National Geographic : 2006 Nov
S- - ' Like a modern child, the Dikika baby may have relied on her mother to hold her (artist's impression, left). As Zeresenay coaxed the bones out of the Rock, classic ape traits emerged, notably the elongated face (top y right) and shoulders suited to climbing. Yet a partial knee and I ''a nearly complete leg and foot S(bottom right) indicate bipedal ism-walking on two legs. "I see SsA. afarensisas foraging bipeds but climbing trees when neces S sary, especially when they were little," Zeresenay says. At some point, bipedal human ancestors Slot the opposable big toes of chimpanzees and other apes, which baby chimps use to grip their mothers with four limbs. "This allows a mother to forage, escape from danger, and travel, while keeping the baby close," says Rebecca Gullott, a chimp expert who supervises the Mary land Zoo's mammal collection. The Dikika baby's big toe-the first ever found in an A. afarensis } fossil-is still locked in sandstone. But if it shows that A. afarensis babies lacked opposable big toes, their mothers might have had to rely on others for food and pro Sj tection while tending their babies.