The mysterious event 19 million years ago almost wiped out sharks on Earth

Surviving the violent events of Earth’s history, but 19 million years ago, 90% of the sharks on our planet were wiped out in a mysterious event.
Mysterious extinction event 19 million years ago

When the Earth’s temperature rose and the amount of oxygen in the oceans decreased about 252 million years ago, most life on our planet suffered the same tragic fate. It is estimated that this extinction event, also known as the “Great Dying”, killed 70% of species on land and about 96% of species in the oceans. Illustration: Getty However, there are no sharks among them. “They’re the last surviving species,” said Elizabeth Sibert, a paleontologist and identifier of fossils and an oceanographer at Yale University. The next extinction event at the end of the Triassic period or even the meteorite event that wiped out the dinosaurs 66 million years ago could not have caused the shark to become extinct. The shark’s survival or longevity is extraordinary, but the animal was also close to the brink of extinction, a study in the journal Science revealed June 3. The study, led by scientist Sibert, shows that a previously unknown extinction event pushed sharks to the brink of extinction 19 million years ago, leaving just one in ten of the sharks. Sharks in the oceans survive. “Something happened and wiped out 90% of the shark population overnight,” said scientist Sibert. The so-called something is still uncertain but it has caused immense destruction. The meteorite that wiped out the dinosaurs on Earth only caused 30-35% of the shark species to be wiped out while the above event was 2-3 times worse. To find this discovery, oceanographer Sibert and his collaborator Leah Rubin went through a remarkable process. Discover the mystery When a marine species dies, its body will fall to the bottom of the sea and decompose into discrete parts. Small parts, such as their teeth, will gradually accumulate in the sediments under the sea. “The seabed is essentially a grave for all aquatic species,” Sibert said. The sediment samples used in this study were collected from two locations in the Pacific Ocean, one in the north and one in the south, covering a period of 40 million years. However, it was not easy to analyze the small teeth inside each of these specimens. These parts are so small, even smaller than the width of a human hair. Oceanographer Sibert filtered dried sediment samples under a microscope and isolated the tiny bits of shark teeth. After separating them, scientist Rubin will identify and describe the features, as well as classify them. These little bits of teeth can reveal a lot to us. There were about 1,300 small tooth pieces identified in the above study with 85 samples with different shapes. Most of them are from the period before 19 million years and only a few samples belong to the later period. So, the question arises, what happened to the sharks? The tip of the iceberg The small tooth fragments suggest a decline in shark numbers and diversity about 19 million years ago, but the cause behind this event is unknown. “This is really a mystery. Right now we don’t know what happened,” Ms. Sibert said. The key to solving this mystery is to learn about the time when the sharks almost disappeared. This period is called the “Miocene” and is described by the scientist Sibert as the “transition phase” of the Earth. 15 million years before the mysterious shark event occurred, the Earth gradually became an “ice house” as permafrost increased in Antarctica. The oceans at that time were no different from the oceans of today, although we cannot find such species as tuna, swordfish and seabirds. Dolphins and whales had not yet evolved. However, there is not much evidence to find out the cause of the shark eradication. Even the discovery, which took place during a rather unusual time in Earth’s history, is just the tip of the iceberg. “There are many questions that need to be answered,” said researcher Rubin. Did some change in the environment lead to the decline in shark populations? This is difficult to confirm because the oxygen and carbon levels show no anomalies, but scientists can use more data around this time stamp. Did the event happen across the oceans and affect other marine species as well? Ms. Sibert said this is a global event but we still need more data. Also, what about other bodies of water? Can sedimentation in lakes and coastal areas occur other phenomena? How were terrestrial species affected during this time? Are there any chemicals that can tell us about the environment then? Ms. Sibert even thought that an epidemic, such as a virus, could be responsible for the decline in shark populations. Still, for this oceanographer, the extinction event was a remarkable phenomenon. The fact that sharks have existed for more than 400 million years, surviving multiple extinction events leads her to believe that something truly intense happened and that the sharks may be the gateway to understanding major changes. collided with Earth during the early Miocene. “There is a lot of data waiting to be discovered,” said researcher Rubin. The discovery not only shows the unpredictable change of the marine environment, but also shows how difficult it is for species to recover when they are pushed to the brink of extinction. “Biology is trying to tell us something and I think we need to listen,” Sibert said.