Due to limited clues, figuring out the cause of death of Lucy, the world’s most famous early human ancestor, has been unsolvable until now. According to researchers at The University of Texas at Austin, the 3.18-million-year-old specimen of Australopithecus afarensis probably died after falling from a tree.

The findings published in the journal Nature required the use of a scanning machine called High-Resolution X-ray Computed Tomography Facility (UTCT) in the UT Jackson School of Geosciences, as well as reviewing the 3D files of Lucy’s shoulder and knee by the Ethiopian National Museum. They found an unusual fracture in the hominin’s right humerus, which lead author John Kappelman says could result when the hand hits the ground during a fall. Stephen Pearce, an orthopedic surgeon at Austin Bone and Joint Clinic, says this indicates that Lucy stretched out an arm to break the fall.

Kappelman, UT Austin anthropology and geological sciences professor, had to scan Lucy’s incomplete skeleton for 10 days. Although the skeleton of this Australopithecus afarensis, which means southern ape of Afar, is among the oldest and most complete of any walking human ancestor, it remains to be only 40 percent complete.

With the help of geological sciences professor Richard Ketcham, Kappelman also observed signs of severe trauma consistent with fractures caused by a fall like a pilon fracture at the right ankle, a fractured left knee, pelvis and a fractured first rib. Scanning also revealed hat Lucy suffered from less severe fractures at the left shoulder.

The researchers believe that the arboreal hominin probably fell from a height of over 40 feet or more than 12 meters. They also estimate that Lucy fell at more than 56 kilometers/35 miles per hour.

Lucy was a small creature, standing at 3 feet 6 inches and weighing 27 kilograms or 60 pounds. Experts believe that the hominin, discovered in the Afar region of Ethiopia in 1974 by Arizona State University anthropologist Donald Johanson and graduate student Tom Gray, was both terrestrial and arboreal.