About 19 million years ago, roughly 90% of the world’s open-ocean sharks died off, and scientists don’t know why.
The recent discovery left researchers stunned, unable to explain the immense loss or the reason behind the deaths of one of the ocean’s most powerful predators. It began when scientist Elizabeth Sibert and her team were trying to learn more about the fish and shark abundance over the last 80 million years, according to a study released on June 3. “We stumbled into this thing completely by accident because what we saw was everything was pretty stable until about 20 million years when sharks dropped off in abundance by over 90%,” Sibert, an oceanographer and paleontologist at Yale University, told CNN. “We found that sharks were doing incredibly well in the open ocean until this one moment in time when they virtually disappeared. We had no idea because no one had ever looked.”
At the time, there were 10 times more sharks swimming throughout the world’s oceans than we see today. The loss was also double the number of sharks that went extinct during the Cretaceous-Paleogene mass extinction 66 million years ago “that wiped out three-quarters of the plant and animal species on Earth,” according to the study’s news release. “We really, truly don’t know anything,” Sibert said. “This particular interval in Earth’s history isn’t all that well preserved in the deep sea sediments we look at. It’s hard to find suitable locations to do additional studies.” Sibert and her team have few theories. Since sharks are intimately tied to the environment they live in, it is likely there was an intense environmental change that wiped out millions of the species. It is unlikely the loss can be attributed to another predator unless it is one that has no existing fossil record.