Shaking the family tree

11 September 2015 - 02:53 By Shaun Smillie and Katharine Child

Long ago a group of our ancestors made their way into a dark cave carrying their dead. What took these creatures, with brains the size of apes', to the dark chamber 90m from the entrance of the cave might have been an understanding of the finality of death, or even a belief in an afterlife.This is the controversial theory scientists have put forward to explain why a hard-to-reach chamber deep in the Rising Star cave, in Gauteng's Cradle of Humankind, is filled exclusively with Homo naledi remains.Homo naledi, described as a new species of a previously unknown branch of the human family tree, was revealed to the world at Maropeng, in the Cradle of Humankind yesterday.This hominid, which stood about 1.5m high, had a unique mix of primitive and modern features, with a tiny brain, about the size of an orange, a slender body and unusually curved fingers.The remains of 15 individuals were excavated from the cave, in an expedition led by Wits University and National Geographic in 2013."Once you have eliminated the probable you have the improbable - they were disposing of their dead in the chamber," said Wits palaeoanthropologist Lee Berger, who led the team that made the discovery.The scientists, he explained, had ruled out the possibility that carnivores had dragged the hominids into the chamber because no other prey items were found nor predator teeth marks on the bones.There was also no evidence that water had moved the fossils or that there was another entrance to the chamber. Scientists also did not find any evidence that the possible hundreds of individuals at the site died in a singular event.That Homo naledi found their way into the dark chamber, also raises the possibility that they used fire to light their way. "The impact of that is significant. Until this moment in history the idea of ritualised behaviour directed towards the dead, things like burial and secreting dead into chambers, was utterly unique to Homo sapiens. It, in fact, identified us," Berger said.Whether this hypothesis is correct is linked to the age of the bones. But Berger and his team have been unable to date the fossils because of the structure of the cave and the absence of animal fossils at the site. They could be anything between more than 2million years old and just a few hundred thousand years, which would make them contemporaries of modern humans.Wits anthropologist Robert Thornton - who did not work on the project - said: "If they were disposing of their dead it suggests that they had an idea that something came afterwards, that they had a concept of an afterlife."To achieve their task would have required cognition and teamwork. Such behaviour, Thornton explained, could mark the origins of human culture, with Homo naledi taking part in ritualised behaviour."Clearly you are not going to spend time dragging bones into a dark cave if they don't mean anything to you," he said.Some scientists have cautioned that further investigation is needed before it can be accepted that Homo naledi was, in fact, participating in a death ritual."I can't imagine them doing what it took modern spelunkers with climbing equipment and lighting to do," said palaeoanthropologist Fred Grine, a professor at Stony Brook University in New York."I would like to see further excavation of the site and investigation of the cave system."US professor John Hawks, part of Berger's team, said: "[Disposing of the dead] is not the way we might imagine it - highly symbolic or highly spiritualistic. It is repeated social behaviour that puts them in a special place. We'd be surprised if a chimpanzee did that, but I don't know if it is very far beyond what a chimpanzee could do."Palaeoanthropologist Chris Stringer of the National History Museum in London said that the age of the fossils needed to be ascertained to establish where they fitted in human evolution. But he said he couldn't see a hominid with an ape-sized brain being involved in such behaviour.Gerrit Dusseldorp of the Centre for Anthropological Research at the University of Johannesburg said the idea the species was disposing of the dead "was not impossible, but highly improbable"."It's logistically problematic to get into this cave, especially for such a primitive species whose brain was a third of the size of humans. No markings on the rock were presented suggesting repeated entry into the cave . There are so many problems and more questions than answers. The data is not secure or strong enough to make such confident claims.''University of California, Berkeley Professor of Paleoanthropology Tim White said: ''Even the authors admit that there is insufficient evidence [for disposing the dead]. Peer reviewers at [journal] Nature said the same thing, and rejected the paper. That is why the publicity claims differ from what is actually reported in the scientific paper.''But world-renowned naturalist Bob Brain, who previously unearthed 140000 fossils near the Cradle of Humankind, said: "It's the most likely hypothesis. You can never prove anything from a remote past, but you can make the most likely conclusions."I think these must have been deliberately put in there."..

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