Shark Week: Could Megalodon still be alive today?

Guest Author: Jack Cooper, MSc
UoB Graduate / PhD Student, University of Swansea

No.

As much as I would love to have seen and dived with this beast, the science is clear: Megalodon is extinct. Trust me, we would’ve noticed if it wasn’t.

You’d be forgiven for thinking that this isn’t necessarily a key question surrounding Megalodon, especially if you’re a fellow scientist. But I would be willing to bet a round of pints that almost every researcher I’ve mentioned in all of these blogs has been faced with this question. I’ve not even started my PhD and I’ve been asked this question; by tourists while I was working for great white shark ecotourism and conservation groups in South Africa, and even by total strangers on a train who happened to see me writing my MSc thesis. I’ve seen countless Facebook and YouTube comments that say ‘I think Megalodon is still alive’ and various shark scientists taking to Twitter to reiterate ‘It’s extinct y’all!’

It probably doesn’t help that there’s so much fiction out there portraying their surprise survival – most notably Steve Alten’s “Meg” book series and “The Meg” film adaptation that theorise that these giant sharks are living at the bottom of the Mariana Trench waiting to be unleashed. Personally, I was always disappointed as a kid that Megalodon never featured in an episode of “Primeval”, as coming through a time portal is the only logical explanation for a Megalodon appearing in the present day. Accordingly, I want to take this final short blog post to explain why Megalodon is definitely extinct, by using what I’ve discussed and more to debunk some of the most popular theories of its continued survival.

By far and away the most common argument you will see on the internet for Megalodon’s survival is “well we’ve only explored 5% of the oceans…” But the thing is, we don’t need to explore all that much to know that a giant, whale-killing shark isn’t there.

Firstly, sharks are constantly losing their teeth throughout their lives, meaning that they’re pretty easy to find if you know their habitats or migration routes. It’s also what makes shark teeth such common fossils. Megalodon’s huge teeth completely vanish from the fossil record beyond the Pliocene. So simple maths would suggest that no fresh teeth equals no fresh sharks.

To drive this point further, we know that, like modern sharks, Megalodon needed productive, shallow habitats for its nurseries [1]. If one were to go looking for any present-day Megalodon nursery, they would be hard to miss considering that we know of similar areas from various other shark species [2,3]. Even without knowledge of their nursery sites, we know from fossils that Megalodon occupied coastal habitats [1,4].

We humans do like the coastlines ourselves, and would have definitely spotted a giant shark swimming around by now. In this day and age, no way would one be spotted without somebody whipping out their phone and filming it.

We can also look at current marine ecosystems to know that Megalodon is not prowling within. The fossil record shows us that Megalodon targeted whales, and perhaps small-bodied ones, for its midnight snacks [5]. As the work of Pimiento has noted, Megalodon’s global abundance and distribution declines at around the same time that cetaceans experience a crash in diversity [6,7]. If you ask me, that’s not a coincidence. Because Megalodon were such enormous macropredators, they probably needed to eat a whole lot of wee whales to sustain that size. If there weren’t enough of these small cetaceans to eat, then Megalodon could not survive. It really is that simple. Even if they were targeting the bigger whales, sharks make their kills near the surface and whale carcasses float [8]. Somebody would’ve definitely spotted floating dead whales with massive bite marks in them with all the whale watching businesses there are.

Furthermore, sharks are being continuously fished throughout the oceans, with over 100 million being killed every year for a variety of reasons – trophy hunting, shark fin soup, fishing or even reactions to shark attacks [9]. This is a horrific number that stresses the importance of shark conservation, but that’s a topic for another blog. With that many sharks being killed every year, and with large sharks considered particularly at risk [9], such a huge shark would’ve been found by now.

Most important to note is that Megalodon was an apex predator. Ecosystems are reliant on animals such as this for keeping them healthy. This is called top down control, as the predators keep lower trophic levels in food chains from overpopulating. Without them, their prey would eat too much of their own prey and tip food webs out of balance. With no Megalodon, whales would’ve likely changed dramatically in typical evolutionary response.

One prime example is how, over the last 2-4 million years, whales have notably gotten more diverse and much larger in body size [10-13]. Although climate may also have had a role in this [12], with no giant sharks around to eat them, baleen whales were free to get as large as they wanted on the abundant krill they ate. What this basically means is that if Megalodon were still around, you would probably not have your gigantic blue whales.

Finally, the absence of a key apex predator would have others flocking to replace it. The great white shark probably took advantage of its giant rival’s disappearance, spreading to new regions where Megalodon once reigned supreme [14].

Let’s look at the idea that Megalodon could be living at the bottom of the Mariana trench, the theory popularised by the “Meg” book series and its film adaptation. Sorry folks, this is impossible.

For one, no shark has ever been recorded living down there, let alone one as big as a Megalodon. The theory also implies these massive sharks could survive the freezing temperatures or the enormous pressures down there. Even with mesothermy, I struggle to buy that. We’re endotherms too and yet we couldn’t survive in the poles without being wrapped up properly so I wouldn’t count on Megalodon living through the trip down to the bottom of the ocean, be it the temperature or the pressure that kills it.

Most importantly, there simply isn’t enough food in the deep seas to sufficiently feed even one giant macropredatory shark. The most common life down in this trench, the deepest on Earth, includes sea cucumbers, tiny shrimp like microorganisms and some single-celled organisms [15]. A giant shark that ate whales could not possibly survive on those.

The story that the “Meg” explanation is based on is that Megalodon teeth discovered near this area by the HMS Challenger in 1873 were unusually white and thus dated to between 24,000 and 11,000 years old. However, it is likely that these supposedly fresh teeth were uniquely well preserved. A study from 1998 revealed that they were preserved by a thick mineral crust of manganese dioxide, significantly reducing decomposition rate and thus allowing the white colour to be maintained [16]. They’re very cool fossils for sure, but definitely not that young.

Some may quote a documentary they saw as presenting evidence for Megalodon’s survival to the present day. If that documentary was called “Megalodon: The Monster Shark Lives” then the argument unfortunately collapses on itself. That documentary was fake, with actors being hired to play scientists and the documentary itself even had a disclaimer (albeit a very vague one that easily confused people) stating this. This pseudo-documentary comes complete with a fake story about a missing fishing boat, doctored photographs, no actual scientific involvement, terrible CGI and a rather manipulative structure to make it appear real. We’re talking “Dino Hunter” levels of bad here. But instead of breaking down all the nonsense presented in this documentary, I’ll simply state this: the same crew who made this documentary also made a similar one about how mermaids were hunted by Megalodon. I think that speaks for itself.

So yeah, sorry guys, but Megalodon is definitely extinct. The presence of massive whales, the absence of big fresh teeth and the fact that nobody’s actually seen one is all the evidence you need to be certain. This doesn’t mean that a good book or movie about a living Megalodon isn’t possible. But to be honest, you’d have to be deliberately vague about how it’s alive. In my opinion, a fictional portrayal of Megalodon would probably be better suited to embodying a wider theme about how humans fear and misunderstand sharks as a whole.

Sharks are some of the most fascinating, and long-lived, animals on the planet, dating back over 400 million years. With all that history comes a gold mine for palaeontologists to understand their prehistoric lives swimming, eating and making little sharks. And Megalodon is very much the queen of shark palaeontology, capturing imaginations worldwide and inspiring a huge array of cool research, with a broad cast of scientists studying them (Fig. 1a-g).

I hope that this short series has provided some interesting insight into just how much work has gone into learning about this giant shark. Every scientist I’ve discussed here has been key to elevating our understanding of Megalodon and I thank them for the parts they’ve played in influencing my ongoing research on this animal; and the roles they will no doubt play in inspiring palaeontologists of future generations.

References

1. Pimiento C, Ehret DJ, MacFadden BJ & Hubbell G 2010. Ancient nursery area for the extinct giant shark Megalodon from the Miocene of Panama. PLoS One 5, e10552.
2. Dewar H, Domeier M & Nasby-Lucas N 2004. Insights into young of the year white shark, Carcharodon carcharias, behavior in the Southern California Bight. Environ. Biol. Fishes 70, 133-143.

3. Heupel MR, Carlson JK & Simpfendorfer CA 2007. Shark nursery areas: concepts, definition, characterization and assumptions.  Ecol. Prog. Ser.337, 287-297.
4. Razak H & Kocsis L 2018. Late Miocene Otodus (Megaselachus) megalodon from Brunei Darussalam: Body length estimation and habitat reconstruction. Neues Jahrb. Geol. Paläontol. Abh.288, 299-306.
5. Collareta A, Lambert O, Landini W, Di Celma C, Malinverno E, Varas-Malca R, Urbina M & Bianucci G 2017. Did the giant extinct shark Carcharocles megalodon target small prey? Bite marks on marine mammal remains from the late Miocene of Peru. Palaeogeogr. Palaeoclimatol. Palaeoecol. 469, 84-91.
6. Pimiento C, MacFadden BJ, Clements CF, Varela S, Jaramillo C, Velez‐Juarbe J & Silliman BR 2016. Geographical distribution patterns of Carcharocles megalodon over time reveal clues about extinction mechanisms. J. Biogeogr. 43, 1645-1655.
7. Marx FG & Uhen MD 2010. Climate, critters, and cetaceans: Cenozoic drivers of the evolution of modern whales. Science, 327, 993-996.
8. Fallows C, Gallagher A. & Hammerschlag N 2013. White sharks (Carcharodon carcharias) scavenging on whales and its potential role in further shaping the ecology of an apex predator. PLoS One, 8, e60797.
9. Dulvy NK, Fowler SL, Musick JA, Cavanagh RD, Kyne PM, Harrison LR, Carlson JK, Davidson LN, Fordham SV, Francis MP & Pollock CM 2014. Extinction risk and conservation of the world’s sharks and rays. Elife 3, e00590.
10. Pimiento C & Clements CF 2014. When did Carcharocles megalodon become extinct? A new analysis of the fossil record. PLoS One 9, e111086.
11. Lindberg DR & Pyenson ND 2006. Evolutionary patterns in Cetacea. Fishing up prey size through deep time. In: Whales, whaling and ocean ecosystems. (eds. Estes JA, DeMaster DP, Doak DF, Williams TM & Brownell RL), 67-81. University of California Press, Los Angeles.
12. Slater GJ, Goldbogen JA & Pyenson ND 2017. Independent evolution of baleen whale gigantism linked to Plio-Pleistocene ocean dynamics. Proc. R. Soc. B. 284, 20170546.
13. Bianucci G, Marx FG, Collareta A, Di Stefano A, Landini W, Morigi C & Varola A 2019. Rise of the titans: baleen whales became giants earlier than thought. Biol. Lett. 15, 20190175.
14. Boessenecker RW, Ehret DJ, Long DJ, Churchill M, Martin E & Boessenecker SJ 2019. The Early Pliocene extinction of the mega-toothed shark Otodus megalodon: a view from the eastern North Pacific. PeerJ 7, e6088.
15. Yayanos AA, Dietz AS & Van Boxtel R 1981. Obligately barophilic bacterium from the Mariana Trench. Proc. Nat. Acad. Sci. 78, 5212-5215.
16. Roesch BS 1998. A Critical Evaluation of the Supposed Contemporary Existence of Carcharodon megalodon. Cryptozool. Rev. 3, 14-24.

Edited by Rhys Charles