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Mysterious Immigrants

Like the jaguar, the people who built the Taino, Maya, and Aztec cultures were ancient immigrants to Central America. But where they came from -- and when they arrived -- remain among the most controversial questions facing archaeologists.

Ancient mask

Of vanished civilizations, only relics remain.

In the early 1900s, the conventional wisdom among archaeologists was that people had arrived in the Americas less than 5,000 years ago, after crossing a land bridge, now submerged, that had once attached Alaska to Siberia. But in 1930, researchers discovered stone spear points near Clovis, NM, that appeared much older. And by the 1940s, the new science of radiocarbon dating had been discovered.

This technique measures the age of artifacts by calculating the amount of radioactive carbon, which decays at a known rate, inside them. Carbon dating confirmed that the spear points were at least 11,200 years old. Suddenly, there was little doubt that people had made their way into North America just as the last ice age was ending.

Today, based on discoveries made over the last 20 years in Chile, archaeologists are again having to turn back the clock on their vision of human settlement of the new world. In 1977, a team of Chilean and American archaeologists, led by Tom D. Dillehay of the University of Kentucky, Lexington, began excavating an ancient village located near Monte Verde, Chile, about 500 miles south of Santiago. This remarkably preserved site, buried beneath a peat bog, yielded extraordinary discoveries, including a chunk of meat from an extinct mastodon (an elephant-like mammal) and a child's footprint beside a fireplace. Most amazing, however, was that fragments of charcoal and bone recovered at Monte Verde were found to be at least 12,500 years old.

If accurate, the dates suggested that people had somehow made the 10,000-mile journey from Alaska to Chile in about 500 years, an incredible achievement for people traveling on foot in unknown territory. Or -- more plausibly, some scientists argued -- the Monte Verde finds proved that people had arrived in the Americas far earlier than previously believed. As support for their belief, researchers pointed to bits of fireplace charcoal from Monte Verde that appeared to be at least 30,000 years old.

Since then, archaeologists have sometimes bitterly debated the meaning of Monte Verde. In 1997, however, Dillehay's team published an exhaustive, 1,000-page report on their findings. They then invited leading figures in the debate to make an extraordinary field trip to Monte Verde, to examine the site for themselves. Even some of the most doubtful critics came away from the visit convinced that Monte Verde was authentically ancient.

Fragments of bone were found to be at least 12,500 years old.

"While there were some very strongly voiced disagreements about different points, it rapidly became clear that everyone was in fundamental agreement about the most important question of all: Monte Verde is real," archaeologist Alex Barker, curator of the Dallas Museum of Natural History, concluded in a report after the trip. "It's old. And it's a whole new ball game."

For Dillehay, the scientist at the center of the controversy, the report came as a relief. "To gain acceptance of the site by my colleagues, the diehard proponents of the old theory, brings the project to culmination," he told reporters. Still, some critics say they will not accept the Monte Verde finds until other scientists find sites that are equally old, a search that is currently underway.

Like many discoveries, however, Monte Verde raises as many questions as it answers. One of the greatest puzzles involves figuring out how the ancestors of the Monte Verdians overcame the ice sheets that covered Alaska and Canada from about 22,000 to 13,000 years ago. It would have been impossible for people traveling on foot to cross the miles-thick glaciers blocking the end of the Bering Sea land bridge, experts say. That means the ancient immigrants from Asia either arrived 13,000 years ago and moved southwards remarkably fast, perhaps by boat, or they came more than 22,000 years ago, when the ice was in retreat.

Ancient mask

When did humans arrive in this hemisphere?

Support for the theory of older arrival comes from two very different sources: scientists studying how languages evolved and those studying human genes. Johanna Nichols, a linguist at the University of California, Berkeley, who uses computer models to estimate how long it takes for new languages to evolve, believes that it has taken up to 40,000 years for the 140 language families now spoken in the Americas to evolve.

Her results suggest that people might well have been at Monte Verde more than 30,000 years ago. She also estimates that it would have taken at least 7,000 years for early settlers to travel from Alaska to Chile, meaning they probably came before the last big glaciers flowed across Alaska. "Her general analysis of the linguistic situation in the Americas is essentially right," Victor Golla, a linguist at Humboldt State University in Arcata, California told SCIENCE magazine in early 1998.

Genetic scientists also believe it must have taken a while for the genetic diversity observed in America's native populations to have evolved. Specifically, several teams of researchers have concluded that it would take at least 30,000 years of migrations and interbreeding to explain genetic differences between tribes in North and South America. Their data suggest that people may have come to the New World in two or three waves from Asia, starting more than 22,000 years ago. Linguist Nichols even offers a further twist on the multiple-immigration concept: that the earliest immigrants first stormed south into South America, then later moved back north, through Mexico into the American Southwest, eventually founding some of the cultures highlighted in SPIRITS OF THE JAGUAR.

Only further study, and new discoveries, will determine if our new vision of the peopling of the Americas is correct -- or whether we await yet another find that will, once again, force us to consider the possibility that our origins in the New World lie in the even dimmer past.

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