Found in Arlington more than 65 years ago, a tusk believed to be some 46,000 years old still prompts more questions than answers.
The tusk, which is from a mammoth that roamed the North American tundra, is all that remains of this gargantuan Ice Age creature. The tusk, found in Arlington’s Spy Pond in 1960, was perhaps used as a tool for foraging plants and self-defense against predators. The Spy Pond Tusk was the subject of a presentation by the Arlington Historical Society on March 31.
Local fisherman Arvid Carlson uncovered the tusk while fishing in Spy Pond with his then 10-year-old son, Steve. Carlson gave the tusk to the Boston Museum of Science, which donated it to the Arlington Historical Society in 1987.
When the Museum of Science acquired the tusk, scientists extracted a sample for carbon-14 dating – a method used to determine the age of organic materials by analyzing the decay of their carbon-14 isotope. The results of this testing showed that the tusk was 43,000 years old. The researchers also assumed that the tusk belonged to a mastodon, because of the animal’s prevalence compared to mammoths in the New England area at the end of the Ice Age.
George Parsons, vice president of the Arlington Historical Society, said he is skeptical of the carbon-14 dating results. Previous corings of sediments taken from Arlington area ponds had shown that the oldest sediments were only 11,000 years old.
“There was an ice age that started here about 26,000 years ago. Ice as much as a mile thick covered this area and it bulldozed everything into the Nantucket Sound,” Parsons said at the talk. “So how does a tusk that’s been dated to 43,000 years old show up on the bottom of the pond, not under anything?”
Parsons contacted archaeologist Stuart Fiedel after reading an article he authored about carbon-14 dating a mastodon tusk found in South Egremont. Alongside Robert Feranec, curator of vertebrate paleontology and mammals at the New York State Museum, the team retested the tusk in 2022.
Since the tusk’s discovery, carbon-14 dating methods have drastically evolved. Previously, the standard procedure involved extracting a fist-sized sample and measuring its radioactivity over long count times. Sixty years later, carbon-14 dating can be done with a smaller sample size using accelerator mass spectrometry – a multi-step process that isolates a fossil’s carbon. The carbon is then placed into a vacuum and exposed to calcium ions and magnetic fields to separate the carbon-14 from other isotopes.
In July 2022, the new test results estimated the Spy Pond Tusk to be between 46,000 and 47,000 years old.
“Let me put that in perspective: 47,000 years ago, the only humans in Europe were Neanderthals. There were no humans at all in North and South America,” Parsons said. “It would be 30,000 years before we invented agriculture and metal working. That’s how old this thing is.”
After examining the tusk’s Hunter-Schreger bands – the growth lines found in mammal teeth — the team made another revelation: The Spy Pond Tusk belonged to a mammoth, not a mastodon.
Although both mammals of the Ice Age, Parsons emphasized that mammoths and mastodons last shared a common ancestor 30 million years ago.
“This is three times our separation from the gorilla,” Parsons said.
The finding was further supported by the tusk’s nitrogen-15 levels, which were more consistent with the mammoth’s grass-based diet compared to the mastodon’s consumption of trees and shrubs. Despite the amount of evidence already gathered, Parsons wanted more and he submitted a sample for mitochondrial DNA testing.
However, the DNA test results dropped the biggest bombshell: The mammoth was not from Arlington. Instead, its DNA matched with a group of mammoths from Alaska.
How the mammoth’s tusk traveled from Alaska to the bottom of Spy Pond remains unknown.
Parsons theorizes that the Fairbanks Exploration Company, a gold-mining enterprise, discovered the tusk while mining. Parsons said that records show that the Fairbanks Company had shipped the tusk and other discovered fossils to the American Museum of Natural History in New York between 1929 and 1951.
Parsons believes that the museum had run out of storage space for the tusk and dumped it in the river.
“Humans are entrepreneurial,” Parsons said. “Somebody saw the tusk being dumped and said, ‘Maybe I can take this tusk up to Boston or Cambridge or Worcester and I can make myself a tiny sum.’”
Parsons also refuted the longstanding myth that Arvid Carlson had lured the 50-pound tusk to shore with his fishing rod after discovering it 75 feet from the shore. He credited Steve with providing him firsthand details about the tusk’s discovery.
Junko Nagano, a former program manager, left the presentation pleasantly surprised.
“It was more fascinating and informative than I had expected, especially the science aspects of it,” Nagano said.
Inspired by the Spy Pond Tusk, Arlington High School changed its mascot to a mammoth in 2024. Adam Lane, the mascot’s illustrator, said a mammoth mascot represents the school perfectly.
“I’m just very happy with how it’s worked out, because it seems like for the most part, the students have embraced it,” Lane said. “[Mascots] are symbols for the whole community, but first and foremost they serve the kids.”
This story, published on April 10, 2026, is part of a partnership between Your Arlington and the Boston University Department of Journalism.