Capybaras are among the most adored animals on the internet, having risen to fame with their stoic demeanor and clumsy antics. These rodents, which look somewhat like giant guinea pigs, have always thrived near rivers and ponds. It may come as a surprise, then, that their ancestors used to live in what is now the Atacama Desert in northern Chile.
A new study published in Scientific Reports has detailed the discovery of a fossilized tooth from a capybara that lived in the Atacama Desert around nine million years ago. Back then, however, the Atacama Desert may not have been much of a desert at all; it may have had a wetter climate, challenging the idea that it is one of the world’s oldest continuously dry regions. And while capybaras are long gone from the area, the fossil tooth suggests that they once enjoyed life in coastal Chile millions of years ago.
"Finding this capybara — which I think everyone can agree is not a desert animal by any means — at that location is going to challenge many of the ideas about the Atacama's history,” said study co-author Mark Clementz, a paleobiologist at the University of Wyoming, in a statement.
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An Unexpected Capybara Fossil
Fossilized capybara tooth
(Image Credit: Carolina Gutstein et al.)
Researchers were in for a surprise when they found the fossilized capybara tooth in a layer of sediments at a site called El Morro, part of the fossil-rich Bahía Inglesa Formation; this formation also hosts Cerro Ballena (or “Whale Hill”), a site where the skeletons of more than 40 whales and other marine mammals have been found, according to Smithsonian Global.
The capybara tooth represents the first and oldest record of a capybara relative in coastal Chile. For the researchers involved in the new study, it also seemed incredibly out of place in the formation.
"Finding a capybara tooth in a marine deposit in what today is one of the driest regions on Earth is just freakish," said the study’s lead author Priscilla Martinez, a doctoral student at the University of Arizona.
Today, capybaras can be seen in wetland environments east of the Andes, migrating along creeks and rivers. But the Atacama Desert, west of the Andes, doesn’t seem like a place where capybaras would’ve ever lived.
Journey to the Atacama Desert
Priscilla Martinez conducting fieldwork in an ancient dry riverbed.
(Image Credit: Joao Gabriel Martínez López)
The researchers first wondered how capybaras would’ve even made it to coastal Chile, considering the massive barrier of the Andes separating the Atacama Desert from capybaras’ original home east of the mountains.
"Not only are the plateau lands of the Central Andes very tall, they're also extremely arid,” Martinez said. "So, if capybaras originated east of the Andes in this foreland region, how in the world could these short-legged rodents make it across?"
The answer, the researchers propose, is that capybaras went around the Andes, not through them. The rodents would’ve potentially journeyed across low-elevation wetlands that connected their original range to coastal areas in northern South America, going “counterclockwise” from Venezuela down into northern Chile.
Ancient Climate Change
The fossilized tooth posed another major question: How could capybaras have lived in the ancient Atacama Desert if they normally thrive around water?
The researchers unearthed other clues indicating that the Atacama Desert may not have been so inhospitable nine million years ago; more specifically, they found phytoliths, microscopically small accumulations of silica that form inside plant cells and tissues as they absorb dissolved silica from groundwater.
By analyzing these phytoliths, they were able to pinpoint which types of plants made them. These specific structures, they determined, came from palms and other flowering plants like dicots, suggesting that the Atacama Desert once had a much different climate.
"Think sunny Southern California full of palm trees," Martinez said. "You don't really expect the Atacama Desert to have palms, and we're not sure if they were blooming extensively there, but they were definitely there."
Such a climate would’ve supported not just a more diverse mix of plant life, but also capybara populations. The study's findings ultimately show that the ancient Atacama Desert may not have always been a true desert, instead having a changing climate throughout its history.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Scientific Reports: Late Miocene capybara in the Atacama Desert reveals a wetter climate and a transcontinental dispersal pathway
- This article references information from Smithsonian Global: Cerro Ballena
