They have two very fragmentary skulls, a beautiful hand, a beautiful foot. The rest is in single fragments and bits… It sounds spectacular, but it is very, very difficult to say.”
A time stamp on this find would help allay some of these concerns, but Berger said: “We didn’t feel it ethical to destroy hominin material until it has been described, and dating the specimen would mean the destruction of the material.”
But scientists who were not involved in the research question whether this is a new hominin find, or whether H. naledi is an example of Homo erectus.
They say that dating these Dinaledi specimens would help researchers gauge where in human evolution these creatures may fit.
But Berger refused to speculate on how old the fossils were, and his ability to find such large numbers of hominin specimens, which were once some of the rarest artifacts on Earth, continues to astound the international community.
Zollikofer said: “It is fantastic that (Berger) finds new fossils in these quantities – it isn’t easy to do.”
However, the Cradle of Humankind is certainly not done with giving up its secrets – neither in the Dinaledi Chamber or in other parts of the World Heritage Site.
The Sunday Independent