The megalodon shark's (Otodus megalodon) extinction may have been caused by the great white shark.

Long before humans walked the earth, the megalodon, which measured up to 60 feet (18 feet) in length, had been prowling the oceans. Scientists estimated that the megalodon may have died off about 2.6 million years ago based on fossils discovered of the shark species. This was around the same time many other marine creatures became extinct as well. 

One recent study published in Astrobiology suggested that a nearby supernova may have caused the extinction of the marine species, including the megalodon over 2 million years ago. However, a new paper has offered another explanation for the reason behind the disappearance of the megalodon, as well as its estimated date of extinction. 

In a research paper published in the journal Peer, scientists found that megalodons may have been alive up until 3.6 million years ago instead of the previously estimated 2.6 million years. They reached this conclusion after re-examining the fossil record of the giant shark species in California and Baja California, Mexico, where many remains of it had been discovered.

The fossils dated between 2.6 million and 3.6 million years ago tended to have issues, so scientists could not get a clear read on their origin. Many of the megalodon fossils seemed to have shifted within the surrounding rock, and this complicated the dating methods the researchers used.

However, if the behemoth really did become extinct 3.6 million years ago, then the megalodon couldn't have been killed off during the mass marine wipeout. Due to this, the researchers offered another explanation as to what exactly caused their extinction: the great white sharks.

The study suggested that the megalodon sharks were "outcompeted" by the smaller, savvier great whites, which arrived in the oceans about 4 million years ago. This was 400,000 years before the megalodon's new extinction date, which means they could have had enough time to spread and force the megalodon to die off.

"We propose that this short overlap (3.6 to 4 million years ago) was sufficient time for great white sharks to spread worldwide and outcompete O. megalodon throughout its range, driving it to extinction," College of Charleston paleontologist Robert Boessenecker, an author of the study, said in a statement.

Boessenecker also explained why scientists may have previously thought the megalodon shark died off 2.6 million years ago. He said this could have been caused by gaps in the fossil record instead of the recently proposed supernova explanation. 

Megalodon The megalodon may have been wiped out by great white sharks. Pictured: One of the world's largest set of shark jaws comprised of about 180 fossil teeth from the prehistoric species, Carcharocles megalodon, which grew to the size of a school bus, is displayed at the Venetian Resort Hotel Casino September 30, 2009 in Las Vegas, Nevada. Auctioneers Bonhams & Butterfields hope the fossil will fetch about USD 900,000-1.2 million when it is auctioned off on October 3 at the Venetian as part of their Natural History auction. Photo: Getty Images/Ethan Miller