Ancient Underground Tunnels in Brazil Found and It's NOT Man-Made!

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1:00Its walls are etched with deep, mysterious claw marks. But this is just one of many. If you travel to the south of Brazil, you'll stumble upon over 1,500 similar caves, ranging from modest tiny burrows to massive passageways. These are not your average spooky, bad-filled caverns. They're what researchers call paleo burrows, also known as ancient underground structures dug by creatures so colossal. They make modern elephants look small. Whatever creature dug those tunnels displaced 800 elephants worth of dirt. I know, I know, it still looks like a normal cave, but experts noticed this one was special because the walls were too neat and rounded. And the floor was too smooth. Besides, no water or erosion leaves such signs of serious digging power. These Brazilian caves are the largest geological records of animal activity on the planet.

2:00It's like stumbling into a prehistoric house made by creatures the size of cars. To unlock this mystery, researchers analyzed the scratch marks on the walls and realized they had probably been made by giant ground slots, a species called Valjopees, which could weigh nearly 9,000 pounds and eat your average annual menu in about three days. Despite being huge, these animals were not earthbenders. They had to work in groups if they wanted to dig such long tunnels. This is why scientists believe many slots share the same tunnel and dug it together. Even some giant armadillos may have helped with the digging. After all, they were ridiculously skilled excavators and lived there too. Okay, but why would a giant sloth or armadillo need a 2,000-foot-long underground layer? Great question. This episode is brought to you by Peloton.

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4:00Especially since the tunnels were big enough for a saber-toothed tiger to crawl in, for example. So unless they installed prehistoric security systems, this theory has holes, haha, pun intended. The best bet is probably climate. Back then, everything was drier and colder, and some species of giant sloths were living their best lives back when Earth was transitioning between cold and warmer periods. Their big bodies usually protected these animals from temperature changes, but drastic fluctuations probably made them hide in order to survive. Besides, just like modern sloths, giant sloths probably had a hard time maintaining their body temperature, and going underground for a while is a great way to protect your babies and save some energy. After all, the bigger you are, the more energy you spend. Some scientists believe these tunnels might have had rotating tenets. One sloth moves in, digs a bit, leaves some scratch marks, moves out.

5:03And sometime later, another one crashes there and adds its own decor touches. A hostel for ancient megafauna. All evidence points to a more time-share situation than a prehistoric private property. After all, these creatures weren't exactly social butterflies. Most sloths and armadillos usually keep things strictly one-on-one, just mom and baby. Yeah, dad slots stuck around only for the good part. But you probably noticed one tiny detail here. These guys are not around anymore. They went extinct 11,000 years ago, right around the time humans started to get popular on Earth, when another ice age was ending. In fact, 80% of all mammals that were heavier than two pounds disappeared then. The first culprit is, of course, the usual suspect, humans. Around 10,000 years ago, a wave of skilled hunters using distinctive tools like spear points spread across North America.

6:04The theory goes that American animals weren't used to this new predator, making them easy targets. Once the big plant eaters started vanishing, the big meat eaters followed. They didn't have enough food to survive, and it wasn't just excessive hunting that caused some damage. Early humans may have also harmed ecosystems in ways that made survival harder for large species. But wait, there's another suspect. Climate change. Around the same time, Earth's climate got a major shake-up. The climate was going from super cold to only slightly cold. Just so you know, Earth's temperature was about 46 degrees Fahrenheit, making seasons change and plants perish. And if plants are no longer around, big animals that eat them, like our friends' giant slots, have less nutrition, making them even more vulnerable. Many scientists now think that both human impact and climate change played a role, just in different ways, depending on the region.

7:05In some places, humans may have tipped the balance. In others, nature itself did the job. Either way, it was a perfect storm that ended the age of giants. Turns out, being huge isn't always a plus. Giant animals tend to live longer and reproduce slowly, which makes them sitting ducks when disaster strikes. Besides, it takes a long time for these guys to bounce back. After Dino's disappeared, for example, it took 15 million years for new mega mammals to stop onto the scene. The last major extinction happened around 12- You know you need fiber for a healthy gut, but do you actually know how to get it? Quakers have been serving up fiber since 1877, with over 100 great tasting good source of fiber options to choose from. Whether you like old-fashioned oats, instant oatmeal, granola, or oatmeal squares, Quaker makes it delicious. Mmm, so good. Get your fiber with Quaker. Shop Quaker's good source of fiber products at a store near you.

8:09Thousand years ago, not really enough time for brand new massive beasts to evolve. Today's biggest ground animals, like elephants, rhinos, and bison, aren't newcomers. They're actually the tough survivors of that ancient chaos. And, well, at least we still live alongside the blue whale, the biggest mammal ever. But why did some prehistoric animals get so gigantic in the first place? Well, being big has some perks, in spite of all the extinction thing. It keeps you safe from predators and helps you win the fight for food. If plant eaters bulked up, predators had to level up too, just to keep up. And the environment plays a big role. You see, cold-blooded animals might grow bigger in hot places to stay cool, and warm-blooded giants thrive in cold places to stay warm. One paleontologist even suggested that some dino-sized vegetarians needed those massive bellies, just to digest the tough, woody plants of their time, as if they had a salad bar inside their bodies.

9:17There's also the thing with oxygen. Back then, Earth's atmosphere had way more of it. That's a big deal, especially for creatures with less efficient breathing systems, like insects. Higher oxygen levels meant their bodies could handle more growth and more activity, kind of like nature's turbo mode. We also have to discuss bones, specifically the lighter ones. Many huge dinosaurs had airsacks built into their skeletons, just like modern birds. This made their bones strong but not ridiculously heavy, meaning they could grow super tall or long without collapsing under their own weight. Those airsacks also helped with cooling down, which is super important when you're basically a walking oven of muscle. On the flip side, modern mammals are limited by gravity and biology. Bigger bodies need stronger hearts, lungs, and blood pressure just to keep functioning, and land doesn't offer much support. This also explains why whales got even bigger than dinosaurs.

10:20The ocean acts like a natural support system, which pretty much means that buoyancy helps hold up all that mass, so blue whales can hit a jaw-dropping 330,000 pounds without turning into pancakes. On land, that kind of size would be a serious health hazard. So ancient giants weren't just freaks of nature. They were the result of the right mix of air, food, physics, and environment working together in just the right way. The whole extinction event surely is a bummer for giant sloths that worked as gigantic engineers of nature, but it surely prevented us from sharing the planet with insects the size of crows, like some types of griffin flies or millipedes reaching almost six feet in length. Yikes! Now, if you'll excuse me, I'm going to appreciate modern sloths, slow, small, and thankfully incapable of terraforming the landscape, and giving me insect-related panic attacks.

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