A fossilized tooth discovered in northern Chile’s Atacama Desert reveals that extinct capybara relatives lived in the region nearly 9 million years ago, indicating that the hyper-arid coastal area once sustained a much wetter ecosystem. Researchers published these findings in Scientific Reports, challenging the long-held assumption that the Atacama has remained continuously dry for an estimated 40 million years.
Unearthing a Capybara Fossil in Marine Sediments
University of Arizona doctoral student and lead author Priscilla Martinez described finding a capybara tooth in a marine deposit within one of the driest regions on Earth as “freakish.” Researchers recovered the specimen from a three-foot-thick sediment bed at El Morro, an area within the fossil-rich Bahía Inglesa Formation. This geological formation also contains Cerro Ballena, or Whale Hill, which is recognized as the world’s largest concentration of whale fossils.
Local merchants originally recovered many of the area’s specimens and donated them to scientists. Carolina Gutstein, head of paleontology at Fosfatos de Caldera and a professor at Universidad Santo Tomás in Santiago, collaborated with local fossil experts to study the material, establishing the first and oldest record of a capybara in coastal Chile.
Did you know? The Bahía Inglesa Formation in Chile is globally famous not only for ancient rodents but also for Cerro Ballena, where scientists have uncovered massive concentrations of prehistoric whale fossils.
Palms, Crocodiles, and a Lush Ancient Landscape
Microscopic plant remains known as phytoliths—tiny silica accumulations that form inside plant cells—offered crucial clues about the ancient environment. University of Washington professor and co-author Caroline Strömberg analyzed these botanical traces, identifying palms and dicots, a major group of flowering plants. Martinez noted that the area resembled a sunny Southern California environment rather than a barren desert.
University of Wyoming professor and co-author Mark Clementz, a paleobiology expert, pointed out that the same sedimentary deposits contain fossils of freshwater fishes and gavials, which are freshwater crocodiles. Together with the plant evidence, these aquatic fossils indicate that the region possessed enough permanent freshwater and vegetation to support long-term capybara populations.
Tracing the Transcontinental Dispersal Pathway
Today, living capybaras inhabit low-elevation wetlands east of the Andes, primarily within the Amazon River basin. Because the towering Andes mountains, reaching elevations up to 18,000 feet, stand between those eastern lowlands and the Atacama, researchers had to determine how the rodents reached the Pacific coast.
To solve this migration puzzle, the study authors propose that capybaras bypassed the high mountains entirely. They suggest the animals traveled along low-elevation wetland corridors, moving in a counterclockwise route from present-day Venezuela through Colombia, Ecuador, and Peru before reaching northern Chile.
Reevaluating Desert History and Climate Change
The discovery forces a reassessment of the Atacama Desert’s climatic history. Martinez emphasized that studying past climate changes unaffected by human activity establishes a reliable baseline for understanding how ecosystems evolve over time.
Frequently Asked Questions
Where was the fossilized capybara tooth found?
Researchers recovered the tooth from a sediment bed at El Morro, located in the fossil-rich Bahía Inglesa Formation of northern Chile’s Atacama Desert.
How old is the capybara fossil?
The fossil dates back approximately 9 million years, placing it in the late Miocene epoch.
Why is this discovery significant?
The find challenges the view that the Atacama Desert has remained continuously dry for an estimated 40 million years, providing evidence of an ancient, water-rich coastal ecosystem.
How did capybaras reach the Pacific coast of Chile?
Researchers propose that the rodents traveled along a low-elevation, counterclockwise wetland pathway around the northern edge of the Andes rather than crossing the high, arid mountain range.