Huge ancient tunnels built thousands of years ago weren't made by humans

A number of ancient tunnels which were discovered in South America have been found not to come from humans.

You may think nothing of it, but the fact that they're about 1.8 metres in height and about 600 metres in length may grab your attention.

These tunnels have been found in souther Brazil, particularly the Grande do Sul region, originally discovered by Heinrich Theodor Frank, a well respected geology professor.

Appearing massive in size, many would assume that they were created by humans in centuries past, or even naturally through some little-known environmental phenomenon, but neither of these may be the case.

They do hold some historical significance, but according to a theory published in a 2018 study, the cause of these tunnels could be linked to animals.

It was suggested that humans may even have hunted the sloths (Science Advances)

According to the paper, which was published in Science Advances, giant extinct ground sloths may have been responsible for these magnificent tunnels.

They are said to have had huge claw scratches among other distinct features, which don't all feature on any of its descendants.

Speaking to Discover, Frank said: "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."

Another paper said that these sloths were like hamsters 'the size of an elephant' and that they share little with existing sloths today, even growing up to four metres long. It's thought there were nearly 100 different species of sloths in the Americas between 15 million to 10,000 years ago.

The professor said that he's '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'.

Erosion and other processes have been ruled out due to the details and geometry of the tunnels.

It's said that the Megatherium or related genera were herbivores and they existed during the Pleistocene epoch (8,000–10,000 years ago) in South America and with their massive claws, it makes sense that they could build tunnels like this.

It's even believed that different generations could have constructed these tunnels to be used as shelters.

The tunnels were made by pre-historic sloths (Getty Stock Image)

Research shows that humans would have come into contact with the sloths and even hunted the animals as human footprints were discovered to follow sloths in a stalking pattern.

“It is possible that the behaviour was playful, but human interactions with sloths are probably better interpreted in the context of stalking and/or hunting,” specialists claimed.

They added: “Sloths would have been formidable prey. Their strong arms and sharp claws gave them a lethal reach and clear advantage in close-quarter encounters.”

As new evidence is discovered, its believed that our previous understandings of the Ice Age are changing, with this discovery teaching us not just about sloths, but also the human-animal dynamics during this time.