California scientist unearths remarkably preserved 10,000-year-old mastodon tooth

A geomorphologist working at a preserve in San Mateo County, California, recently made an unexpected discovery: what looked like an odd rock turned out to be a molar from an adult Pacific mastodon, an ancient relative of modern elephants. The find was announced this week by the Midpeninsula Regional Open Space District (Midpen).

Paleontologist Wayne Thompson described the tooth as being in exceptional condition, calling it the most complete mastodon molar recovered from the region and the most impressive he has personally encountered. He said the discovery adds another piece to the broader understanding of the Ice Age period.

A species lost to climate change and hunting

Pacific mastodons roamed much of the American West—including present-day California, Oregon, the northern Rocky Mountains, and parts of Mexico—for roughly 2.5 million years. The herbivorous mammals disappeared more than 10,000 years ago, a decline driven by shifting climate conditions that altered their habitat, compounded by hunting pressure from early humans.

The fossilized molar has since been handed over to Stanford University, where specialists at the school of sustainability plan to use carbon dating techniques to pin down its precise age.

Christine Garcia, who curates the geoscience specimen collection at Stanford, said fossils offer a rare window into past biodiversity, allowing researchers to reconstruct ancient ecosystems and apply those lessons to protecting wildlife and ecosystems going forward.

The discovery follows a string of similar finds in recent years. In 2024, a resident of New York state discovered a mastodon jawbone buried beneath their lawn, while in 2023 a woman came across a foot-long mastodon tooth protruding from the sand on a beach along California's central coast.