“There’s no geological process in the world that produces long tunnels with a circular or elliptical cross-section, which branch and rise and fall, with claw marks on the walls,” says a geologist.
“I’ve [also] seen dozens of caves that have inorganic origins, and in these cases, it’s very clear that digging animals had no role in their creation.”
Experts in Brazil have discovered hundreds of underground tunnels which date back over 10,000 years.
The discovery was made by Heinrich Theodor Frank, a geologist at the Federal University of Rio Grande do Sul — one of the largest federal universities in Brazil.
As Heinrich was driving on the national Novo Hamburgo highway, he noticed a strange hole of around one meter in diameter at a construction site which caught his attention.
Since he was in a hurry to get home, he did not stop. However, a few weeks later he went back to the same place with his family, where he stopped and asked them to wait a moment in the car while he investigated the tunnels.
“I noticed that it was a tunnel, about 70 centimeters high and a few meters in length. The interior was full of scratches,” explains Theodor Frank to National Geographic.
“When I got home I looked for an explanation on the internet, but I did not find anything.”
“Since then I have heard that the tunnels are huge anthills or that they were created by Indians, Jesuits, slaves, revolutionaries and even bears. Some even talk about a great mythological serpent, which dug the tunnels,” he says.
“For example a worm in the Cambrian, a mollusk in the Mesozoic or a rat in the Pleistocene.”
“I didn’t know there was such a thing as paleoburrows,” says Frank. “I’m a geologist, a professor, and I’d never even heard of them.”
So who could have dug those terrifying labyrinthine tunnels, with their walls covered with scratches?
“When you explore the burrows you sometimes have the feeling that there is a creature waiting for you after the next curve as if it were the lair of a prehistoric animal,” says Frank in an article published by Discovery.
Certainly, these tunnels were not created by the natives of Brazil.
“The Indians who lived in Brazil before the arrival of the Europeans did not know about the existence of iron and therefore had no tools to dig through the hard rocks in which these tunnels are dug,” explains National Geographic.
Geologist Amilcar Adamy of the Brazilian Geological Survey has confirmed the discovery of a large complex of 600-meter-long tunnels in the state of Rondonia.
Furthermore, Frank notes that “in neighboring countries such as Uruguay, Paraguay, Chile and Bolivia we have detected a few caves that could also be paleoburrows. In Argentina, there are many of them, mainly in the cliffs of the Atlantic coast, in Mar del Plata.”
As noted by Alfredo Carpineti from IFLScience, over 2,000 burrows have been found, including one just last Wednesday. Scientists believe they were dug between 10,000 and 8,000 years ago, although researchers are yet to properly date them.
Frank says that speleothems, or mineral deposits, growing on burrow walls could be used to calculate an age, although that hasn’t been tried yet either.
“The biggest giant armadillo had a body width of 80 centimeters, while the tunnels reach widths of 1.4 meters and in addition, the ceiling is full of scratches
“I personally believe they were excavated by land sloths, a group of mammals that became extinct in that area about 10,000 years ago,” says Frank.
“There are large tunnels up to two meters high and four meters wide that were undoubtedly excavated by sloths. We do not know the specific species, but surely the largest ones (megatheriums and eremoterios) were too large to dig,” he added.
“We also do not know what the function of the paleoburrows is, perhaps the climate is an explanation: it was drier and hotter than today and the tunnels were isothermal, but this can hardly explain the complex system of tunnels several hundred meters long, which were most likely inhabited by groups of sloths or armadillos.
“The roofs and walls of many tunnels are polished, probably thanks to the friction of the animals’ fur, which moved through the tunnels for decades or even centuries,” concluded Frank.
“So if a 90-pound animal living today digs a 16-inch by 20-foot borrow, what would dig one five feet wide and 250 feet long?” asks Frank. “There’s no explanation – not predators, not climate, not humidity. I really don’t know.”
However, as noted by Discovery, another mystery is the strange geographic distribution of the tunnels.
The so-called paleoburrows are common in southern parts of Brazil, in the states of Rio Grande do Sul and Santa Catarina, they are, so far, almost unknown just to the south in Uruguay.
Furthermore, experts note that very few of them have been discovered in northern parts of Brazil, and only a handful of possible burrows have been found in other South American countries.