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CSI: 3.2 MILLION BCE

Lucy, one of the most ancient human ancestors, probably died because she fell out of a tree

Reuters/Denis Balibouse
Tree house.
  • Katherine Ellen Foley
By Katherine Ellen Foley

Health and science reporter

Published This article is more than 2 years old.

Lucy was a tiny—just three and a half feet tall and about 60 pounds. When she lived 3.2 million years ago in Ethiopia, she likely spent her days foraging for food and her nights sleeping in trees to avoid predators.

Unfortunately, her makeshift tree house was probably the cause of her death.

On Aug. 29, researchers from the University of Texas at Austin published (paywall) work in Nature that uncovers new evidence about how Lucy, one of our oldest ancestors, died. Based on close inspection and computed tomographic (CT) scans of a subset of breaks in her skeleton, they concluded Lucy probably fell about 40 feet to her death, and the fall happened close to the crevasse where she was found.

The University of Texas at Austin/Liberal Arts Instructional Technology Services
An artist’s rendering of what Lucy may have looked like.

John Kappelman, a paleoanthropologist at the University of Texas at Austin and lead author of the paper, says that the compression fractures found in Lucy’s bones likely resulted from her hands and arms being outstretched to brace for some kind of impact. “That is the kind of fracture that occurs when people fall,” he says. 

Lucy was an Australopithecus afarensis, an early hominid species that helped connect the evolutionary dots from apes to humans. Don Johanson, a paleoanthropologist, first discovered her partial remains in 1974, and fully categorized all the breaks they found in her bones in 1982. Previously, the fractures in her skeleton were attributed to damage done to her bones after her death or to usual geological wear and tear.

Kappelman and his team were examining Lucy’s remains more closely to learn more about how she may have lived. In doing so, they discovered some fractures that stood out from the rest. Upon closer scrutiny using a CT scan, those fractures appeared to be the result of acute trauma while she was still alive. Although Kappelman’s team agrees that the majority of the breaks in her skeleton probably came later, they noticed that some of them—including breaks in her shoulders, right ankle, left knee, pelvis, and one of her ribs—are consistent with the types of injuries modern orthopedists see in patients who have experienced accidents like a fall or a car crash.

Marsha Miller/University of Texas at Austin
Lucy’s wrist bone undergoing CT scans.

Because the area where Lucy was found was relatively flat, Kappelman and his team believe the most likely story is that she fell from a tree. Chimpanzees—Lucy’s closest evolutionary ancestor—typically spend their nights in nests in trees that are on average, about 40 feet tall. Since Lucy was so small, the researchers say, it’s also likely she would take refuge in trees at night to escape predators.

Of course, researchers can’t know exactly what was happened to Lucy. But her bones, Keppelman said, work kind of like a time machine. He and his team will continue to study her remains to learn more about how she may have been when she was alive.

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