A treasure map, an ancient jaw, an old scientific hunch. These might be the ingredients to solving a century-long dispute about the origins of the great white shark.
For years, researchers have been divided on this topic. Some argued that the great white descended from the broad-toothed mako, while others maintained that it was clearly related to the megatooth. Now, paleontologist Dana Ehret has proposed a new species that makes a powerful link between the broad-toothed makos and the great white. “The idea has been around for a while, but we haven’t had the specimens to show it,” says Ehret.
Ehret’s investigation began when fellow paleontologist Gordon Hubbell donated his extensive private fossil collection to the University of Florida. Among Hubbell’s boxes was a rare find: the intact jaw of an ancient, big-toothed shark.
Shark skeletons are made of cartilage, a material that doesn’t hold up well over time. That means that teeth, which are bony, become vital to the study of shark history. But teeth are usually found only one or two at a time, which makes definitive identification harder. “Being able to identify a shark from its teeth is a little bit like trying to identify a flower from its petals. You need the whole dentition to be absolutely certain,” explains British paleontologist David Ward.
Originally, researchers associated the great white shark with the megatooth because both sharks have teeth with serrated edges. However, the serrations on the megatooth fossils are much finer, and their teeth have a unique V-shaped band near the root.
Meanwhile, the mako’s teeth are more similar to the great white’s, but they lack any serrations at all. To prove that the great white was descended from the mako, scientists needed to find an intermediate species whose teeth fell in-between. Hubbell’s fossil looked like it could be that link.
However, Ehret needed to confirm that this new species lived long enough ago to be the missing connection. He traveled to Peru with a team of paleontologists to find the spot where Hubbell had first discovered the jaw years earlier.
The Peruvian desert is a rich area for fossil hunters, with everything from ancient seashells to baleen whales. Knowing the exact site where the jaw had come from was important, because the surrounding dirt and other fossils would provide vital clues to when the shark had lived.
Using an old map and a photo of the original dig site, the group searched for a spot where the horizon line matched up with the horizon in the photo. On the second day, they found it.
“Without knowing exactly where the shark mouth came from, pinning this story to actual numbered ages would have been a little difficult,” explains researcher Thomas Devries, who took part in the expedition. “The whole trip cost was spent to find this fossil.”
Using isotopic analysis—a chemistry technique that reveals the age of different elements within—the researchers estimated the age of ancient mollusks found alongside the jaw. Results showed that the shark had lived six million years ago, right in-between the mako shark and the great white.
The new shark species, named Carcharadon hubbelli in honor of Hubbell’s discovery of the jaw, may finally settle an old hunch about the great white’s origins. “What Dana did, in the innocence of youth, is wade straight in and say the obvious,” says Ward. “He has tidied up a bit of shark taxonomy that no one else actually did.”
Still, some scientists remain skeptical. Michigan State University’s Michael Gottfried cautions that our understanding of the shark evolutionary tree depends a lot on what fossils we happen to be looking at.
“We typically find one tooth at a time, so it’s difficult to get a fully realized idea of the total range of variation of the teeth,” he says. “What’s needed is a much broader scale of analysis that pulls in the wider array of data that’s out there.”