New species in human lineage's evolution discovered
Friday, April 9, 2010
Researchers have discovered in South Africa two partial skeletons of a new species of evolving primate that incorporates ape and human features in a previously unseen combination.
The skeletons, of a boy and a young woman, have orangutan-length arms but human-shaped hands. Changes to the legs and pelvis suggest that the creatures spent much of their time upright, although their feet are primitive. They have small, humanlike teeth but an ape-size braincase.
Although anthropologists long ago rejected the notion of a missing link in human prehistory waiting to be found, few doubt that there are "missing strands" in the tangled braid of co-evolving pre-human lineages.
The new species, named Australopithecus sediba, appears to be one of them. Whether it led to the final, successful strand, Homo sapiens, or died out is not known. Either way, the discovery is likely to shed light on a key transition in which pre-human primates took to the ground, eventually acquiring modern appearance and behavior.
"What this shows us is something very surprising," said the skeletons' discoverer, Lee R. Berger of the University of Witwatersrand in South Africa. "Sediba is becoming a terrestrial biped first but is almost maintaining a sort of reserve parachute in having very long apelike arms. . . . The face is beginning to show [more modern] characters, and yet it sits with this remarkably small brain."
The discovery has attracted attention for other reasons, too.
Berger said that Google Earth helped him recognize a series of unexplored caves along a geologic fault northeast of Johannesburg and that the Internet application "is really the reason I could make this discovery." The first bone found -- the collarbone of the child -- was spotted by Berger's 9-year-old son, Matthew, in the remains of a collapsed cave called Malapa, now eroded to the surface.
Other researchers agreed that Australopithecus sediba -- "sediba" means "wellspring" in the Sotho language spoken in the Malapa area -- is an unusual addition to the family tree.
The remains "definitely show that it has a constellation of features that is different from anything else to date," said Rick Potts, director of the human origins program at the Smithsonian Institution's National Museum of Natural History. "What we don't know is how ephemeral or how persistent that combination of features was," he added.
"The South African finds from Malapa are most interesting," said Donald Johanson, an anthropologist at the University of Arizona and co-discoverer of "Lucy," the famed 3.2 million-year-old skeleton found in Ethiopia in 1974.
The Malapa skeletons were found in 2008. At least two more have been found since, Berger told reporters in a telephone briefing, although he did not give details. Work is underway to reconstruct what Australopithecus sediba, standing a few inches over four feet, looked like, he said, adding that his colleagues are also drawing inferences about some of its behavior.
The discovery is already contributing to the taxonomic arguments so common in anthropology.