Why Megalodon (Definitely) Went Extinct

About 8 million years ago, a small baleen whale swam in the warm coastal waters of Peru. It was only about 3 or 4 meters long, about the size of a beluga whale, and as it filtered out mouthfuls of plankton-rich water, it didn't know that a predator was swimming just below. Like the great white sharks of our times, this predator probably hunted whales from below or from behind, in case its prey was capable of echolocation. It turns out that this small whale, known as Piscobalaena, did not have that ability, but for the hunter the element of surprise was enough. He swam to attack and that was it for Piscobalaena.

We know who the predator was because he left a tooth in the whale's body, which eventually fossilized. It is usually named after its species, Megalodon, and was the largest shark that ever lived. Standing up to 18 meters tall, it was almost three-quarters the size of a modern blue whale. Its teeth were as big as your hand... or bigger. And its jaws were wide enough to swallow you whole. Megalodon lived all over the world, from the Netherlands to New Zealand. And for more than 10 million years, it was at the top of its game as the oceans' top predator... until 2.6 million years ago, when it became

extinct

.

Yes, really, don't let Hollywood convince you otherwise. I know you're smarter than that. Megalodon completely disappeared from the fossil record, just as the Pliocene epoch gave way to the Pleistocene. And there is also evidence of their

extinct

ion in the composition of the marine life we ​​find today, especially in the types and sizes of whales that swim in our modern oceans. So what happened to the largest shark in history? Well, it turns out that while Megalodon may have been the biggest shark to ever swim, he would eventually be defeated by the biggest one. Megalodon was the largest and scariest shark in a family of large and scary sharks.

It belongs to the diverse order of sharks known as Lamniformes, which today includes sand tigers, goblins, foxes and the great white shark. And when Megalodon was first described in 1835, scientists thought its large, serrated, blade-like teeth so closely resembled those of the great white shark that Megalodon was originally placed in the same family. But today, based on features around the base of its enormous teeth, most experts think it probably belonged to a separate family whose members are now extinct, called Otodontidae, also known as megatooth sharks. Now, one of the oldest and smallest of the group of Megateeth that gave rise to Megalodon was a shark known as Otodus obliquus, which lived in the early Eocene, almost 20 million years before Megalodon appeared on the scene.

And some scientists think that Megalodon belonged to this same genus, Otodus, while others assign it to another genus of extinct sharks, called Carcharocles. Either way, Megalodon was the largest of all Megateeth and first appeared in the fossil record about 23 million years ago. So how and why did it get so big? Well, the enormous size of the Megalodon was related to the size of its prey. And both were shaped by forces far greater than themselves. These external forces began in the late Mesozoic, when plate tectonics caused mountains to rise in North America and Asia. The erosion of these growing mountain ranges dumped enormous amounts of nutrient-rich sediment into the oceans, increasing the productivity of nearshore ecosystems.

And as the algae and plants grew, so did the preferred food group: marine mammals. Marine mammals such as whales, dolphins, and seals have fairly high fat contents, making them a nutritious, high-calorie snack for any predator that might catch them. And as marine mammals grew over time, so did sharks. Over the course of about 20 million years, marine mammals and the line of Megatooth sharks that led to Megalodon doubled in size! And Megalodon in particular began to grow rapidly. Fossils of newborn

megalodon

, found in places such as Panama, show that they were between 2 and 3 meters long, half the size of a modern great white shark and about one and a half times the size of their ancestor Otodus obliquus.

And these huge baby sharks grew like weeds. We know this because shark vertebrae show growth rings, just like tree rings. And these rings show that Megalodon babies grew almost twice as fast as Otodus obliquus, reaching their maximum length around 25 years old. So growing over time and then growing faster likely helped Megalodon keep up in the ongoing size race with the marine mammals they hunted. And hunt him he certainly did. Their teeth have been found stuck in the ribs of many unidentified whale species, as well as the tiny Piscobalaena, and even a pinniped the size of a sea lion.

So size was a very useful adaptation for giant sharks, until it wasn't. Because 2.6 million years ago, Megalodon disappeared. And there are a couple of possible reasons for this. On the one hand, 2.6 million years ago marked the beginning of the Pleistocene, when colder temperatures and long periods of glaciation, also known as Ice Ages, began to occur. This temperature change could have directly affected Megalodon or could have impacted its food source. This is because climate change caused a restructuring of how and where whales lived. As the climate changed, more productive environments with more food began to form closer to the poles, so the whales began to spend much more time there and became more migratory.

So maybe the problem for Megalodon was that its prey started moving toward where the water was colder—too cold, perhaps, for Megalodon to follow. For a long time, scientists thought this might have been what happened to the world's largest shark. But in 2016, a group of researchers led by Dr. Catalina Pimiento decided to test that hypothesis. Specifically, they tested the assumption that Megalodon could not live in cold water. Pimiento and her team used a climate forecast model to recreate ocean temperatures during the Pliocene and Miocene, and compared those temperatures to where Megalodon had lived. They found that while the shark preferred water between 12 and 27 degrees Celsius, its fossils were still found in places where the water was as cold as 1 degree.

So Megalodon was probably fine with colder water. Which makes sense, because many large sharks today are mesothermic: they can keep their bodies slightly warmer than the temperature of the surrounding water, which helps them stay active even in colder waters. So if changes in whale movement and habitat weren't the problem, what was? Well, the disappearance of the Megalodon seems to coincide with two great and important changes in the animal kingdom. The first was the appearance of new predators with which Megalodon had to compete. For example, beginning in the mid-Miocene, we find the giant sperm whale with the epic name of Livyatan melvilli, named after none other than the author of Moby Dick!

But unlike modern-day sperm whales that fed by suction, Livyatan had short, powerful jaws. And their teeth were large, strong and designed to bite into flesh. Furthermore, at 17 meters long, Livyatan didn't just eat squid. It was eating other whales. And it was just one of many species of carnivorous whales of the middle Miocene. In the late Miocene, another adversary appears in the fossil record: the oldest ancestor of the great white shark, Carcharodon hubbelli. This shark was a direct competitor to Megalodon, as evidenced by its tooth marks that have been found on fossils of the same species of whale that we knew Megalodon ate.

That is, that little Piscobalaena. Then, a few million years later, in the early Pliocene, the first fossils of the modern white shark, Carcharadon carcharias, appear. Now, in addition to having to compete with newer, more agile sharks like these, some of the Megalodon's most important prey (i.e. whales) were in decline. Towards the end of the Pliocene, whale numbers declined dramatically from about 60 whale species to about 40. Many of these species were filter feeders, eating krill and other organisms, which in turn ate microscopic algae called diatoms. And starting about 3 million years ago, the oceans began to experience a significant drop in diatom diversity.

It's not 100% clear why this happened, but it could be related to changes in ocean circulation that took place when North and South America were finally joined, and water could no longer circulate between the Pacific and the Atlantic. Regardless of the reason, fewer diatoms meant fewer krill, which in turn meant fewer whales. And with less food, Megalodon had to compete even harder with the smaller, faster great white shark. Being bigger is great if it gives you the advantage of having access to a different food group. But when that's no longer the case, it simply means that you are bulkier and need more food to survive.

That's why, 2.6 million years ago, the last Megalodon disappeared from the fossil record. And the absence of the Megalodon may have had a major impact on the world's oceans. Over the past two million years, great white sharks and killer whales have taken on the role of top predators, but these much smaller carnivores couldn't hunt the larger whales that Megalodon could likely eat. For example, we know that modern white sharks frequently eat dolphins half their size, so it is possible that the 18-meter Megalodon was eating whales that measured up to 9 meters, too large for other predators to handle.

And after Megalodon became extinct, the size of the whales skyrocketed. During the Pleistocene, waters became colder and new and improved productivity at the poles meant diatoms recovered. And this newly productive environment, along with the absence of large predators, meant that the whales were able to become twice as large as the largest whales of the Pliocene. This is why the blue whale, the largest animal our planet has ever seen, appeared in the fossil record only recently, less than 2 million years ago. Without 18-meter sharks swimming, the oceans could finally support 25-meter whales. So, Megalodon and its ancestors had a great run.

Over 30 million years, they grew larger so they could feed on larger marine mammals. But when those mammals began to disappear and when competition with great white sharks and other predators became too fierce, Megalodon didn't make the evolutionary cut. But it's worth noting that today's largest great white sharks are about a meter longer than their Miocene ancestors, and they also grow a little faster when young, just as Megalodon did. It took almost 30 million years for megatooth sharks to reach the enormous size of Megalodon, a slow transformation that took place as whales and other marine mammals slowly grew in size.

But today whales are already huge and face very few predators. Which leaves the super shark niche completely open. So it could be that the Great White Shark becomes the Megalodon of the future, and that giant sharks can patrol our oceans once again. Thanks for joining me today and a special thanks to our eontologists, Jake Hart, Jon Ivy, John Davison Ng, and STEVE! If you want to join them in supporting this channel, head over to patreon.com/eons and take your pledge for some cool and nerdy perks. Now, what do you want to learn about? Leave your girl a comment and don't forget to go to youtube.com/eons and subscribe.