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Sunday, May 22nd, 2005, 04:57 AM
Dig near Las Vegas continues to yield fossils

(Keith Rogers)

Fifty years ago, 27-year-old archaeologist Charles Rozaire had high hopes he would find clues around charcoal deposits at Tule Springs that could be linked to the earliest humans in North America.

First thought to be evidence of fire pits or hearths, the charcoal smudges that dotted cross sections along the upper Las Vegas Wash in the valley's north end were near the area where giant animals camels, horses, lions, bison, bears, sloths and mammoths roamed what is now southern Nevada 11,000 to 40,000 years ago.

"We were literally scratching the surface," Rozaire, 77, told students and scientists at a recent Geoscience Summit at Shadow Ridge High School, a 10-minute walk from Tule Springs. The site, listed on the National Register of Historic Places, is in Floyd Lamb State Park, 10 miles northwest of Las Vegas.

The school's earth sciences program is funded by a $150,000 grant from the National Science Foundation and $40,000 from Nevada Power Co.

It lets students do research at Tule Springs through hands-on activities and a special curriculum that serves as a model for the Clark County School District, according to Paul Buck of the Desert Research Institute and Steve Rowland of the University of Nevada, Las Vegas, summit co-sponsors.

"Tule Springs is our La Brea tar pits," Rowland said, referring to a Los Angeles site that has become a rich trove of extinct animal fossils.

After his first visit to Tule Springs in May 1955, Rozaire, returned from Los Angeles in the fall of 1962 as a member of the much-publicized "big dig" expedition that set out with bulldozers and a new age-dating technique to answer questions about the region's early inhabitants and animals.

"It was quite a tremendous undertaking," Rozaire said, recalling how the team worked through rain and windstorms that once blew down all but one tent.

When a significant find was made, animal fossil experts would converge on the site from Chicago, New York, Denver and Arizona.

As the students and scientists walked through the high-walled, mile-long trench, Robert Orlins, a member of the 1962 expedition, remembered how Tule Springs captured the attention of prominent paleontologists and archaeologists.

"I realized when I got here and saw the size of the crew and the level of expertise ... you knew this was big stuff. This was really an important investigation," Orlins said. "After more than 40 years later, people still think it's important. That's what blows me away, is the continued interest in the site."

If the team had found a stone spear point lodged in the fossilized bones of one of these beasts, an argument could be made that humans lived in the area perhaps three times earlier than 13,000 years ago, the era generally accepted for people arriving in North America from Siberia across the Bering land bridge.

The team of about 25 scientists found plenty of fossils from extinct animals, but only a handful of artifacts a drilled stone, bone awl and polished tusk fragment from much younger soils, none of which could be linked to more ancient times.

And the charcoal was found to be carbonized plant remains, which later proved important in dating soil layers.

Finding no human link to the extinct animals was nevertheless significant, Rozaire said.

"There's a certain disappointment, but on the other hand to know there wasn't a 40,000-year-old man was important," he said.

Historically, the 1962 Tule Springs expedition marked a milestone in demonstrating chemist Willard Libby's radiocarbon age-dating technique, for which he had won a Nobel Prize.

Asked how scientists know there weren't humans in North America before 13,000 years ago, Orlins said, "We don't. We don't have the evidence yet."

However, he said, some day a man-made tool or projectile point could turn up in extinct animal fossils from an earlier period.

Meanwhile, work continues in the vicinity of Tule Springs by a California team from the San Bernardino County Museum led by curators Kathleen Springer and Eric Scott.

Scott said the team discovered 438 fossil sites in the area and is analyzing them to learn what the animals ate and how their numbers changed over time. Of particular interest are mammoths, each of which ate 700 pounds of vegetation per day.

The research could shed light on how climate change played a role in the animals' demise.

"When climate changed at the end of the Ice Age, there was less water," Scott said. "The plants took a hit, and then the animals took a hit."