跟读练习: Why Can’t We Have Unicorns? - 通过YouTube学习英语口语
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It’s the dream of every little kid out there to befriend a unicorn.
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It’s the dream of every little kid out there to befriend a unicorn.
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Riding through a magical land astride your magical companion, the wind blowing through your hair… No?
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Just me? But on the scale of mythical creatures, compared to dragons and basilisks and stuff, unicorns seem downright realistic.
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It’s just a horse who knows how to accessorize!
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You could just as easily ask, why don’t they exist?
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Well, we did ask, and we found some answers.
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Come with me on this highly specific deep dive into the science of how animals evolve to grow stuff out of their heads.
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[intro] Okay, if we’re going to unpack this, we need to agree on our definition of a unicorn.
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I know that seems obvious, but this is science!
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We’ve gotta define our assumptions.
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For our purposes today, a unicorn is a horse-adjacent animal with one single horn or pointy appendage growing out of the front of its head, like mine.
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By horse-adjacent, I mean the ungulates: four-legged mammals divided into two main groups based on how their toes work.
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Yes, I know, taxonomy is like that sometimes.
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Horses belong to the odd-toed ungulates, or perissodactyls, but we’re also going to include the even-toed ungulates, or artiodactyls – the group that includes stuff like deer and cows.
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And if that’s all we need, guess what?
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We’re done!
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We’ve got not one but two animals that fit this particular bill.
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The first is almost definitely going to make some of you mad, because it’s narwhals.
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Hear me out!
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They’re cetaceans, which fall into our category of horse-adjacent.
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Cetaceans are a type of ungulate, and they’re so closely related to artiodactyls that some researchers even mash the two names together and call the group “cetartiodactyls,” which is… a mouthful.
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So like it or not, narwhals totally count under our definition.
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And they’ve got a big horn right on the front of their noggins, so that’s one more tick in favor of them being our planet’s unicorns.
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And yes, technically they’re rocking a tooth, not a horn, but we never said what it had to be made of!
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Now a few of you might have clued in to another animal that meets the description we’ve already given, and you are very smart.
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But save it, we’re going to get to that one later.
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Regardless, these real-world animals aren’t exactly going to hit the spot if you want a unicorn.
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They’re like having an oatmeal raisin cookie when you really want chocolate chip - it’s just a poor substitute for the real thing.
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It’s also worth mentioning that humans have manipulated animals like cows and goats to have a single horn in the middle of their heads, whether it’s in the interests of science or hucksterism.
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But we wanna know why unicorns never happen on their own – as a species, rather than a human ploy or a one in a million accident.
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So if we want to look Mother Nature in the eye and ask her how to make a unicorn, we need to look at other animals that have evolved a lot more of the classic horse-y unicorn traits, including anything bone or bone-adjacent growing out of their heads.
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And there are no perissodactyls with any bony head ornaments.
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So to look at the evolution of unicorns, we have to make a quick hop to the next branch of the tree of life, back to artiodactyls.
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Specifically, we’re looking at pecorans, which are things like deer, cows, and pronghorns.
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All of the animals that have evolved bony headgear fall into this category, so to study how to make horns on your head, they’re the perfect animals to examine.
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Plus there’s a lot of old timey illustrations of unicorns with deer-like cloven hooves so I say it counts.
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Now there are technically some differences even within the pecorans.
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For instance, not all headgear is created equal.
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There are anatomical differences between say, horns and antlers.
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Even so, we’re pretty sure all pecoran headgear evolved from one common ancestor that had its own funky headset.
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Which means that the neat trick of growing these specific kinds of horns… only evolved once.
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In evolution, something that happens once could happen again, but it’s not super likely.
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Sorry, horses.
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But does this mean we can have our deer-icorn, if two horns could somehow become one horn?
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A 2019 paper looked at how these guys’ headgear forms and attributed them to neural crest cells: cells that migrate outward from the midline of an organism during embryonic development to create new structures.
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Headgear-starting cells migrate to either side of the skull, towards the back of the braincase, and then become boney sticky outy bits.
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And there are a few genetic changes specific to pecorans that make that happen.
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Like some modifications to the gene OTOP3, which makes a protein associated with biomineralization.
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You know, to make bone grow where it didn’t used to.
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And some changes to the gene OLIG1, which is the one that tells those neural crest cells what to be, and where to go.
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Finally, there’s a bit of shuffling around some of the big boss genes of developmental biology.
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We’re talking Slug, Twist, the Hox genes – I promise these are genes and not words I just chose at random.
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See, while OLIG1 makes the neural crest cells move, these guys are the ones that make sure everybody’s working together properly to make a lovely, finished head-bone.
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Taken together, you have a set of instructions that tell neural crest cells to go to either side of the head and build a brand new bony structure in two very specific places.
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In order to get a deer-icorn, we’d need those genes to tell the neural crest cells to go to the front and center of the head, not onto the sides.
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And they’d have to form just one new bony protuberance, not two.
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Meaning re-re-writing all those headgear gene changes.
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And you don’t mess with genes like that lightly, because if you do interfere with the basic developmental program, odds are you just never get a grown-up organism that can pass those changes on.
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It’s not impossible.
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It seems to have been documented, once, when a deer with a single, centered horn was spotted in Italy in 2008.
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But the folks who spotted him think that that deer’s specific situation probably couldn’t be passed down to its offspring, which means he was in all likelihood, one-of-a-kind.
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So until we see it happen to the genes that do get passed down, we aren’t going to get any deer-icorns.
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And to get a horse-icorn, all that stuff that happened in pecorans would have to happen again in horses.
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Which… is a stretch.
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Okay, so biology basically says we get two horns or nothing, at least in the even-toed ungulate group .
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But what if I told you that the real unicorns have been with us the whole time?
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Get ready because it’s about to blow your mind - it’s rhinos.
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It’s a horse-adjacent animal with one horn on the center of its head!
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Are you not entertained?!
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What do you mean, people have been confusing them since medieval times at least?
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Eat your oatmeal raisin cookies!
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Rhinos and horses are both perissodactyls, meaning that rhinos are a lot more closely related to horses than deer are.
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And as for their sick headgear, I would tell you how rhino horns grow in order to compare them to hypothetical unicorns, but… I can’t.
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Because of the whole poaching thing, rhino horns are extremely illegal to own, and researchers don’t get to have them either.
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Which is valid, but it means we don’t know as much about rhino horn development as we do with deer and cows.
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But we do know rhino horns are made of keratin, so they’re more like a hair-or-fingernail horn instead of a bone or a tooth.
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Could a horse go that route and grow a giant fingernail-horn?
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Well, even though they’re pretty closely related in the grand scheme of things, the two groups are still separated by 50 million years of evolution.
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So it’s really hard to say just when that mutation arose in rhinos, or how many changes the horses would have to go through to get there.
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And again, when there’s a mutation that only happened once, that tells us how unlikely it is to happen a second time.
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So there you have it.
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The reason we can’t have unicorns is basically a developmental biology lecture… you’re welcome.
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But maybe the real reason is that our world just doesn’t have enough unicorn magic.
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Hey, if this episode made you crave a bit of that unicorn magic in your life, we’ve got just the thing for you.
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It’s not this headband though - this is mine.
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We do, though, sell a sticker set highlighting all the real-life unicorns of the world, including our lovely rhinos.
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Head over to the DFTBA store to check them out, along with the rest of our sweet, sweet merch.
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That link is down below in the description.
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Thanks for watching!
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关于本课
在本课中，学习者将会通过观看有关独角兽的视频，练习英语口语和发音。我们将讨论神话生物的概念并分析其科学背景，让你在提升英语能力的同时，也能了解动物进化的奇妙之处。本课还将帮你掌握一些实用的词汇与短语，并提供有效的影子跟读技巧，确保你在学习过程中能够更自信地进行英语口语练习。
关键词汇与短语
- 独角兽 (unicorn)
- 神话生物 (mythical creature)
- 进化 (evolution)
- 动物 (animal)
- 头饰 (headgear)
- 角 (horn)
- 颅骨 (skull)
- 神经脊细胞 (neural crest cells)
练习技巧
在进行影子跟读时，建议你在跟读每一个句子之前先仔细听一遍。这段视频的节奏适中，适合用作 英语影子跟读 的练习。试着模仿发音、语调和节拍，这样可以帮助你提高英语发音。把注意力集中在每个词的重音和句子的语调上，尤其是在讨论复杂主题时。通过不断重复这些句子，你将能够在 英语口语练习 中变得更加自信。记得慢慢来，确保你完全理解每个表达方式，而且不要害怕在练习过程中发出声音，以增强语言记忆和口语流利度。这是一个提高能力的好方法！
什么是跟读法？
跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。