Human-Sized Rat Fossils Found in South America

Human-Sized Rat Fossils Found in South America

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We’re always on the lookout for cryptid sightings. From the skunk apes of Florida to the mothmen of Chicago, we’re on the case. Today, we’re looking at the human-sized rat fossils that were discovered on a dig in South America. What were these creatures–and why were they so monstrously huge?

Paleontologists Find Fossilized Skulls of Giant Rats

Paleontologists working in Brazil discovered a pair of massive rat skulls earlier this year. They quickly determined that the fossilized skulls belonged to a human-sized rat creature that would have measured about five feet long and weighed 180lbs.

In other words, this prehistoric creature was a Rodent of Unusual Size.

Thankfully, you don’t have to worry about meeting a human-sized rat in person. These beasts lived 10 million years ago. They are nothing but fossils now.

Really, Really Dumb

Even though the skulls belonged to monstrously large creatures, it turns out they weren’t using them to store equally large brains. Scientists use what’s known as the “encephalization quotient” to compare the size of an animal’s skull to its brain. While bigger brains don’t automatically equate to greater intelligence, the EQ can give us a good idea of how smart different creatures can be.


For example, humans have an EQ of about 6, while normal rats have an EQ around 1. Despite its big ol’ noggin, the estimated EQ of the giant rats found in South America is about .3. In fact, the 200lb creature had a brain that weighed about as much as a Wendy’s cheeseburger.

Scientists believe that the mega-rat didn’t need a big brain because it had few natural predators. However, its low EQ also meant that it ended up going extinct while its smaller, smarter cousins evolved and thrived.

Related to the Capybara?

The internet loves capybaras, the world’s largest rodents. They’re friendly, cheerful, and love to swim. It seems likely that these funny, barrel-shaped creatures are even kept as pets.

According to paleontologist José D. Ferreira, the giant rats belonged to the same group as capybaras:

Neoepiblema acreensis is one of the largest rodents that inhabited South America. N. acreensis belonged to a diverse group of rodents known as caviomorphs that derived from African forms that rafted to the continent around 50 million years ago. Today’s caviomorphs include the capybaras, porcupines, guinea pigs and chinchillas, among several others.”

The Age of Megafauna

During the Pleistocene era, huge animals roamed the earth. These megafauna included the cave bear and cave lion, the megalodon, and of course the woolly mammoth. My personal favorite is the megatherium, an elephant-sized land sloth with massive claws that could weigh up to 9000 pounds. They towered over almost every other creature on the planet other than the paraceratherium.

Sadly, these creatures almost all died out before the end of the last ice age. Some of them were hunted by prehistoric humans, while others succumbed to habitat loss. It’s unlikely that we’ll find a colony of human-sized rats living in the South American jungle. But the fossil evidence doesn’t lie: these creatures existed, and they were very big and very dumb.