Imagine swimming in the ocean. You’re
splashing around, minding your own business, when all of a sudden a shark fin the size
of a boat pops out of the water and heads straight towards you. That would probably be
the last time you stepped foot in the ocean, if you made it out alive that is. The only
shark that could have a dorsal fin of that size would belong to a megalodon. Luckily
for you—and all of us—the megalodon went extinct around 3.6 million years ago. But what
caused this massive apex predator to die off? And is there a chance that it is still
lurking in the depths of the oceans? The megalodon or Carcharocles megalodon first
inhabited the oceans of planet Earth around 23 million years ago. They were the largest
shark to ever live. Megalodons varied in size, but studies suggest that on average a female
meg could be between 45 and 59 feet long. This range varies so widely because scientists need
to extrapolate the size based on teeth and jaw fragments found in the fossil record. At this
point in time a full megalodon skeleton has not been found. However, from the remains we do have,
it is clear that these creatures were enormous. Adult megalodons had no predators because
of their massive body size. The shark’s main prey was small whales. That’s right,
they ate whales, that's how big they were. Megalodons roamed every ocean of
the world, although they stayed away from the polar regions where the water would
be too cold. What we know about the megalodon species comes from fossil remains, and scientific
observations of their much smaller relatives that live today. The largest predatory shark
species alive today is the great white. The largest great white ever recorded
was around 36 feet long. This makes it 20 feet shorter than the megalodon.
Megs were truly massive sharks. Megalodons were incredibly successful at what
they did. They outcompeted other predators for about 20 million years, and stayed at the top of
the food chain for that entire time. Their size, razor sharp teeth, and speed allowed them to
hunt and kill prey with deadly efficiency. So, what caused the Megalodon to go extinct? Why isn’t this incredibly successful killing
machine ruling over the oceans today? There were probably several factors, but evidence
points to a few clear changes that had a big impact on the megalodon survival rate. Between
3 and 5 million years ago the climate began to change on planet Earth. The world began to cool
as it entered the epoch known as the Plioscene. As global temperatures dropped the oceans were
affected. One major change that occurred as temperatures cooled was that the sea levels
began to drop. This happens during ice ages, and periods of cooling, because the water of
the oceans gets trapped in ice and glaciers. As water gets converted into its solid form, it is removed from the oceans. This
causes the overall sea level to drop. The dropping of the global sea level wouldn’t
have been a problem for megalodon if that was the only change that occured, but when the
sea level dropped, new land started to form that had previously been underwater. During
the Pliocene the Isthmus of Panama began to take shape. The collision of tectonic plates in
the area caused volcanic activity that resulted in the formation of the mountains that
now stretch from North to South America. The emergence of this new land that connected the
Americas had a huge impact on the animals of the oceans. The land that would become Central America
had been under water for millions of years, meaning that there was nothing blocking marine
species from crossing between what would become the Atlantic and Pacific Oceans near the equator. Once the access between the Americas was blocked
off by land, many species were now stuck either on one side of the continents or the other. This
meant that access to some of megalodon’s prey may have been separated from them. Ocean currents and
movement of nutrients in the oceans began to shift once the equatorial connection between the oceans
was impeded. This would have caused species to migrate to new areas, or if they could not adjust
to the new environment they would go extinct. The currents and nutrients that once flowed
between the Americas would have been abruptly brought to a halt. Without these nutrients,
biodiversity would drop. This change would have a domino effect on all species living
throughout the oceans. Nutrients would no longer be where they once were, and entire
ecosystems would have vanished. This alone would have caused mass extinctions of aquatic
organisms, leaving room for new species to evolve. Even if this lowering of ocean levels,
and the blockage between the oceans, did not directly cause megalodon to go extinct,
it most likely had an impact on their prey. Since megalodon was large and slow to
reproduce, it filled one specific niche, that of apex predator. If the environment
suddenly changed, it was unlikely that megalodon had the genetic diversity to
adapt to a new environment with less prey. Another impact of the lowering of ocean levels
is that the oceans become saltier. As more and more water is trapped in ice and glaciers
the salt to water ratio in the ocean changes. The salt does not get trapped with the water, so
salt levels remain constant, while water levels decrease. This causes an increase in salinity
throughout parts of the oceans. The difference in saltiness would have shifted the ocean currents,
and nutrient cycles, ever more. In fact, this change in salinity is one of the main
reasons we have the ocean conveyor belt of today. All of these changes to the
oceans would have meant the environment that the megalodon had been
so successful in for millions of years, was now different. It is very difficult for large
specialist predators to adapt to changes in their environment. Think about what is happening in
the arctic right now to polar bears. They are highly specialized for the environment they
evolved in, but if the ice continues to melt, and global temperature continues to rise, they
will go extinct. The polar bear species just does not have enough genetic diversity to allow
them to be successful in a warmer environment. As the environment changed during the Pliocene,
marine diversity diminished for a while before natural selection caused new species to evolve
and thrive. Unfortunately, this would have taken thousands and thousands of years; time that the
megalodon did not have. With less biodiversity, and animals to eat, all predators in the
ocean would need to compete for similar food sources. The prey that megalodon
once thrived on would have diminished, which meant that either they had to compete for
a different food source, or starve to death. Before the change in the environment of the
Pliocene, the oceans were filled with large marine animals. Many of these animals ate krill or small
fish like the baleen whales of today. This meant that there was an abundance of prey for megalodon
to hunt. However, after the climate shift organisms such as toothless walruses, aquatic
sloths, and dwarf baleen whales did not survive into the new environment. Slowly, but surely,
the megalodons variety of food was diminished. This is where the real problem for megalodon came
in. Changing of climate most likely contributed to the extinction of the species, but scientists
now believe there was one main culprit that drove the nail into the coffin of the megalodon. At
around the same time as megalodon went extinct, a new apex predator had just started to
make its appearance, the great white shark. Carcharodon carcharias, or the great white
shark, appeared around the same time as the megalodon species began to decline. It would seem
this new species of shark could out compete the megalodon. The smaller size of great whites
allowed them to catch and eat smaller prey, which was more abundant after the climate shift.
The ability to eat many different species, other than just small whales, gave
the great whites an advantage. Not only did the great white have a wider
variety of food it could choose from, but the smaller body size actually worked in its
favor. Since the megalodon had such a massive body it needed to stay in relatively warm waters,
so that it could maintain its body temperature. Sharks are ectotherms meaning that they don’t
regulate their internal body temperature, but instead, rely on factors such as sunlight
and muscle movement to increase the temperature of their bodies. The smaller bodies of the
great white sharks meant they could venture into cooler waters, since they had less body
mass to keep warm. Their muscles did not need to work quite as hard as megalodon to keep
their body temperature up, and therefore, they didn’t need as much energy from
food as their larger cousins either. It was also likely that great whites hunted
some of the same prey as megalodon. Perhaps the great whites targeted the young of
the species that megalodon was hunting, thus reducing the amount of adult prey available
for the megalodon to eat. The great white sharks were by no means trying to outcompete and cause
the megalodon to go extinct, but they were, and still are, very efficient predators, who
in the new ocean environment thrived. The great white shark’s success most likely played a role
in the extinction of the once great megalodon. Scientists also think that the evolution of other
smaller species of shark could have put pressure on the megalodons. For example, tiger sharks
which lived during the same time as megalodon, and in very similar environments, may have
contributed to the larger shark's demise. It has been suggested that great whites and
tiger sharks may have fed on megalodon young that had not grown to their full size
yet, causing even fewer numbers of the species to reach maturity. As we gather more
evidence, we may find that megalodon was not just outcompeted by smaller species of shark, but
their babies may have been hunted by them as well. One theory of what caused the megalodon
to go extinct is really out there, literally. Some astronomers suggest that
a supernova may have contributed to the extinction of the largest sharks that ever lived.
The claim is that a nearby star went supernova, enveloping the Earth in harmful muon radiation.
This radiation would have been harmful to many species. But ones that reproduce slowly like the
megalodon, would have been affected much more drastically because of the build up of mutations
and lack of genetic diversity in the species. All of these factors may have played
a role in the extinction of megalodon, but are we so sure that the species is really
extinct? Could there be a gigantic 60 foot shark lurking in the blackness of the oceans? Well,
let's look at the evidence. Humans have been exploring the oceans, and recording their
observations, for hundreds of years. In all that time there have been no reliable accounts,
or documentation, of megalodons being sighted. If megalodons were still alive, we would at
least expect to find whales or other prey with 10 foot bite marks on them from the jaws of a
megalodon. But such evidence has never been found. We would also expect to find at least some
megalodon fossils in layers of the Earth younger than 3.5 million years old, but to
this day no such fossils have been found. Scientists also believe that megalodons
established nurseries for their young in shallow seas, which means that we should see
baby megalodons near the surface of the ocean. Even a baby megalodon would be a massive shark,
and would most definitely make the news. Yet, this has never occurred. It is important to
remember that for any species to continue on it needs to reproduce, and megalodons, like
all sharks and animals, don’t live forever. The fact that there has never been a reliable
sighting of a full grown, or baby megalodon, is a good indication the
species went extinct long ago. Megladon also likely hunted in
shallower waters or near the surface, because that was where their food source lived.
Whales are mammals, and therefore need to come to the surface to breath air. It would seem highly
improbable that a megalodon would wait until a whale dove into the far far depths of the ocean to
attack it. For one thing, how would the megalodon see its prey in the deep ocean where no light
reaches? Sharks have a very keen sense of smell, but they still rely heavily on their eyes
to attack prey once they are within sight. So, no, there are no more megalodon left in the
oceans of planet Earth. And to be fair, it’s probably better that way. I don’t know about you,
but I would be much more hesitant to go swimming, or get in a boat, if I knew there was a fifty
foot killing machine swimming around the ocean. Now watch “YOU vs THE MEG - How
Can You Defeat and Survive It (The Meg Shark Movie).” Or check out “CROCODILE
vs GREAT WHITE SHARK - Who Would ACTUALLY Win?”
