Give Me a Crash Course In . . . ‘Homo naledi’

Who is the monkey man I saw a lot of pictures of this week? The discovery of a new species of early human always produces plenty of coverage, and this week's announcement of Homo naledi was no exception. The news prompted the usual pictures of a half-human, half-ape visage with thick brows and a cross face, with reports about the significance of the find. The coverage is always warranted, given that the discovery feeds into our somewhat patchy knowledge of the evolution of humans and their triumph over competing species, such as the Neanderthals and other species of human-like primates.

What's special about Homo naledi? The story of fossilised bones recovered from the Rising Star cave complex, 50km north of Johannesburg, in South Africa, carried with it a shocking additional finding. Although highly primitive and animal-like, these creatures were placing their dead in an underground tomb that may hold the remains of hundreds, if not thousands, of these early humans. Behaviour like this has never been seen before in animals this old.

Tell me more Homo naledi intentionally deposited dead members of its group in the compact Dinaledi chamber at the back of the 100m-long cave complex. This chamber is empty of any other form of life. There are no pets, no prey items and no sign of any bone damage indicative of physical attack or animal disruption. It contains only the fossils, with the bones in pristine condition.

What motivated these creatures? It is unclear if they were protecting deceased loved ones from predation or were victims of some attack, driven back into a final death trap from which there was no escape. The researchers who discovered them believe they were intentionally depositing the bodies of their dead in the chamber. No known Homo animals until the Neanderthals and modern humans conducted burial practices.

How significant is the find? The fossil deposits are incredibly rich. The researchers pulled more than 1,500 fossil elements from an excavation site no bigger than a square metre, digging to just 50cm, the authors write in the journal eLife. Even if the cave system reveals nothing else, it already ranks as the largest single assemblage of fossils found in Africa and provides an abundance of information about this species and where it might fit into the human family tree. It contains the remains of at least 15 individuals, men and women, children and the elderly. It readily shows differences and similarities between ourselves and these ancestors who date back perhaps two million years.

How much have we in common with Homo naledi? They have similar wrists and feet, as well as legs that were built for upright long-distance walking. Yet the skull and face are quite primitive and the brain is only about the size of an orange. The team that discovered the fossils was led by Prof Lee Berger of the University of the Witwatersrand. They argue that this new creature is sufficiently human-like to warrant being counted among the Homo animals, including humans, chimps, gorillas and earlier Homo ancestors, such as Homo habilis, who dates back 2.8 million years. These fossils will undergo extensive examination in the coming years, but the deposition of the bodies in the chamber will remain a mystery that will be difficult to explain.