SAN FRANCISCO — The fossilized remains of a human- like species that lived 2 million years ago suggest the ancestor ate forest food and used its unique anatomy to climb trees and walk upright on the ground to fetch it.
In a report that was among six research papers about the species, Australopithecus sediba, published Thursday in the journal Science, scientists said a mixture of ancient and modern traits were found in the pelvis, hands and teeth. Its chimpanzee-like heel meant the human species walked with its feet and knees rotated inward, according to the research.
The Australopithecus family, including the Lucy fossil, is what many scientists theorize evolved into the human genus Homo. Previous research suggests the brains, hands, feet and pelvis of Au. sediba were human-like and may have represented an intermediate step. Another earlier report found that Au. sediba ate forest food such as tree bark rather than savanna food, making them more like modern chimpanzees.
"These guys are remarkably mosaic," Steven Churchill, an author of one of the studies and an evolutionary anthropologist at Duke University, said in a telephone interview. "Their lower limbs mean they had a gait unlike anything else."
That may be because when walking upright first emerged, there were many possible ways it happened, he said. Its stride wasn't the same as the Lucy's species, he said.
Thursday's research represents the last of the initial reports on the skeletons discovered in South Africa in 2008, Churchill said. This work further suggests that Au. sediba is a probable ancestor of the Homo genus, the group that includes contemporary humans.
Another paper found Au. sediba's spine bones differed from those of chimps and gorillas, though weren't completely similar to human spines. Au. sediba's walk may have required more flexibility in the lower back than a human's, and the anatomy of their backbones suggest they may be closer to other Australopiths, Churchill said.