Take a drive through South Dakota's Black Hills and you're likely to see antelope, deer, the occasional coyote and, of course, American bison. But if you could step back in time, 26,000 years or so, you'd see other wildlife roaming the area: giant short-faced bear, camels, and mammoths, an ancient relative of today's elephants.

Hot Springs was apparently a favorite spot for mammoths, which came to a local water hole for refreshment. Unfortunately, the spring-fed pond they drank from was also a sinkhole. Once in the water, the massive creatures were unable to climb back out and died there.

When their remains were discovered in 1974 during a construction project, the location quickly became a significant spot for paleontological research. Over the past 30 years, the Mammoth Site has developed into the world's largest mammoth research facility.

The site's director and principal investigator, Dr. Larry Agenbroad, says it is unique. "We have other sites where we might have accumulation of mammoth bones, but usually they're in a [bend] in a river, that's been accumulating bones like driftwood logs for maybe even centuries." In contrast, he explains, the ancient spring was a walk-in trap. "They had to come in here intentionally. And found out they couldn't get out." The result is the world's highest concentration of Columbian mammoth fossils.

That uniqueness draws volunteers here each summer as part of the Earthwatch Institute's cooperation with scientific sites around the world. The opportunity costs several thousand dollars, but Earthwatch representative Yoka Heijstek says it gives the average person a chance to be a part of science and not just a visitor. "You don't need to be an archeologist to work here, for instance, at the Mammoth Site," she stresses. "And you really can make a difference by helping scientists collect data they use for their research."

One of those people who really made a difference was Pennsylvania resident Ruth Clemmer. She struck pay dirt on her first day. "I actually found a fragment there that no one had anticipated, because they haven't found any in that area at all. And I was the first one to find one there, on the first day? when we were practicing. So that was pretty exciting." Not bad for a retiree on her first visit to the bone bed.

Another first-time volunteer to the dig site is Julie Patullock from Australia. Last year, she visited an archeological site on Easter Island, but she says looking for 26,000 year-old mammoth bones is different. The first week on the dig, she learned to be patient, "because I really wasn't finding a lot where I was digging. But all good things come to those who wait, and I finally found my first bone this morning."

Vetris Lamb first volunteered at the Mammoth Site in 1989 and has come back every summer since. "I've been very lucky in finding important bones," she says proudly. "The tusk is my favorite thrill. It's a special thrill. I've found two tusks."

But whether they find a tusk, a small bone, or just help remove 26,000 years of dirt, Dr. Agenbroad says every volunteer's efforts are important.

"It also has side benefits for the people who come. Some of them have actually changed their life progression," he points out, recalling one volunteer who was a dental technician. "She liked it so much, she went back to school and became a scientist in archeology and was very sad when a major institution hired her away from here and she couldn't come back anymore!"

Larry Agenbroad sees that process as part of what he calls the pass-it-on club. Just as the Mammoth Site has passed on his interest in science to others, Dr. Agenbroad hopes that volunteers at the dig will, in turn, pass on their interest to the world.