Rural Sherman County These days, on the banks of the dry Middle Beaver Creek, Janice McLean gets excited about tiny rocks.
It was Friday afternoon, just after lunch, and volunteer archaeologists at this dig site had uncovered one of the largest finds of the weeklong dig: a stone about the size of a nickel.
To the untrained eye, it looked like any other rock near a western Kansas cow pasture.
But McLean, a Kansas University graduate student, knew the churt rock wasn't native to the area. Someone had to bring it there.
Rock by rock, and bone by bone, McLean and her fellow archaeologists are trying to prove the people who once camped at this site were among the earliest inhabitants of the Great Plains - and may have been there 700 years before historians previously thought.
"It's exciting every day," McLean said. "You find one really exciting thing, and you can live off that for three or four days."
This is the third summer archaeologists from KU and the Denver Museum of Nature and Science have been at this rural site near Kanorado, about a mile from the Colorado border.
This year's dig has taken on new importance based on radiocarbon dating results completed in February. The tests showed that mammoth and prehistoric camel bones found at the site dated back to 12,200 years ago.
The bones appear to have tool marks made by humans, who probably broke the bones apart to extract marrow for food or to make bone tools, said Steve Holen, curator of archaeology at the Denver Museum. If workers can find tools in the same area where the bones were found, it could disprove the widely held belief that humans arrived in North America around 11,500 years ago.
"The best thing we could find is a very patterned artifact - one that it's obvious humans made it," Holen said. "It would change the way we think about early humans in North America."
So far, that irrefutable evidence hasn't been found. But the archaeologists - more than 100 in all from KU, the Denver Museum, the Kansas Archaeological Assn., the Kansas Archaeology Training Program of the Kansas State Historical Society - have plenty of digging left to do.
The dig is being funded, in part, by the Odyssey Archaeological Research Fund, an endowed program that aims to find the earliest evidence of humans on the Great Plains.
A paleontologist from the Denver Museum first came to the site in 1976, when artificial creek channels created by the Kansas Department of Transportation caused mammoth and camel bones to become exposed.
Holen decided to return to the location after seeing some of the artifacts collected.
The archaeologists on the site are working in shifts of about 50, spread across three dig sites in the side of the creek bed. Each excavation site is divided into grids with 1-meter-square sections.
Using levels and tape measures, workers scrape off 5 centimeters of dirt at a time, keeping an eye out for rock and bone. They sift each section of dirt through screens to make sure no artifacts go undetected.
When an artifact is found, it is placed in a bag, and KU graduate students use surveying equipment to pinpoint the exact location where it was uncovered. Those artifacts will be taken to the Denver Museum for analysis.
The work can be tedious.
"We find a lot of rat holes," said Allen Wiechert, of Lawrence, one of the Kansas Archaeological Assn. volunteers. "But you never know what one might find in the next 15 centimeters."
Nearby, 15-year-old Niki Orth, of Bushton, was sifting through dirt Wiechert removed from one of the dig locations.
"I like history a lot," she said. "And I also like to dig in the dirt. So this is perfect for me."
Kim Kilmartin, a Baker University sophomore from Topeka, decided to spend part of her summer at the site after completing an internship in a processing lab at the Kansas State Historical Society.
"It's actually a lot more fun than it looks," she said. "In the lab, you actually know what you're looking for. Finding it in the field is very cool, even if it's the smallest stone flake or bone fragment."
Even if evidence pushing back the arrival of humans in the plains isn't found, the site is still one of the best-preserved campsites for early plains people, the researchers said.
Pieces of tools and a bead from the Clovis era - from about 10,800 years ago to 11,500 years ago - have been uncovered.
In the past, most Clovis-era artifacts have been found away from campsites, such as arrowheads found in fields, said Rolfe Mandel, an archaeological geologist with the Kansas Geological Survey. Mandel said this was the first site uncovered from the period in Kansas or Nebraska, and one of only a handful from the Midwest.
"We knew they were here," he said of Clovis-period people. "We didn't know anything about how they may have spent their time while they weren't traveling across the landscape. That's been very elusive."
In prehistoric times, the Kanorado site likely had marshlike water that drew large animals, which in turn drew humans there, Mandel said. People of the era were highly mobile, though, so they likely didn't stay there more than a few days or weeks.
While the artifacts from 10,800 to 11,500 years ago are interesting, workers digging near Kanorado clearly would like to find something to push back dates of humans in the Great Plains - and thus make history themselves.
If such an artifact was found, the researchers say, it would raise questions about whether the earliest inhabitants of North America came across the Bering Strait from Asia. Instead, they may have arrived by boat in South America, and journeyed northward.
That, Holen said, would fly in the face of scientific doctrine that has long held humans have been in North America for about 11,500 years.
"There is a strong contingent that still believes that," he said. "We're going to do what we can to disprove that."
And while no such artifact has turned up so far, the possibility that an arrowhead is lying under the next layer of dirt is enough to keep workers digging away at the site.
"This," Mandel said, "is tantalizing."