London - Two immediate questions are prompted by this astonishing find - and it really is one of the most staggering finds in the history of human palaeontology, certainly on the continent of Africa.
The first is whether these humans truly constitute a new species, or whether they were a population of Homo erectus who just happened to be smaller than usual. The second is whether they really did bury their dead as part of some repeated ritual.
Professor Chris Stringer, head of human origins at the Natural History Museum in London, said that, overall, the fossilised bones appear most similar to those of small-bodied examples of H. erectus, the first species of humans known to have roamed widely outside Africa.
However, he accepts that the skeletons' features indicate a mix of old and modern characteristics. The small brain size (one third that of modern humans), curved fingers and the shoulder and hip joints are similar to those of the older Australopithecus, which predated Homo, and the early human species Homo habilis, or “handy man”.
Yet the wrist, hand, legs and feet more closely resemble those of the Neanderthals, which lived as recently as 35 000 years ago, and of anatomically modern humans, Professor Stringer says. His analysis is published in the online journal eLife, where the description of Homo naledi is published.
So the mixture of ancient and modern features appears to set these hominins apart as a separate species of Homo. Certainly the scientists behind the research discount any suggestion that they have merely stumbled upon another kind of H. erectus.
The question of ritual burial is even more intriguing. If the theory is true, and it seems the only plausible explanation so far, how could a species with a brain no bigger than an orange communicate and organise itself to take part in this highly symbolic behaviour?
It challenges our notion of the brain power needed for language, for instance, and even our concept of the link between intelligent behaviour and brain size. As Professor Stringer said: “The intentional disposal of dead bodies is a surprisingly complex behaviour for a creature with a brain no bigger than H. habilis or a gorilla.”
Another unanswered question is how old are these fossils? Dating is now under way, but the species itself could go back further than two million years, to the birth of the human lineage itself.
The Independent