A team led by Professor Lee Berger, a palaeoanthropologist from the University of the Witwatersrand in Johannesburg found two well-preserved skeletons of a human ancestor species that has never before been seen. Berger and his team described the new hominid and named it Australopithecus sediba.
Professor Lee Berger with a skull of the newly discovered hominid Australopithecus sediba (Photo courtesy Witwatersrand U.)
"Sediba, which means natural spring, fountain or wellspring in Sotho, one of the 11 official languages of South Africa, was deemed an appropriate name for a species that might be the point from which the genus Homo arises," said Berger.
Two papers related to this find will be published in the journal "Science" on Friday, authored by Professor Berger and Professor Paul Dirks, former head of the Wits School of Geosciences and now at Australia's James Cooke University.
The site of the remains, a 10-by-10 cave about eight feet deep, was discovered in August 2008. It was Berger's nine-year-old son Matthew who spotted the first bone.
The fossils, a juvenile male and an adult female, were found deposited within a single debris flow and occur together in the remains of a deeply eroded cave system known as the Malapa cave site.
The sedimentary and geological context indicates that the timing of their death was closely related and occurred shortly before the debris flow carried them to their place of burial, the researchers say.
Darryl de Ruiter of Texas A&M University was the lead craniodental specialist who helped determine the gender and age of the remains. He says the skulls are human-like but smaller, and their teeth are similar to human teeth.
"What we have here is a clearly transitional form," de Ruiter said. "We actually think we have found the best candidate for a direct ancestor of Homo, the genus to which humans belong."
Skulls and teeth from the two specimens of Australopithecus sediba (Photo courtesy "Science" magazine)
The genus name Australopithecus translates into "southern ape," and the species is loosely referred to as an "ape man," because they could still move around in the trees but once on the ground could walk on two legs as humans do, said de Ruiter.
The newly found species has long arms like an ape, short powerful hands, a very advanced hip bone and long legs capable of striding and possibly running like a human. It is likely that these hominids could have climbed.
"It is estimated that they were both about 1.27 meters (50 inches), although the child would certainly have grown taller. The female probably weighed about 33 kilograms (72 pounds) and the child about 27 kilograms (59 pounds) at the time of his death," said Berger.
"The brain size of the juvenile was between 420 and 450 cubic centimeters, which is small," said Berger, when compared to the human brain of about 1200 to 1600 cubic centimeters, "but the shape of the brain seems to be more advanced than that of australopithecines."
The most sophisticated scanning and dating technology has been used to extract secrets of existence nearly two million years ago.
Skull of the male juvenile Australopithecus sediba (Photo courtesy Witwatersrand U.)
"Through a combination of faunal, U-Pb and palaeomagnetic dating techniques, the age of the rocks encasing the fossils has been determined at 1.95-1.78 Ma [million years]," says Dirks. "Cosmogenic dating was used to interpret the landscape formation and to determine the depth of the cave at the time."
The skeletons were found amongst the articulated skeletons of a sabre-toothed cat, antelope, mice and rabbits. They are preserved in a hard, concrete like substance known as calcified clastic sediment that formed at the bottom of what appears to be a shallow underground lake or pool that was possibly about 30 to 50 meters underground about 1.9 million years ago.
Fossil preparators have worked over the last year and a half to extract the bones from the rock. About 60 scientists from around the world and dozens of students have had the opportunity to work on these precious fossils.
Indiana University anthropologist Kristian Carlson is one of the seven scientists in the core research group.
"Being a member of the team interpreting the Malapa fossils is an extraordinary privilege in that I have an opportunity to be at the forefront of paleoanthropology," Carlson said. "I feel a duty to the field to proceed with cautious scientific analysis, but yet there is also the undeniable excitement of being able to study and interpret previously unknown morphologies and constellations of traits."
Indiana University anthropologist Kristian Carlson, left, and University of the Witwatersrand paleoanthropologist Job Kibii at the Malapa cave site (Photo by L.R. Berger)
Indiana University anthropology Professor Kevin Hunt said this discovery is important because the bones create newly-identified links between the Australopiths and Homo, and also suggest that the transition between the small-bodied Australopithecus africanus and the bipedal Homo erectus occurred not only in East Africa, but across the whole of Africa.
"The intriguing thing is that they still have traits found in the more rugged species, Au. africanus, that is found half a million to a million years earlier," said Hunt. "This suggests that just like humans all over the world have evolved but retained their regional characteristics, we had regional characteristics of Homo habilis at two million years ago."
"It's late enough that it is contemporaneous with our ancestors that were, at the time, evolving into Homo erectus." Hunt said. "The fossils in South Africa tend to be very rugged, with heavy faces and huge molars. These aren't like that, and suggest that they're related to East African fossils that many have put in the taxon Homo habilis."
"The fossils clearly link fossils in East Africa to South Africa," Hunt said.
Berger said, "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]."
Also contributing to the research were Darryl de Ruiter of Texas A&M University, Steven Churchill of Duke University, Peter Schmid of the University of Zurich, and Job M. Kibii of the University of the Witwatersrand.
Funding for this research came from the South African Department of Science and Technology, the South African National Research Foundation, the Institute for Human Evolution, the Paleontological Scientific Trust, the Andrew W. Mellon Foundation, the AfricaArray Program, the U.S. Diplomatic Mission to South Africa and Sir Richard Branson.
The site continues to be explored and without a doubt there are more groundbreaking discoveries to come forth, the scientists say.
In celebration of this find, the children of South Africa have been invited to develop a common name for the juvenile skeleton.
The fossils are owned by the people of South Africa, and curated by the University of the Witwatersrand, Johannesburg. They will be on public display at Maropeng in the Cradle of Humankind until April 18. They will them be moved to Cape Town for the launch of Palaeo-Sciences Week from April 19 and will again be on public display at the Wits Origins Centre during May, on dates to be announced shortly.
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