X-ray scans of the remains of a 3.2-million-year-old human relative known as Lucy suggest she was built for climbing trees.
Members of Lucy's species, Australopithecus afarensis, walked upright, but researchers have long debated whether they routinely climbed trees. Christopher Ruff at Johns Hopkins University in Baltimore, Maryland, and his colleagues used computed tomography X-ray scans to gauge the strength of Lucy's arm and leg bones. Compared with the fully bipedal and ground-dwelling Homo sapiens and Homo erectus, Lucy would have put more weight on her arms than her legs. The authors say this shows that she actively climbed trees, despite walking on two legs on the ground. A study published earlier this year argued that damage to Lucy's arm, leg and shoulders were caused by a fatal fall from a tree.