RIO DE JANEIRO— A human skull that is prominently displayed at the National Museum here has been attracting crowds and controversy in equal measure since it was first unveiled early this month. After two decades in storage, the fossilized cranium has now been identified by Brazilian scientists as the oldest human remains ever recovered in the Western Hemisphere.
The skull is that of a young woman, nicknamed Luzia, who is believed to have roamed the savannah of south-central Brazil some 11,500 years ago. Even more startling, a reconstruction of her cranium undertaken in Britain this year indicates that her features appear to be Negroid rather than Mongoloid, suggesting that the Western Hemisphere may have initially been settled not only earlier than thought, but by a people distinct from the ancestors of today's North and South American Indians.
''We can no longer say that the first colonizers of the Americas came from the north of Asia, as previous models have proposed,'' said Dr. Walter Neves, an anthropologist at the University of Sao Paulo, who made the initial discovery along with an Argentine colleague, Hector Pucciarelli. ''This skeleton is nearly 2,000 years older than any skeleton ever found in the Americas, and it does not look like those of Amerindians or North Asians.''
If the date is confirmed, the find could transform thinking about the peopling of the Americas. It may be some time before that work is completed, but meanwhile, archeologists here and abroad say the find is potentially very important.
Until Luzia, named as a playful homage to Lucy, the 3.2-million-year-old human ancestor found in Africa, the oldest known human remains recovered in the Western Hemisphere were those of a woman found in Buhl, Idaho, and repatriated to the Shoshone tribe in 1991. Radiocarbon dating tests have established the age of that skeleton as a bit more than 10,000 years old.
Luzia's discovery at a location in the state of Minas Gerais called Lapa Vermelha is consistent, however, with recent findings made at the celebrated Monte Verde site in southern Chile. There, evidence of human habitation as early as 12,500 years ago, including stone tools and a footprint, has been uncovered, though no human remains have yet been found.
The finds, along with recent discoveries in North America like those of the so-called Kennewick Man and Spirit Cave Man, are forcing a reassessment of long-established theories as to the settling of the Americas. Based on such evidence, Dr. Neves suggests that Luzia belonged to a nomadic people who began arriving in the New World as early as 15,000 years ago.
Luzia's Negroid features notwithstanding, Dr. Neves is not arguing that her ancestors came to Brazil from Africa in an early trans-Atlantic migration. Instead, he believes they originated in Southeast Asia, ''migrating from there in two directions, south to Australia, where today's aboriginal peoples may be their descendants, and navigating northward along the coast and across the Bering Straits until they reached the Americas.''
About one-third of Luzia's skeleton has been recovered, enough to indicate that she appears to have perished in an accident or perhaps even from an animal attack. She was in her 20's when she died, stood just under five feet tall, and was part of a group of hunter-gatherers who appear to have subsisted largely on whatever fruits, nuts and berries they came across in their meanderings, plus the occasional piece of meat.
''This is intriguing and interesting and I want to know more,'' Dr. David J. Meltzer, a professor of anthropology at Southern Methodist University and an expert on the paleo-Indian populations of North America, said in a telephone interview from Dallas. ''Skeletal material of this age is extraordinarily rare, both here and in South America, so I am delighted to know that something of this antiquity is popping up.''
The region where Dr. Neves and his associates are working has been the focus of archeological inquiry since the mid-19th century, when Peter Wilhelm Lund, a Danish naturalist, first encountered human skeletal remains there. Many of the specimens he uncovered are now stored at the University of Copenhagen, but when Dr. Neves went to examine them, he found that the material had not been catalogued by geological strata and therefore could not be used for his research.
Luzia herself was originally discovered in 1975 in a rock shelter by a joint French-Brazilian expedition that was working not far from Belo Horizonte, Brazil's third-largest city. The skull was buried under more than 40 feet of mineral deposits and debris, separated from the rest of the skeleton but otherwise in remarkably good condition.
''This is a site where the soil was high in limestone content, which helped to preserve these remains for so long,'' explained Dr. Andre Prous, a French archeologist at the Federal University of Minas Gerais, who was part of the initial team and continues to work in the area. ''In other places, the bones disappear after a short time.''