Maropeng

BOUCHERCON HIATUS #3

MICHAEL - THURSDAY

Over the last couple of years I've posted a couple of times about the startling discoveries of new hominid species that have been coming to light at the Cradle of Humankind cave complex north west of Johannesburg.  Last week I made a trip to the visitors' center at Maropeng to see a special limited-time exhibition of the actual fossils discovered two years ago and subsequently described as a new species of homo, Homo naledi.  The center is excellently done and absolutely worth a visit if you pass through Johannesburg on your way to a more attractive part of the country.

Being with the actual remains of a being so like, and so unlike, us who lived possibly two million years ago, and who has left only these traces was a very moving experience.

Homo naledi with a few examples of Homo sapiens with him
Photo: Jonathan Everitt

Michael with Australopithecus sediba - sediba is the good looking one on the right
Photo: Jonathan Everitt

HOMO NALEDI:

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.

A selection of the remains

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.

AUSTRALOPITHECUS SEDIBA:

Earlier this month a team of scientists at the Institute for Human Evolution of the University of the Witwatersrand in Johannesburg announced an amazing discovery. It was nothing less than the holy grail of paleoanthropologists – the fossilized remains of a new species of hominid. Excitement spread through the expert community at once, but the discovery caught the imagination of the general public also. It’s not hard to understand why. Few prehistoric issues are more intriguing than our linage and where it branches from the great apes, our close genetic relatives. There is even some possibility that the new species – named Australopithecus sediba (Sediba is a natural spring in the Sotho language) - is a link between the previously known southern African Australopithecus specie - Australopithecus africanus – and Homo habilis or Homo erectus. In other words a connection between the two genera, one of which is our own.

Lee Berger with sediba

The first Australopithecus specimen was also discovered by a Wits professor. Raymond Dart wrote up his discovery of the so-called Taung Child in the journal Nature in 1925. Other discoveries followed first by Dart and then under the leadership of Dart’s successor, Professor Phillip Tobias. Several are from the same area where the new specimens where found. Pictures of Dart and Tobias, with friends, are below:

It seems that Australopithecus evolved some four million years ago in east Africa and spread over much of the continent. It is thought to have become extinct some 2 million years ago. Thus the age of the new specimens is a very important issue. Paul Dirks, then the head of the School of Geosciences at the university, was involved with the dating issues. They attacked the problem three ways. Various other fossil creatures were found in the same sediments; several of these are well-known as are their periods of existence. Next, the magnetic polarity reverses which took place in the geological past put the fossils between 1.78 and 1.95 million years of age. Finally uranium/lead dating puts them at around 2 million years. 2 million years mean that sediba lived in the same time frame as the homo species; possibly they were contemporaries. More controversially, Berger has suggested that humans may be descendents of sediba. Reaction to that has been mixed. Either way it is a branch of our tree which was unknown before.

The species had long ape-like arms, short hands and long legs which might have made it possible to run or walk like a human. Two more specimens have been discovered, preserved in a hard conglomerate of calcified clastic sediments, apparently deposited at the bottom of an underground lake nearly two million years ago.

Makapansgat where some earlier specimens of Australopithecus were discovered.

The New York Times featured Lee Berger and his young son, Matthew, with his dog, Tau, at the site, and delighted in the story of the boy picking up the first piece of fossilized clavicle bone. Tau means Lion in Setswana, which is the unofficial language of Botswana but also widely spoken in South Africa. Apparently the dog ran off and Matthew followed, returning with the fossil. It would have been an even better story if the bone had been dug up by Tau! The full story of that first discovery is at

http://www.nytimes.com/2010/04/09/science/09fossil.html?th&emc=th

What makes the discovery particularly remarkable is the location. The specimens were found at the Cradle of Mankind, a world heritage site where some of the Australopithecus africanus specimens were discovered. It is a rich collection of (now filled) caves which seems to have hosted a variety of species for millennia. Now it seems it hosted at least two different species of hominid over time.

The scientists have been working with the specimens, and finding additional ones, for eighteen months. I recall Paul Dirks telling me about a year ago that he was working on dating a marvelous fossil discovery at the Cradle. At the time we were discussing the use of certain geophysical techniques to try to find additional filled caves and promising sites in the area. In the end none of the high tech was necessary. It all came down to a boy and his dog.