‘Cousin’ Lucy may have fallen from a tree to her death 3.2 million years ago | Science News for Students

‘Cousin’ Lucy may have fallen from a tree to her death 3.2 million years ago

Disputed fossil autopsy says this early hominid broke many bones
Aug 30, 2016 — 9:19 am EST
Lucy hominid

Lucy is the name given to a 3.2-million-year-old partial skeleton of an Australopithecus afarensis. Scientists say that its damaged bones suggest the ancient hominid plummeted to her death from high in a tree. Not everyone accepts that.

DAVE EINSEL/GETTY IMAGES

A fossil named “Lucy” may be the most famous member of the human family tree. Scientists working in Ethiopia found her fossil bones in 1974 . Those researchers named her Lucy after a Beatles song  “Lucy in the Sky with Diamonds.” Now, a controversial study claims Lucy may have met a sad end. It argues that she appears to have tumbled to her death from high up in a tree.

Lucy lived some 3.2 million years ago. She belonged to the species Australopithecus afarensis (Aw-STRAAL-oh-PITH-eh-kus AFF-ur-EN-sis). It's a hominid, meaning she came from a family that includes humans and our most recent ancient relatives. Some damage to Lucy’s partial skeleton most likely occurred when she fell from a tree, researchers now say. She may have fallen, while climbing or sleeping, from a height of 13 meters (43 feet) or more.

Lucy had bone breaks from head to ankle. Her right shoulder blade slammed into the top of her upper arm bone. The shoulder end of her arm bone displays sharp breaks. Bone fragments and slivers had been forcibly driven into the bone's shaft. All of these breaks fit a scenario in which Lucy fell as far as from the top of a four to five story building. The breaks would have occurred if she landed feet first before thrusting her arms out in an attempt to break her fall, says John Kappelman. He is a paleoanthropologist at the University of Texas at Austin. He led the new study, whichwas published online August 29 in Nature.

lucy bone
Scans of Lucy’s partial skeleton provide evidence of a fatal fall, researchers claim. Here, one of Lucy’s lower arm bones undergoes computerized tomography, or CT, scanning.
Marsha Miller/UT Austin

Such damage often shows up in people today who fall from great heights or are in serious car accidents, he notes. Massive internal bleeding typically follows a body slam as hard as Lucy’s, he says. Indeed, he adds, “Lucy probably bled out pretty fast after falling.”

Nonsense, responds Tim White. He is a paleoanthropologist at the University of California, Berkeley. The new paper is an example of scientific storytelling, he charges. It is “being used as clickbait for a commercial journal eager for media coverage.”

The cracks and breaks throughout Lucy’s skeleton occurred after her death, White asserts. Bone cracking was caused by fossilization, he says. Pressure on fossils embedded in eroding sandstone also can cause such cracks. Breaks much like Lucy’s, and due to fossil-forming, can be seen in the bones of many  nonclimbing animals. These include gazelles, hippos and rhinos, White notes. Those bones show extensive shoulder-joint damage similar to Lucy’s, he says.

Doctors have documented frequent bone breaks when people accidentally fall from heights between two and 21 meters (seven and 69 feet), White adds. Such breaks have been found in the spine, head, elbows, wrists, ankles and feet. But they have not been found in the shoulders. 

Donald Johanson is now an anthropologist at Arizona State University in Tempe. Back in 1974 he led the team that found Lucy. He was joined at the time by his then-graduate student Tom Gray. Since her discovery, scientists have been unable to figure out how Lucy died. In 1982, a Johanson-led team, which included White, attributed Lucy’s bone damage mostly to fossilization.

lucy horse
Lucy’s upper right arm bone is held in a person’s hand. It shows breakage and distortion much like that seen on a corresponding fossil bone from a horse that was unearthed in the same part of Africa. Such damage could have come from the fossilization process — not the steep fall being proposed, one researcher argues.
Courtesy of T. White and the National Museum of Ethiopia

Kappelman, though, was intrigued by extensive crushing and breakage at Lucy’s right shoulder joint. He consulted Stephen Pearce. Pearce is an orthopedic surgeon at the Austin Bone and Joint Clinic in Texas. Pearce was shown a 3-D printed model of Lucy’s skeleton. It was enlarged to the size of a modern human adult. (Lucy stood only about 107 centimeters tall, or 3 feet, 6 inches.) Pearce thought the arm damage looked like that caused by extending an arm to break a steep fall.

Kappelman and his colleagues then scoured high-resolution CT scans of Lucy’s bones. They had been taken in 2008. That was when the ancient skeleton was brought from Ethiopia to the University of Texas during a U.S. museum tour.

Damage consistent with hitting the ground after a long fall also appeared in bones from an ankle, legs, pelvis, lower back, ribs, jaw and braincase, the researchers say. Fossilization and the forces of geology caused additional cracking and breaks in Lucy’s remains, they add. A report had described these back in 1982.

William Jungers was initially skeptical that a cause of death could be discerned in a fossil hominid as old as Lucy. He is a paleoanthropologist at the Stony Brook University Medical Center in New York. But the evidence indeed points to a fatal fall, he now argues. 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, rather than tree climbing.

Even today, Jungers says, human deaths from accidental falls out of trees occur among some African hunter-gatherers. That especially occurs when they may be raiding bees’ nests for honey. It also occurs in wild chimpanzees. And these are animals more adept at tree climbing than Lucy was.

Lucy’s species could climb trees, White says. But, he notes, “we do not know how often, or whether for shelter or food.”

A new study contends that Lucy fell from a tree to her death. Reconstructions of Lucy’s upper arm and shoulder blade twirl in this video to demonstrate what may have happened. 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

Power Words

(for more about Power Words, click here)

Australopithecus     An extinct genus of hominids that lived in east Africa from about 4 million to 2 million years ago.

braincase     A part of the skull that protects the brain.

colleague     Someone who works with another; a co-worker or team member.

commercial     (in research and economics) An adjective for something that is ready for sale or already being sold. Commercial goods are those caught or produced for others, and not solely for personal consumption.

computerized axial tomography    (CAT or CT, for short). A special kind of X -ray scanning technology that produces cross-sectional views of the inside of a bone or body.

CT scan     (see computerized axial tomography )

fossil     Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.

geological     Adjective to describe things related to Earth’s physical structure and substance, its history and the processes that act on it. People who work in this field are known as geologists.

graduate student     Someone working toward an advanced degree by taking classes and performing research. This work is done after the student has already graduated from college (usually with a four-year degree).

hominid     A primate of an animal family that includes humans and their ancient, fossil relatives.

journal     (in science) A publication in which scientists share their research findings with the public. Some journals publish papers from all fields of science, technology, engineering and math, while others are specific to a single subject. The best journals are peer-reviewed: They send out all submitted articles to outside experts to be read and critiqued. The goal, here, is to prevent the publication of mistakes, fraud or sloppy work.

orthopedics       A medical specialty that involves diseases and injuries affecting bones and the tissues that attach them to form the human skeleton.

paleoanthropology     The study of ancient humans and hominid biology and behavior and how hominids evolved, based on the analysis of fossils, remnants, artifacts or markings created or used by these individuals. People who work in this field are known as paleoanthropologists.

pelvis     Bones that make up the hips, connecting the lower spine to leg bones. There is a gap in the middle of the pelvis that is larger in females than in males and can be used to tell the sexes apart.

pressure     Force applied uniformly over a surface, measured as force per unit of area.

sandstone     A type of sedimentary rock. It formed as sand-size grains of mineral grit became compacted or glued together over time.

scenario     An imagined situation of how events or conditions might play out.

skeptical     Not easily convinced; having doubts or reservations.

species     A group of similar organisms capable of producing offspring that can survive and reproduce.

3-D printing     A means of producing physical items — including toys, foods and even body parts — using a machine that takes instructions from a computer program. That program tells the machine how and where to lay down successive layers of some raw material (the “ink”) to create a three-dimensional object.

NGSS: 

  • MS-LS4-2
  • HS-LS4-1

Citation

Journal:​ J. Kappelman et al. Perimortem fractures in Lucy suggest mortality from fall out of tall tree. Nature. Published August 29, 2016. doi: 10.1038/nature19332.

Further Reading

S. Ornes. “Shoulder bones fuel debate.” Science News for Students. November 16, 2012.

S. Gruber. “Hobbits: Our tiny cousins.” Science News for Students. April 25, 2012.

S. Ornes. “Old relative steps down.” Science News for Students. April 20, 2012.

S. Ornes. “Old bones ignite fresh debate.” Science News for Students. September 28, 2011.

S. Ornes. “Meet your mysterious relative.” Science News for Students. October 14, 2009.