The Science of "The Meg"

I'm a real Science author, I promise

 Pleased to Eat You
    Yesterday I went to see the new Jason Statham movie The Meg directed by John Turtletaub.  Firstly, I can't say no to a Jason Statham movie and secondly, it's a movie about a giant prehistoric shark terrorising an oceanography lab.  If you don't want to see it, I question your moral values.
    I'll just get it out of the way, so we're clear form the beginning: I thoroughly enjoyed myself from start to finish.  It's not a film which takes itself seriously - the theme song is a Thai version of Oh Mickey You're So Fine - and if you shut your brain off for a couple of hours, you'll have a whale of a time.  Pun absolutely intended.  It's an over-the-top schlockbuster, full of jump scares and cool Statham one-liners so provided you can deactivate your snob-button, you'll find The Meg is dumb, fun and laced with chum.
    The plot is as follows.  A group of researchers are investigating the bottom of the Marianas trench when they discover the ocean floor isn't rock at all but a layer of liquid hydrogen-sulfide, concealing a second ocean beneath it!  While down there they accidentally provoke a megalodon, a thought-to-be-extinct giant shark which makes Jaws look like Nemo.  This is obviously a megaloproblem, so Jason Statham, the world's most skilled deep-sea-rescue-man (that's a job), is brought in to save the day.  Chaos ensues of course when the meg escapes its underwater prison and is released into the Pacific ocean, irritable and hungry.  Water nightmare!
    As I was outlining this premise to a friend, she complained that sharks get demonised too much in movies.  She pointed out that more people die from killer-bee stings than shark attacks and the view of sharks as rampant sea-murderers is a load of nonsense.  I pointed out in return that this is a film where Jason Statham roundhouse kicks a 75-foot dino-shark in the eyeball, so they're obviously not going for accuracy.  Nevertheless it got me thinking...how scientifically accurate is The Meg and can we justify its jawesome premise?  Let's take a look.  Oh, and fun fact: I did once teach a girl who studied oceanography and her name really was Meg.  Coincidence?  I think not.

This is what a scientist looks like

Did Megalodons Really Exist?
    Absolutely.  The species Otodus Megalodon was the apex predator of Earth's oceans for at least 17 million years and the largest shark to ever swim the deep.  The surviving fossils largely consist of teeth and jawbones (the word megalodon literally means 'huge tooth') because shark skeletons are not hardened the way ours are, they're more like the cartilage in your ears, so we have to do most of our detective work from teeth and there's a fair amount we can say. 
    Radiometric dating puts the earliest known megalodon at about 20 million years old and the most recent at 2.6 million.  It's hard to say how big they were for definite due to the lack of full skeleton, but if we use the teeth as a guideline it probably grew to about 18 meters in length (60 feet), with 276 teeth in its bite, the longest of which were 18 centimeters long (8 inches).  That's bigger than a T-rex or a Mosasaurus. 
    As for their appearance, we used to picture them as larger Great Whites, but we've recently discovered their evolutionary lineage makes them closer related to modern day Blue Sharks (pictured below).  For a split second this might make them seem less scary, but please remember this was a shark the size of a double-decker bus.  It's maw was bigger than two humans side to side and it could have swallowed you without chewing.  We've found megalodon tooth marks and fragments in the bones of whale fossils from the same era so we know it was a carnivore, feeding on whales and probably smaller sharks.  We've also estimated its bite force to be roughly 180,000 Newtons.  For comparison, a human bite is 1,300 Newtons, so Megalodon was undoubtedly the biggest, baddest thing in the ocean.
    And it seems to have roamed far and wide from what we can tell, with tooth fossils found off the coast of every continent apart from Antarctica.  This tells us megalodons probably preferred warmer temperatures and likely stayed near the surface, moving from one basin to the next, feeding on anything unlucky enough to get in its path.     

Imma eat yo

Where Did They Go?
    Honestly we don't know what happened.  Around 2.6 million years ago something occured which caused widespread extinction for a lot of Earth's ocean life, an event called the Pliocene-Pleistocene boundary.  We have to remember that by "event" we're talking about something which took place over hundreds of thousands of years, so it wasn't quick and simple.  Nevertheless, during this period a third of the ocean's large animals started dying for some reason.
    All sorts of ideas have been put forward to account for the mass extinction, some pedestrian and some exotic.  For instance, the asteroid Eltanin hit us at this time somewhere off the coast of South America which would have put a lot of water into the atmosphere, potentially disrupting the climate.  The Earth was also entering a natural cooling-phase (one of the many ice ages) which would have chilled the oceans and reduced the territory for larger animals, as well as shrinking their food supply.  Even a supernova in the region of Scorpius-Centaurus has been put forward as a possible cause, releasing a bunch of neutrinos which could have shredded our ozone layer, leading to lots of nasty cancer for animals in the surface ocean.
    Nobody really knows what happened, but something during this period killed off the megalodons.  Hmmmm...how old is Jason Statham, really? 

If this portrait is to be believed, older than he's letting on

Could They Still Be Lurking Down There?
    After seeing the movie, I read an interview with a scientist who said the chances of finding a live megalodon today would be like finding a dinosaur.  I dispute that.  Dinosaurs died off 65 million years ago but megalodons were still around 2.6 million!  Also, dinosaurs roamed the land and sooner or later the google-street-view camera would catch one. 
    The ocean is big, dark and largely unmapped.  We don't know a lot about what's going on down there, so if you wanted to hide a giant shark, the ocean's the best place to do so.  Well...obviously it would have to be the ocean.  It's a shark, tim. 
    Would it be possible for megalodons to still exist without us knowing about it.  If we're absolutely honest with ourselves (damn you scientific integrity!) the answer is pretty much no.  The temperatures megalodons enjoyed were warm which means it would have to live near the surface and we'd see them regularly.  I mean...how could you miss one?  If a megalodon wanted to go unnoticed, it would need to live in the extreme deep but there isn't much food down there and a shark, especially an epic one, needs to eat a lot.  Most sea creatures live in the top few hundred meters of the water and anything lower down is stuff like tubeworms and blobfishes, not sharks.
    Also, if I've not stressed this enough already, megalodons were really big.  Big creatures leave traces and we'd be finding whale remains with big bite-marks, not to mention megalodon corpses themselves.  Giant Squid had never been photographed until 2002, but their remains washed up regularly so we knew they existed. 
    I mean we're talking about something which was the apex predator for millions of years.  If it was roaming the waters today it would still be the apex predator and we'd know about it, mostly because the smaller apex predators like Great Whites would go down in number.
    The best reason to believe they're extinct though is the lack of modern teeth.  Sharks  lose and re-grow their whole set of gnashers every two weeks and the average shark sheds 40,000 teeth during its lifetime.  If you stand at the bottom of the ocean with an umbrella, it's basically raining shark-teeth down there, so if megalodons were still around, we'd be gathering their teeth with all the other ones, and we don't. 
    But wait, I hear you exclaim, a few years ago The Discovery Channel ran a series of documentaries with scientists presenting evidence for megalodons still being alive!  Shows entitled Megalodon: The Monster Shark Lives (2013), Megalodon: The New Evidence (2014) and, my personal favourite title Shark of Darkness (2014) all claimed there are recent fossils, or footage and photographs of these sharks still around today.  Unfortunately, we have to remember that The Discovery Channel also aired shows called Voodoo Shark and Mermaids: The Body Found.
    Sadly, these "documentaries" were faked.  The scientists and eyewitnesses were actors, the  fossil evidence was discredited decades ago and the footage was doctored and photoshopped.  It's a bit of a shame that Discovery would do something like that, but they did run a disclaimer in small writing at the start of the show explaining it was not a real documentary and the evidence for these giant sharks existing is "controversial" aka "not real."

Two of the scientists interviewed

Could We Somehow Justify Them Being Alive Though?
    Alright, screw it.  Megalodons are awesome, so let's see if we can fudge a way to keep them alive.  I did it with dragons, I can do it with giant sharks too!  Evolution permits creatures to change habitat over time so maybe megalodons got used to cooling waters at a rapid rate (it's a push for natural selection to work this quick, but not completely outside the realm of plausibility).  Perhaps they could have acclimated to cold water and are living down in the dark depths of the abyss. 
    After all, the megamouth shark which grows up to 4 meters (15 feet) wasn't discovered until 1976 and the coelacanth fish which can grow up to 2 meters (6 feet) were thought to have been wiped out with the dinosaurs 65 million years ago, until we caught one in 1938.  Both species live in deep water and spend time in caves so it's clearly possible for large aquatic fauna to go unnoticed for years.  And missing a 15 foot thing is basically the same as missing a 75 foot thing, right??? 
    Besides, weird stuff goes on in the ocean all the time.  My favourite spook-story is the mystery of the 2003 Riggs shark tag.  Dave Riggs put a tag onto the fin of a 3 meter (10 foot) female Great White off the coast of Australia.  Four months later the tag showed up a long way from where he'd tagged it, without the shark.  By looking at the data, Riggs was able to figure out that something strange had happened.  At about 600 meters below the surface, the tag recorded a sudden increase in temperature within a few seconds.  It stayed at that temperature for 8 days, moving between the surface and lower depths, before suddenly going back to normal.  Something swallowed Riggs' shark and digested the tag for a week.
    The obvious conclusion is that the Great White was eaten by a slightly bigger Great White, or at least had a chunk bitten out of it.  Qualified oceanographers have said it was most likely a territorial dispute with another shark.  But I (not a qualified oceanographer) reckon it was either a megalodon or Jason Statham out for a swim and feeling peckish.
    Thing is, it's hard to prove the non-existence of something.  The only way to conclusively prove beyond doubt that megalodons are extinct would be to simultaneously scan every cubic inch of the ocean and see if it was there.  Since we've not done that and probably never will, we can't say for definite what isn't in the ocean.  But by the same logic, I could argue Hogwarts School for Fish-Wizards is down there with its own submerged trainline and you can't prove it's not.  I'm afraid arguing the case for megalodon is pushing biological knowledge a bit.  There's no evidence for them still being alive and a fair amount against.  But what's really cool is that The Meg acknowledges this and comes up with a fanciful way around the problem. 

Told you

Pushing The Boundary
    In The Meg the explanation given for why we aren't seeing megalodons is that they're living below a thick layer of hydrogen sulfide we've previously mistaken for the bottom of the Marianas trench.  To date only three people have been down to the bottom of Marianas and the sonar surveys we've done disagree on exactly how deep it is or what the shape of the bottom really looks like. 
    We also keep discovering new species of snailfish down there (sequel anyone??!?!?!?) so the film suggests there could be an ecosystem hidden below a boundary and that's where megalodon has been hiding all these years...until we came along and ruffled its gills. 
    The thing is, such boundaries really do exist!  Most bodies of water are stratified into layers based on heat and density.  The warmth from sunlight and wave-churning tends to be absorbed in the first few centimeters, and below that a colder layer sits in separation.  Below that, another layer continues several hundred meters down where the thickness and turbulence of water change phase.  It's not a sharp boundary like the one between oil and water, but the sea does have layers.  Different creatures inhabit these layers and animals we find in the lowest water-strata are often isolated from those in the upper ones.
    What's more, in the movie, the boundary between the ocean and "sub-ocean" is made from a layer of hydrogen sulfide and guess what...that's real too!  It's called a chemocline layer (in the film they refer to it as a thermocline for some reason) and it's a real phenomenon.  The Black Sea for example has a chemocline of hydrogen sulfide at certain times of year produced by bacteria on the seabed.  The density of hydrogen sulfide in liquid form is just thick/thin enough to separate an upper and lower layer of water, so it's not out of the question that some parts of the ocean floor are actually hydrogen sulfide clouds hiding tiny pockets of life below.
    I'm actually really impressed the film went to all this trouble of researching how such a boundary could arise...and got it mostly right!  The only problem is that the water below the chemocline would be significantly oxygen-depleted, so a creature living there wouldn't survive above.  If the megalodon truly was hiding under the hydrogen sulfide blanket it would never be able to surface because it would have adapted to an oxygen-starved environment and regular seawater would poison it.  However, it's more accurate Science than I was expecting to find, so bravo The Meg!  Jason Statham's Science ain't too shabby.

And the Nobel prize goes to...

Based on the novel???
    The biggest shock to me while watching the credits for The Meg was seeing the words "based on the novel by Steve Alten" follow the screenwriting credits.  This movie was based on a book?  Apparently so.  Not only that, the book has seven sequels, one of which is titled Hell's Aquarium.  Apparently Meg: A Novel of Deep Terror was originally published in 1997 and optioned for movie rights but took twenty years to develop, presumably because they wanted to get their ocean chemistry right.  Hats off to them.  I'd like to imagine that given twenty years, my own recently published book about Chemistry will get a similar adaptation with Jason Statham playing the periodic table.  We've all got dreams.

Image credits
The Meg Poster: joblo
Statham and The Shark: geektyrant
Blue Shark: Naturalhistorymuseum
Baron von Statham: wikia
Beaker and Honeydew: YouTube
Underwater Train: pinterest
Nobel Prizes: criticalhit