Across two very different continents, scientists are mapping vast systems of ancient tunnels that were not carved by rivers or humans. In southern Africa, microscopic passageways etched into solid rock hint at a lifeform that may have burrowed through the crust millions of years ago, while in South America, walkable caverns snake through hillsides in patterns that point to giant mammals as their architects. Together, these discoveries are forcing researchers to rethink how life has shaped the planet’s interior over at least 2 million years.
What links these finds is not a single species, but a shared mystery: both the micro‑scale tubes in African rocks and the mega‑scale caverns in South American hills appear to be biological in origin, yet their makers are either only partly known or not identified at all. I see in this convergence a rare opportunity, where geology, paleontology, and microbiology intersect to illuminate an underground chapter of Earth’s history that has barely been read.
Micro‑tunnels in Africa and the Middle East that should not exist
The most puzzling structures sit locked inside ancient rocks in southwestern Africa and the Arabian Peninsula, where geologists have uncovered bands of perfectly aligned micro‑tunnels that cut across mineral grains instead of following natural fractures. In outcrops in Namibia, researchers described a Band of heavily eroded micro‑burrows that only became visible when erosion sliced through the rock, revealing a dense fabric of tubes that look more like engineered conduits than random cracks. Similar textures have now been reported beneath parts of the Middle East, including carbonate rocks in Oman and sedimentary layers under Saudi Arabia, tying the phenomenon to a broad swath of crust rather than a single isolated site.
When scientists sampled these tubes, they found a fine calcium carbonate powder lining the walls, a residue that points to biological activity rather than simple chemical dissolution. Analyses described earlier this year showed that the powder likely represents the remains of microorganisms that once burrowed through the rock, leaving behind a network of micro‑scale tunnels that cut across grains in a way no known physical process can easily explain, a pattern highlighted when researchers noted that When the tubes were analyzed, this distinctive residue appeared. One team described the structures as a potential trace of a “Lifeform Never Before Identified,” a phrase that captures both the excitement and the caution around the discovery, as summarized in coverage of Scientists Discover Ancient a new type of burrowing organism.
A possible new branch on the tree of life, written in stone
What makes these African and Middle Eastern tunnels so provocative is their scale: they are microscopic, yet they run in long, straight lines that maintain a constant diameter, as if laid out by a machine. In one report, These microscopic tunnels, perfectly aligned, were described as cutting through a freshly cut sample in a way that immediately distinguished them from ordinary pores or weathering features. The structures are several million years old, yet they preserve a level of organization that suggests a coordinated community of burrowers, not random single cells drifting through cracks. For geologists used to reading rocks as records of pressure and temperature, the idea that the crust itself might be riddled with such biological etchings is a profound shift.
Researchers quoted in one analysis stressed that “We don’t currently know” what kind of creature made them, underscoring that even the broad category of life involved remains uncertain. Reporting on the find noted that, But the story is far from over, because the tubes could represent anything from an unknown microbial consortium to a completely new mode of subsurface life. Another account framed the discovery as an “Ancient Underground Tunnel Discovery, Hint at Unknown Life,” emphasizing that Researchers recently uncovered micro‑scale tunnels inside the planet’s solid crust that do not match any known trace fossils. I read these cautious phrases not as hype, but as a sign that scientists are confronting a pattern that does not fit existing categories, which is often how new branches on the tree of life first come into view.
Megafauna paleoburrows that you can walk through
On the other side of the Atlantic, the mystery is not whether animals dug the tunnels, but which animals, and how they reshaped entire landscapes. Across southern Brazil, Uruguay, Paraguay, and northern Argentina, scientists have documented enormous underground passageways known as paleoburrows, some large enough to drive a small car through. One account describes how, Across southern Brazil, Uruguay, Paraguay, and Argentina, these structures appear in hillsides and fields, suggesting that ancient animals dug them for protection, climate control, or nesting. In his home state of Rio Grande do Sul, geologist Heinrich Rio Grande do Sul, Brazil, Frank has documented at least 1,500 paleoburrows so far, a figure that hints at how widespread this behavior once was.
These caverns are not random voids; they carry claw marks, consistent cross‑sections, and branching patterns that point to deliberate excavation by large mammals. The Brazilian paleoburrows have been described as the world’s largest ichnofossils, with Sizes S and L used to classify them and The Brazilian examples assigned to the ichnofossil genus Megaichnus. Some of these tunnels extend a whopping 100 metres long, as highlighted in a discussion where These enormous tunnels were linked to giant ground sloths. Another report notes that, in one Brazilian state alone, at least 1,500 such structures have been cataloged, reinforcing the idea that these were not rare shelters but a dominant feature of the Pleistocene landscape.
Giant ground sloths and armadillos as master engineers
Most researchers now agree that at least some of these South American tunnels were excavated by giant ground sloths and massive armadillo relatives, animals that rivaled small cars in size. One detailed account explains that These enormous tunnels were excavated by giant ground sloths, with some individuals standing close to 10 ft tall and weighing as much as a small elephant, their claws leaving deep grooves in the walls. Another description refers to a Tunnel Dug by a Giant Ground Sloth in Brazil Over 10,000 Years Ago, Known as a paleoburrow, underscoring that some of these structures date to the late Pleistocene while others may reach back a few million years. A separate synthesis notes that Paleoburrows, located primarily in South America, reveal a chapter of the Pleistocene epoch dating back roughly 10,00 years, highlighting how megafauna used digging to shape their environment.
What remains contested is the full roster of species involved and the exact age range of the largest systems. One report on Ancient tunnels built thousands of years ago notes that these huge ancient underground tunnels were not made by humans, but were instead identified by geology professor Heinrich Frank as the work of extinct megafauna. A separate video feature emphasizes that Scientists Have Found in South America, And They Weren, Made by Humans Across large parts of the continent, reinforcing the non‑human origin. I find it striking that, while the African micro‑tunnels hint at a lifeform never before identified, the South American caverns point back to familiar megafauna behaving in unfamiliar, almost architectural ways.
Two continents, one deeper story about life reshaping Earth
Placed side by side, the African micro‑tunnels and South American paleoburrows sketch a continuum of biological engineering that spans at least 2 million years and a vast range of scales. In Africa and the Middle East, coverage framed the discovery as Scientists Intrigued by Strange Tunnels Under Africa and the Middle East, with Noor Al Sibai reporting that erosion had exposed the tubes in places where they could be studied directly. Another detailed account described how a Credit image by Cees Passchier showed the unusual structures of unknown origin, reinforcing the sense that the crust itself holds a fossil record of microbial behavior. In South America, social media posts and field reports have turned obscure ichnofossils into viral images of walkable tunnels, with one summary noting that Brazil Over 10,000 Years Ago, these burrows were already ancient when the first humans arrived.
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