We Still Don’t Know What Killed the Biggest Shark of All Time

We just can’t let Carcharocles megalodon rest. From Peter Benchley’s JAWS to the dreck that regularly bobs up to the surface of basic cable “science” channels, we can’t seem to resist invoking the specter of a shark so large that it could easily engulf a person without a drop of blood spilled into the sea.

Art by Fernando G. Baptista; Research by Ryan T. Willians, Fanna Gebreyesus; Source: STEPHEN J. GODFREY, CALVERT MARINE MUSEUM
Art by Fernando G. Baptista; Research by Ryan T. Willians, Fanna Gebreyesus; Source: STEPHEN J. GODFREY, CALVERT MARINE MUSEUM

Despite our fascination with this enormous, extinct relative of today’s great white shark, there’s still a great deal we don’t know about the life and death of the biggest shark that ever lived. For starters, we still don’t know why the last of the megatooths died over 2.5 million years ago.

In the entire history of cartilaginous fish, Carcharocles megalodon was a huge success story. And that’s not just because of the predator’s size and inferred ferocity. This species patrolled the coasts of the Atlantic, Pacific, and Indian Oceans for about 20 million years. Few creatures can claim such a record. And that only makes the disappearance of the shark all the more puzzling.

Changes brought on by a cooling climate have been the focus of the traditional explanation for the monstrous shark’s demise. C. megalodon has often been thought of as a warm-water hunter, and so, the argument goes, as sea temperatures dipped at the end of the Pliocene the whales, seals, and other fatty mammals the shark relied upon migrated to chilled seas where the shark couldn’t follow. The pitiful selachian was simply left behind as cetaceans spouted off for the poles.

But was the great shark so restricted by temperature? To find out, paleontologist Catalina Pimiento and colleagues drew from the Paleobiology Database to analyze occurrences of C. megalodon over time in relation to climate.  Contrary to what had previously been thought, temperature probably didn’t freeze the shark into extinction.

Curator Jeff Seigel stands in the five–-foot mouth of a fossil shark jaw. The shark is called Carcharoles Megalodon and was large enough to swallow a small car. Photograph by Rick Meyer, Los Angeles Times, Getty
Curator Jeff Seigel stands in the five–-foot mouth of a fossil shark jaw. The shark is called Carcharoles Megalodon and was large enough to swallow a small car. Photograph by Rick Meyer, Los Angeles Times, Getty

The big picture looks something like this. During the shark’s early years, around 20 million years ago, C. megalodon primarily swam through waters of the northern hemisphere. Populations expanded around 15 million years ago to include every major ocean basin on the planet, the researchers write, but from there the sharks populations steadily declined.

All of this happened irrespective of climate. During times of major temperature spikes and dips, Pimiento and coauthors note, C. megalodon occurrences didn’t seem to show any direct response. Not to mention that the shark seemed fully capable of coping with a range of temperatures from 53 to 80 degrees Fahrenheit, and there have been waters in this range from the shark’s time until today. As Pimiento and coauthors write, “C. megalodon would have not been affected significantly by the temperature changes during the Pleistocene, Holocene and Recent.”

Populations of C. megalodon over time. From Pimiento et al., 2016.
Populations of C. megalodon over time. From Pimiento et al., 2016.

So if it wasn’t cooler waters, what drove the shark to extinction? There’s still no definitive answer. Even today, when we can witness species disappear, it’s often difficult to precisely retrace the road from the vanishing point back to the first signs of trouble. In the case of C. megalodon, though, Pimiento and coauthors have some ideas about possible killswitches.

Through hindsight, we can see that the road to extinction for the megatooth shark started in the middle of the Miocene. This coincided with two major events, as previously pointed out by paleontologist Dana Ehret as well as the authors of the new study. Against a background of crashing whale diversity during this time, the world saw the evolution of some stiff competition for C. megalodon: large sharks close to the ancestry of the great white and sperm whales that behaved and hunted more like today’s orcas. This trend continued only through the Pliocene, with fewer big baleen whales and an increasing array of predators that young megatooth sharks would have struggled against to get enough food down their throats. There was less food to go around for an expanding guild of predators who relied upon warm, blubbery prey.

The case isn’t closed yet, though. So much of what’s known about C. megalodon comes from teeth, the occasional vertebra, and some bite marks. Those pieces only reach so far in revealing the massive shark’s biology, including how much the fish actually relied on filter-feeding whales for food or the other predators it was striving against to survive.

We can be sure the megatooth shark is dead. The fish’s fossil record taps out by 2.5 million years ago, and we surely wouldn’t miss populations of fifty-foot-long sharks patrolling the global coastlines. But why the shark vanished is a secret still waiting to be dredged from the fossil record.

Reference:

Pimiento, C., MacFadden, B., Clements, C., Varela, S., Jaramillo, C., Velez-Juarbe, J., Silliman, B. 2016. Geographical distribution patterns of Carcharocles megalodon over time reveal clues about extinction mechanisms. Journal of Biogeography. doi: 10.1111/jbi.12754

26 thoughts on “We Still Don’t Know What Killed the Biggest Shark of All Time

  1. Of course, I don’t–and can’t–know, but I find it difficult to believe that there were ever enough great whales to support a large population of megasharks as a prey base. If I’m right and, if there actually was a large global population of megalodon predators for millions of years, there must necessarily been an additional major prey base. These sharks would have seem to have been ill-suited to feed on many very large fish, because really large fish like giant tuna, marlin and swordfish, are also generally spaced fairly thinly. The giant squid species might provide a major source of food. Even now, it is suspected that migrating, great white sharks make deep dives in search of large squid.

    Still, even this wouldn’t explain megalodon extinction even an extinction of ‘the usual type’, in which a disappearing species simply has a slightly lower birth rate than death rate over a long period of time. Therefore I’m left with no alternative but to assume australopithecine-induced global climate change.

    1. There was a black and white photo of a German submoren that was 1943 of a a magladon shark have you ever seen it and is there any one still alive to day that either took that photo or on that sub ? And what about the so called vido of the deep sea oil rige cout by there underwater camera seen by a kid watching the cameras on line !food for thought and with out the achall great white that was Killed how can any one say yes or no to what killed it!.

  2. Although C. Megalodon is an apex predator, perhaps it was simply too large and, at one time, too numerous to sustain its immense girth in comparison to smaller predators who were perhaps faster required fewer caloric requirements to survive.

  3. What if they fed on their own species? If they radically multiplied and eventually ran low on sources of food, wouldn’t they have started attacking/feeding on each other?

    1. Good point nicole……great whites feed on other sharks and even the make great white had better watch out after mating !……..if they became hungry enough….they would def have attacked each other.

  4. Is it possible that it didn’t die off but it evolved? Maybe as time went on it had less large food sources and it could have had an effect on the size of the shark and eventually became the great white?

  5. @Ron: cetacean numbers used to be massively higher than current populations, on account of centuries of whaling, certainly enough to support a stable population of megalodon, which doesn’t necessarily have to be a big population. I don’t know what similar teleost fish were around at the time, but tuna etc do school with a certain density – not like mackerel insofar as they can be scooped up in bulk, but then they provide enough nutrition per prey item that they shouldn’t need to. It would be unsurprising if megalodon wasn’t something of an omnivore given it would have been larger than most everything it encountered; the issue I suppose it whether it’s getting enough of its primary, nigh nutrient prey (blubbery mammals) vs scattered pickings of other prey types.

    @Nicolette: sharks are natural cannibals but tend to partition spatially in order to avoid this, whereby the females will tend to give birth in shallow protected areas to avoid the juveniles being in the same place at the same time as adults.

  6. What if they evolved into small predators like great white sharks? Or they may be in the depths of the seas. We still dont know what kind of amazing and facinating creatures live in the dephts of the seas.

  7. Megladon is rumored to still be alive…..a satellite in space caught a giant fish near a oil spill which was clearly larger than the largest sea animal a blue whale.

  8. I believe that a hero from Atlantis hunted them to death as they were eating underwater atlantis farmers, it was a survival matter.

  9. I had to chuckle about your phrase “the dreck that regularly bobs up to the surface of basic cable “science” channels”. I agree, there’s a lot of dreck out there.

    OTOH, watching some of the stuff on the National Geographic Channel makes me cringe just as much. Setting aside the paid programming on late night, some of the “reality” programming that National Geo puts its name and reputation to “wonders me”, to borrow a Pennsylvania Dutch phrase. Then again, I suppose it pays the cable TV bills and supports the more scientific and cultural programs.

  10. Is it not possible that the Great White Shark is a stunted version of Megalodon? In other words, maybe Megaladon didn’t go extinct at all but just got smaller over thousands of generations as its food supply became unable to support the larger members of the species.

    1. Hello Ruth. Yes I believe you are probably right . Any fish that begins to outnumber prey becomes smaller to survive, i.e. needs less food.

  11. Or, maybe, if all the “kumbaya”, “we’re-all-interconnected” stuff has any basis, it means that the Universe itself is conscious. Which in turn means that the Universe’s “trial and error” approach to Life is the equivalent of a two-year-old with building blocks. Oh joy.

  12. Hello Ed Ruth. Yes, I believe you are probably right. From my studies of fish waters that contain populations of fish that are too many for the available feeding results in smaller specimens.

  13. The obvious cause of Megalodon’s extinction: They all drowned in the Great Flood. (LOL) Bible Scientists (again lol) are still struggling with this question: God created Woman to keep Adam company- but why did God make women such a PITA? 😉

  14. My guess is that with the bigger fish heading north into colder waters, megladon’s were faced with following the food, or settling for smaller prey. I’d bet they adapted to smaller prey. This would be the easier and quicker evolutionary adaptation to survive than developing the metabolism to stay in colder water would have been. There is possibly a few extinct species of shark out there between megladon and one of the current species. Of course everything is simply theory and speculation until we uncover the fossil record to support it.

  15. Perhaps we should also take into account that many larger land animals died out as well– megalodons actually seem to be some of the later holdouts against massive extinctions that took out 25 foot crocodiles, 8 foot turtles, 10 foot kangaroos, giant lions and other such megafauna. (And that’s not even beginning to cover dinosaurs and archosaurs.) Perhaps we should not be asking why the giant sharks died when they did, but why they lasted so much longer than so many other huge species.

    And perhaps, since there seems to have been a trend from larger to smaller animals across the board as we move from ancient to modern, we should start looking at the possibility of a virus– perhaps more than one– that rewrote part of the genetic code, selecting for smaller size, without killing the host. Over thousands (even millions) of years, such a virus could easily mutate enough to be spread through many different organisms.

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