Cracking what must be one of the coldest cases of all time, scientists at the University of Texas claim to have figured out what killed “Lucy,” the iconic human ancestral specimen who lived and died more than 3 million years ago.
In a paper published Monday in the journal Nature, the researchers argue that the pattern of fractures seen in Lucy’s 3.2-million-year-old fossilized bones show that she died as the result of a “vertical deceleration event.”
In other words, a severe fall from a considerable height.
Scientists have long debated whether Lucy, a small bipedal creature who belonged to an extinct species known as Australopithecus afarensis, spent time in trees (arborealism) as well as on the ground ― a point referenced by the paper’s lead author in a written statement.
“It is ironic that the fossil at the center of a debate about the role of arborealism in human evolution likely died from injuries suffered from a fall out of a tree,” Dr. John Kappelman, a professor of anthropology and geological sciences at the university, said in the statement.
For their research, Kappelman and and Dr. Richard Ketcham, a geological sciences professor at the university, used a CT scanner to create an archive of more than 35,000 “slices” of Lucy’s fossilized skeleton (which was found in Ethiopia in 1974 and whose name was inspired by the Beatles song “Lucy In the Sky with Diamonds,” according to the website of Arizona State University Institute of Human Origins).
Subsequent analysis of the slices revealed sharp, clean breaks seen at the end of Lucy’s right humerus (the long bone that runs from the shoulder to the elbow) that the researchers maintain are similar to bone fractures seen in victims of falls.
The researchers concluded that these and other fractures in her skeleton show that Lucy, who is believed to have stood about 3 feet 6 inches and weighed about 60 pounds, fell feet first and used her arms to brace herself ― but that the impact was too severe to have been survivable.
The researchers estimate that Lucy was going about 35 miles an hour when she hit the ground after falling from a height of roughly 40 feet, according to the statement.
That sounds plausible, if a bit gruesome. But other scientists are skeptical.
Dr. Rebecca Ackermann, an archaeologist at the University of Cape Town in Africa, told The Washington Post that the study had failed to disprove alternative explanations for the breaks ― though she didn’t dismiss the research out of hand.
“In my opinion this is a nice study that tells us something interesting about an individual who has played an important role — both scientifically and historically — in our understanding of human evolution,” she told the Post.
But others were harsher in their appraisal of the new research.
“There is a myriad of explanations for bone breakage,” Dr. Donald C. Johanson, director of the Institute of Human Origins and one of the scientists who discovered Lucy, told The Guardian. “The suggestion that she fell out of a tree is largely a “just-so story” that is neither verifiable nor falsifiable, and therefore unprovable.”
Johanson said it was more likely that Lucy’s fractures occurred long after she died, telling The New York Times that “elephant bones and hippo ribs appear to have the same kind of breakage. It’s unlikely they fell out of a tree.”
But the new research focused on “a small subset of fractures” that are consistent with “high-energy bone-to-bone impacts” and which differ from the sorts of breaks commonly seen in fossilized bones, Kappelman told The Huffington Post in an email. “These appear to have occurred perimortem (at or near the time of death).”
In any case, the fresh look at Lucy’s old bones seem to have humanized her ― at least for Kappelman. As he told HuffPost in the email:
“Our hypothesis suggests that the fractures in Lucy’s shoulder were produced when she stretched out her arms in a last desperate attempt to break her fall. We have all done this when we fall. It was in the moment of understanding her death, of literally being able to experience what she went through, that I felt empathy for her. My understanding of her death brought her to life for me.”