A project to understand how Lucy lived might also show how she died.
In 2008, anthropologist John Kappelman and colleagues at the University of Texas at Austin scanned the partial skeleton of Lucy, the famous 3.18 million-year-old Australopithecus afarensis discovered in 1974.
Using super high-resolution CT scans, Kappelman originally planned to learn more about Lucy’s movement and lifestyle — researchers have long debated how much time, if any, A. afarensis spent in trees.
In the images, Kappelman saw signs of a catastrophic fracture in Lucy’s upper arm, and multiple other fractures occurring shortly before her death. Kappelman consulted clinicians who agreed it was the type of severe break you’d see in a car accident, or a rock-climber’s fall.
Without cars or cliffs in her environment — Lucy was found near a stream on a relatively flat landscape — the only way she could have incurred those fatal injuries, concluded Kappelman’s team, was by falling out of a tree.
Published in Nature in August, the study fanned the flames of the old ground- versus tree-dwelling debate. Critics also complained the team did not provide enough evidence to support their conclusions.
Donald Johanson, the paleoanthropologist who found Lucy more than 40 years ago, noted that other fossils discovered nearby also appear damaged, possibly from a stampede, or from the weight of sediment and other material collecting over millennia.
“The suggestion that she fell out of a tree is . . . neither verifiable or falsifiable, and therefore unprovable,” he says. “Australopithecus afarensis was essentially a terrestrial animal.”
Kappelman shrugs off the controversy, noting he is a trained geologist, and that study co-author Lawrence Todd has worked extensively on the bones of bison driven off cliffs by prehistoric hunters.
“Between Larry and me, we have 80 years of experience of looking at bones,” says Kappelman. “We know what broken bones look like. We’re not clinicians, but this subset of fractures cannot be explained by geological processes. We looked at being trampled by, say, an elephant. But nothing we looked at explained these injuries.”
Harvard University evolutionary biologist Daniel Lieberman, who was not involved in the study, called it a “creative analysis” and saw the team’s conclusions as reasonable.
“The fact is that Lucy has all kinds of adaptations both for walking upright and for being arboreal,” says Lieberman. “The findings tell us one thing: She spent time in trees. In eastern Africa, if you want to sleep somewhere at night, and you don’t have fire and you don’t have weapons, you’d probably want to climb a tree to stay safe.”