The very modern human traits of complex and abstract thinking may have evolved in Africa 77,000 years ago--almost twice as early as previously believed--according to a team of anthropologists who unearthed intricate geometric carvings on bits of rock from a South African cave.

The finding, if verified, could overturn much current thinking in anthropology. But the sweeping claim is already generating controversy among experts in the field.

The discovery suggests that modern human behavior evolved in Africa rather than Europe. The artifacts, pieces of red rock etched with geometric shapes, are more than 40,000 years older than another milepost of complex behavior: the dazzling paintings of animals and humans on the walls of French caves. "In light of this new evidence it seems that, at least in southern Africa, Homo sapiens was behaviorally modern about 77,000 years ago," wrote Christopher S. Henshilwood, the anthropologist who led the research. His findings are being published online today in the journal Science. The etchings, he said, "may have been constructed with symbolic intent."

Anthropologists consider the production of art, particularly the use of symbols, a hallmark of modern human behavior. Others include the development of specialized tools, including flaked spear points and fishing nets, and the use of decoration.

Modern humans evolved in Africa about 100,000 years ago. About 50,000 years ago, they spread into Europe and began to displace the Neanderthals--a separate humanlike species.

Almost all ancient traces of modern behavior, carved bone tools and cave paintings have been discovered in Europe. That fact has led paleoanthropologists such as Stanford's Richard Klein to suggest that some kind of behavioral revolution occurred 50,000 years ago that fueled improved abilities to hunt and gather, a population boom, worldwide migration and some artistic abilities.

Klein suggests that the behavior changes were due to a biological advance, perhaps a change in brain structure. Others say the primary change more likely was cultural. Still others argue that no abrupt change occurred, but that art and culture developed slowly.

Early humans living in Africa, many surmised, led a more primitive way of life--one that did not include symbolic artworks.

The newly discovered objects could challenge all of those assumptions. The find consists of seven carved pieces of ochre, a red stone used to make pigment powders. Ochre powder is often mixed with animal fat to create body paint for ceremonial and ritualistic use. Two of the ochre pieces carry what look to be abstract carvings: parallel lines in a crosshatched design.

Henshilwood said the patterns appear to be carefully and deliberately carved onto rocks that were rubbed smooth beforehand. He believes the patterns are abstract symbols that were probably created by one artist but understood by others--an ability that would likely require the use of language.

But some skeptics say that because the newly discovered etchings are not found throughout Africa, they may have been a fluke or the work of a single genius who left no cultural legacy.

Anthropologist Meg Conkey of UC Berkeley, who has studied the world's oldest known paintings on the walls of France's Grotte Chauvet, says the more interesting question is why the carvings were found in this cave and not others.

Henshilwood said the coastal dwellers who occupied the cave could have advanced more quickly because of a rich seafood diet. There is evidence to suggest that early coastal civilizations often thrived, said Henshilwood, an affiliate anthropologist at the Iziko South African Museum in Cape Town and an adjunct researcher at the State University of New York at Stony Brook.

He also predicts that more early art will be found in other African caves when they are excavated as thoroughly as those in Europe.

But Klein, who has worked in several caves in Africa, including the Blombos cave where the new carvings were discovered, counters that there are excellent recent excavations throughout the continent. If civilization was advanced so early, he asks, "Why are these [carvings] so rare?"

Anthropologists, much like modern art critics, are also vigorously debating the importance of the etchings. "Is it art, or somebody with a stone tool just sitting there scratching?" asked Klein, who said the patterns are "interesting" but not as compelling as the depictions of animals and humans created on cave walls 30,000 to 33,000 years ago.

Added Steve Kuhn, an anthropologist at the University of Arizona: "It could be just doodlings."

Henshilwood discovered the Blombos site in 1991, in a 120-foot cliff overlooking the Indian Ocean 180 miles east of Cape Town.

In December, Henshilwood's team published the discovery of specialized, decorative flaked stone and bone tools in the cave. Found in 70,000-year-old sand deposits, the tools suggested unexpected advancements in civilization.

The carvings were found in sediments conclusively dated to 77,000 years. The rocks themselves were not dated.

The carvings are far older than the oldest previously recorded artistic artifacts in Africa--ostrich eggshell beads thought to be 40,000 to 50,000 years old and discovered by anthropologist Stanley Ambrose of the University of Illinois.

A few carvings and ornaments older than 50,000 years have been discovered elsewhere. One, which seems to be the etched form of a woman with an elaborate hairdo, is 250,000 years old. But anthropologists consider those to be rare, crude and lacking in any kind of systematic symbolic representation.