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.''
Along with other material from the same expedition, Luzia was then taken to the national museum here. But she was put away in storage, and it was not until 1995 that Dr. Neves examined the skull, quickly noticed its unusual characteristics and invited other scientists, including Dr. Joseph Powell, an anthropology professor at the University of New Mexico, to join him in drawing up a profile of Luzia.
Dr. Neves bases his estimate of Luzia's age on the fact that the skull was found in a geological strata where the age of other organic material has been established through radiocarbon dating. The same procedure would ordinarily have been done with Luzia, but the specimen does not have enough collagen, the protein that gives bone its resiliency, to allow that standard technique to be used.
''We're sort of stuck,'' said Dr. Powell, who is also curator of human osteology at the Maxwell Museum. ''We know that she is so old that most of the organic portion of the bone has leached out. It would have been great to have the radiocarbon dating, but that is not going to happen unless techniques improve dramatically, which they may.''
With that avenue of verification closed, Dr. Neves is making other efforts to determine the racial and other characteristics of Luzia. Early this year, a computerized image of Luzia's skull was sent to Richard Neave, a forensic specialist on the faculty of medicine at the University of Manchester in England, with a request that he reconstruct her face.
''It was in much better shape than many other forensic subjects we have had to do,'' Mr. Neave said in a telephone interview. What he ended up with when he finished was a face ''with the features one associates with Negroid skulls, particularly the nose'' and jaw.
''When you do this sort of work, it is very important to have no preconceived ideas,'' Mr. Neave said. ''I personally would stick my neck out and say it is conclusive support for his findings and demonstrates without any doubt at all'' that Luzia is of non-Mongoloid origins.
When her remains were discovered, Luzia was alone. But more than 40 other skeletons that appear to be from the same general period have been found in a nearby area called Lagoa Santa, and scientists in Brazil hope to be able to test Dr. Neves's theory by doing radiocarbon dating on at least some of them.
''There are a large number of skeletons at this site, some of them in better condition than that of Luzia,'' Dr. Prous said. ''There is a great density of skeletons there, buried in an organized fashion, and so we conclude this was a cemetery for them, perhaps the oldest in the Americas.''
Initial indications are that these skeletons indeed have many of the same facial features and other characteristics that first made Luzia stand out. ''We see this pattern with other skeletons of the same age'' from the Lagoa Santa site, Dr. Powell said. ''We have seen 37 of them now, and they all have this sort of unusual appearance.''
In an effort to test the theory that Luzia belonged to a people ethnically distinct from the ancestors of modern North and South American Indians, scientists have also begun DNA sequencing in the Lagoa Santa skeletons. Dr. Sergio Pena, a geneticist at the Federal University of Minas Gerais, is conducting one set of tests while other samples have been sent to the Max Planck Anthropological Institute in Germany, where the DNA of Neanderthal Man was isolated in 1997, for examination.
''We know that today's Amerindians have four main groups,'' said Dr. Pena, who found a genetic marker common to 17 different widely dispersed Indian groups across the Americans in the course of an earlier project. ''What would constitute molecular proof of Walter's hypothesis is to find DNA sequences completely different from those four groups.''
Dr. Meltzer said: ''This is clearly the way to resolve the issue. The skull is intriguing morphological evidence, but in order to really nail down this issue of affinity, you need evidence, and DNA is the way to go.''
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