Deep beneath the hills of southern Brazil and northern Argentina, researchers have discovered massive tunnels carved into solid rock. These impressive structures can’t be linked to human activity or natural geology. They don’t follow river routes and look distinctly different from typical caves.
Some of these tunnels stretch more than 600 yards (about 550 meters) and are spacious enough for adults to walk through comfortably. Scientists believe that giant, extinct ground sloths may have created these tunnels, transforming parts of South America into a complex underground network.
Mapping the Tunnels
In the last ten years, more than 1,500 of these ancient burrows have been identified across southern Brazil. The tunnels can extend for hundreds of feet and often split into smaller passages decorated with long claw marks. Led by Heinrich Frank, a geologist from the Federal University of Rio Grande do Sul, this study focuses on “paleoburrows”—tunnels made long ago by large animals reshaping landscapes.
These tunnels appear in hard materials like consolidated sands and weathered volcanic rock. The patterns of collapsed areas and reused paths suggest that animals played a big part in maintaining these spaces over generations.
The Design of the Tunnels
Geological events rarely create tunnels that are long, rounded, and intricately connected like these. Frank observed that the tunnel walls are lined with claw marks, indicating they were dug out by a powerful creature.
Similarly structured tunnels can also be seen along road cuts in Argentina, where they connect in dense clusters. Together, this layout indicates a planned network rather than simply the result of erosion.
Who Made the Tunnels?
To figure out who the creators were, scientists compared the size of the burrows and the claw patterns with fossil skeletons found nearby. The largest tunnels measure at least 6 feet (1.8 meters) wide, which limits the candidates to species like giant ground sloths or armadillos. The evidence points toward sloths due to the long, curved claw marks left in the walls.
One leading candidate is Megatherium, a well-known giant ground sloth from the late Ice Age. These colossal creatures weighed up to four tons and stood 12 feet (3.7 meters) tall, not much smaller than modern elephants.
Humans and Sloths: A Shared Past
These tunnels date back to the Pleistocene, more than 11,700 years ago, a time when humans and giant sloths roamed the Americas together. There’s even evidence from New Mexico showing human footprints alongside sloth tracks, hinting that early humans hunted these massive creatures.
David Bustos, a park scientist, noted that humans likely stalked sloths, which were dangerous as they could rear up and use their powerful claws if threatened. This would mean the underground tunnels provided sloths with refuge from hunters and climate changes.
Importance of Paleoburrows Today
Paleoburrows offer insights that bones alone cannot provide. They detail tunnel shapes, sizes, and textures that help scientists understand ancient animal behavior. Moreover, the excavated burrows help map where different sloth species lived and how they interacted with their environment.
According to a review, Pleistocene sloths inhabited diverse areas, from grasslands to forest edges. Analyzing paleoburrows allows scientists to connect these creatures with their habitats more comprehensively, shedding light on how their extinction affected ecosystems and nutrient distribution in the landscape.
What We Can Learn
Studies of extinct megafauna show that their disappearance has had lasting impacts on ecosystems. As more paleoburrows are explored, our understanding of Ice Age life will deepen, revealing the intricate relationships between ancient sloths, early humans, and their environment.
These tunnels are not just scientific curiosities; they symbolize a rich tapestry of life, connection, and change during a crucial period in Earth’s history.
For more on the ancient world, take a peek at articles in Science Advances which delve into the significance of these massive burrows.
