Sharks barely survived a mysterious and previously undiscovered catastrophe 19 million years ago that nearly wiped them off the planet. A new paper in Science lays out the unexpected discovery, reports Gizmodo. Researchers were using soil samples from the ocean floor to map shark populations over the eons when they discovered an abrupt falloff in what's known as the early Miocene period. Abrupt is an understatement, actually. Based on observations of shark scales, or denticles, and other evidence, researchers found that the global shark population fell by 90% and the diversity of sharks fell by 70% in the relatively short span of 100,000 years, per National Geographic. In fact, sharks have never recovered their previous numbers or diversity, notes the New York Times.
“The sharks are screaming, 'Something really big happened here,'” lead study author Elizabeth Sibert of Yale University tells the Geographic. “Sharks have a 400-million-year evolutionary history; they’ve been around a long time; they’ve seen a lot. And there’s something that could knock out 90% of them?” What's especially puzzling is that the mass die-off doesn't coincide with any known cataclysm that struck the planet. However, the sediment cores studied suggest that whatever happened was indeed a global event, say paleontologists. By contrast, shark populations declined by a relatively modest 30% during the extinction event that wiped out dinosaurs 66 million years ago. (Meanwhile, the modern shark population has plunged since 1970.)
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