Fifty years ago, scientists discovered a nearly complete fossilized skull and hundreds of pieces of bone of a 3.2-million-year-old female specimen of the genus Australopithecus afarensis, often described as “the mother of us all.” During a celebration following her discovery, she was named “Lucy,” after the Beatles song “Lucy in the Sky with Diamonds.” Though Lucy has solved some evolutionary riddles, her appearance remains an ancestral secret. Popular renderings dress her in thick, reddish-brown fur, with her face, hands, feet and breasts peeking out of denser thickets. This hairy picture of …