Fossil ape's grasp gets two thumbs way up.

Ancient apes, like their modern counterparts, typically had hands equipped for tree climbing and branch swinging. But a little-studied set of fossil remains tells a gripping tale of surprisingly deft digits in an apelike creature that lived 9 million to 7 million years ago on what was once a Mediterranean island.

The animal, known as Oreopithecus bambolii, boasted an opposable thumb and a grasping ability much like that exhibited by members of the human evolutionary family 3 million to 4 million years old, according to a new report.

Possession of such a hand, which may have given this primate an advantage in gathering sometimes scarce food supplies, laid the groundwork for the evolution of its ability to walk upright (SN: 10/18/97, p. 244), propose anthropologist Salvador Moya-Sola of the M. Crusafont Paleontological Institute in Sabadell, Spain, and his colleagues.

A two-legged gait may have evolved similarly in ancient human ancestors, such as the australopithecines, after they developed a grip suitable for extensive food gathering and rapid feeding, the scientists suggest.

Moya-Sola's team studied Oreopithecus fossils previously found at an Italian site and now held at the Natural History Museum in Basel, Switzerland. The collection includes many isolated hand bones, several partial hands, and a nearly complete right hand.

Several features of the Oreopithecus hand signify the presence of a thumb-assisted grip capable of precise manipulations, the researchers report in the Jan. 5 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES. First, short hands relative to estimated body weight combine with long thumbs, considered essential for forming a humanlike grip. Oreopithecus thumb bones also exhibit large, deep pits for the attachment of what was apparently an unusually strong muscle for flexing that digit.

Moreover, the fossil ape's finger joints show no evidence of having supported knuckle-walking, the investigators say.

Overall, Oreopithecus hands display evidence of the improved finger control and greater ability to exert force observed in early members of the human evolutionary family, they contend.

"I have doubts about that conclusion," remarks anthropologist Peter Andrews of the British Museum of Natural History in London.

Hand and foot bones that in some ways resemble those of australopithecines do not conclusively show that Oreopithecus preferred to walk upright and use its hands for precise manipulations, Andrews argues. The few hand bones recovered from other fossil apes look much like those of Oreopithecus, he notes, although those creatures are generally thought to have dwelled in trees and knuckle-walked while on the ground.