Despite what the Discovery Channel claims, the megalodon shark is extinct. But why is this great ship no longer with us?
It's possible that I skipped shark week.
I figure an article about the largest and most famous prehistoric shark, Megalodon, the 15-meter whale killer, will suffice to atone for my transgression. While I've previously discussed Megalodon, I believe I didn't devote enough time to the reasons why Megalodon became extinct. Despite what some dubious Shark Week content claims, we know with certainty that it went extinct near the end of the Pliocene Epoch - approximately 3 million years ago. The paleontological community, on the other hand, is divided over how they became extinct. In this article, I'll go over some theories about Megalodon's extinction and determine which are most plausible.
The First Theory: An Ice Age Puzzle
Something profound was happening in the world when Megalodon became extinct at the end of the Pliocene. Earth began to cool gradually around fifteen million years ago, during the Miocene Epoch. A variety of factors had transformed this cooling process into a full-fledged ice age by the end of the Pliocene. Global temperatures plummeted as glaciers formed across the Northern continents, both on land and at sea.
While it was previously assumed that such a drop in oceanic temperatures would be disastrous for Megalodon, new research suggests that this may not be the case. A March 2022 study looked at Megalodon global size trends and discovered that larger individuals lived at higher latitudes in cooler waters[i]. If this is correct, Megalodon may have followed Bergmann's rule, which states that animals at higher latitudes grow larger than those at lower latitudes to better accommodate the cold.
One thing to keep in mind is that this may have been true during the Miocene Epoch, but not during the Pliocene. Even as global temperatures dropped further, Megalodon may have been unable to cope. However, it appears that Megalodon's extinction would not have been caused solely by climate change.
Theory number two: Where has all the Prey gone?
It would not have been safe to live alongside a 15-meter-long shark. Megalodon ate anything it came across, whether it was smaller prey like seals or larger organisms like whales. Smaller baleen whales appeared to be favourites, with fossil evidence of attacks found in Peru and Venezuela. A whale fossil from the eastern United States even shows signs of healing, indicating that it was bitten in the chest and survived!
Their reliance on large prey, however, may have contributed to their demise. The diversity of large marine animals (mammals, sharks, turtles, and seabirds) plummeted at the end of the Pliocene, with 36% of species becoming extinct before the Pleistocene (2.6 million years ago). Whales experienced a particularly difficult period, with a significant decrease in diversity at the start of the Pliocene. The ones that did survive were mostly the massive species we see today, which could indicate that their size protected them from Megalodon. Megalodon may have been more vulnerable to extinction if their preferred prey was not abundant.
Theory #3: The New Killers in Town
Have you ever had a new neighbour move in and completely ruin your mood? That's what Megalodon might have experienced when a swarm of rambunctious predators appeared on the scene.
The first of these predatory toothed whales were giant odontocetes, which are closely related to the living Sperm Whale. The most famous was Livyatan, a 15-meter predator that appeared around 10 million years ago in the mid-Miocene. Livyatan fossils have been discovered in the same locations as Megalodon, implying that the two likely competed for a tasty morsel of whale. Despite outliving Livyatan, the threat of new killers displacing Megalodon persisted throughout the Miocene and into the Pliocene.
Enter the Carcharodon carcharias, also known as the Great White Shark. Great White sharks, the most famous and recognisable of sharks (for better or worse), first appeared alongside Megalodon during the Late Miocene and quickly provided fierce competition. The enamel of Pliocene Great Whites and Meg's teeth revealed that the two played similar ecological roles. Perhaps more intriguing is the fact that Megalodon's diet changed throughout the Miocene and into the Pliocene, possibly as a result of declining whale populations.
Megalodon's size may have helped the Great Whites outcompete them in a cruel twist of fate. Being large brings with it a slew of issues, the most obvious of which is that you require an abundance of resources, most notably food, to survive. Megalodon may have been forced to eat smaller prey like seals and fish if there were a scarcity of whales. Megalodon would have found it difficult and unsatisfying to hunt quick and manoeuvrable prey.
Megalodon & The Great White Shark. Courtesy of Christina Spence Morgan
The smaller and more agile Great Whites, on the other hand, had no such issues. We've all seen footage of Great Whites breaching the surface in pursuit of a weak seal, demonstrating their abilities as hunters of agile prey. Could a Megalodon hunt in this way? Perhaps, though it's not difficult to imagine its massive frame preventing it from catching faster and more athletic prey. Megalodon's greatest strength may have become its greatest weakness in the world of the Great White, allowing a much more modern killer to take over.
Theory #4: Ice Age Coming: Hide your Kids?
Aside from the issue of freezing temperatures, the Ice Ages presented Megalodon with another challenge. Glacier formation trapped much of the Earth's water at the poles, causing sea levels to plummet. Though this would not have affected adult Megalodon, it would have had a disastrous effect on a much more vulnerable population: their young.
Baby Megalodon tooth.
Megalodon used nursery sites to raise their young, according to fossil sites from around the world. Fossils of Megalodon juveniles ranging in size from 10-meter-long subadults to 2-meter-long infants have been discovered in what were once shallow coastal regions in places such as Panama, Spain, and the Eastern United States. These locations would have provided protection for the young Megs while also providing a feast for smaller fishes.
Unfortunately for the baby Megalodon, large-scale glaciation ended their shallow paradise. Baby Meg's would have had to fend for themselves in the open oceans, where they may have been subject to predation from Great Whites, toothed whales, or worst of all: their parents. The environmental stability provided by sheltered coastal areas would have been replaced by the unpredictability of deeper water currents. Finally, the small Megalodon lost the easy supply of small fish and sharks provided by nurseries, making hunting more difficult.
Livyatan munching on a Megalodon juvenile.
The entire Megalodon population would have been vulnerable if their nurseries had not existed. Another disadvantage of being large is that your species reproduces slowly, which means that any large-scale changes that affect your progeny can have a significant impact on your species' viability. If Megalodon juveniles, which were probably not that common to begin with, were subjected to environmental stress, fewer individuals would survive to adulthood. Repeated over generations, the once abundant Megalodon may have faced extinction.
Bottom line: Why not all of them?
One of the most common misconceptions about extinction is that it is the result of a single event. The extinction of a species is the result of multiple factors acting in concert over thousands, if not millions, of years. The mighty Megalodon was most likely brought down by a combination of factors, including cooling oceans, whale extinctions, new competitors, and disappearing nurseries. With Megalodon gone, predators like Great Whites and Orcas rose to the top of the food chain, and whales grew larger than any animal before them.
Another advantage is that we can swim in the ocean without fear of being eaten by Megalodon...unless you're in a Jason Statham movie. If you ask me, it's a good trade-off...
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