The fossil of a 1.98 million-year- old, human-like animal found in South Africa may be a direct human ancestor and help explain how Homo sapiens evolved, scientists said.
The brains, hands, feet, and pelvis of Australopithecus sediba, found in the Malapa Cave outside Johannesburg, may represent an intermediate stage between the Australopiths and the human genus, Homo, according to five papers published online by the journal Science.
The Australopithecus family, which includes the Lucy fossil, is what many scientists theorize evolved into the human group Homo, the researchers said. That the group of human-like features evolved together suggests that Au. sediba is related to the human lineage, the researchers said.
Those four parts of the skeleton “really represent some of the most critical areas for discussions of major events in human evolution,” said Lee Berger, a study author and paleontologist from the University of the Witwatersrand in Johannesburg.
The finding may mean that Au. sediba is the ancestor of Homo erectus, which is the first species that archaeologists agree was a member of the human family. If the South Africa fossil is an ancestor, it may mean that Homo habilis, sometimes known as the Handy Man, isn’t an ancestor of the human species, said Derryl de Ruiter, another study author. There is very little information on what Homo habilis’s skeleton looked like, so it’s hard to determine where it fits in the evolutionary tree, he said.
The shape of Au. sediba’s brain was inferred from the inside of the skull, and the structure of the grapefruit-sized organ looks human-like, one paper reported. The pelvis was shorter and broader than other Australopiths, making it look more like a modern human pelvis, a second paper said. If Au. sediba is a human ancestor, that suggests that the pelvis evolved before the brain got bigger.
The right hand of the adult female skeleton found looks more human than ape-like, with a thumb that’s longer relative to the fingers than ape hands, another paper reported. The ankle joint in the foot was also human-like, and the foot may have had an arch, as in a human foot. The heel was ape-like.
The hands and feet suggest that the animal both walked and climbed trees, said Steven Churchill, another study author and an anthropologist at Duke University.
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