LONDON (Reuters) - Two partial skeletons unearthed in a South African cave belong to a previously unclassified species of pre-human dating back almost 2 million years and may shed new light on human evolution, scientists said on Thursday.
Fossils of the bones of a young male and an adult female suggest the newly documented species, called Australopithecus sediba, walked upright and shared many physical traits with the earliest known human Homo species.
The finding of the pre-human, or hominid, fossils -- which scientists say are between 1.78 and 1.95 million years old -- was published in the journal Science and may answer some key questions about where humans came from.
Lee Berger of the University of the Witwatersrand, Johannesburg, who led the team that found the fossils in August 2008, told a news conference held near the cave outside Johannesburg the discovery was "unprecedented."
"I am struck by the exceptional nature of something right on our doorstep ... there are more hominid fossils than I have ever discovered in my entire career," he said.
"When we found it we never imagined that we were looking at a new species."
Berger earlier told reporters by telephone the team were hoping to reveal a possible two further skeletons from the same site.
He was reluctant to define the new species as a "missing link" in human evolutionary history, but said it would "contribute enormously to our understanding of what was going on at that moment where the early members of the genus Homo emerged."
South African Deputy President Kgalema Motlanthe told the news conference: "As any parent knows, one of the most common questions a child asks is, 'where do I come from?' It has become clear the answer is 'Africa'.
"With the World Cup in 63 days, we will now be able to welcome people from the world with fresh news of our past."
Many experts believe the human genus Homo evolved from the Australopithecus genus about 2 million years ago. One of the best-known pre-humans is "Lucy," the skeleton of a species called Australopithecus afarensis, and this new species is about 1 million years younger than "Lucy," the scientists said.
The fossils, a juvenile male and an adult female, were found in the Malapa caves in the "Cradle of Humankind" World Heritage Site, 40 km (25 miles) outside Johannesburg.
The species had long arms, like an ape, short powerful hands, a very advanced pelvis and long legs capable of striding and possibly running like a human, the researchers said.
The scientists estimate both hominids were about 1.27 meters, although the child would have grown taller.
The brain size of the younger one was probably between 420 and 450 cubic centimeters, which is small when compared with the human brain of about 1200 to 1600 cubic centimeters, they said.
"These fossils give us an extraordinarily detailed look into a new chapter of human evolution ... when hominids made the committed change from dependency on life in the trees to life on the ground," said Berger.
Paul Dirks of James Cook University in Australia, who also worked on the study, said he and a team of researchers from around the world identified the fossils of at least 25 other species of animals in the cave, including saber-toothed cats, a wildcat, a brown hyena, a wild dog, antelopes and a horse.
Additional reporting by Diana Neille, editing by Alison Williams