Lucy fell from tree, study claims: disputed analysis says tumble killed famed early hominid.
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 colleagues. Lucy, an 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 at least four 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 often 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."
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 in the bones of a variety of nonclimbing animals, including gazelles, hippos and rhinos, White says.
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, now of Arizona State University in Tempe, and his graduate student at that time, Tom Gray. In a 1982 report, a Johanson-led team, which included White, attributed Lucy's bone damage primarily to fossilization.
Intrigued by 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 model of Lucy's skeleton enlarged to the size of a modern human adult (Lucy stood about 107 centimeters tall, or 3 feet, 6 inches), Pearce said the damage resembled 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 skeleton was brought to the University of Texas during a U.S. museum tour.
Along with the right upper 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 geologic forces caused additional cracking and breaks on Lucy's remains, as described in the 1982 report, they add.
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 School of Medicine in New York says the evidence 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.
Even today, Jungers says, deaths from accidental falls out of trees occur among some African hunter-gatherers, especially when raiding bees' nests for honey, and in wild chimps, animals more adept at tree climbing than Lucy was.
Caption: CT scans of the hominid Lucy's partial skeleton (lower arm bone shown, left) provide evidence of a fatal fall, scientists report. But Lucy's right upper arm bone (right, held in a person's hand) has breakage similar to that of a fossilized limb bone from a horse found in the same part of Africa. Such damage resulted from fossilization, not a fall, a critic of the new research contends.
Please note: Illustration(s) are not available due to copyright restrictions.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||HUMANS & SOCIETY|
|Date:||Sep 17, 2016|
|Previous Article:||Bird nest riddle: which shape came first?|
|Next Article:||Out of the dark: scientists identify bacteria lurking in the shadows.|