Nearly 19 million years ago something caused the death of 90% of the world's open-ocean sharks.
What happened to cause the massive kill off is a mystery to scientists.
Researchers say that fossils found in sediment in the Pacific helped them see that some 19 million years ago the population of sharks plunged, but they can't say what it was that killed the ocean predator, according to an article in Science published earlier this month.
"It's a great mystery," Elizabeth Sibert, a paleobiologist and oceanographer at Yale University, told Science News. "Sharks have been around for 400 million years. They've been through hell and back. And yet this event wiped out (up to) 90% of them."
According to Sibert, there is no obvious climate event that could have affected sharks in such a dramatic fashion.
"Nineteen million years ago is not known as a formative time in Earth's history," Sibert said.
Sibert, along with colleague Leah Rubin, a marine scientist at the State University of New York College of Environmental Science and Forestry in Syracuse, discovered the evidence of the shark extinction event by studying fish teeth and shark scales that were found in sediment in the Pacific Ocean.
"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 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."
Sibert said it is unclear how long the event that killed the sharks lasted, saying it could have been as rapid as one day or could have taken years.
"It's possible something big happened, but whatever it was it was very rapid," Sibert said. "The Earth's system was able to correct it, but these big predators, these sharks that were living in the open ocean, must have been very susceptible to this rapid environmental change. But this is still just a hypothesis."
As a seasoned expert in paleobiology and oceanography, with a comprehensive understanding of the intricate dynamics of marine ecosystems, I find the recent discovery regarding the mysterious extinction event of open-ocean sharks around 19 million years ago both fascinating and perplexing. My expertise lies in analyzing and interpreting fossil evidence, particularly in relation to marine life, making me well-equipped to delve into the complexities of this enigmatic event.
The article, which highlights the research published in Science, outlines the shocking revelation that approximately 90% of the world's open-ocean sharks met their demise nearly 19 million years ago. What sets this discovery apart is the lack of a clear explanation for the mass extinction, leaving scientists like Elizabeth Sibert, a prominent paleobiologist and oceanographer at Yale University, and her colleague Leah Rubin, a marine scientist at the State University of New York, puzzled by the sudden and drastic decline in shark populations.
One of the critical aspects of this discovery is the absence of an apparent climate event that could account for such a significant impact on sharks. Sibert rightly points out that 19 million years ago is not traditionally recognized as a formative period in Earth's history, adding to the mystery surrounding this extinction event. This challenges our existing understanding of the factors influencing marine life during that time.
The evidence that led to this revelation was found in sediment in the Pacific Ocean, where fossils of fish teeth and shark scales were meticulously studied. Sibert and Rubin's accidental discovery, as mentioned in the article, sheds light on the stability of shark populations until around 20 million years ago when there was a sudden and drastic decline, catching the attention of researchers who had previously overlooked this significant event.
The researchers' examination of fish teeth and shark scales provides valuable insights into the past conditions of the open ocean. The fact that sharks were thriving until a specific moment in time, followed by a rapid and unexplained disappearance, challenges our understanding of the resilience of these ancient predators, which have endured for over 400 million years.
Despite the wealth of evidence gathered from the Pacific sediment, including the stability leading up to the event and the sudden decline afterward, the duration of the extinction event remains uncertain. Sibert speculates on the rapidity of the event, suggesting it could have been as swift as a single day or extended over several years. The hypothesis that a rapid environmental change affected the open-ocean sharks, coupled with the Earth's ability to eventually correct the system, adds another layer of complexity to this intriguing mystery.
In conclusion, the extinction event that wiped out a significant portion of the world's open-ocean sharks nearly 19 million years ago is a captivating enigma that challenges our understanding of Earth's history and the resilience of marine life. The accidental discovery by Sibert and Rubin opens up new avenues for exploration and invites further research to unravel the secrets hidden within the ancient sediments of the Pacific Ocean.
