The first Americans reached the New World as long as 40,000 years ago, more than three times earlier than previously realized, scientists reported Monday.
Until recently, scholars believed that a single group of humans trekked across a land bridge from Siberia about 11,500 years ago and gradually spread south across North and South America.
New discoveries and analytical technologies have pushed back the probable arrival of the first immigrants to at least 30,000 - and perhaps as long as 40,000 - years ago.
Based on linguistic evidence, experts also now distinguish four separate waves of colonization from Asia. Three took place before the last ice age, which peaked about 19,000 years ago. The fourth wave was the entry of the Eskimo-Aleut population about 5,000 years ago.
The early arrivals hung out in the sunny southern latitudes during the ice age, and some of them migrated back north after the Earth warmed up again, according to Johanna Nichols, an expert on native American languages at the University of California at Berkeley.
During the groups’ long wanderings, their original dozen languages split into more than 140 separate tongues, rather like ancient Latin gave birth to modern Italian, French, Spanish and Portuguese.
Based on the time it typically takes a new language family to develop, Nichols said, she was able to determine when the first speakers left Asia. According to her calculations, “the linguistic population of the New World is 40,000 years old,” she said at a convention of the American Association for the Advancement of Science.
Another recent development - discovery of the oldest known settlement in the Western Hemisphere - puts humans at Monte Verde, Chile, as long as 33,000 years ago, according to Tim Dillehay, chairman of the anthropology department at the University of Kentucky.
Dillehay said seven or eight “clearly human” artifacts were found at Monte Verde buried in a layer of soil that was dated by geochemical analysis.
If confirmed, these discoveries reveal that the peopling of the new world was not a one-time north-south migration, but a highly complex process.
“People didn’t move in Rand-McNally fashion from the Bering Straits to Tierra del Fuego,” Dillehay said.
The new knowledge of the origin and movements of prehistoric people rests in part on a new tool - analysis of hair.
Robson Bonnichsen, director of the Center for the Study of the First Americans at Oregon State University in Corvallis, explained that human hair resists decay and can be preserved over thousands of years. It contains carbon, which can be accurately dated, and DNA, which can be analyzed for its genes.
Bonnichsen is studying some 9,400-year-old sheep hair found in Nevada, in preparation for analyzing human hairs recovered from an early-American site in Montana. Fortunately for researchers, hair is not protected by laws restricting scientific experiments on bones claimed by Native Americans.
Native American objections, on religious and cultural grounds, have blocked further study of ancient human skeletons recently discovered in Nevada and Washington state. Some observers thought the two skeletons must have belonged to Caucasians who arrived in the new world before the ancestors of modern American Indians.
But Dennis Stanford, chairman of the anthropology department at the Smithsonian Institution in Washington, D.C., said the skeletons appeared to be “significantly different” from any modern population.
“They may have come from an original population in Asia, out of which many groups, including Europeans, developed,” Stanford said.
In view of these developments, some controversial early American settlements in Pennsylvania, Virginia and elsewhere may be re-examined.
Some experts had put these finds at older than 11,500 years, but their conjectures were dismissed as impossible under the previous timeline for the colonization of the new world.
xxxx ROOTS OF DISCOVERY Hair is becoming a powerful tool for unraveling mysteries of the ancient past. By sifting DNA from individual strands of hair from the dust and rubble at archaeological sites, scientists can make the first firm connections between genetic identities and the times and places where ancient animals and people lived.