If you have ever fallen you know your first instinct is to reach out your hands to break your fall. This is exactly what our ancient ancestor Lucy did as she tumbled to her death, according to a study from researchers at the University of Texas at Austin that recently appeared in Nature. The pattern of fractures in Lucy’s bones suggest she died due to a “vertical deceleration event” such as falling out of a tree.
At 3.18 million-years old, Lucy (named for The Beatles song “Lucy in the Sky with Diamonds”), is the oldest known, most complete human ancestor whose fossils we possess. Donald Johanson, professor at Arizona State University discovered Lucy, a member of the species Australopithecus afarensis, in the Afar region of Ethiopia in 1974.
Over the past few years, John Kappelman, anthropology professor at The University of Texas at Austin and colleagues used high resolution X-ray computed tomography, visual inspection and microscopy to analyze Lucy’s bones. More recently, Kappelman used 3D printing to produce a full scale model of Lucy’s skeleton and study her thoroughly. His group observed a compression fracture along the right upper arm bone that is typical of a bone grinding against the shoulder plate, which suggests that Lucy stretched out her arms during a “high energy impact.” “That tells us that Lucy was conscious at the point of impact, at that instant in time right before her death,” Kappelman said via email.
They also saw fractures in the legs, an ankle, pelvis, ribs, vertebrae, jaw and the skull. This damage seems to be consistent with falling from a great height as proposed by Dr. Stephen Pearce, an orthopedic surgeon at the Austin Bone and Joint Clinic in Austin, Texas, and co-author of the September 2016 paper. But not everyone is convinced. “I am skeptical about this whole reconstruction,” said Matt Cartmill, professor of anthropology at Boston University. “This doesn’t add anything to what I already knew.”
Kappelman’s theory is that Lucy was foraging, hiding or settling in for the night when she fell. This implies that Lucy and other hominins at the time still climbed trees, like their ape ancestors. This study could provide perspective for those studying arborealism – the ability to live in trees – in early hominins, a point of contention among anthropologists. However, Steven Churchill, a professor of evolutionary anthropology at Duke University said that although Lucy may have fallen out of a tree, Kappelman’s support for the hypothesis is weak. “There’s all kinds of animals from fossilized deposits that show very similar kinds of breakage – there are horse remains, antelope remains, rhinoceros remains,” said Churchill, “and it is hardly likely that those things fell out of a tree.”
Kappelman insists that anyone who looks at the fossil will likely agree with his fall-from-tree theory. To that end the Ethiopian National Museum has released 3D files of CT scans of Lucy’s fossils to the public on eLucy.org. “Anyone, anywhere on the planet can download the files, print them out, and more thoroughly evaluate our hypothesis for themselves,” said Kappelman.
The cause of Lucy’s demise will continue to stir up arguments. But understanding her death, Lucy’s fossilized remains have become more significant to Kappelman. “I could picture her broken body lying there at the foot of the tree. I could empathize with her. It is remarkable to identify with another species that lived over 3 million years ago.”