シャドーイング練習: What If The Megalodon Never Stopped Evolving? - 動画で英語スピーキングを学ぶ

Twenty million years ago, the Megalodon was king of the oceans.

The largest shark that ever lived, it ate other mega sharks for breakfast.

But as an ice age engulfed the world, this enormous sea giant's time came to an end.

What if, through a miraculous twist of fate, the Megalodon had managed to survive?

just how large and scary would the Megalodon be today?

And what would happen to humans who went into the ocean?

This is What If, and here's what would happen if the Megalodon never stopped evolving.

A Megalodon living in the 21st century, one that never stopped evolving, would be a truly frightening and majestic creature.

Today's Meg would likely have expanded to the size of a blue whale,

about 30 meters long and a hefty 200 tons in weight.

That's as heavy as 33 elephants, with a beating heart as big as a car.

Today's Megalodon would need to eat 3600 kilograms of food a day, and would be the largest animal that's ever existed.

It would also be equipped with some new survival traits, ones that have helped it last these 3 million years.

What do you think those traits would be?

Well, before we get into the making of Meg 2.0, let's look at what the Megalodon was like in its heyday.

Let's go back 23 million years ago, during the Miocene and Pliocene epics.

The Megalodon was roaming about, conquering the oceans.

It spanned about 18 meters long.

That's three times longer than the biggest great white shark we've ever encountered.

Since it was so massive, obviously it weighed a lot.

As much as a space shuttle, about 30 to 65 metric tons.

It was equipped with enormous teeth, the size of a human hand.

In fact, the word megalodon, when translated from its origin in ancient Greek, means big tooth.

Serrated on one side, these teeth were perfect for sinking into large, meaty fish and tearing them apart.

Throughout its life, the Meg, like other sharks, would shed and grow new teeth, possibly growing up to 40,000 teeth over its lifetime.

These teeth chewed through a lot of food, about 1,100 kilograms, that's 2,500 pounds, every single day.

That's the equivalent of two cows.

10,000 quarter pounders every single day.

But those were off the menu in this era.

What was around were the baleen whales.

These were a key part of the Meg's diet.

And the Meg was also a cannibal if it got a chance.

It would happily feast on another Meg if it could.

This giant shark was also a ruthless killer.

had a pretty straightforward but effective strategy to finish off its victims.

It would slide into the water beneath its prey so it couldn't be seen.

Then it would shoot up vertically to slam into the animal at high speed.

Imagine being pummeled with 65 tons of pure meg.

The prey, usually large whales, didn't stand a chance against this high-pressure assault.

While they were recovering from this full-body blow, the Meg would sink its teeth into the whale, usually in the rib cage area.

After that kind of injury, the fight was over.

Then the Meg could settle into a nice meal.

As a victim of the Meg, he could also get swallowed up whole.

Yeah, with a skull four and a half meters long, it could comfortably take in something as large as a whole family car.

so watch out for this terrifying creature when it comes into the modern day.

And of course, the Meg had mega babies.

Baby Megs were 3 to 4 meters long, so good luck coming out alive if you run into one of those.

The Megalodon really came into its own during the Miocene Epic, from 23 to 5 million years ago.

At the start of the period, the Earth was warm, but then later it began to cool.

During this time, the Meg preferred hanging out in warm, tropical waters.

In fact, it roamed multiple places across the globe.

Meg teeth as old as 3 million years have been found in waters everywhere, except Antarctica.

As long as there was enough food to feast on in the water, the Meg was happy.

So, with a creature this deadly and powerful conquering the seas, how did it manage to go extinct?

Well, maybe it was climate change.

During the Miocene period, a cooling trend had begun.

This carried all the way into the Pliocene and gave way to a big freeze.

During the era after that, 2.6 million years ago, an ice age began.

According to one theory, these freezing temperatures from the ice age may not have been suitable for the Meg.

They could have led to its extinction.

But other scientists disagree.

Studying the Meg found that temperature fluctuations seen in earlier periods didn't impact the shark.

It managed to survive.

The Meg was able to survive changes in temperature because it was partially warm-blooded.

It had an adaptation, so it could warm its blood using heat from its muscles as it moved.

This allowed it to maintain a body temperature 7 degrees Celsius higher than the surrounding water.

So while it preferred warmer weather, it could survive in cooler temperatures as well.

So, what was different about the Pleistocene Ice Age?

Well, for one, this Ice Age was a lot colder than before.

The mag and other creatures

that had evolved in the last tens of millions of years had never experienced such a deep freeze.

The Pleistocene Ice Age, 2.6 million years ago, was the most severe temperature drop that Earth had faced in the last 500 million years.

As the ice crept over the Earth, there was a severe decrease in habitat for both land and sea creatures.

Sea levels dropped 200 meters, and coastal land areas dried up.

As water turned to ice and sea levels dropped, the baleen whale, the Meg's main prey, was fighting to survive.

And it wasn't just the cold.

Changes in ocean currents reduced the flow of nutrients in parts of the ocean.

areas that were prime feeding grounds for the baleen whale.

This affected its population.

And there was another problem.

Baleen whales give birth in warmer waters, but then migrate to colder waters to feed.

With the rapid reduction in warmer waters, their breeding grounds would have also been disrupted, another pressure leading to extinction.

With baleen whales going extinct, the Meg had to focus on smaller prey, like dolphins and seals.

But this would have been a problem because the Meg was facing competition for prey from a smaller and more agile competitor,

the Great White Shark.

One third the size of the Meg, the Great White Shark was nimbler, needed less to eat, and was competing for the Meg's food.

Both baleen whales and the quicker dolphins and seals.

And in the battle for fast-moving smaller prey, Great Whites were the winners.

The Meg's breeding grounds would also have been disrupted.

Its babies lived in nurseries and shallow waters.

As sea levels oscillate up and down, these shallow waters would have risen and then receded unpredictably.

They would no longer have provided a safe spot for baby Meg's to survive.

And at the same time, the Meg's massive feeding requirements for energy and to maintain its high internal body temperature we're not getting any smaller.

So that's what led to the Meg's extinction.

Too big to maintain, too much competition, and too little to eat.

It feels a little wild that this apex predator essentially starved to death.

But could we rewrite history?

Could the Megalodon somehow survive into the modern day?

Well, let's take a look at a scenario where the Meg was able to evolve to get bigger

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and more powerful than ever before.

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In order for the megalodon to survive, maybe we should see what would happen if we avoided the Ice Age altogether.

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Ice Ages are triggered by several things.

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One key factor is how far away the Earth is from the Sun, because this impacts the amount of heat Earth receives.

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Then there are shifts in plate tectonics, affecting the movement of land masses and the flow of ocean currents on Earth.

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So what if this ice age never happened?

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Well, massive volcanic eruptions could have warmed Earth.

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This happens if they throw large amounts of greenhouse gases like water vapor and carbon dioxide into the atmosphere.

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So how about the kind of volcanic action that led to a massive heat spike 56 million years ago?

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At that time, Earth suddenly got super hot.

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Massive amounts of carbon dioxide entered the atmosphere, raising the temperature by up to 8 degrees Celsius.

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The seas also became incredibly warm, and the tropics was like a warm bathtub with temperatures around 38 degrees Celsius.

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Maybe this could have offset the coming ice age, but on the other hand, this heat spike also caused a bunch of creatures to go extinct.

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So it's not clear if this would have been a sure way to save the Megalodon.

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So we're going to have to look for another miracle to save the Meg.

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Could the Meg have survived the Ice Age some other way?

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After all, many other species did.

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Gray-white sharks made it through.

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So did gray whales.

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So are there traits that the Meg could have borrowed to make it through this time?

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The Meg found it difficult to compete with great white sharks for food because the Meg was three times larger.

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The Meg's metabolic requirements would have been significantly higher to maintain that body weight.

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At the same time, it would have made them less nimble than the great white shark.

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One solution?

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The Meg needed to adapt with the times, shrink a little.

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Maybe the Meg could have borrowed a trait from the skate.

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This is another fish made of cartilage, just like the Megalodon.

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Winter Skate, living in Canada, have shrunk their body size 45% in response to water temperatures going up 10%.

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And this didn't take them millions of years.

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They did this over a period of 7,000 years.

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This was a response to environmental changes, not a result of gradual natural selection.

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And the knowledge to do this can be preserved in sharks' genomes.

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Some sharks have very large genomes, containing traits that they can draw on when they need.

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Kind of like a fire extinguisher stored away in a glass box, break open during an emergency.

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So let's give the Meg this kind of fancy genome.

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Okay, so now as the ice sets in, our Meg has shrunk.

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It's 55% as large as it used to be.

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Don't worry, this change isn't going to last forever.

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It's just an adaptation the megalodon will make to get through the ice age.

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Now that it's smaller, its energy needs are lower, and it's better able to compete with those vicious great white sharks.

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I told you earlier that adult Megs were solitary creatures.

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Well, that was fine when they were super large.

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They'd bash other large creatures with their superior weight, but now that we've shrunk the Meg down a bit, it's gonna need some other strategies.

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To further help our Megs survive, we're gonna take a lesson from killer whales.

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They're gonna form a pod.

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Maybe the Megs would mimic a behavioral feature of transient orcas.

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These form smaller pods of up to five individuals, which are mainly geared towards hunting.

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This would be in line with the solitary nature of the adult megalodon, while at the same time incorporating a behavioral feature that helps the Meg to survive.

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And while it's doing that, it's going to diversify its diet.

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It's no longer just baleen whales.

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Meg, you're going to eat squid, fish, and any other marine animal you come across.

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This broad diversification of diet helped the orcas survive the last ice age, and it'll help the Meg get through it too.

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Sharks actually have a super efficient digestive system that makes use of almost everything they eat.

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Because of this feature, shark poop mostly looks like goo.

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That's all that's left at the end of digestion, after they squeeze all the nutrients out.

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And now the Meg's goo is going to have even more variety.

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Good.

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Next, we'll make the Meg omnivorous.

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This is a trait we'll take from the bonnethead shark.

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So occasionally the Meg will eat some sea grass when it needs to survive.

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Okay, so now we have a smaller Meg, one that hunts and packs and eats a more diverse diet.

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This Meg is better suited to ward off the threat from great white sharks.

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And as baleen whales die out, this Meg has other stuff to eat.

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Okay, I'm feeling pretty good about our Meg's chances.

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But there's one more modification we need to make.

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We'd like to give the Megalodon an additional feature to help it in colder waters.

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The Meg already was partially warm-blooded, but it definitely preferred warm subtropical waters.

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A cold-water adaptation would definitely help it survive the future ice ages.

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So we'll borrow another feature from the whale.

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We'll give it a thick layer of blubber.

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This will serve as insulation when waters become super chilly.

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Okay, are we done?

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No, no. Maybe just one more thing.

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During the Pleistocene Ice Age, the Meg's babies suffered when water receded from the nurseries on the shore.

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So maybe a change to where the Meg gives birth to its babies would be a good adaptation.

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For this, we want to borrow a secret from the white shark.

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Where the white shark gives birth is a mystery to scientists.

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There are theories that white sharks give birth far out in the water.

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This trait would have made their babies less vulnerable to the shifting shoreline, as the ice ages came and went.

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If the mag could adopt this trait, well, it would ensure the survival of the next generation.

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Okay, so I think our refurbished Meg, I'm gonna call it Meg 2.0, is now equipped to take on pretty much anything Mother Nature throws at it.

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Time for you to jump into the time machine and see how the new Meg fares with this ice age.

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Then we'll come back to the modern day.

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2.6 million years ago.

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Over the course of the next 7,000 years, you'll see the Megalodon, with its new, larger genome, draw on specific traits to shrink its size.

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It's now about 50% of what it used to be.

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Still larger than the great white sharks, but with lower feeding and energy requirements than before.

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The baleen whales have gone extinct, but the Meg is happy to sink its teeth into any creature.

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Squids, seals, they're all fair game.

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The white sharks find their old enemy is smaller and more nimble

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and they're surprised that the Meg is now hunting in a pod of four or five.

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White sharks can't get close as a group of Megs are circling their prey.

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Just like before, a blow is dealt from beneath, and then, before you know it, the rest of the Megs have pounced on the desperate victim, tearing it to shreds.

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The white sharks are the losers in the fight with Megalodon 2.0.

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They pick their spots, but stay clear of direct competition in order to survive.

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As the Pleistocene era continues, the Earth goes through multiple glaciation cycles.

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In addition to its partial warm-bloodedness,

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the additional layer of blubber that Meg 2.0 has enabled it to survive as Earth's waters turned cold.

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At the height of the Ice Age, the Meg migrates to the warmest waters it can find, around the tropics and subtropics.

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This was a strategy used by orcas, many of which survived in the warmer waters around Africa during the Ice Age.

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As Megs from different parts of the globe migrate to these regions to weather the cold, the gene pool becomes more diverse.

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13,000 years ago!

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Okay, while megafauna are going extinct on land because of both shifts in climate and human predators, you can see Meg 2.0,

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King of the Oceans, is able to survive these shifts.

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Adapted to both warm and cold waters, and with its new layer of blubber, It seeks refuge in deep, cold waters to survive human hunting expeditions.

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It gives birth to babies deep in the sea, far from human eyes.

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11,700 years ago.

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Okay, the last Ice Age ends.

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The Megalodon undergoes a new shift.

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Its DNA recognizes a change in the environment, signaling that it can grow larger again.

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In a few thousand years, it doubles its size and it's back to where it was 2.6 million years ago.

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There's a lot of food in the oceans.

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Its hunting strategy is flawless and its secretive breeding approach ensures the survival of new baby Megs.

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New generations of the Meg grow bigger and stronger.

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The Meg reaches a staggering 200 tons.

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It's 30 meters long, and its teeth are longer and sharper than ever before.

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Everything in the ocean and on land fears this creature.

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This is Meg 2.0, the unchallenged king of the oceans.

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Whales won't be able to grow to the massive size they do today.

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The Meg's voracious appetite keeps them in check.

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Modern era.

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In the 19th and 20th century, humans hunt whales, but they learn to stay clear of the megalodon.

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If hunting boats go after them, a pack of Meg 2.0s swarm around the boats and destroy them, attacking in a coordinated effort.

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The lessons from fighting great white sharks 2.6 million years ago come in handy for this predator.

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Today, for humans, swimming in the ocean comes with a warning.

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You may be attacked by a stray megalodon 2.0.

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only swim in areas where lifeguards are around.

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But I'm not sure there'll be much help.

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The Meg 2.0 is somewhat misunderstood.

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It's not that this massive shark targets humans as a food source.

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After all, the Meg needs 3600 kilograms of food a day.

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That means it would have to eat 45 to 60 humans in order to make a meal of us.

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That's like eating a ton of candy instead of a proper meal.

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But that doesn't mean they wouldn't still want to eat you if given the chance.

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And if the water's choppy and humans are splashing about, a stray Meg floating along might mistake a human for a smaller fish.

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Chomp.

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But once it realizes you're not a fish, the Meg might back away and try to find something more nutritious.

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Fishing boats will need to steer clear of the Meg as well.

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The Meg 2.0 will be dominating the oceans, and most popular fishing spots.

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And it wouldn't take kindly to any competition, even the humankind.

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These are the areas modern fishing boats would have to fear and avoid.

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And if they don't, they might end up getting attacked by a pod of angry Megs.

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This could also affect our ability to fish.

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Maybe sushi would eventually be off the menu in certain parts of the world.

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With a creature as dominant as the Megalodon, fishing may become a lot more rare for us humans.

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But that's if we choose not to fight back.

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Maybe we'll end up hunting down megalodons, if we're given the right technology.

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Or we'll just stay clear of the areas the Meg hunts in.

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If the Meg were around today, it would be at the top of the marine food chain.

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As apex predators, they'd keep populations of fish under control.

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But would the Meg be able to dominate forever?

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The only thing that threatens their future would be decreasing food in our oceans.

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With climate change and the oceans becoming more acidic, the marine life that the Meg depends on are dying out.

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But sea levels are rising.

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Warm waters are no longer confined to the tropics.

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The warmth is migrating northward and southward.

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As sea levels rise to engulf Bangladesh today, Venice tomorrow, will Meg 2.0 have to change its feeding strategy?

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In a weird and completely unexpected turn of events, will a species of Meg break off and become vegetarian, eating sea grasses to survive?

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Or will it ride the warm waters to attack coastal populations of humans? humans.

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Or maybe humans will have to be worried about an entirely new creature that fought back against extinction.

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Talking about the Titanoboa.

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But that sounds like a story for another WHAT IF.

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この動画で鍛えるスピーキングの目標

この動画は、科学的な仮説を説明する際の流暢な語り口と情報量の多い表現を鍛えるのに最適です。巨大生物の特徴や進化を説明する場面では、比較表現や具体的な数値を使って鮮明に伝えるスキルが必要です。shadowing siteを使って繰り返し練習すれば、「～倍の大きさ」「～トンの重さ」などの表現を自然に口に出せるようになり、英語スピーキング練習のマイルストーンとなるでしょう。

フレーズバンク：使い回せる表現

...was king of the oceans：～が海の王者だった
ate...for breakfast：朝食に～を食べる（軽々しく対処するニュアンス）
What if...?：もし～だったらどうなる？
equipped with：～を備えている
sink its teeth into：歯を食い込ませる
come into its own：本領を発揮する

これらのフレーズは、物語を語る時や説明する時に頻繁に使えます。shadowspeaksのような動画で英語学習をする際は、これらの表現をメモして、shadowing practiceで発音とリズムを覚えましょう。

弱点を直そう：発音とリズムのポイント

この動画の中では、「Megalodon」「serrated」「baleen whales」などの難しい単語が出てきます。特に「Megalodon」は発音が癖になりやすいので、分割して「Me-ga-lo-don」と発音し、リズムを捉えることが重要です。また、長い文が続く場合、息継ぎのタイミングを間違えると流暢さが損なわれます。shadowspeakの手法を使い、動画をゆっくり再生しながら、文中のコンマや句読点で息を吸う練習をしましょう。これで、自然なスピーキングリズムが身につきます。

動画で英語学習をするのは楽しいですが、継続が大切です。shadowing siteを活用して毎日少しずつ練習すれば、必ずスピーキング力が上がりますよ！

この動画の文法

話し手がよく使っている文型を、動画の実際の表現とともに紹介します。

文型	動画での表現
「used to」 used to + 動詞 — 今はもう違う過去の習慣や状態	used to be
現在完了形 have/has + 過去分詞 — 過去の出来事が今も関係している	have expanded · have helped · we've ever encountered
受動態 be + 過去分詞 — 誰がするかより、何が起きるかに焦点を当てる	be equipped · was equipped · be seen

シャドーイングとは？英語上達に効果的な理由

シャドーイング（Shadowing）は、もともとプロの通訳者養成プログラムで開発された言語学習法で、多言語習得者として知られるDr. Alexander Arguelles によって広く普及されました。方法はシンプルですが非常に効果的：ネイティブスピーカーの英語を聞きながら、1〜2秒の遅延で声に出してすぐに繰り返す——まるで「影（shadow）」のように話者を追いかけます。文法ドリルや受動的なリスニングと異なり、シャドーイングは脳と口の筋肉が同時にリアルタイムで英語を処理・再現することを強制します。研究により、発音精度、抑揚、リズム、連音、リスニング力、そして会話の流暢さが大幅に向上することが確認されています。IELTSスピーキング対策や自然な英語コミュニケーションを目指す方に特におすすめです。

シャドーイングのやり方: ステップ別の完全ガイドを読む →

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この動画で鍛えるスピーキングの目標

フレーズバンク：使い回せる表現

弱点を直そう：発音とリズムのポイント

この動画の文法

シャドーイングとは？英語上達に効果的な理由