It’s not every day that we get an explanation for the girth of one of the largest oceanic predators ever to exist. But researchers at Swansea University in Wales have uncovered some telling information about what could have caused this excessive growth among a planet of relatively smaller creatures.

Published in the journal Evolution, scientist Catalina Pimiento aimed to explain why such gigantism exists in sharks and rays. Why can the giant ocean manta ray grow a wingspan of 23 feet? Why can a great white grow to an intimidating 16 feet on average? And, more to the point, why could the megalodon dwarf all these animals with its magnificent size?

The Meg

The megalodon was formidable. While there’s some debate over its actual size, most estimates place it at around 60 feet in length. That’s about the size of two school buses.

What’s even more unsettling is the size of its teeth. Coming in at a staggering 13 centimeters, these things were longer than your standard number two pencil. Their abhorrent length was specifically designed to tear through the largest of oceanic fauna, including everything from fish to whales. In other words, our ancient primate cousins wouldn’t have stood a chance.

Fortunately for those who enjoy swimming in the ocean, the megalodon went extinct around 2 million years ago. But the question remains: how did it get to grow so big?

A Tale of Two Trajectories

The primary way in which an animal of the sea grows in size is to change the way it eats. The megalodon was no exception.

There are approximately two ways that can cause an aquatic creature to change its eating habits. First, they can evolve a way to regulate their internal body temperature, affording them a new and wider territory in which to hunt for food (meaning they no longer would be restricted to the warmer waters, for example). This is called a mesothermic pathway. The second is by becoming a filter-feeder, thriving on ample tiny critters like plankton that exist in the ocean.

Research points to “the Meg” using the mesothermic pathway of controlling its own body temperature, giving it the ability to hunt large game in more of the Earth’s seas.

When Size Becomes a Problem

Unfortunately for the megalodon, this evolutionary trajectory wouldn’t bear well in the future. As ocean temperatures began to cool and ocean life became more stressed, the larger animals it would have otherwise feasted on became more scarce. And this scarcity would prove deadly.

With massive size comes a massive appetite, and if the food that satiates that appetite no longer exists, neither will you. This is why the megalodon is thought to have gone extinct: It couldn’t survive in response to the changing oceanic conditions and dwindling big-prey creatures.

While filter-feeders don’t necessarily face the same dilemma (they feed on something small that exists in great abundance), they have suffered their own problems. In the modern era, we have filled the oceans with mass amount of microscopic plastic. This plastic is perilous for the whale shark and other gigantic filter-feeders that consume it in huge quantities.

It remains to be seen how the oceanic changes we are currently observing across the globe will have an impact of the sea life within its depths.