This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Ask any zoo-goer and they will tell you that capybaras are adorable. Ask a scientist specializing in the rodents, which resemble oversized guinea pigs, and they will tell you they are obligate semiaquatic herbivores that indicate persistent riparian ecosystems.
In plain English: Capybaras like it wet. Accordingly, scientists were stunned when they discovered a fossilized tooth from a capybara that lived in the Atacama Desert in northern Chile almost 9 million years ago. The discovery not only provides the first and oldest record of a capybara in coastal Chile—a country where no capybaras live today—but also calls into question the longstanding textbook version of the Atacama Desert as one of the oldest continuously dry regions on Earth, dating back an estimated 40 million years.
The work is published in the journal Scientific Reports. The fossil was found in a layer of sediments deposited in a shallow marine environment between 10 million and 7 million years ago at a site called El Morro, part of the fossil-rich Bahía Inglesa Formation. The formation also hosts Cerro Ballena, or "Whale Hill," famously recognized as the world's largest concentration of whale fossils.
"Finding a capybara tooth in a marine deposit in what today is one of the driest regions on Earth is just freakish," said Priscilla Martinez, the study's lead author and a doctoral student at the University of Arizona Department of Geosciences. Capybaras, the largest living rodents, and their close cousins, guinea pigs, are native to South America. Today, capybaras thrive east of the Andes in low-elevation wetlands, with their core range roughly outlining the Amazon River basin.
Their semiaquatic lifestyle tightly links them to persistent surface water, wetland vegetation and the ability to migrate along riparian corridors along creeks and rivers. "We don't have any other evidence of capybaras in that part of coastal Chile," added co-author Barbara Carrapa, a professor of geosciences and Martinez's doctoral adviser. "They're not supposed to be there.
So, we immediately asked ourselves, 'Why were they there? Where did they come from?'" Geologists estimate that long before capybaras appeared roughly 9 million years ago, the Andean mountain chain would have presented a formidable barrier, rising to 18,000 feet, effectively walling off the Atacama Desert from the eastern lowlands stretching across parts of Venezuela and Colombia to northeastern Argentina and Uruguay, the animal's current range. Geography is one factor in determining the range of a species, but by far not the only one.
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