Megalodon: The Monster Shark’s Dead

Megalodon is dead. This shouldn’t come as a shock. The fossil record is clear that after about 14 million years of feasting on marine mammals, the 50-foot-long, “mega-toothed” shark exited the evolutionary stage by two and a half million years ago.

But the monstrous shark is too good to let go. If a great white shark is scary, the supersized version is even more thrilling, and despite our ancient fear of sleek, hungry shapes slicing through the water, people really want Carcharocles megalodon to still be alive somewhere in the deep. Peter Benchley toyed with the idea that the great shark might still be out there in JAWS, cryptozoological lore has often spoken of massive sharks, and nature documentaries traditionally state that the prehistoric leviathan is extinct… maybe. Unlike the shark itself, the legend of living megalodon just won’t die.

Discovery gave audiences what they wanted. Megalodon had taken up recurring roles in many of their Shark Week programs – including a life-sized “Sharkzilla” solely employed smash stuff – and last year the channel dipped deep into their burbling chum bucket to dredge up Megalodon: The Monster Shark Lives. The program was a shark version of Forrest Gump, with fabricated evidence showing the shark popping up through human history, and had just enough polish to convince many viewers that megalodon is still chomping whales and snaffling up the occasional boat.

The fauxumentary was popular enough that Discovery hastily threw together a sequel for this year’s Shark Week carrying the unimaginative title Megalodon: The New Evidence. To quote Marty McFly, “The shark still looks fake.” But I don’t want to simply despair over Discovery’s penchant for trading in on their reputation to peddle attention-grabbing sludge. Bit by bit, we’re getting a closer look at megalodon. Paleontologists are continuing to investigate the life of prehistory’s most famous shark, including some new, real evidence about when the celebrity selachian slipped into extinction.

University of Alabama paleontologist Dana Ehret is one of the researchers who has been poring over the remains of megalodon. He’s helped figure out that the huge carnivore was actually a relatively distant cousin of today’s great white shark that should be properly called Carcharocles megalodon, and he’s also worked on a trove of teeth that preserve a nearshore nursery for the infants of this imposing species. He’s among the scientists who are showing that megalodon doesn’t need the reality TV treatment to inspire awe.

Most often, C. megalodon is portrayed as a pumped-up great white. That’s because of shared habits. Megalodon were “large macropredatory sharks that ate marine mammals,” Ehret says, “and white sharks are a good model for that.” The teeth of the extinct shark are distinct from those of any living shark, and the fact that the megatooth lineage split from the great white lineage over 66 million years ago indicates that the megatooth sharks probably had other anatomical differences, but, at least in terms of lifestyle, a huge white shark “is really the closest thing we can imagine megalodon to be,” Ehret says.

That megalodon preferred meals of whale and seal fat comes from more than analogy. “We find lots of broken or partial whale ribs that have nice scrape marks or drag marks across them,” Ehret says, adding “I’ve actually taken meg teeth [to compare to the bite marks] and the serrations match up perfectly.” Megalodon may not have been above cannibalism, either. “I’ve seen a tooth with the same scrapes running down the surface of the tooth,” Ehret says, although he cautions that this could be a sign of the tooth sliding past another while being shed rather than one shark biting another in the mouth.

Even if they weren’t regularly eaten by their own kind, though, megalodon had to cope with competition. Their fossils are found all around the world, Ehret says, in the remnants of coastal environments patrolled by sand tiger sharks, lemon sharks, and other species, including ancient great whites that grew to be 30 feet long. Even at six feet long – as estimate Ehret calculated from a well-preserved vertebra – a newborn megalodon had to cope with similarly-sized neighbors who were chasing after the same food sources.

Striving to find meals may explain a key difference between C. megalodon and modern great whites. From the same vertebra he used to calculate the shark’s birth size, Ehret calculated that megalodon grew comparatively faster than great whites. “They just wanted to get  a big as they could as fast as they could, and they were a big shark to begin with,” Ehret says. Packing on the pounds would have allowed young megalodon to start taking larger prey, and would have prevented them from ending up in the stomachs of their sharp-toothed cousins. “They were trying to get big and get out into more open waters to not have as much competition for resources,” Ehret says.

Even with an amped-up growth rate, though, megalodon were never truly able to fully escape early life rivalry. This may have been part of their ultimate demise.

Researchers have traditionally pointed to a cooling global climate as the principal C. megalodon killer, the temperature dip spoiling the shark’s warm, nearshore haunts as the water chilled and whales started to migrate towards polar ice. But Ehret suspects that megalodon was able to maintain a high body temperature, much like modern great whites, and would not have been as restricted in range as scientists previously supposed. “I have a bit of a problem saying meg couldn’t follow resources to colder waters,” Ehret says. Instead, megalodon might have suffered a one-two punch related to growth and food supply.

The evolution and extinction of megalodon tracks the proliferation of prehistoric whales. “You see a peak in whale diversity in the mid-Miocene when megalodon shows up in the fossil record and this decline in diversity in the early-middle Pliocene when meg goes extinct,” Ehret says. Without a rich supply of fatty, medium-sized whales, Ehret says, “Meg might’ve gotten too big for its own good and the food resources weren’t there anymore.” On top of that, huge great white sharks were still around and vying for the same remaining food sources as juvenile megs. Rather than a victim of temperature, megalodon might have been a victim of “diversity, abundance, and competition,” Ehret says.

So when did the last megatoothed shark go extinct? Some sources say that megalodon persisted into the Ice Age, or even into the last 10,000 years. That would make the idea of modern megs seem plausible, but, Ehret says, these late dates are based on faulty evidence. “These teeth get moved, they get tumbled, they get washed down, washed around,” Ehret says, and so it’s not surprising that dredgers sometimes pluck up megalodon teeth alongside mammoth or mastodon bones. When paleontologists look at in situ megalodon teeth, still in the sediment they were originally buried in, they come up with much older dates.

Robert Boessenecker, a paleontologist at the University of Otago, has led a new study with Ehret and other authorities that pins down the disappearance of megalodon along the California coast. (The research has not yet been published, but soon will be.) The research started with a lucky find.

In late 2007, on the day before Christmas Eve, Boessenecker found a big, bluish green C. megalodon tooth in the Purisima Formation along California’s coast. “I got lucky”, Boessenecker says, “but I also wondered why we don’t find C. megalodon in younger deposits, and why it’s so damn rare in latest Miocene/earliest Pliocene deposits.” While amateurs and collectors pick up hundreds of megalodon teeth from East Coast sites every year, Boessenecker notes, only about 150 teeth have ever been found in California and the Baja Peninsula.

Comparing the occurrence of the shark along the California coast to records of teeth found elsewhere, Boessenecker and colleagues found that the Carcharocles megalodon did not survive past the end of the Pliocene, about 2.5 million years ago. “No credible records of Pleistocene (or Holocene) C. megalodon exist anywhere,” Boessenecker says, “and if we cannot even prove that a giant shark survived past 2-3 million years ago, the case for C. megalodon survival is hopelessly poor.” Much of the ocean has yet to be explored, it’s true, but it’d be really difficult to miss a 50-foot-long, nearshore shark with a taste for whales. The shark is long gone.

[This clip from Shark Attack 3 is just as educational as Discovery’s Megalodon programs.]

Yet the ghost of the shark lives on. Ehret often fields questions directly inspired by the Discovery fiction. “Not only do I see a surge in people asking about megalodon’s survival,” Ehret says, “it seems that a lot of people that ask really want it to be true.” The science Discovery claims to purvey in their fictional programs is getting totally lost. “I really think it does diminish the message [for science] they’re putting out there,” Ehret says, adding “I think it’s all about audience, and it’s a little bit like selling out.”

Boessenecker has even harsher words for Discovery. The channel still holds a high reputation for factual programming amongst the public, Boessenecker says, which makes “docufiction” like Mermaids and Megalodon especially loathsome. Says Boessenecker:

I find the willful distortion of science by Discovery in favor of entertainment and ratings reprehensible. Discovery may have a short disclaimer in front of the documentary, but it’s just lip service; they either know full well that they’re being intentionally misleading, or being hopelessly naive in thinking that the public will be able to separate fact from fiction while watching a show advertised as a documentary on a network with a reputation for putting out informative nature documentaries.

For Boessenecker, Discovery’s chicanery cuts even deeper because he grew up watching the channel’s nature programs and was partly inspired to become a scientist because of them. “And now,” Boessenecker says, “that same channel which was so great and educational only two decades ago has dismissed over a century of research in my field with the casual wave of an arm, and for nothing more than ratings.”