シャドーイング練習: How Fire Made Us Human - 動画で英語スピーキングを学ぶ

There is a cave in South Africa called Vondervörg.

The name means miracle in Afrikaans.

This cave contains up to 7 metres of sediment,

deposits, layers that have built up millimetre by millimetre over hundreds of thousands of years,

like a huge tower of human and even pre-human history.

About one metre down, in a layer dating to roughly one million years ago,

researchers from Boston University found charred plant material and burned bone fragments.

Both had been heated to temperatures of around 500 degrees Celsius,

almost 1000 degrees Fahrenheit.

This was not a wildfire that swept through.

The burning had happened inside the cave, repeatedly, over time, in the same spot.

It was the oldest known fireplace in the world.

The creatures who most probably made this fire were called Homo erectus.

That name, as the Latin scholars among you will know, simply means upright human.

They were not homo sapiens, not quite us.

Their brains were smaller, their bones heavier, their foreheads thick and heavy.

But they walked on two legs, they made stone tools, and importantly for what we're talking about today.

They used fire.

Now, nobody knows exactly when the first of our ancestors started using fire.

One million years ago is simply as far back as the reliable evidence goes.

What we do know is that for a very long period, our ancestors were not making fire, they were finding it.

Fire breaks out in the wild, as it always has and always will.

Lightning strikes a dry tree.

A lava flow ignites grassland.

Dry grass catches in the heat of a long summer.

And almost every animal on earth, when this happens, does the same thing.

It runs.

Fire is scary.

It's hot.

Instinct kicks in and even the fiercest predator will run in the opposite direction.

Homo erectus did something different.

At some point, they approached.

Perhaps they picked up a burning branch and carried it back.

Perhaps they found smouldering wood and kept it alive.

However it happened, the crucial step was this.

They stopped merely fleeing fire and started managing it.

Of course, this wasn't a simple task.

As any seasoned camper will know, tending a fire and keeping it alight requires real effort.

You have to find wood to burn, carry it, arrange it properly, and protect the flame from wind and rain.

So keeping a fire alive required attention, planning and cooperation.

It required something that looks, in other words, very much like care.

And as for why Homo erectus would want to have a fire, well, there are numerous immediate benefits.

Warmth through cold nights, light to see by, and perhaps most importantly, safety.

A fire keeps large predators away.

And in a world where leopards, lions, hyenas and sabre-toothed cats were a constant menace,

especially in the darkness of night, fire was a wonderful deterrent.

But fire changed humans in ways that go far deeper than warmth and safety.

In 2009, a Harvard professor named Richard Wrangham published a book called Catching Fire,

How Cooking Made Us Human.

The argument, as you might guess from the title,

is that cooking food rather than eating it raw is one of the fundamental differences between humans and every other animal.

And the consequences go far deeper than simply getting to enjoy a hotter and, dare I say, tastier meal.

His argument is this.

Raw food is hard to digest.

Your body has to work extremely hard to extract calories from uncooked meats, roots and plant material.

Cooking changes all of that.

It breaks down the cellular structure of food before it even enters your mouth.

Proteins unravel.

Starches become easier to absorb.

Tough fibers soften.

And cooked food releases anywhere between 30 and 100% more calories than the same food eaten raw.

So if you are getting more energy from the same amount of food, you do not need such a large,

energy-hungry digestive system to process it.

And the energy you are no longer spending on digestion becomes available for something else.

Wrangham's argument is that this surplus energy went to the brain.

He points to Homo erectus, who appeared roughly 1.8 million years ago.

Earlier homonyms, like Australopithecus, had large guts,

small brains, and big teeth suited to chewing tough, raw food.

Homo erectus had dramatically smaller teeth and a smaller gut, but a noticeably larger brain.

This shift happens at roughly the time we see the first signs of fire use.

Wrangham's claim is that this is not a coincidence.

cooking made this transition possible perhaps cooking drove it now not everyone agrees some researchers argue

that energy came from raw meat and bone marrow their argument is

that eating more animal protein not cooking explains the anatomical changes

but here is what is not in dispute we are the only animal on Earth that cooks its food.

Chimpanzees are our closest living relatives.

They share roughly 98% of our DNA, and they have never in any documented setting cooked anything.

And it's not because they don't want to.

In a series of experiments by researchers at Harvard and Yale,

chimpanzees were given a choice between a raw piece of food and a cooked one.

All 29 chimpanzees in the study chose the cooked option.

And more strikingly, when the chimps were shown

that they could place a raw piece of food into a device that would produce a cooked version afterwards, they were willing to wait.

So even though they wanted to eat, they held back from eating the raw food,

specifically in order to get the cooked version.

So chimpanzees understand the transformation from raw to cooked food.

They prefer the result.

They will even delay gratification to get it.

They just don't know how to use or make fire.

Humans do, and that single difference may be the most consequential in the entire history of life on Earth.

Now, there is one more physical consequence of fire we need to talk about.

It concerns sleep.

Before fire, our ancestors almost certainly slept in trees, as most great apes still do.

Trees are safer from predators, but you don't have to have slept in many trees yourself to know

that trees are not particularly comfortable places to spend the night.

You wake up frequently, you sleep lightly and uncomfortably.

Chimpanzees sleep around 10 hours a night because their sleep is so frequently disturbed.

Humans sleep 7 to 8 hours and we sleep deeply.

And to bring this back to fire, with a fire burning through the night, you could sleep on the ground and be safe.

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And because you felt safe, and you were safe, you could sleep properly.

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The deep, dreaming sleep that consolidates memory, repairs the body, and allows the brain to do its work.

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The depth of human sleep, tied to memory, learning, creativity, and health, may itself be,

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in part, a consequence of learning to manage fire.

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And by moving our beds from the branches to the ground, we created a new physical space, the circle.

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And it was in this circle, protected by the flames, that the second great transformation happened.

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We started to talk in a different way.

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An anthropologist at the University of Utah named Polly Weissner spent

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four decades studying a group of Kalahari desert bushmen in southern Africa.

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This group is one of the oldest surviving hunter-gatherer cultures on Earth.

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She analysed hundreds of their conversations and she found a very clear pattern.

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During the day, conversations were mostly practical,

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economic decisions, disputes, complaints, discussions about food and hunting.

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Around the fire at night, the topics were very different.

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Storytelling accounted for 81% of all conversations, compared to only 6% during the day.

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night, by firelight, people told stories about distant lands, about people they had never met,

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about ancestors and spirits and the distant past.

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They speculated about things they could not see, they laughed, they imagined.

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Many researchers argue this is where human language,

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storytelling and imagination really grew around the calm of the fire.

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Stories bind communities, they carry knowledge across generations,

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they let us think about distant places and people, past events and futures that have not yet happened.

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And the fire restructured domestic life in practical ways too.

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Cooking with fire requires different tasks, collecting the wood, starting the fire, tending the fire, doing the cooking,

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and of course someone still needs to go and hunt the unfortunate animal everyone is going to eat.

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This requires cooperation, specialisation, and division of labour.

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Often, though not always, cooking became associated more with women, and hunting more with men.

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And Wrangham, in the book I mentioned earlier, makes another more provocative suggestion.

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He argues that cooking may have been one of the early drivers of pair bonding,

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of a more stable relationship between a man and a woman, based less on romantic love than on mutual advantage.

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Imagine a woman crouching over a fire with cooked food in front of her.

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That food was valuable.

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It had taken time to prepare.

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And because it was soft, warm, and ready to eat, it could also be stolen.

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Wrangham's argument is that a man could provide protection,

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especially from other members of the group in exchange for a share of that cooked food.

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Over time, he suggests, this practical arrangement may have helped shape something closer to human pair bonding.

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Not marriage as we understand it today, but an early form of domestic partnership.

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It is, I should stress, simply a theory but an interesting one nonetheless

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that the first human couples got together

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and stayed together in order to protect their dinner

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so for hundreds of thousands of years then early humans found fire kept it

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and built their lives around it but importantly they were entirely at the mercy of finding it.

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If the flame went out, that was it.

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You had to wait for lightning to strike again or travel far to find fire somewhere else.

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The warmth, the safety, the cooked food, the community, all of it depended on a flame that someone,

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somewhere, had to have been lucky enough to find.

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That dependence is what changed around 400,000 years ago.

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We stopped waiting for the lightning and learned how to make fire ourselves.

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First, it's thought it was through percussion,

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striking pieces of flint against iron pyrite to create sparks that could catch in a small bundle of timber,

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small dry pieces of wood or leaves.

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Later came the friction method, spinning a dry wooden rod against a flat piece of softer

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wood until there's enough heat built up to set dry leaves or wood alight.

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There is of course no way to know what it felt like when the first person, wherever he or she was,

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figured out how to create fire.

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But it must have felt like magic, like you had just figured out the secret to one of the world's greatest puzzles.

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And they had, really.

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But for most of the million-year story of fire, the fuel was simple.

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It was wood for the most part.

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Sometimes dried grass, peat, charcoal or animal dung.

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Things that had grown under the sun, stored its energy and released it again as heat and light when they burned.

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And it was enough.

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Enough to build every civilization before roughly 300 years ago.

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The ancient Egyptians, classical Greece, the Roman Empire, medieval Europe, all of it ran on burning wood and charcoal.

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You could smelt metals, fire pottery, heat homes, cook food and light streets.

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Then, gradually, the wood started to run out.

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In Britain, by the 17th century, forests had been stripped.

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Wood for building ships, for building houses, for heating.

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All of it was scarce and getting increasingly expensive.

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But people still needed fire, or rather the heat that fire gave out.

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The answer was right under their noses, or to be precise, under their feet.

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Coal and later oil.

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Now, the existence of coal had been common knowledge for centuries.

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It washed up on the beach

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and you could collect it in small quantities from hillsides or from relatively close to the surface.

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And people in northeast England and south Wales had been burning it in small quantities for generations.

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But it was regarded as a poor substitute.

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Dirtier, smellier, and compared to wood, which you just got from trees,

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it was much harder to get at in any sort of useful quantity.

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But there wasn't an alternative.

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England was running out of trees.

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It was running out of wood.

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And this need, this desperation, was the first domino in the Industrial Revolution.

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And you could even argue every technological development that you and I benefit from today.

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In 1709, a man named Abraham Darby worked out how to make iron using coke,

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a purified, high-carbon form of coal.

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This was the first time someone had managed to make iron with coal rather than with charcoal, burnt wood.

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And this had considerable advantages.

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Using coal was much cheaper.

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It turned iron, and later steel, from scarce, expensive materials into industrial commodities.

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And more importantly, coal appeared to be virtually limitless.

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Before this, iron production was limited by the rate at which forests could grow back.

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After Derby, it was limited only by how fast you could dig.

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And Britain dug very fast.

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In 1700, roughly five-sixths of all coal mined in the entire world came from Britain.

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Annual iron output, which stood at around two

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and a half thousand tons in the early 1700s reached 2.5 million tons by 1850,

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a thousand-fold increase in just a century and a half.

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Now, I don't want to turn this into an episode about the Industrial Revolution, we already have one on that,

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it's episode number 150, But the main point is that this was primarily a fire revolution.

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It was about inventing better and better ways to create energy,

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to create heat, and then transform that into different forms of energy and industrial output.

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And after that came oil, which is an even more energy-dense fuel than coal, and being liquid is far easier to transport.

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What followed was the fastest transformation of human life in the entire million-year story of fire.

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Cars, aeroplanes, ships, factories, central heating, electric light, all of it at its root,

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a consequence of setting fire to stuff and using its heat.

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Now, it would be remiss of me not to mention the environmental side effects of all of this.

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The trillions of tons of CO2 this is all estimated to have released into the atmosphere, and what this might mean for the planet's future.

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But to come back to where we started, sometime around a million years ago,

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our early ancestors found fire in the wild and kept it burning.

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Then we learned how to make it ourselves.

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We used it to cook our food, shape our societies, and build things our ancestors could never have imagined.

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Fire might seem like just another part of the natural world, but for us humans, it changed everything.

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Okay then, that is it for today's episode on the history of fire.

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I hope it's been an interesting one and that you've learned something new.

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As always, I would love to know what you thought of this episode.

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Let me know in the comments below if you're listening somewhere where you can comment.

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And for the members among you, you can head right into our community forum at community.leonardoenglish.com and get chatting away to other curious minds.

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You've been listening to English Learning for Curious Minds by Leonardo English.

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I'm Alistair Budge.

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You stay safe and I'll catch you in the next episode.

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Thank you.

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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 →

シャドーイング練習: How Fire Made Us Human - 動画で英語スピーキングを学ぶ

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シャドーイングとは？英語上達に効果的な理由