In a macabre twist, the hominid evolutionary tree’s most famous fossil star, Lucy, tumbled to her death from high up in a tree, a controversial new study suggests.
Some of the damage to Lucy’s 3.2-million-year-old partial skeleton most likely occurred when she fell from a height of 13 meters or more, say paleoanthropologist John Kappelman of the University of Texas at Austin and his colleagues. Lucy, an ancient ambassador of a prehuman species called Australopithecus afarensis, must have accidentally plunged from a tree while climbing or sleeping, the scientists propose online August 29 in Nature.
Bone breaks from head to ankle fit a scenario in which Lucy dropped the equivalent of least four to five stories, landing feet first before thrusting her arms out in an attempt to break her fall, Kappelman says. Tellingly, the ancient female’s right shoulder blade slammed into the top of her upper arm bone, Kappelman says. The shoulder end of Lucy’s arm bone displays sharp breaks, as well as bone fragments and slivers forcibly driven into the shaft.
Such damage frequently appears in present-day people who fall from great heights or are in serious car accidents, Kappelman says. Massive internal bleeding typically follows a body slam as hard as Lucy’s, he adds.
“Lucy probably bled out pretty fast after falling,” Kappelman says.
Nonsense, responds paleoanthropologist Tim White of the University of California, Berkeley. He calls the new paper “a classic example of paleoanthropological storytelling being used as clickbait for a commercial journal eager for media coverage.”
Cracks and breaks throughout Lucy’s skeleton occurred after her death, White asserts. Bone cracking was caused by fossilization and by pressure on fossils embedded in eroding sandstone. Fossilization-related breakage much like Lucy’s — including extensive shoulder-joint damage — appears on the bones of a variety of nonclimbing animals, including gazelles, hippos and rhinos, White says.
Lucy’s upper right arm bone, held in a person’s hand, displays breakage and distortion much like that seen on a corresponding, fossilized limb bone from a horse unearthed in the same part of Africa. Such damage resulted from the fossilization process, not from a steep fall, as proposed for Lucy, one researcher contends.
When people accidentally fall from heights between two and 21 meters, he adds, physicians have documented frequent fractures of the spine, head, elbows, wrists, ankles and feet — but not the shoulders.
Scientists have been unable to decipher how Lucy died since her 1974 discovery in Ethiopia by anthropologist Donald Johanson of Arizona State University in Tempe and his graduate student at that time, Tom Gray. A Johanson-led team, which included White, attributed Lucy’s bone damage primarily to fossilization in a 1982 report.
Intrigued by extensive crushing and breakage at Lucy’s right shoulder joint, Kappelman consulted orthopedic surgeon and study coauthor Stephen Pearce of the Austin Bone and Joint Clinic. When shown a 3-D printed model of Lucy’s skeleton enlarged to the size of a modern human adult (Lucy stood only about 107 centimeters tall, or 3 feet, 6 inches), Pearce said the arm damage looked like that caused by an individual extending an arm to break a steep fall.
Kappelman and colleagues then scoured high-resolution CT scans of Lucy’s bones obtained in 2008, when the ancient skeleton was brought to the University of Texas during a U.S. museum tour.
Along with the upper right arm bone and shoulder blade, damage consistent with hitting the ground after a long fall appeared in bones from an ankle, legs, pelvis, lower back, ribs, jaw and braincase, the researchers say. Fossilization and geological forces caused additional cracking and breaks on Lucy’s remains, as described in the 1982 report, they add.
JOINT IMPACT Reconstructions of Lucy’s upper arm and shoulder blade twirl in this video to demonstrate what happened when, as proposed in a new study, she fell from a tree to her death. In the first rotation, the bones are intact before Lucy hits the ground. Then, colorized fragments appear as the arm smashes into the shoulder socket during impact. On the third rotation, the bones appear in their final state.J. Kappelman
Although initially skeptical that cause of death could be discerned in a fossil individual as old as Lucy, paleoanthropologist William Jungers of the Stony Brook University Medical Center in New York says the evidence indeed points to a fatal fall. No other explanation can account for Lucy’s pattern of bone damage, he says.
If Lucy toppled out of a tree while climbing or snoozing in a nest, her kind must have split time between life on the ground and in trees, Kappelman says. Some researchers have long argued that A. afarensis was built mainly for walking (SN: 12/1/12, p. 16).
Even today, Jungers says, deaths from accidental falls out of trees occur among some African hunter-gatherers, especially when raiding bee’s nests for honey (SN: 8/20/16, p. 10), and in wild chimps, animals more adept at tree climbing than Lucy was.
Lucy’s species could climb trees, White says, but “we do not know how often, or whether for shelter or food.”