In the sediment layers of one of Earth's most forbidding landscapes, a single fossilized tooth has quietly rewritten the biography of the Atacama Desert. Discovered in Chile's Bahía Inglesa Formation and dated to 8.8 million years ago, the tooth of Cardiatherium — an ancestor of the modern capybara — speaks to a time when wetlands and palms flourished where only stone and dust now remain. The find reminds us that the planet's most extreme places were not always so, and that understanding how they became what they are may be essential to understanding what our own world is becoming.
Ancient Capybara Tooth Reveals Atacama Desert Was Once Lush and Wet
Finding a capybara tooth in one of Earth's driest regions is just freakish
Mark
So we found a capybara tooth in the Atacama Desert. Why does that matter so much?
Mimi
Because capybaras need water to survive, and the Atacama is one of the driest places on Earth. Finding one there from 8.8 million years ago means the desert wasn't always a desert—at least not in the way we understand it now.
Luke
But it's one tooth. How confident are we that this actually changes what we know about the Atacama's climate history?
Mimi
It's not just the tooth. They found palms and flowering plants in the same sediment layers. That's multiple lines of evidence pointing to wetter conditions.
Mark
What do we still not know?
Mimi
The researchers are honest about the gaps. They don't know exactly how these capybaras got to Chile, or what caused the desert to dry out over time. The migration routes are still hypothetical.
Luke
So we have evidence that it was wetter, but we don't actually understand the mechanism of change or the full geography of how these animals moved through the landscape?
Mimi
Right. That's what makes this a discovery that opens questions as much as it answers them.
Mark
And the practical value—why does understanding ancient desert climates matter now?
Mimi
Because deserts are sensitive to climate shifts. If we understand how they changed in the past without human influence, we have a baseline for predicting how they'll respond to the climate changes we're causing now.
Luke
That's a reasonable argument, but it assumes the past is a reliable guide to the future—which isn't always true when the rate of change is so different.
Mimi
Fair point. But it's still better than having no baseline at all.
Il Polso
- A fossilized capybara ancestor tooth has surfaced in the Atacama Desert — a region so arid that the animal's modern descendants cannot survive there — creating a profound scientific paradox.
- The discovery, paired with fossil evidence of palms and flowering plants from the same late Miocene period, suggests that portions of the world's oldest non-polar desert were once lush freshwater ecosystems.
- Researchers are now grappling with two unresolved mysteries: how ancient capybaras migrated into what is now Chile, and what forces drove the Atacama's dramatic transformation into hyperaridity over millions of years.
- The study, published in Scientific Reports by University of Arizona researchers, is pushing the scientific community to revise long-held assumptions about the Atacama's climatic history.
- Beyond the fossil itself, scientists see urgent practical value — the Atacama's deep past offers a rare baseline for modeling how modern deserts may respond to accelerating, human-driven climate change.
In the sediment layers of one of Earth's most forbidding landscapes, a single fossilized tooth has quietly rewritten the biography of the Atacama Desert. Discovered in Chile's Bahía Inglesa Formation and dated to 8.8 million years ago, the tooth of Cardiatherium — an ancestor of the modern capybara — speaks to a time when wetlands and palms flourished where only stone and dust now remain. The find reminds us that the planet's most extreme places were not always so, and that understanding how they became what they are may be essential to understanding what our own world is becoming.
The Atacama Desert is widely considered the oldest non-polar desert on Earth, a hyperarid expanse along Chile's northern coast that scientists believed had persisted in its current state for at least 40 million years. A single fossilized tooth, unearthed from the fossil-rich Bahía Inglesa Formation buried within the Atacama itself, is now challenging that story.
The tooth belongs to Cardiatherium, an extinct genus ancestral to modern capybaras, and has been dated to approximately 8.8 million years ago. The discovery carries an almost surreal quality: capybaras are semiaquatic animals that depend on wetlands and abundant water to survive, yet they are entirely absent from Chile today. Lead author Priscilla Martinez, a doctoral student at the University of Arizona's Department of Geosciences, described the find as "freakish" — a word that captures just how dissonant the evidence feels against the Atacama's current reality.
The tooth did not stand alone. Researchers also found fossil evidence of palms and other flowering plants from the same late Miocene period, together suggesting that freshwater ecosystems once flourished across at least portions of what is now one of the world's most inhospitable regions. How capybaras reached this landscape, and what forces eventually drove the Atacama into its extreme aridity, remain open questions — the migration routes are hypothetical, and the mechanisms of transformation are still being investigated.
For Martinez and her colleagues, the stakes extend well beyond paleontology. The Atacama's ancient climate record offers a baseline — a window into how deserts evolve through natural variability alone — that becomes increasingly valuable as scientists attempt to predict how these fragile environments will respond to human-driven climate change. A tooth preserved in stone for nearly nine million years has become an unlikely but concrete guide to the future.
The Atacama Desert stretches along the coast of northern Chile as one of the driest places on Earth, a hyperarid expanse that scientists believe has persisted in that state for at least 40 million years—longer than any non-polar desert known to exist. But a fossilized tooth discovered in sediment layers at the Bahía Inglesa Formation, a fossil-rich site buried within the Atacama itself, is now forcing researchers to reconsider what that desert was actually like nearly nine million years ago.
The tooth belongs to Cardiatherium, an extinct genus that likely gave rise to the capybaras we know today. Dated to approximately 8.8 million years ago, it was unearthed in what had once been a shallow marine environment. The discovery, announced this month in the journal Scientific Reports by researchers from the University of Arizona and collaborating institutions, carries an almost absurd quality: capybaras are semiaquatic rodents that require abundant water and wetland vegetation to survive. Finding evidence of one in what is now one of the world's most inhospitable regions suggests something fundamental has changed.
Priscilla Martinez, a doctoral student at the University of Arizona's Department of Geosciences and lead author of the study, called the discovery "freakish"—and the word captures the genuine strangeness of it. Capybaras do not live in the Atacama today. They inhabit nearly every country in South America except Chile, thriving in wetlands and along riverbanks where water is plentiful. Yet here was evidence that their ancestors once occupied this landscape.
The tooth alone might seem insufficient to overturn decades of assumptions about the Atacama's history. But the researchers found more. Alongside the capybara fossil lay evidence of palms and other flowering plants from the same period, the late Miocene epoch. Together, these discoveries paint a picture of freshwater ecosystems that once flourished where only sand and rock exist now. The researchers argue that at least portions of southern Atacama were substantially wetter during that time, with conditions far more hospitable than anything the region experiences today.
How these ancient capybaras reached the Atacama region remains unclear. The researchers present two hypothetical migration routes in their paper, but the exact geography of the ecosystems that would have connected Chile to the rest of South America—where capybaras were more widespread—is still unknown. Equally mysterious is the mechanism behind the Atacama's transformation from a landscape of freshwater habitats to the barren desert it became. The shift happened over millions of years, but the precise drivers remain to be determined.
Martinez and her colleagues see broader significance in these questions. Understanding how deserts respond to climate shifts—particularly changes in monsoon intensity—could help predict how these fragile environments will fare as human-driven climate change accelerates. The Atacama's deep history offers a baseline, a record of how climate can evolve without human influence. That baseline becomes increasingly valuable as scientists try to model what comes next, to distinguish between natural variability and the unprecedented changes now underway. A capybara tooth, preserved in stone for nearly nine million years, has become a small but concrete window into that larger story.
Citazioni salienti
The presence of Cardiatherium in the Atacama Region implies the existence of substantially wetter conditions along the Pacific coast during the late Miocene than occur today— Researchers in Scientific Reports
The more we understand deserts, which are extremely sensitive to changes in climate, including shifts in monsoon intensity from year to year, the better we can predict how they fare long term— Priscilla Martinez, University of Arizona
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