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.
One of these sites, known as Mud Lake, sits near Kenosha, Wis. It was discovered by accident in January 1936, the same year as the first find of a Clovis point, when a Works Progress Administration crew was digging a drainage ditch and unearthed most of a foreleg from a juvenile mammoth. Turned over to the Kenosha Historical Society, it sat there until 1990, when an amateur archaeologist noted cut marks on the bones. Bones from nearby sites, known as the Fenske and Shaefer sites, showed similar markings. In 1992 and 1993, researchers excavated Shaefer and found bones with cut marks on them and stone tools underneath a pelvis bone. Radiocarbon dates on the bones and on plant material at the same level of the dig ranged from 12,500 to 12,300 years ago, nudging them beyond the Clovis time scale.
Dates from the Mud Lake bone were more stunning, says Dan Joyce, senior curator at the Kenosha Public Museum. Purported hunters slew the mammoth 13,450 years ago. He remains cautious about the presence of hunters. Cut marks are suggestive, but not conclusive. This past August, he and his team searched for the rest of their mammoth. But so far it has remained elusive enough to earn the beast the sobriquet Waldo, after the children's "Where's Waldo?" series.
While Dr. Joyce and his colleagues were planning their hunt for Waldo, Goodyear was taking a deeper look at Topper, a site he had been studying for 20 years. An adherent to the Clovis-first idea, he began to rethink his position after reading a site report from Cactus Hill, a pre-Clovis site in Virginia, in 1998.
His subsequent work at Topper uncovered what looked to be industrial-scale toolmaking well below the level at which Clovis artifacts were found. With no organic material available to radiocarbon-date the level, the team had to use a different technique that stunned them with date estimates of 16,000 to 20,000 years ago.
In May, he took his crew back to Topper for another, deeper look. They found what they interpret as tools in a layer roughly two meters (6.5 feet) below their earlier pre-Clovis finds. The soils and geology suggest that the artifacts are several thousand years older, he says. But nothing beats radiocarbon dates. Fortuitously, they found a sample of wood charcoal to derive three radiocarbon dates.
"I'd be very surprised if they're less than 25,000 years old, but I'm preparing myself mentally for the possibility that they could be a lot older," perhaps as old as 30,000 or 40,000 years, he says.
Such finds raise intriguing questions. Clovis groups were thought to have crossed a broad land bridge across the Bering Strait, hiking through breaks in the glaciers to what is now the lower 48. But if people lived on the continent at least 2,000 years earlier, they would have arrived at a time when the glaciers were impassable. This has led some to argue for a sea route along the land bridge and then the western coastline. Others suggest some may have come from Australia or the Iberian peninsula.
Not everyone is convinced by the evidence so far for pre-Clovis finds, although some doubters don't rule out the possibility that some groups where here earlier.
"The tools people find are not self-evidently hunting or butchering tools" in the way Clovis artifacts are, says Stuart Fiedel, an archaeologist with the Louis Berger Group in Washington, D.C.
Like Vikings making landfall in North America before any other modern European group, pre-Clovis sites don't seem to represent the first long-term colonization of the Western Hemisphere, he says. Interest in Clovis grew out of their apparent role as a continent-wide colonizing population and a key to the origins of the native Americans Europeans encountered after they arrived.
But others see potentially deeper insights coming from pre-Clovis finds.
"This could help us get a better handle on the amount of genetic variability we see in the descendants of these populations," says David Meltzer, an archaeologist at Southern Methodist University in Dallas. It also could reset the clock for the development of civilizations in the New World.