A Sea without Sharks?

By Jim Brace-Thompson

For hundreds of millions of years, sharks and oceans have gone together like salt and pepper, ebony and ivory, bread and butter, bananas and monkeys, or whatever your favorite analogy for two things that, well, just seem to belong together. So imagine: A sea without sharks?

Apparently, it nearly happened back in the early Miocene Epoch!

Per a research report by Elizabeth C. Sibert (Harvard University) and Leah D. Rubin (College of the Atlantic) in the June 4, 2021 issue of the journal Science, populations of pelagic sharks were decimated by an extinction event that has only now been fully recorded, recognized and appreciated thanks to detailed studies Sibert and Rubin have made of deep-sea sediments.

The pelagic zone is defined as the so-called “open ocean.” Sibert and Rubin estimate that 19 million years ago sharks in the open ocean declined in morphological diversity by 70 percent and in overall population abundance by as much as 90 percent! And it all seems to have happened within less than 100,000 years, or a mere blink-of-the eye, geologically speaking. Following this extinction event, sharks never recovered their prior diversity.

Per the report, the proximate cause of the extinction event is something of a mystery but the event itself indicates “the early Miocene was a period of rapid, transformative change for open-ocean ecosystems.”