Ancient Ape Shuffles to Prominence

Scientists have long viewed an upright, two-legged stride as a trait unique to hominids, the approximately 6-million-year-old human evolutionary family. However, it's time to give that assumption its walking papers, contend two anthropologists.

 According to their new fossil analysis, a 9-million- to 7-million-year-old apelike animal also spent much of its time standing upright, methodically shuffling short distances to collect fruit and other edible goodies on what was once a Mediterranean island.

 This achievement represents a small step for hominids, but it's a giant leap for apekind. Until now, it appeared that the fossil apes that preceded hominids could only climb, swing through trees, and walk on all fours.

 Further study of the ancient Mediterranean creature, known as Oreopithecus bambolii, should help to clarify how evolutionary pressures led to an upright stance, say Meike Kohler and Salvador Moya-Sola, both of the M. Crusafont Paleontological Institute in Sabadell, Spain.

"This a major contribution," remarks anthropologist David Pilbeam of Harvard University. "It convincingly shows that [an upright stance] did not evolve only in hominids."

 Oreopithecus fossils have been excavated for more than a century in parts of central Italy. The ancient ape, along with many other mammals, inhabited this area when it was an island in the Mediterranean Sea.

 About 40 years ago, a few researchers suggested that Oreopithecus possessed skeletal features consistent with upright walking. Their unorthodox view was generally rejected for lack of sufficient anatomical evidence.

 Over the past 2 years, Kohler and Moya-Sola have studied previously undescribed Oreopithecus specimens held at the Natural History Museum in Basel, Switzerland. The partial fossils include sections of the lower back, pelvis, leg, and foot. Overall, the creature's lower body falls in between that of apes and australopithecines, an early group of hominid species, the scientists report in the Oct. 14 Proceedings of the National Academy of Sciences.

 Like hominids, Oreopithecus possessed a lower back that arched forward and a vertically aligned knee joint, two features crucial to upright walking, the Spanish investigators contend. Parts of the ancient ape's pelvis resemble corresponding areas of Australopithecus afarensis, the hominid species that includes the partial skeleton of the specimen known as Lucy, they add.

 However, Oreopithecus displays a foot like that of no other primate. Its big toe sticks out at about 90o from the remaining toes, all of which are shorter and straighter than toes of living apes. The foot provided a firm base for an upright stance, although its birdlike, tripod design probably restricted the animal to a short, shuffling stride.

 Life on an island inhabited by no predators and containing abundant foraging opportunities apparently fostered the evolution of Oreopithecus' unique style of walking, the researchers theorize.

 Further study of Oreopithecus may help researchers sort out influences on the evolution of upright walking in hominids, Pilbeam notes.