About twenty million years ago a creature evolved that was more fearsome than anything that ever stalked the land or ever would; something that was reputed to have been between fifty and seventy feet in length (with some oversized at one hundred feet), and perhaps weighing in at eighty to one hundred tons. The Megalodon Carcharodon – the dinosaur shark – was the apex predator of apex predators. Not only was it the biggest prehistoric shark that ever lived; it was the largest predatory marine creature in the history of the planet. It vastly outweighed the ancient sea reptiles like Liopleurodon and even the Kronosaurus.

Its hunting grounds were the warm shallows seas of the Cenozoic Era, and its only rivals were bigger Megalodons than itself. Records indicate it last existed a little over one-point-five million years ago, so when early man walked the land, Megalodon swam just off the coast.

Would they have seen each other? Probably. Man was an observant, intelligent species, and Megalodon would have been just as watchful. After all, it had probably developed the same vision as its smaller cousin, the Great White shark – an ability to raise its head above water and use eyes that saw above and below the surface.

The flooded estuaries would have provided plenty of opportunities for the massive hunter. There it could circle, just offshore, waiting patiently for something to wash in, stumble in or venture out into the depths. Because once in its domain, then all belonged to it.

But the world that bred the Megalodon was changing. In fact from the moment it had evolved, the seas were already cooling. Between thirty-five and two million years ago, the continents were still sliding around the Earth’s surface. This titanic movement had significant effects on both land and sea – while the Indian subcontinent crashed into Asia, throwing up the Himalayas, more tectonic impacts pushed up the Rockies and Andes mountains. These colossal alterations to the geography affected worldwide weather patterns. As well, these land-based events changed the ocean’s topography – newly formed mountains changed rainfall patterns, creating rain shadows, and therefore, the water run off redistribution meant shallow inland seas dried up.

Below the mighty Atlantic Ocean, a colossal tear opened up in the seabed, caused by the continental spread that extruded magma from the deep earth and distorted abyssal currents. In addition, this seafloor spreading caused the Gulf Stream to become sluggish, and so reduced the surfacing of cold, nutrient-rich water near North America’s southeast. Such upwellings were critical to supporting the diverse marine life that provided a food source for Megalodon. It is also important to note that the cetotheriids (primitive baleen whales), undoubtedly one of the dinosaur shark’s food sources, became extinct at the same time as Megalodon.

Then the cooling climate began to lock up water in glaciers. This caused the global sea levels to drop by nearly seven hundred feet. Estuaries that were the breeding habitat for the Megalodon vanished.