Signs of an earlier American

Al Goodyear is holding his breath in anticipation. Within days, the affable archaeologist expects to read the results of lab tests indicating that stone tools he recently found in South Carolina are 25,000 years old - or older.

Such results would be explosive. They would imply that humans lived on this continent before the last ice age, far earlier than previously believed. Even if the dates came in younger than 25,000 years old, researchers say, the find would add to the mounting body of evidence that humans trod North and South America at least 2,000 years before the earliest-known inhabitants, known as the Clovis culture.

Dr. Goodyear's efforts are among the latest from a growing group of archaeologists and anthropologists who have become emboldened to buck conventional wisdom and probe far deeper into the hemisphere's past than many of their predecessors did. What they are finding not only could rewrite old chapters in the history of two continents, it could write new ones.

"With all these new discoveries, it's almost a rebirth of excitement in the field. All sorts of new ideas are coming forward about migration routes and timing of arrival," says Michael Waters, a geoarchaeologist at Texas A&M University who is involved in several pre-Clovis digs around the United States. "You still have to be careful. Every claim of pre-Clovis occupation needs to be looked at quite carefully."

And they are. When stunning discoveries surface in North America's paleolithic past, they can ignite debates conducted with all the gentility of the Stanley Cup finals - as Goodyear knows.

"When these dates come back, I'll be hiding in a coal mine. I've already got a little Groucho Marx disguise I'm going to put on," quips the University of South Carolina scientist, who along with colleagues is working what's called the Topper site in Allendale County, S.C., along the Savannah River.

For decades, the Clovis culture has held sway as the oldest in the New World. Evidence for this group's presence was first unearthed in 1936 near Clovis, N.M. A second site that emerged in Arizona in 1959, and others since. A uniquely fluted spear point became the culture's icon. Radiocarbon dating at Clovis sites so far has bracketed their presence from roughly 11,200 to around 10,800 radiocarbon years ago. (Archaeologists prefer expressing dates in radiocarbon years because converting to modern calendar years becomes tricky beyond a certain age threshold.)

As evidence for the Clovis culture's presence cropped up throughout the continent and the sites became the subject of intense study, the notion that Clovis people were the oldest immigrants to the Western Hemisphere became firmly entrenched. Although some research teams periodically claimed to have found older sites, their evidence was shaky or later proved to have a less radical explanation. To claim a pre-Clovis find was akin to claiming to spot Big Foot.

Researchers often hesitated "to dig below the Clovis horizon for fear of ridicule," Dr. Waters says.

By many accounts, the turning point came seven years ago when anthropologist Tom Dillehay published the second of two encyclopedic volumes of results from a site in southern Chile known as Monte Verde. His team's evidence pointed to a human presence there 13,000 years ago. Other sites began to appear with evidence for pre-Clovis occupation that many saw as more credible than evidence from earlier efforts.

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