Capybara Tooth Unearthed in Chile’s Atacama Challenges Desert’s Dry Legacy

When researchers lifted a slab of sediment from the Bahía Inglesa Formation at El Morro, they probably expected another marine shell or a dinosaur fragment. Instead, a small, worn‑down molar emerged – the oldest capybara tooth ever recorded, dating to roughly 8.8 million years ago.

Modern capybaras are semi‑aquatic rodents that hug riverbanks, wetlands and dense vegetation. Their presence in today’s Atacama, a place famed for its relentless aridity, seemed impossible. Yet the fossil, assigned to the extinct genus Cardiatherium, forces us to rethink that assumption.

It isn’t just the tooth that tells a story. Embedded in the same layers were the remains of freshwater fish and gavial‑like crocodilians, creatures that would have needed permanent water bodies to survive. Tiny plant remnants, called phytoliths, pointed to palms and other flowering plants – a clear sign of lush, C3‑dominated vegetation.

All these clues converge on a surprising picture: during the Late Miocene, parts of northern Chile were not a barren stone desert but a patchwork of lakes, marshes and river corridors. The region likely experienced a climate far wetter than the hyper‑arid conditions that dominate it today.

How did capybaras get there? The Andes would have been a formidable barrier, so scientists propose a low‑elevation wetland corridor that linked the Amazon basin to the Pacific coast. Such a route would have allowed a range of water‑loving mammals and reptiles to migrate across the continent.

Importantly, the find does not imply the entire Atacama was a swamp. Rather, it highlights that the desert’s climate has swung dramatically over millions of years, with localized wet phases interrupting the long‑term dry spell. Understanding these ancient oscillations could improve our models of how deserts respond to future climate change.