|Artists reconstruction of Homo naledi from the skeletons found|
Last week, University of the Witwatersrand anthropologist Lee Berger announced the discovery of a new species of hominid – Homo naledi. It followed his remarkable discovery of Australopithecus sediba some years before, but this discovery is widely regarded as still more significant and surprising.
Naledi – a star in the Sesotho language – is an extraordinary creature, somehow mixing features of Australopithecus and Homo. The skull is really small—the brain was about the size of an orange—yet adult individuals were comparatively large at around 5 feet and 100 pounds. The hands share many of the features of our own, yet the fingers curl and the shoulders slope which is more characteristic of the Australopithecines who were probably tree climbers. The feet are quite similar to ours and the legs are long, suggesting that naledi walked and ran in a similar way to us, and spent much time on the ground. If you would like to read a much more in depth account, Homo naledi makes the cover of National Geographic next month and you can preview the article HERE.
So then is naledi claimed as the so-called ‘missing link’ between Australopithecus and Homo? Is South Africa—indeed Johannesburg!—truly the ‘cradle of humankind’? The answer is no, or at least not yet. The missing piece of information is age. So far no one has been able to determine the age of the fossils from the Cave of Stars. And the age options for naledi are truly fascinating.
|Researchers at the Dinaledi cave|
If nadeli is more than 3 million years old, then Australopithecus was just a side bar; Homo had evolved from something else already. Naledi would probably be our ancestor. Yet the similarities of certain features to each genus suggest rather an age of between two and two and a half million years and then naledi could indeed be the link between the two genera. And if naledi is younger still—less than a million years, say—then there were at least two very different species of Homo living in Africa at the same time.
The discovery of the fossils was made about two years ago almost by accident at a cave near the Cradle of Humankind some 30 miles north west of Johannesburg. Two amateur speleologists were exploring a popular cave system and one came upon a hidden tunnel dropping steeply downward. The two of them were looking for something new and exciting, and decided to take on this chimney. At the bottom they found a treasure trove of fossil hominid remains.
|Lee Berger and his new friend|
I said the discovery was almost by accident, but Professor Berger had gone to a lot of trouble to get the word out to keep an eye open for interesting fossils in the area, and that made the link. The two cavers brought him their news and pictures, sparking off the discovery of the largest collection of hominid fossils ever found in Africa. Realizing he had to act quickly, Berger assembled a team of volunteers who were brave enough and slender enough to get into the chamber. He called them his cave astronauts and all of them are women. Already more than 1500 individual fossils have been collected and come from at least fifteen different individuals of various ages. Also amazing is that the fossils are almost exclusively human, apart from a few birds and rodent-like creatures. This is not a cave full of victims of some predator; the bones are unmarked by teeth. And there is no sign of a river washing the fossils into the cave as then there would be an appropriate mix of other materials. No, these creatures are alone in the dark. How did that happen?
Watch Lee Burger giving a fascinating summary HERE.
|The Dinaledi 'astronauts'|
For all the excitement about a new man, the most fascinating part of the whole story is that naledi apparently disposed of its dead; indeed the Dinaledi cave seems to be a graveyard. Until now there has been no suggestion that any species other than Homo sapiens took pains to remove the bodies of the dead from the natural environment, certainly not by following a difficult route into a hidden chamber to leave them there. But the scientists have considered every other reasonable possibility and rejected it by careful argument.
“When you have eliminated the impossible,” Sherlock Holmes once observed to Watson, “whatever remains, however improbable, must be the truth.” Professor Berger rather charmingly misquoted this at the press announcement as “When you have eliminated all the probable, you are left with the impossible.” Various people have vehemently agreed with that judgement! On the one hand, some scientists have rejected his conclusions and insisted that there must be other explanations, while at the other extreme the whole scenario is rejected by creationists with one even describing the discovery as a white racist plot designed to keep black people at a subhuman status. (How this argument could possibly be made is beyond me; indeed the Wits Vice Chancellor, Professor Habib, pointed out at the press announcement that the implications of all humans arising from a common ancestor emphasises our similarities not our differences.)
But in the scientific community there seems to be no disagreement that we have just met an ancient member of our genus, never before even suspected. And the mystery of when they walked the earth remains.
Michael - Thursday