By Zoe Sottile, CNN
Justin Blauwet noticed something unusual while working on a construction site in Iowa. At first glance it appeared to be a block of stone, just under a foot long, covered in ridges.
But Blauwet had a better idea what it was, thanks to a lifelong interest in prehistoric animals: a woolly mammoth tooth probably dating back tens of thousands of years.
Blauwet was observing a construction site March 4 on property owned by Northwest Iowa Community College in Sheldon when he spotted the dent, according to a press release issued Wednesday by his employer, DGR Engineering.
He said he recognized the tooth through extensive knowledge of fossils and prehistoric creatures. “I’m a ‘nerd’ like that,” he told DGR, adding that his two young sons are also passionate about fossils and dinosaurs.
The company asked Tiffany Adrain, a professor of paleontology at the University of Iowa, to review the find. She confirmed that it was a real woolly mammoth tooth.
The tine is 11 inches long and weighs 11.2 pounds. Adrain said it was probably over 20,000 years old.
“Mammoths have really distinctive teeth,” Chris Widga, chief curator at East Tennessee State University, told CNN on Saturday. Almost resembling a loaf of bread, their unique shape makes mammoth teeth really easy to identify.
“They evolved to basically take advantage of a grazing niche, eating a lot of abrasive vegetation like grasses,” he said. This particular specimen was likely a mammoth in its 30s, based on how worn the tooth was, Widga said. “It would be an adult in the prime of life,” he said.
Experts believe woolly mammoths went extinct just 4,000 years ago. Ice Age giants could grow up to 13ft tall at the shoulder and roamed the planet for hundreds of thousands of years: World’s oldest DNA sequence recovered from a mammoth tooth over a million years old.
It’s more common to find individual mammoth teeth than bones or complete remains, Widga said, because they’re made of enamel, which is denser and “more resistant to the kinds of things that break down a skeleton.”
Over time, a tooth can erode away from the original area where it was deposited and end up in a new deposit, away from the rest of the remains. Their distinctive appearance also makes them more likely to be noticed than other types of fossils.
And northwestern Iowa is “kind of a hotspot” for mammoth finds, Widga noted, with finds generally dating from 24,000 to 15,000 years ago.
In general, mammoth remains tend to occur in one of two geological settings: gravel deposits and clay swamp deposits. “One of the interesting things about Iowa is that, given its geological history, it’s home to some very interesting Pleistocene fauna, Ice Age animals,” Widga explained.
About 18,000 years ago, central Iowa was covered in ice. But the edges of the state have been exposed – and those areas tend to reveal mammoth remains.
In 2013, the remains of three mammoths were discovered after flooding dislodged the bones, according to CNN affiliate KCCI. The bones have been estimated to be between 14,000 and 16,000 years old. Sites with multiple animals are quite rare, according to Widga.
Blauwet’s discovery should soon have a new home at the Sheldon Prairie Museum at Northwest Iowa Community College. Sheldon is located approximately 60 miles northeast of Sioux City.
“We are pleased to display the tooth at the Sheldon Prairie Museum as a semi-permanent loan exhibit,” college president Dr. John Hartog said, according to DGR’s press release. “That way everyone from our service area can come to the museum to see and appreciate this artifact.”
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