When scientists first dated the bone bed at the Mammoth Site in Hot Springs, it appears they underestimated its age by more than 100,000 years.
Scientists at the research facility and tourism attraction first dated the site in the early 1980s. At that time, the bones were thought to be 26,000 years old. But new testing methods performed in 2016 and analyzed for the past two years showed that site is actually 140,000 years old.
"We decided to retool what we are doing, make sure we're up to snuff and see what new technology can do," said Jim Mead, Mammoth Site chief scientist.
The new date was established using optically stimulated luminescence — a dating technique which measures the time a mineral grain has gone without being exposed to light.
Scientists from the University of Nebraska, Lincoln, and the U.S. Geological Survey worked alongside individuals from the Mammoth Site for two years to verify the new age. The previous date was established with radiocarbon dating of the actual bone material. Since the date was originally established, scientists have learned that technique can significantly underestimate the age of sites.
"We figured it would be older, we didn't expect it was that old though," said Mead.
The new age gives Mammoth Site scientists a better understanding of why certain species were found at the site and others weren't. Around 140,000 years ago, the Black Hills were in an inter-glacial period. The climate was warmer than today. Bison would have been present in the area 26,000 years ago, but may not have been 140,000 years ago.
Part of the Mammoths Site's retooling process involves broadening research to learn about the Ice Age in the Black Hills, not just at the site. "I view the Mammoth Site as a hub," said Mead, adding that many other Ice Age remains can be found throughout the Black Hills.