Last year the discovery of a foot bone revealed that, more than three million years ago, the hominid species whose most famous member is known as Lucy probably walked upright.
Now a new study reveals that the species, Australopithecus afarensis, was also quite apelike, and very capable of climbing trees. The research is based on the analysis of the shoulder bones of Selam, a 3-year-old of the same species.
"The position or orientation of the shoulder joint was very gorillalike," said Zeresenay Alemseged, a paleoanthropologist at the California Academy of Sciences in San Francisco and one of the study's authors.
"We compared it to the primate database," Dr. Alemseged said. "This is the earliest, most complete scapula ever analyzed."
He and his colleague David J. Green, an anatomist at Midwestern University, report their findings in the current issue of the journal Science.
Dr. Alemseged speculates that Lucy, Selam and their kin climbed trees to hide from predators and search for food, and perhaps even to nest.
Exactly how much time they spent in trees is hard to say. Other research has revealed that many traits of the species' hip bone, lower limb and foot are humanlike and well suited for upright walking.
Dr. Alemseged was part of the team that discovered Selam in 2000, in Ethiopia. It took about 10 years to analyze the paper-thin scapula, which was embedded in sandstone, Dr. Alemseged said.
Lucy, a partial skeleton of the species, was discovered in 1974.
This article originally appeared in The New York Times.