Lucy was a small-bodied female that probably stood about 3”6” (107cm)8 tall and weighed roughly 60 pounds (27.3 kg)9. Scientists can tell that Lucy is female because the anatomy of her pelvis generally resembles that of female modern humans. In addition, Lucy’s body size overall, as well as those of other female A. afarensis, is smaller than the body sizes of male A. afarensis specimens. A difference in body size between males and females of the same species is called sexual dimorphism, meaning two (“di”) forms (“morph”) between sexes.
Lucy’s face was chimpanzee-like. Below her eyes, her face projected forward beyond the plane of the eyes, a character trait known as prognathism. Features that Lucy shares with chimpanzees are called retained primitive features, meaning that these features were present in the ape-like species from which Lucy’s species evolved, and that Lucy’s species, A. afarensis, kept these features even after the species diverged from that last common ancestor.
