Ice Age Mastodon Tooth Found in California Creek Is Far Older

Brigid Lynch was not looking for Ice Age fossils, let alone an Ice Age mastodon tooth. The geomorphologist with Balance Hydrologics was wading through a creek in a San Mateo County redwood forest, surveying a habitat restoration project for the threatened California red-legged frog, when something in the water caught her eye. It looked like a strangely shaped rock.

"As a geologist, I've gone out and seen stuff in the field, but definitely nothing as exciting as this," Lynch said in a release.

Lynch studies how landscapes form for Balance Hydrologics, according to Palo Alto Online.

The rock turned out to be an Ice Age mastodon tooth: a fossilized molar from an adult Pacific mastodon, a massive elephant-like herbivore that roamed the American West during the Pleistocene epoch. The Midpeninsula Regional Open Space District, which manages the preserve where Lynch was working, announced the find on September 9.

A molar in remarkable condition

The Ice Age mastodon tooth drew superlatives from the paleontologists who examined it. Wayne Thompson, the owner of Pacific Paleontology who assessed the fossil and the site where it was found, called it "the most complete mastodon molar from our area, and the most spectacular mastodon molar that I've ever seen." In the district's press release, he added: "I had chills and shivers up and down my spine."

Thompson told Fox News Digital that the molar is in "immaculate condition," a rarity for fossils pulled from moving water, where teeth usually get worn down or broken apart. The strange shape that caught Lynch's eye was the tooth's natural ridged crown, built for grinding down the coarse plants mastodons ate.

She was studying the creekbed as part of an effort to improve habitat for the threatened California red-legged frog, according to Fox News. Finds like this are rare for routine fieldwork. "It doesn't happen often," Thompson said. "[It's] quite uncommon."

Early reports on the discovery, carried by KTLA and other outlets, estimated the fossil at about 10,000 years old. But Thompson says that figure is off, and possibly by a wide margin.

How old is it, really?

"There is a lot of misinformation going around about the age of the tooth," Thompson told Fox News Digital. "Most of the reports out there are saying it's 10,000 years old, but it's not 10,000 years."

Based on the location where the specimen was found, he said the tooth likely dates back between 50,000 and 100,000 years. "From the location where the specimen was found, we can pretty confidently say that it's much, much older than 11,700 years," he added, referring to the end of the Pleistocene epoch, when the mastodons vanished.

The exact age should get clearer soon. The tooth has been donated to Stanford University's Doerr School of Sustainability, where researchers plan to carbon-date it for a more precise estimate. Scientists also plan to 3D-scan the fossil and create a replica for educational use.

Why a tooth matters

Pacific mastodons were large herbivores that roamed California, Oregon, other parts of the western United States and Mexico during the Pleistocene, according to the open space district. They went extinct roughly 11,700 years ago, near the end of the last Ice Age. The Pacific mastodon was only recognized as a species distinct from the American mastodon in 2019, following extensive study of mastodon bones found in Southern California. The Pleistocene itself began about 2.5 million years ago, according to the open space district.

Christine Garcia, curator and manager of Stanford's Geoscience Specimen Collection, said discoveries like this fill in the picture of what lived in the Bay Area long before the region had a name. "Fossils are our only opportunity to see into past biodiversity," she said.

The California find arrives in a busy stretch for ancient discoveries. Peruvian archaeologists recently opened a 600-year-old Chimú tomb that had been sealed for centuries, and researchers in China reported 15-million-year-old fossil flowers preserved in amber.

For Lynch, the find was a reminder that the creek she was studying holds stories far older than the frogs she came to help. She arrived to improve habitat for a threatened amphibian and left with an Ice Age mastodon tooth, the most complete mastodon molar ever documented in the area, a find that may push its first reported age back by tens of thousands of years once the dating comes in.