The huge, lumbering animals with long tusks known as mammoths are closely related to the modern elephant and became extinct about 10,000 years ago. Mammoth fossils have been found in many parts of the world, especially in Siberian Russia and the central United States. One of the best-preserved sites of mammoth remains is in the southwest corner of South Dakota. There, a Russian paleontologist is among the researchers exploring the bones of as many as 100 mammoths that died in a large sinkhole. As paleontologist Olga Potapova unlocks a fence gate, she explains how the Hot Springs, South Dakota mammoth site was almost destroyed. " When they found the site, the owner, a contractor, was digging no, leveling- this hill," she explains. "He hit a tusk or something, so he stopped."
A construction crew with bulldozers was clearing the site for a new housing project in 1974, when the discovery was made. One of the workers was curious about the strange bone and asked a local college professor to identify it. It turned out to be a 26,000-year-old mammoth bone. Not long after, hundreds of bones were found nearby many were full, intact skeletons of mammoths that apparently fell into the large sinkhole, became trapped and died. Eventually, the 2,000 square meter site was protected with a huge enclosure that also houses a visitors center. Now, collections curator Olga Potapova is undoing some of the earlier preservation efforts of the mammoth bones. "It turns a brown or reddish color that's not natural for the bones which were found here," she said. "The natural color is white, off-white or yellowish and it has some black spots, especially on the tusks. So what I'm doing is removing old preservative with acetone. When I'm done, I'll put just a thin layer of preservative. I'll try to soak it as much as I can. But the idea is to keep the bones natural looking - the way they looked when they were discovered."
The new preservation effort is tedious, exacting work, as Ms. Potapova spends hours each day meticulously scraping layer upon layer of the bone covering. "Yeah, we're using a lot of dental picks … different kinds. They're very good." says Olga Potapova.
A graduate of the prestigious Russian Academy of Sciences in St. Petersburg, Russia, Olga Potapova knew about the South Dakota mammoth site before coming to America because of the visits by her Russian colleagues to the area. "This is a unique site in North America because it has so many specimens in one place," she said. "You can hardly find any kind of place like it, except Siberia, North Siberia - where the remains are not in an anatomical position like they are here, but were brought in from rivers. In Russia, they're called cemeteries of mammoths."
Scientists are especially interested in mammoths because they are among the major animals that bridge the time periods between the dinosaur age and the beginning of human civilization on earth. "They occupied the New and Old Worlds very widely," she said. "The larger groups didn't live very long; they were suddenly extinct, which happened approximately 10,000 years ago. Some of the smaller populations survived, particularly the Woolly Mammoth on Wrangell Island in Siberia. The remains were dated back about 3500 years B.C. So they were contemporaries of the early Egyptians. Most people don't realize that."
Just as paleontologists have competing theories over how dinosaurs became extinct, so too are the arguments made over how mammoths disappeared, as Ms. Potapova explains. "It was an animal that lived together with modern humans," said Olga Potapova. "It became extinct because of over-hunting, many scientists believe. Others believe that it happened because of a non-reversible environmental change."
Paleontologist Olga Potapova, who is among the researchers exploring one of the world's largest concentrations of mammoth fossils in Hot Springs, South Dakota. Every summer, dozens of volunteers join Ms. Potapova and staff scientists in research at the mammoth site.