Phalanges: Curvature of finger and toe bones in A. afarensis has figured in the debate over how much time this species spent in trees versus on the ground. Lucy's remains include just one finger bone, which is slightly curved. Femur: Lucy's thigh has an inward slant or carrying angle, strong evidence that she walked upright.Humerus: Lucy's ratio of upper-arm-bone to thighbone length (85 percent) equals a baboon's, but is less than that of tree-dwelling apes. She may have been more comfortable moving about on the ground.Scapula: With her shoulder blade joint oriented upward, Lucy climbed trees at least as well as a gorilla, but may have been less adept than a chimpanzee.Third molar: The "wisdom tooth" has erupted in the lower jaw, so despite her small stature Lucy died as an adult. Her minimum age at death depends on whether A. afarensis matured quickly like chimpanzees or more slowly like modern humans. Cranial fragments: Only five pieces of her cranium were found, but Lucy's brain would have been chimp-sized, about 380 cc in volume. A female A. afarensis skull found in 2002, the most complete one yet, will show what Lucy's facial features looked like.Tibia: Like an A. afarensis knee joint found in 1973, the shape of Lucy's shinbone strengthens the case that she was an adept bipedal walker. Study of the cross sections of limb bone shafts permits a body weight estimate for Lucy of about 60 pounds. The petite primate stood 3.5 feet tall.Ilium: The largest bone of her pelvis is curved and flared at the top to support the trunk, more like that of a modern human than a four-legged chimp. Whether Lucy had a gait just like ours remains unknown.Vertebrae: Several bones in the upper back have lipped edges that could be the result of arthritis or another bone disease.Canine: The socket for the missing tooth suggests that her canine was small, one clue that Lucy was a female. Much larger A. afarensis canines, from males, reveal a big size difference between the sexes, a likely trait among other hominid ancestors.
