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Find May Rewrite Americas' PrehistoryBy Curt Suplee
Washington Post Staff Writer
Tuesday, February 11 1997; Page A01
The Americas were inhabited by human beings at least as early as 12,500 years ago -- far earlier and a half a world farther south than previously believed -- a team of archaeologists announced yesterday.
Artifacts unearthed at a site near Monte Verde, Chile, the nine-member group determined, predate by at least 1,300 years the evidence of human habitation from Clovis, N.M., conventionally accepted as the oldest known in the Western Hemisphere.
More portentous, however, is the fact that the discovery is in South America, thousands of miles away from the Clovis site. That suggests that the first Asian immigrants arrived by a different path from the one traditionally assumed (across what is now the Bering Strait) or got there much earlier than the current scientific consensus allows, or both. Indeed, the Monte Verde dig also has revealed preliminary evidence that Homo sapiens may have been in residence there as long as 33,000 years ago.
"It totally changes how we think of the prehistory of America," said Monte Verde team member Dennis J. Stanford of the Smithsonian Institution. "Our models clearly are not right," he said, and the new results "open up a whole new time period for people to investigate."
Since 1977, researchers headed by Tom D. Dillehay of the University of Kentucky have been excavating the riverbed site some 500 miles south of Santiago. They discovered remnants of dwellings with wooden frames and animal-hide roofs, tools made of stick and bone, a piece of what is apparently mastodon meat, more than 700 stone tools and a child's footprint.
When recent dating of the excavation (using an accurate method that depends on the rate at which radioactive forms of carbon decay) indicated an age in excess of 12,000 years, many scientists expressed grave doubt. So in January, a consortium of sponsors -- including the National Geographic Society and the Dallas (Tex.) Museum of Natural History -- sent the nine-member team down to investigate the controversial site.
Among them were several prominent skeptics, including Dena F. Dincauze of the University of Massachusetts and C. Vance Haynes Jr. of the University of Arizona. After 10 days, the group unanimously endorsed the Monte Verde find. Dincauze yesterday told a news conference at the Dallas museum that the work was "a kind of paradigm-buster" and "a new benchmark in knowledge." Haynes said from his Arizona office that the site was clearly valid, with many artifacts that are "indisputably" human in origin.
The Clovis record has stood since the late 1930s, though numerous contenders for evidence of earlier human habitation have arisen. Until now, none had proved convincing to a majority of scientists. Flakes of rock initially thought to be stone tools were shown to have cracked naturally, for example, or specimens thought to be from the site were found to have traveled there later.
One major advantage of the Monte Verde site, Dillehay said in Dallas yesterday, was that shortly after habitation the area was covered with a peat bog, ensuring preservation of a wide variety of evidence. "There are, for example, stakes that are still lashed in place with string that is knotted," said Alex W. Barker, chief curator of the Dallas museum.
At a minimum, the new find will oblige scholars to reconsider the standard explanation of what Dillehay called "the first chapter of human history in the Americas."
The accepted theory is that restless prehistoric peoples from northeastern Asia managed to migrate into Alaska when global cooling trapped ocean water in glaciers, thus lowering the sea level and exposing enough of the Bering Strait sea floor to provide a land bridge. This hypothesis also requires that there have been an ice-free corridor -- formed between two retreating ice masses -- that would have allowed the first New World humans to survive a trek southward through the Yukon. Both essential conditions for this climatic "window" existed about 14,000 to 12,000 years ago.
So when scientists first dated the Clovis artifacts (typically stone "points" used to kill mammoths or other animals) to about 11,200 years ago, the chronology seemed ideal. Presumably, the first settlers crossed the land bridge on schedule and their descendants then took about a thousand years to get as far south as New Mexico.
The new findings make this notion far less tenable. If the Monte Verde site is 12,500 years old, that means that the ancestors of those Chilean settlers somehow managed to travel some 10,000 miles from the Bering Strait to southern South America in only a few hundred years.
In short, said Stanford, curator of North American archaeology and director of the paleoindian program at the National Museum of Natural History, "they either had to go like hell to get to South America, or they simply came in earlier." Climate data and other evidence show that the next earlier window of migratory opportunity existed about 22,000 years ago.
Alternatively, many experts speculate, the early Asian immigrants may not have traveled by land at all. Instead, they may have gone by boat, hugging the shoreline all the way from Alaska to Chile. The closing of the Bering Strait, Stanford said, would have caused a backup of seawater nutrients and ocean life in the North Pacific that might have given early nautical explorers an ample food source.
But the real date of the first arrival of Homo sapiens in the Americas may be far earlier than any consensus theory now permits. The Monte Verde team has found a second, deeper layer of putative human artifacts that can be reliably dated at 33,000 years old. The evidence so far is tentative, though Stanford said that "most of [the nine-member team] thought it looked pretty good." Dillehay's group is continuing its excavation.
Meanwhile, Stanford said, the Monte Verde results will likely revive flagging research interest in many other putative pre-Clovis sites, including the Meadowcroft Rockshelter in Pennsylvania, which has yielded stone tools and basketry that are estimated to be more than 19,000 years old.
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