The megalodon first inhabited the oceans of planet Earth around 23 million years ago. They varied in size, but studies suggest that, on average, a female meg could be between 45 and 59 feet long. This range varies widely because scientists must extrapolate the size based on teeth and jaw fragments found in the fossil record. At this point, a full megalodon skeleton has not been found.
Adult megalodons had no predators because of their massive body size. The shark’s main prey was small whales. Megalodons roamed every ocean, although they stayed away from the polar regions where the water would be too cold. The largest predatory shark species alive today is the great white. The largest great white ever recorded was around 36 feet long. It makes it 20 feet shorter than the megalodon.
They outcompeted other predators for about 20 million years and stayed at the top of the food chain for that entire time. Their size, razor-sharp teeth, and speed allowed them to hunt and kill prey with deadly efficiency. So, what caused the Megalodon to go extinct? Why isn’t this incredibly successful killing machine ruling over the oceans today?
Why megalodon went extinct?
Megalodon lived all over the world, from the Netherlands to New Zealand. For over 10 million years, it was at the top of its game as the oceans’ apex predator until 2.6 million years ago, when it went extinct. Megalodon disappeared entirely from the fossil record as the Pliocene epoch gave way to the Pleistocene. There’s also proof of its extinction in the composition of marine life. So, what happened to the largest shark in history?
It turns out that while Megalodon may have been the biggest shark that ever swam, it would eventually be defeated by the greatest. Megalodon was the biggest, scariest shark in a family of enormous, dangerous sharks. It belongs to the diverse order of sharks known as Lamniformes, including sand tigers, goblins, threshers, and the Great White.
When Megalodon was first described in 1835, scientists thought its big, serrated, blade-like teeth looked much like the Great White. That Megalodon was initially placed in the same family. Based on features around the base of its massive teeth, most experts think it was probably in a separate family whose members are now extinct. They are called Otodontidae, also known as the Mega-Toothed Sharks.
One of the oldest and smallest of the group of Megatooths that gave rise to Megalodon was a shark known as Otodus obliquus. They lived in the Early Eocene, nearly 20 million years before Megalodon appeared. Some scientists think Megalodon belonged to this same genus, Otodus. At the same time, others assign it to another genus of extinct sharks called Carcharocles. Either way, Megalodon was the largest of all the Megatooths, first appearing in the fossil record about 23 million years ago.
So, how and why did it get so huge? Megalodon’s massive size was linked to the size of its prey. Both were shaped by forces much bigger than themselves. These external forces began at the end of the Mesozoicinitially placed when plate tectonics caused the uplift of mountains in North America and Asia. The weathering of these growing mountain ranges pumped massive amounts of nutrient-rich sediment into the oceans. That increased the productivity of ecosystems near the shore.
Marine mammals like whales, dolphins, and seals have pretty high-fat contents, making them a nutritious, high-calorie snack for any predator that can catch them. As the marine mammals grew over time, so did the sharks. Over about 20 million years, marine mammals and the line of Megatooth sharks that led to Megalodon doubled in size! Megalodon, in particular, started to grow fast.
Fossils of newborn megalodon are found in places like Panama. It shows they were about 2 to 3 meters long, half the size of a modern great white shark, and about one and a half times as large as their ancestor Otodus obliquus! These massive baby sharks grew like weeds. This is because shark vertebrae show their growth rings, like tree rings. Also, these rings show that Megalodon babies grew almost twice as quickly as Otodus obliquus, reaching their maximum length at around 25 years old.
So, getting bigger over time and faster probably helped Megalodon keep up in the ongoing size race with the marine mammals they hunted. Their teeth have been found stuck in the ribs of many unidentified whale species and the Piscobalaena. The size was a useful adaptation for the giant sharks until it wasn’t. So 2.6 million years ago, Megalodon disappeared. There are a couple of potential reasons for this:
- Survival in the ice-ages.
- Volcanic activity.
- Genetic diversity & biodiversity.
- Saltier low-level ocean.
- Big size, less food.
- Food web competitor.
- Supernova radiation.
Survival in the ice-ages
Earth’s climate began to change between 3 and 5 million years ago. The world began to cool as it entered the epoch known as the Pliocene. As global temperatures dropped, the oceans were affected.
One significant change as temperatures cooled was the sea levels dropping. It happens during ice ages and periods of cooling because the water of the oceans gets trapped in ice and glaciers. This temperature change could have affected Megalodon directly, or it could have impacted its food source. That’s because climate change led to the restructuring how and where whales lived.
More productive environments with more food became closer to the poles as the climate shifted. So whales started to spend more time there and became more migratory. Maybe the problem for Megalodon was that its prey started moving to where the water was colder. Scientists thought this might have been what did to the world’s biggest shark for a long time.
In 2016, a group of researchers led by Dr. Catalina Pimiento decided to test that hypothesis. Specifically, they tested the assumption that Megalodon couldn’t live in cold water. Pimiento and her team used a climate forecasting model to recreate ocean temperatures during the Pliocene and Miocene. By comparing those temperatures to where Megalodon had lived. While the shark preferred water from about 12 to 27 degrees Celsius, its fossils were still found where the water was as cold as 1 degree!
So Megalodon probably was okay with colder water. It makes sense because many large sharks today are mesothermic. They can keep their bodies a little warmer than the surrounding water temperature. It helps them stay active even in colder waters.
Due to volcanic activity
As the water gets converted into its solid form, it is removed from the oceans. It causes the overall sea level to drop. The dropping of the global sea level wouldn’t have been a problem for megalodon if that was the only change that occurred. But when the sea level dropped, new land that had previously been underwater started to form.
During the Pliocene, the Isthmus of Panama began to take shape. The collision of tectonic plates in the area caused volcanic activity. That resulted in the formation of the mountains stretching from North to South America.
This new land that connected the Americas impacted the oceans’ animals. The land that would become Central America had been underwater for millions of years. It means that nothing was blocking marine species from crossing between what would become the Atlantic and Pacific Oceans near the equator.
Genetic diversity and biodiversity
Many species were stuck on the continents once land blocked access between the Americas. Some of the megalodon’s prey might have been separated from them. Ocean currents and the movement of nutrients in the oceans began to shift once the equatorial connection between the oceans was impeded. This would have caused species to migrate to new areas. They would go extinct if they could not adjust to the new environment.
The currents and nutrients flowing between the Americas would have been abruptly halted. Without these nutrients, biodiversity would drop. This change would have a domino effect on all species living throughout the oceans. Nutrients would no longer be where they once were, and entire ecosystems would have vanished. This alone would have caused mass extinctions of aquatic organisms, leaving room for new species to evolve.
Even if this lowering of ocean levels, and the blockage between the oceans, did not directly cause megalodon to vanish. It most likely had an impact on their prey. Since the Megalodon was giant and slow to reproduce, it filled one niche: apex predator. If the environment suddenly changed, the megalodon would unlikely have the genetic diversity to adapt to a new environment with less prey.
Before the change in the environment of the Pliocene, the oceans were filled with large marine animals. Many animals ate krill or small fish like today’s baleen whales. This meant an abundance of prey for the megalodon to hunt.
However, after the climate shift, organisms such as toothless walruses, aquatic sloths, and dwarf baleen whales did not survive in the new environment. Slowly but surely, the megalodon’s variety of food was diminished. This is where the real problem for megalodon came in.
Saltier low-level ocean
Another impact of lowering ocean levels is that the oceans become saltier. As more and more water is trapped in ice and glaciers, the salt-to-water ratio in the ocean changes. The salt does not get trapped in the water, so salt levels remain constant while water levels decrease. It causes an increase in salinity throughout parts of the oceans. The difference in saltiness would have shifted the ocean currents and nutrient cycles evermore. This change in salinity is one of the main reasons for the ocean conveyor belt of today.
These ocean changes would have meant that the megalodon environment that had been so successful for millions of years was different. It is challenging for large specialist predators to adapt to environmental changes. Think about what is happening in the Arctic right now to polar bears. They are highly specialized for the environment they evolved in. But if the ice continues to melt and the global temperature rises, they will go extinct. The polar bear species lack the genetic diversity to succeed in a warmer environment.
Big size, less food
As the environment changed, marine diversity diminished before natural selection. It caused new species to evolve and thrive. Unfortunately, this would have taken thousands and thousands of years that the megalodon did not have. With less biodiversity and animals to eat, all predators in the ocean would need to compete for similar food sources. The prey that megalodon once thrived on would have diminished. They had to compete for a different food source or starve to death.
The disappearance of the Megalodon seems to coincide with two significant, essential changes in the animal kingdom. The first was the appearance of new predators that Megalodon had to compete with. In the Late Miocene, another adversary shows up in the fossil record, the earliest ancestor of the Great White Shark, Carcharodon Hubbell. This shark was a direct competitor with Megalodon, as proven by its tooth marks found in fossils of the same whale species.
A few million years later, the first fossils of the modern great white Carcharodon carcharias appeared in the early Pliocene. In addition to competing with newer, more agile sharks like these, some of Megalodon’s most important prey, namely, whales, declined. Toward the end of the Pliocene, whales dramatically decreased from about 60 to about 40.
Many of these species were filter feeders fed on krill and other organisms, eating microscopic algae called diatoms. Starting around 3 million years ago, the oceans began to experience a severe drop in diatom diversity. It’s not 100% clear why this happened. But it might relate to changes in ocean circulation that took place when North and South America finally came together. Water could no longer circulate between the Pacific and the Atlantic.
Regardless of the reason, fewer diatoms meant fewer krill, which meant fewer whales. Megalodon had to compete even harder with the smaller, faster, great white shark with less food. Being bigger is excellent. It gives the advantage of having access to a different food group. But when it no longer does, it requires more food to survive.
This is why, 2.6 million years ago, the last of the Megalodon disappeared from the fossil record. The absence of the Megalodon may have greatly impacted the world’s oceans. Great white sharks and Orcas have taken over apex predator roles in the past couple of million years. But these much smaller carnivores couldn’t hunt the larger whales that Megalodon would likely eat.
For instance, modern Great Whites frequently eat dolphins half their size. The 18-meter Megalodon ate whales that were as big as 9 meters. After Megalodon went extinct, the size of whales exploded. During the Pleistocene, the waters grew colder. The new, improved productivity at the poles meant diatoms bounced back. That whale became twice as big as the biggest whales of the Pliocene.
This is why the blue whale, the largest animal our planet has ever seen, appeared in the fossil record less than 2 million years ago. Without 18-meter sharks swimming around, the oceans could finally host 25-meter whales. So, Megalodon and its ancestors had a great run.
Over 30 million years, they became larger to eat larger marine mammals. But Megalodon didn’t make the evolutionary cut when those mammals started disappearing. It’s worth noting that today’s biggest Great White Sharks are about a meter longer than their ancestors were in the Miocene. They grow a little faster when they’re young, too, like Megalodon did.
Climate changes most likely contributed to the extinction of the species. Scientists now believe there was one main culprit that drove the nail into the coffin of the megalodon. Around the time the megalodon went extinct, a new apex predator started to appear: the great white shark.
Carcharodon carcharias, or the great white shark, appeared when the megalodon species began to decline. It would seem this new species of shark could outcompete the megalodon. The smaller size of great whites allowed them to catch and eat the smaller prey, which was more abundant after the climate shift.
The ability to eat many species, other than small whales gave the great whites an advantage. Not only did the great white have a wider variety of food it could choose from, but the smaller body size worked in its favor. Since the megalodon had such a massive body, it needed to stay in relatively warm waters to maintain its body temperature.
Sharks are ectotherms meaning that they don’t regulate their internal body temperature. But instead, rely on factors such as sunlight and muscle movement to increase the temperature of their bodies. The smaller bodies of the great white sharks meant they could venture into cooler waters since they had less body mass to keep warm. Their muscles did not need to work as hard as megalodons to maintain their body temperature.
Therefore, they didn’t need as much energy from food as their larger cousins. It was also likely that great whites hunted some of the same prey as megalodon. Perhaps the great whites targeted the young of the species that the megalodon was hunting. The great white sharks were not trying to outcompete and cause the megalodon to disappear.
The great white shark’s success most likely played a role in the extinction of the once-great megalodon. Scientists also think that the evolution of other smaller shark species could have put pressure on the megalodons.
For example, tiger sharks living simultaneously as the megalodon and in similar environments may have contributed to the larger shark’s demise. It has been suggested that great whites and tiger sharks may have fed on megalodon young that had not grown to their full size yet. It caused even fewer numbers of the species to reach maturity.
Some astronomers suggest that a supernova may have contributed to the extinction of the most giant sharks that ever lived. The claim is that a nearby star went supernova, enveloping the Earth in harmful muon radiation. This radiation would have been harmful to many species. But ones that reproduce slowly, like the megalodon, would have been affected much more drastically. It is because of the build-up of mutations and lack of genetic diversity in the species.
Scientists thought Megalodon disappeared, containing high amounts of an iron isotope called iron-60. This isotope could have only come to Earth by way of a supernova. Or the explosion caused by the death of a star. However, the consensus is that the stellar explosion may have been partly responsible for the mass extinction of marine animals at the time.
These factors may have played a role in the extinction of the megalodon. It took nearly 30 million years for the mega-toothed sharks to reach the enormous size of Megalodon. As whales and other marine mammals slowly grew in size, a slow transformation occurred.
But whales today are already giant and face very few predators. It leaves the niche of super-shark wide open. So it might be that the Great White Shark could become the Megalodon of the future. That giant shark might patrol our oceans once again.
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Cappetta, H. (1987). “Mesozoic and Cenozoic Elasmobranchii.” Handbook of Paleoichthyology.
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“A new elusive otodontid shark (Lamniformes: Otodontidae) from the lower Miocene, and comments on the taxonomy of otodontid genera, including the ‘megatoothed’ clade.”
Shimada, Kenshu (2019). “The size of the megatooth shark, Otodus megalodon (Lamniformes: Otodontidae), revisited”.
“Giant ‘megalodon’ shark extinct earlier than previously thought.”
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