Ancient ape suggests human, chimp lineage.

Hungarian fossils of an ancient ape provide comparative data supporting the view that chimpanzees and humans are more closely related to each other than either one is to gorillas or any other living primate, contends a report in the Sept. 25 SCIENCE.

A majority of studies examining DNA and its molecular products in living primates conclude that humans and chimps form a distinct evolutionary lineage with a common ancestor that lived between 6 and 8 million years ago, although a substantial minority of molecular studies dispute that conclusion. Moreover, studies of modern and fossil primate skeletons suggest that the African apes lie within an evolutionary group separate from hominids, the evolutionary family that includes humans.

The Hungarian fossils provide an unusually good opportunity to gauge whether different groups of hominids and living apes share anatomical features of ancient or more recent origin, asserts anthropologist David R. Begun of the University of Toronto.

Begun and Lazlo Kordos of the Hungarian Geological Institute in Budapest reconstructed fossils uncovered about 20 years ago at a site known as Rudabanya. The specimens include large portions of two skulls, two pieces of upper jaw, four partial lower jaws, isolated teeth, and several fragments of bone from the lower body.

Begun assigns these specimens to the genus Dryopithecus, a fossil ape that lived in western and southern Europe between 9 million and 11 million years ago.

Dryopithecus and modern gorillas - but not chimps or fossils belonging to the first hominid genus, Australopithecus - share a number of features that apparently arose early in their evolutionary history, Begun says. These traits congregate in the lower part of the face and the teeth, especially the teeth at the front of the mouth, he asserts. Australopithecus and chimps share different facial and dental features that evolved from the Dryopithecus-gorilla pattern, Begun says.

Most attributes shared by gorillas and Dryopithecus also show up on specimens of Ouranopithecus, another ancient ape (SN: 6/23/90, p.390), he adds.

The evolutionary separation of Australopithecus and chimps from gorillas implies that anatomical traits occurring exclusively in chimps and gorillas, such as knuckle-walking, evolved independently, Begun says. Or, knuckle-walking may be the evolutionary endowment of an ancestor of apes and hominids, which disappeared in the latter group, he theorizes.

"Begun's conclusion doesn't surprise me," remarks anthropologist Steve Ward of Northeastern Ohio University College of Medicine in Rootstown. But the results remain tentative, he adds. "The jury is still out" regarding much of the facial anatomy of Dryopithecus, Ward cautions.

Fossil evidence currently cannot pin down the proper anatomical traits for comparison in a study such as Begun's, contends anthropologist Lawrence Martin of the State University of New York at Stony Brook.

Begun disagrees. Dryopithecus specimens from Rudabanya, which continue to emerge in ongoing excavations, offer insight into key areas of anatomical variation among apes and hominids, he says.