According to recent reports, Australopithecus afarensis may have spent part of their time on trees. Despite having had the ability to walk upright, the relatives of humanity represented by the popular "Lucy" fossil are highly likely to have spent a good amount of their time swinging from trees (Venkataraman, Kraft, & Dominy, 2012). The species Australopithecus afarensis are among the earliest well known human relatives to walk upright, and are also the leading candidates for direct ancestors of the human lineage. Although the question about whether or not Lucy and her kin spent much of their time in trees has been hotly debated on, scientists have extensively analyzed two complete shoulder blades from the fossil "Selam" (Green & Alemseged, 2012 p 514-517).
In 2000, a well preserved Au. afarensis specimen was discovered in Ethiopia and was named "Selam" a 3 year old girl. Selam quickly became significant because of the fact that she was one of the few hominions proving that the species had feet with arches like those of human. Moreover, she also had a well preserved shoulder blade/ scapula, which provided some evidence about her tree swinging abilities. Following an analysis of the arms and shoulders of the fossil, it was clear that they were well structured for climbing.
A comprehensive study of the bones suggested that they had several details that were common with those of modern apes, which goes to suggest that they lived part of their time in trees (a partially arboreal lifestyle). The socket for the shoulder joint in both Selam and modern apes is pointed upwards, which is a sign of an active climber. For humans, these sockets face out to the sides. Although the scapula of Au afarensis change over their lifespan, that of Selam looks more like that of an ape than that of a human, and also matures like that of apes according to the researchers. With the orientation being suited for suspensory behaviors, the muscles involved in hanging from branches are placed with the most efficient orientation possible (Green & Alemseged, 2012 p 514-517).
