Austalopithecus afarensis Definitely Climbed Trees

Analysis of the partial skeleton of “Lucy”, the best-known skeleton of Australopithecus afarensis discovered in 1974, revealed that the species was capable of standing and walking upright.  Many scientists presumed, based on the probable shape of her shoulder bones (some bones were missing) that she also still climbed trees, like her ancestors.  Others disagreed, arguing that the shape of her shoulder was just a vestigial retention from her ancestry, no longer of any real functional value.

To resolve this issue, researchers compared the anatomy of the scapula bone of a partial skeleton of a recently-discovered juvenile A. afarensis to the growth patterns of scapula bones of humans and modern apes.  They concluded that A. afarensis, like modern apes, used its upper limbs to climb and move through trees, at least part of the time.  Perhaps they slept in trees as a protective strategy, or climbed trees to harvest food.

The unique shoulder anatomy that permits overhead use of the upper limbs to climb and swing from trees disappeared in Homo erectus, a later transitional species in the human lineage.