A Blue View: Tracking Down the Great White's Ancestors

The great white shark’s origins were a point of contention among shark experts for over a century—that is, until an unusually well-preserved prehistoric shark specimen unlocked some of the species’ evolutionary history in 2009.

Published August 04, 2015


Image via Wikicommons.

Prior to this discovery, many scientists had adopted the popular theory that the great white evolved from the 50-foot, 50-ton megalodon (Carcharocles megalodon). It was easy to see the resemblance: The two massive apex predators shared similar tooth structure, with saw-like edges on their teeth. The great white could have been a miniature megalodon, though its 2.5-inch-long teeth pale in comparison to its prehistoric predecessor’s 6- to 7-inch long chompers.

As it turns out, this theory was founded on relatively superficial similarities. A cartilage skeleton of megalodon has never been found, leaving researchers with only teeth to compare it to the great white. The tide shifted in 2009 with the analysis of a new, 5-million-year-old shark fossil that was surprisingly intact—complete with jaws full of 222 teeth, as well as 45 beautifully preserved vertebrae.

The new species, Carcharodon hubbeli, quickly replaced the megalodon as the likely ancestor of the great white shark. Since its teeth were still located in the proper positions of the jaw, rather than being excavated in a general geographic area, scientists were able to analyze them in a way they never could with megalodon.

Carcharodon hubbeli’s pearly whites shared the same saw-like shape as megalodon and the great white, but weren’t quite as sharp. Instead, they resembled a combination of the sharp, jagged teeth seen in today’s great white shark and the smooth teeth found in an extinct ancestor of the mako shark (Carcharodon hastalis).

Advanced computer-assisted imaging and measurement methods furthered this discovery’s impact by uncovering the similarities and differences among the great white, megalodon and extinct mako teeth. Results showed that the extinct mako and great white teeth and roots were similar in shape, differing greatly from that of the megalodon.

Finally, the new fossil shark was estimated to live 6.5 million years ago, contributing to the theory that it may have been an intermediate species between the mako shark ancestor and the great white. Thanks to this relatively recent research, the great white is now widely believed to have descended from a more moderate-size, smooth-toothed relative of mako sharks.

Episode Transcript

This summer, as we mark the 40th anniversary of the movie “Jaws,” all things shark continue to fascinate us. We're enthralled by the superb acrobatics of “air jaws,” the great white sharks of South Africa; amazed by the general grace of the school bus-sized whale shark; and intrigued by the bizarre cookiecutter shark, which latches onto prey 100 times its size to cut out a chocolate chip cookie-sized chunk from its flank. Yuck!

What is it about this family of cartilaginous animals, whose ancestors predated even the dinosaurs, that so captivates our attention? Fear? Awe? Fascination? It’s perhaps all of these things, for sharks remind us how much we still don’t know about the world around us.

What we do know is that there are over 400 shark species, and they inhabit every ocean. They are a biological success story, having survived—virtually unchanged—numerous terrestrial mass extinctions in the 420 million years of their existence. That’s 100 times longer than even our earliest hominid ancestors. Their very presence is, in the words of ocean scientist Sylvia Earle, “the best indicator of a healthy ocean.”

And they are tremendously diverse. The biggest fish that ever lived—the whale shark—weighs in at 20 tons, yet it gets all its protein from tiny plankton, which it sucks up through massive gill rakers as it plies the ocean’s surface. Its carnivorous ancestor, megalodon, was almost three times larger than today’s great white shark, and its fist-sized teeth attest to its prodigious appetite.

The shortfin mako—the fastest of all sharks—is capable of speedy bursts of 20 miles per hour, and can leap from the water in hot pursuit of fast-moving prey like swordfish and tuna. This apex predator, nicknamed “the wolf of the sea,” is described by the Florida Museum of Natural History as "likely to fall prey only to one species: humans.”

The smallest is the dwarf lantern shark, which would fit in the palm of your hand—if you could find one, which you might if you could only figure out a way to stay in the cold depths of the Southern Ocean for a while. There, at around 1,400 feet deep, lantern sharks light up the twilight waters with bioluminescent photophores like lightning bugs, perhaps luring in prey and warding off predators with their ghostly light.

New shark species continue to appear. Recently, the second of only two pocket sharks ever found made headlines when a 5-inch specimen was discovered in the Gulf of Mexico. So called for the distinctive pocket above its pectoral fin, this elusive elasmobranch still keeps the secret of its origins and the purpose of its pocket. Stay tuned!

On this day I invite you to join me in saluting the world’s many species of sharks and rays, for whom we have cause for both deep respect and great concern. They have plied the seas longer than nearly any other class of animals, and it now falls to us to ensure they will continue their success story for many millennia to come.

To learn about prehistoric sharks like megalodon and the amazing evolution that led to today’s great white shark, please visit aqua.org/ablueview.

A Blue View is produced by the National Aquarium for WYPR. For the National Aquarium, I’m John Racanelli.

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