South Dakota Town Supports Site for Fun and Profit : Excavations Reveal Mammoth Bone Cache

An ancient elephant graveyard on the outskirts of this Black Hills community has stirred scientists and the public, and excavations that began 13 years ago continue to turn up bones and tusks.

The Mammoth Site, only 15% of which has been explored, is the largest known accumulation of remains of Columbian mammoths, a North American species. The bones are estimated to be more than 26,000 years old.

Bones of 41 mammoths have been unearthed since the initial discovery in 1974, said Larry Agenbroad, who is the principal investigator at the site.

Visitors are able to see the fossilized bones exactly as they were found in the sinkhole that trapped the animals.

Better Than Museum

“I thought that they would look better in the ground where the animals died rather than in any museum,” said Agenbroad, calling the setting unique.

In 1986, all of the bones that had been found up to that time were set out at the site, which is protected by a 20,000-square-foot building.

Visitors may also watch excavations during the one month each year that is set aside for exploration.

The cache of bones was discovered by chance during construction work on a housing development.

George Hanson, operating an earthmover, had shaved about 20 feet off the top of a hill when he spotted hundreds of bones.

Passes Word On

He mentioned them to his son, Dan, who had been a student of Agenbroad, then a professor at nearby Chadron State College in Chadron, Neb., but now affiliated with Northern Arizona University.

Agenbroad gives much of the credit for establishing the Mammoth Site to the owner of the land, developer Phil Anderson.

“The common attitude (among builders) is, if you hit bones, cover them up and don’t let anybody know (because) it will slow us down.”

Instead, Anderson told Agenbroad that he could have three years to decide if the site was worthwhile. “We found that out very quickly in the first year.”

The Hot Springs Gem and Mineral Society formed a nonprofit corporation and raised money to buy the 14-acre site from Anderson at his cost. A second fund drive resulted in construction of the $1.13-million building.

More Facilities Planned

Plans call for a second phase of development to include a museum, exhibits, theater, library, laboratory and bone storage.

So far this year, nearly 30,000 people have paid admission, said business manager Joe Muller. Admissions, sales of souvenirs and donations pay the operational expenses of the Mammoth Site.

Many local people didn’t initially appreciate the value of the discovery, said Kathy Anderson, daughter-in-law of the developer and a volunteer at this year’s dig, which was completed Aug. 2.

“The community has gotten behind it in the last few years. Now people understand how wonderful it is,” she said.

Many of the diggers were volunteers from Earthwatch, a Watertown, Mass.-based nonprofit organization that matches volunteers with scientific research projects.

Large Bear Found

The major discovery of the season was the lower jaw of a giant short-faced bear, a predator estimated to have weighed 1,430 pounds, larger than a grizzly.

Barb Barrish, a scientist at Case Western Reserve University in Cleveland made the discovery.

She had recovered the bear’s skull in 1983, and last year she found the large bone of the lower leg. “I have sort of become the bear person,” she said.

The bear and mammoths--along with a number of smaller animals--somehow were attracted to the water of the sinkhole or fell in. The mammoths may have been grazing on the bank, and when they were trapped, the bear may have been attracted to them as food. For some reason, the animals could not get out. No one is sure precisely why.

11,000 Years Ago

Mammoths, a little larger than modern elephants, became extinct about 11,000 years ago, Agenbroad said.

Although dinosaurs and man were never on Earth at the same time, mammoths and man were contemporaries, Agenbroad said. “Dinosaurs were only with man in Alley Oop.”

Evidence exists that humans killed and ate mammoths, Agenbroad said. What he doesn’t know is whether man caused their extinction.

No human artifacts have been found at the Mammoth Site.