The famous human ancestor Lucy spent at least a third of her time in the trees, new research shows.

The 3.2 million-year-old ancestor, whose fossilized skeleton was found in Ethiopia in 1974, probably lived a life similar to what the chimpanzee does today, according to US researchers who have published their findings in PLOS One.

By scanning Lucy’s skeleton with a High-resolution computed X-ray tomography (CT), powerful enough to get through the mineral layers that cover her remains, the scientists have produced 35,000 high-resolution images.

The images reveal internal structures suggesting that her upper limbs were built for heavy load bearing — much like chimpanzees’ arms, which they use to pull themselves up tree trunks and to swing between branches.

“It is a well-established fact that the skeleton responds to loads during life, adding bone to resist high forces and subtracting bone when forces are reduced,” co-author John Kappelman, a paleoanthropologist at the University of Texas at Austin.

The study is grounded in mechanical engineering principles, lead author Christopher Ruff, a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine, said in a statement.

Lucy’s legs appear to have been relatively weak, and not well adapted for climbing or walking. The researchers believe that Lucy, like chimpanzees, likely spent a good portion of time in trees, perhaps to escape from predators or to find food.

Reference:
Christopher B. Ruff , M. Loring Burgess, Richard A. Ketcham, John Kappelman, Limb Bone Structural Proportions and Locomotor Behavior in A.L. 288-1 (“Lucy”), Published: November 30, 2016http://dx.doi.org/10.1371/journal.pone.0166095