‘New hominid species’ at the Cradle

9 April 2010

    A South African-led team of scientists have announced the discovery of what they say is an entirely new hominid species at the Cradle of Humankind world heritage site outside Johannesburg, sparking fresh debate about the nature of our immediate ancestors. Lucille Davie reports.

I stare at the incomplete skeleton in the glass case – did this creature really walk this area almost 2-million years ago? Scientists say so.

Two skeletons have been unearthed at Gladysvale in the Cradle of Humankind, and have been called Australopithecus sediba, an entirely new hominid species.

Wits University, led by professors Lee Berger and Paul Dirks, discovered the new species, dating back 1.9-million years, in the Cradle, north-west of Johannesburg. Berger is a palaeoanthropologist and Dirks a geologist now based at James Cooke University in Australia.

Fragments of the skeleton of a child were on display at the announcement on Thursday at Maropeng, part of the Sterkfontein cave area, a UN world heritage site. Estimates are that the child skeleton is of a boy between 11 and 13 years old, and an adult female in her late 20s or early 30s.

More finds expected

“There are more hominid fossils [here] than I have discovered in my entire career,” Berger said.

Berger, whose 11-year-old son Matthew (nine at the time) found the first fossil, says that two skeletons have been uncovered so far, and he expects many more fossils to be excavated from the site. They are the most complete hominid skeletons ever found.

Sediba, Sotho for “well” or “spring”, is so-named because it is hoped that “a great source of information will spring from the fossils”. The particular site has been named Malapa.

The announcement of the remarkable find is to make the cover story of the prestigious Science journal, with two articles, written by Berger and Dirks, appearing on 9 April.

“I believe that this is a good candidate for being the transitional species between the southern African ape-man Australopithecus africanus (like the Taung Child and Mrs Ples) and either Homo habilis or even a direct ancestor of Homo erectus (like Turkana Boy, Java man or Peking man),” Berger said.

The australopithecines are believed to be the ancestors of the homo genus.

The find promises to turn the palaeontological world upside down, with textbooks having to be re-written, Berger said.

Long arms, short powerful hands

The new species has long arms, like an ape, and short powerful hands, making it likely that it could have retained its ability to climb. A very advanced pelvis and long legs suggest that it was capable of striding and possibly running like a human.

“It is estimated that they were both about 1.27 metres, although the child would certainly have grown taller. The female probably weighed about 33 kilograms and the child about 27 kilograms at the time of his death.

“The brain size of the juvenile was between 420 and 450 cubic centimetres, which is small (when compared to the human brain of about 1 200 to 1 600 cubic centimetres) but the shape of the brain seems to be more advanced than that of australopithecines.’

The world that australopithecus sediba would have lived in would have been a mix of open savannah grassland and forest.

‘Time travellers’

In the audience at Thursday’s announcement was South African Deputy President Kgalema Motlantlhe, Science and Technology Minister Naledi Pandor and her deputy, Derek Hanekom, Gauteng Premier Nomvula Mokonyane, other scientists and members of the international media.

“The discovery opens an unusually panoramic window, revealing more about our African origins,” said Motlanthe. “These time travellers have found their way into the present, and, with the assistance of our scientists, they are able to speak to us from the distant past.’

What is unusual about the find is that two partial skeletons have been found – some 130 pieces have so far been unearthed – opening up the possibility that they belong to a family. Berger is confident that the missing pieces of the skeletons will be found.

“I am having the adventure of my life,” he said.

He said that Australopithecus sediba could turn out to be the “Rosetta Stone” of fossils, explaining where Australopithecines went – and calling for a complete relook at homo habilis.

International team of scientists

Berger and Dirks have assembled an international team of scientists, in all a team of around a dozen people, although some 60 scientists from around the world have been involved in the unravelling of the discovery.

The first step was to do a geological study to help determine the age of the fossils. Other means of dating the fossils have been used: assessing the uranium lead components in the rock; establishing the magnetic signals in the rock, which change over time; and dating the rate of erosion of the site.

Dirks embarked on a study to establish the context of how the fossils landed in the cave. This involved taking a series of sedimentary deposits and a detailed description of different rocks up to two metres deep.

“Ït is a hole in the ground – it must have been a cave,” said Dirks.

Investigation revealed that there had been a muddy flow of water that deposited fossils, with pieces remaining together, suggesting that they were carried down the flow together. Among the fossils found were a 1.5 million-year-old sabre-tooth cat, and 2.36-million-year-old wild cats and dogs.

The erosion rate of the opening was measured, and it was established that it had been between 30 and 50m deep.

“The animals probably smelt the water in the cave,” suggests Dirks, “and fell into the cave trying to get to it.” They would have died instantly, and their skeletons were carried down into a deeper chamber of the cave, joining others that suffered the same fate. This is supported by the fact that the fossils have no scavenger or insect damage.

Excavations have not yet begun, says Dirks; only the surface has been cleared.

18 months ago

The “adventure” began some 18 months ago, in early 2008, says Berger. He first charted the area on Google earth, finding 600 new sites in the Cradle, then walked it with his dog, Tau.

On the day the first fossil was found, he was walking with his son, Matthew, post-doctoral student Job Kibbii, and Tau. They walked to the edge of a pit, and Berger encouraged his companions to look around.

“Within one-and-a-half minutes Matthew called out that he had found something,” says Berger. At first Berger thought it was a fragment of antelope, a common find. Then he recognised the fossil as the collarbone of a hominid.

He soon found other fossils – a clavicle or shoulder blade, normally never found because it is so fragile and erodes quickly – and arm bones, while two hominid teeth “fell into my hands”.

Matthew says he has been on sites with his father more than 20 times, and intends becoming a palaeoanthropologist too.

Treasure chest

Professor emeritus Philip Tobias, also present at Thursday’s announcement, described the area as a “treasure chest”

“I am thrilled that our expectations of the Cradle area have so soon been realised,” he said. “This evidence a kilometre or two from Sterkfontein has yielded several hominid individuals, and that is something to get very excited about.”

Describing the find as “a great joy”, Tobias said that the fact that two skeletons had been found meant that scientists could study a family or community, which was much more valuable than studying individual fossils.

“Truly, visitors to South Africa … will be coming home,” Deputy President Motlanthe said. “And, like all home comers, they will no doubt wish to explore their home – to see where their ancestors lived and to discover their roots.”

Source: City of Johannesburg