Massive Die-Off Discovered by Accident: A Shark Mystery Millions of Years in the Making

A new study has turned up a massive die-off of sharks roughly 19 million years ago.

The biggest shark attack in history did not involve humans.

A new study by Earth scientists from Yale and the College of the Atlantic has turned up a massive die-off of sharks roughly 19 million years ago. It came at a period in history when there were more than 10 times more sharks patrolling the world’s oceans than there are today.

For now, researchers don’t know the cause of the shark die-off.

“We happened upon this extinction almost by accident,” said Elizabeth Sibert, a Hutchinson postdoctoral associate in Yale’s Department of Earth and Planetary Sciences and the Yale Institute for Biospheric Studies. She is lead author of the new study, which appears in the journal Science.

“I study microfossil fish teeth and shark scales in deep-sea sediments, and we decided to generate an 85-million-year-long record of fish and shark abundance, just to get a sense of what the normal variability of that population looked like in the long term,” Sibert said. “What we found, though, was this sudden drop-off in shark abundance around 19 million years ago, and we knew we had to investigate further.”

How big was the drop-off? Sibert said more than 70% of the world’s sharks died off — with an even higher death toll for sharks in the open ocean, rather than coastal waters. It was twice the level of extinction that sharks experienced during the Cretaceous-Paleogene mass extinction event 66 million years ago that wiped out three-quarters of the plant and animal species on Earth.

Adding to the mystery is the fact that there is no known climate calamity or ecosystem disruption that occurred at the time of the steep drop in shark populations. “This interval isn’t known for any major changes in Earth’s history,” said Sibert, “yet it completely transformed the nature of what it means to be a predator living in the open ocean.”

Co-author Leah Rubin, an incoming doctoral student at the State University of New York College of Environmental Science and Forestry, was a student at the College of the Atlantic at the time of the research.

“The current state of declining shark populations is certainly cause for concern and this paper helps put these declines in the context of shark populations through the last 40 million years,” Rubin said. “This context is a vital first step in understanding what repercussions may follow dramatic declines in these top marine predators in modern times.”

The researchers noted that past discoveries of extinction events have led to waves of new research to learn the origins of the die-off and whether it signaled a larger, previously unknown, perturbance in global ecosystems.

For example, further research might confirm whether the shark-off caused remaining shark populations to change their habitat preferences to avoid the open ocean, Sibert and Rubin said. Additional research might also help to explain why shark populations did not rebound after the die-off 19 million years ago.

“This work could tip-off a race to understand this time period and its implications for not only the rise of modern ecosystems, but the causes of major collapses in shark diversity,” said Pincelli Hull, an assistant professor of Earth and planetary science at Yale, who was not part of the study. “It represents a major change in ocean ecosystems at a time that was previously thought to be unremarkable.”

References:

“An early Miocene extinction in pelagic sharks” by Elizabeth C. Sibert and Leah D. Rubin, 3 June 2021, Science.
DOI: 10.1126/science.aaz3549

 “When sharks nearly disappeared: A previously unidentified extinction event in the open ocean decimated pelagic sharks” by Catalina Pimiento and Nicholas D. Pyenson, 3 June 2021, Science.
DOI: 10.1126/science.abj2088

Extinction EventOceanographyPaleontologyPopularSharksYale University
Comments ( 16 )
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  • Anonymous

    Chaos theory might explain the sudden die off of the sharks. Chaos theory has its origins in biology after all.

    • Eric Shoes

      You obviously have no idea what “chaos theory” is.

    • Derek

      This is a site for adults and serious postings. Please – go away.

  • Codex

    So if I was just using the data that has been found about sharks in the last 10 years. Sharks use earths magnetics waves as a form of gps, army ants use sent trails to tell others where to go/follow. If army ants get lost they just move in circles, creating a death ball (bunch of dead ants in a ball that died from exhaustion or starvation). I would suspect that a large electromagnetic event (solar flare) or polarity of the planet was impacted thus creating a similar issue for the sharks migratory patterns, thus leading to starvation. In Army ants case, they sometimes are able to discern following the previous path doesn’t work and followers of the explorer ant, thus saves the others.

  • Ben

    Isn’t that about the same time dolphins and orcas were entering the ocean?

    Cause, meet effect. I think you’ll have lots to talk about.

  • Karl

    19 million years ago? That is almost halfway to the time when that asteroid hit and wiped out all the higher life on Earth then, leaving behind shrews and little birds and snakes etc.. I mean that is a long time ago. But second, we don’t know what happened? Wow.

    • Derek

      Nowhere near “half” – try one-third and take a remedial mathematics course.

  • Oger

    What if C A T really spelled dog?

  • Matt

    Hello woke peoples. Why does our history have to be such a mystery we all could have learned and done Soo much more, Soo much more. We have come this far. Only to have come this far?

  • BADKING

    Admittedly I scanned the Article,
    It didn’t really offer any information at all.
    No mention of what area of the planet, No mention of what layer how deep or process of acquisition of material studied, or specifically what species of sharks? Theres no description of what was found, sharks are 90% cartilage so one would assume just jaws & teeth were happened upon.
    If he or she were applying for grant money to continue a study Id decline the proposal sounds really suspicious. Def click bait

    • Derek

      Please grow up.

  • Natoshia

    I agree with a mix of Codex and Ben’s theories… maybe they are one in the same, and the disruption of electromagnetic fields lead to the creations of orcas and dolphins who use a type of sonar instead…

  • Bob

    66 million yrs ago huh? Try about 6,000 and change ya knuckleheads. thx Peter North

    • Derek

      Speed kills, Bob.

  • Cody Munro

    Im not a scientist or college educated but I believe the earth has a way of cleaning house and restoring balance when things are tipped one way to far for to long.There could possibly just been to many sharks in the ocean at this time and mother nature just did what was necessary?

  • Ryan Napolitano

    Completely off topic, but am I the only one who sees the cover pic and thinks of Alec Baldwin in Beetlejuice?