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  • Translator: Joseph Geni Reviewer: Camille Martínez

    譯者: Lilian Chiu 審譯者: Helen Chang

  • We've all heard about how the dinosaurs died.

    我們都聽過恐龍是怎麼滅絕的。

  • The story I'm going to tell you

    我要告訴各位的故事

  • happened over 200 million years before the dinosaurs went extinct.

    發生的時間至少在 恐龍絕種前兩億年。

  • This story starts at the very beginning,

    故事開始於最早的時期,

  • when dinosaurs were just getting their start.

    恐龍剛剛發跡時。

  • One of the biggest mysteries in evolutionary biology

    演化生物學中最大的謎題之一

  • is why dinosaurs were so successful.

    就是為什麼恐龍能如此成功。

  • What led to their global dominance for so many years?

    是什麼讓牠們能 主宰全球這麼多年?

  • When people think about why dinosaurs were so amazing,

    談到為什麼恐龍如此了不起時,

  • they usually think about the biggest or the smallest dinosaur,

    通常大家會想到最大或最小的恐龍,

  • or who was the fastest,

    或者哪種恐龍最快,或羽毛最多,

  • or who had the most feathers,

    或者最可笑的裝甲、尖刺,或牙齒。

  • the most ridiculous armor, spikes or teeth.

    但也許,答案和牠們的 內部解剖結構有關——

  • But perhaps the answer had to do with their internal anatomy --

    可以說是一種秘密武器。

  • a secret weapon, so to speak.

    我和我同事認為 關鍵在牠們的肺部。

  • My colleagues and I, we think it was their lungs.

    我是古生物學家, 也是比較解剖學家,

  • I am both a paleontologist and a comparative anatomist,

    我感興趣的是了解

  • and I am interested in understanding

    特殊化的恐龍肺部 如何協助牠們掌管地球。

  • how the specialized dinosaur lung helped them take over the planet.

    所以,我們要回到超過兩億年前,

  • So we are going to jump back over 200 million years

    三疊紀時期。

  • to the Triassic period.

    當時的環境非常嚴酷,

  • The environment was extremely harsh,

    沒有會開花的植物,

  • there were no flowering plants,

    這就表示也沒有草。

  • so this means that there was no grass.

    想像一片滿是松樹 和蕨類植物的地景,

  • So imagine a landscape filled with all pine trees and ferns.

    同時,還有小型蜥蜴、

  • At the same time, there were small lizards,

    哺乳類動物、昆蟲,

  • mammals, insects,

    還有肉食性和草食性的爬蟲類——

  • and there were also carnivorous and herbivorous reptiles --

    全都要競爭搶奪同樣的資源。

  • all competing for the same resources.

    對這個故事很重要的一點是

  • Critical to this story

    估計當時的氧含量只有 15% 這麼低,

  • is that oxygen levels have been estimated to have been as low as 15 percent,

    相對之下,現今是 21%。

  • compared to today's 21 percent.

    所以,很重要的是,恐龍要能夠

  • So it would have been crucial for dinosaurs to be able to breathe

    在這種低氧的環境中呼吸,

  • in this low-oxygen environment,

    不僅要能生存,

  • not only to survive

    還要能茁壯和產生多樣性。

  • but to thrive and to diversify.

    那麼,我們要怎麼知道 恐龍的肺部是什麼樣子,

  • So, how do we know what dinosaur lungs were even like,

    畢竟恐龍留下來的部分 通常都只是骨骼的化石?

  • since all that remains of a dinosaur generally is its fossilized skeleton?

    我們用的方法叫做 「延伸親緣包圍法」。

  • The method that we use is called "extant phylogenetic bracketing."

    這是種很炫的說法,其實意思 就是我們會去研究解剖結構——

  • This is a fancy way of saying that we study the anatomy --

    在這個例子中, 是研究肺部和骨骼——

  • specifically in this case, the lungs and skeleton --

    從恐龍的演化樹上找出 現存的後裔來當研究對象。

  • of the living descendants of dinosaurs on the evolutionary tree.

    所以,我們會研究 鳥類的解剖結構,

  • So we would look at the anatomy of birds,

    鳥類是恐龍的直屬後裔,

  • who are the direct descendants of dinosaurs,

    我們會去研究鱷魚類 動物的解剖結構,

  • and we'd look at the anatomy of crocodilians,

    牠們是恐龍最近的活親戚,

  • who are their closest living relatives,

    接著,我們會研究 蜥蜴和烏龜的解剖結構,

  • and then we would look at the anatomy of lizards and turtles,

    我們可以把牠們視為恐龍的表親。

  • who we can think of like their cousins.

    接著,我們把這些解剖學 資料套用到化石記錄上,

  • And then we apply these anatomical data to the fossil record,

    然後,我們就可以依此 重新建造出恐龍的肺部。

  • and then we can use that to reconstruct the lungs of dinosaurs.

    在這個特殊的例子中,

  • And in this specific instance,

    恐龍的骨骼最接近現代鳥類。

  • the skeleton of dinosaurs most closely resembles that of modern birds.

    因為,在這個時期, 恐龍要和早期的哺乳類競爭,

  • So, because dinosaurs were competing with early mammals during this time period,

    很重要的是要了解 哺乳類肺部的基本藍圖。

  • it's important to understand the basic blueprint of the mammalian lung.

    此外,為了讓各位 對肺部有一般性的了解,

  • Also, to reintroduce you to lungs in general,

    我們要用我的狗, 特洛伊的米拉(標誌),

  • we will use my dog Mila of Troy,

    牠的臉出現在一千種 市面上的零食上,

  • the face that launched a thousand treats,

    用牠來當我們的模型。

  • as our model.

    (笑聲)

  • (Laughter)

    這個故事發生在胸腔內。

  • This story takes place inside of a chest cavity.

    請各位視覺化想像狗的胸廓。

  • So I want you to visualize the ribcage of a dog.

    想想看牠的脊柱

  • Think about how the spinal vertebral column

    完全和地面呈水平。

  • is completely horizontal to the ground.

    在我們等下要談的所有動物身上, 脊柱都是這個樣子的,

  • This is how the spinal vertebral column is going to be

    不論是用兩隻腳或四隻腳走路。

  • in all of the animals that we'll be talking about,

    現在,請各位爬入 想像的胸廓中,向上看。

  • whether they walked on two legs

    這是胸腔的頂部。

  • or four legs.

    肺部的上表面會直接接觸到

  • Now I want you to climb inside of the imaginary ribcage and look up.

    肋骨和脊椎骨的這個地方。

  • This is our thoracic ceiling.

    我們的故事就始於這個交界面。

  • This is where the top surface of the lungs comes into direct contact

    現在,請各位視覺化想像狗的肺部。

  • with the ribs and vertebrae.

    它的外部就像是一個 巨大的可充氣袋子,

  • This interface is where our story takes place.

    在吸氣時,袋子的各部分都會擴張,

  • Now I want you to visualize the lungs of a dog.

    在吐氣時會收縮。

  • On the outside, it's like a giant inflatable bag

    袋子內部,有一連串分歧的管子,

  • where all parts of the bag expand during inhalation

    這些管子叫做支氣管樹。

  • and contract during exhalation.

    吸入的氧氣

  • Inside of the bag, there's a series of branching tubes,

    最終會被這些管子送到肺泡。

  • and these tubes are called the bronchial tree.

    它們會透過擴散的方式, 穿過薄膜進入血液中。

  • These tubes deliver the inhaled oxygen to, ultimately, the alveolus.

    這部分十分關鍵。

  • They cross over a thin membrane into the bloodstream by diffusion.

    哺乳類的整個肺部都是移動式的。

  • Now, this part is critical.

    意思就是,在整個 呼吸過程中它都在動,

  • The entire mammalian lung is mobile.

    因此,這片薄膜:血液-氣體屏障,

  • That means it's moving during the entire respiratory process,

    不能太薄,不然就會破裂。

  • so that thin membrane, the blood-gas barrier,

    請記著這片血液-氣體屏障, 我們等下會再談到它。

  • cannot be too thin or it will break.

    各位還在吧?

  • Now, remember the blood-gas barrier, because we will be returning to this.

    因為我們要開始談鳥類, 這部分會很讓人抓狂。

  • So, you're still with me?

    所以,坐穩了。

  • Because we're going to start birds and it gets crazy,

    (笑聲)

  • so hold on to your butts.

    鳥類和哺乳類完全不同。

  • (Laughter)

    而我們要用鳥類來當模型,

  • The bird is completely different from the mammal.

    重新建造出恐龍的肺部。

  • And we are going to be using birds as our model

    在鳥類體內,

  • to reconstruct the lungs of dinosaurs.

    空氣會穿過肺部, 但肺部不會擴張或收縮。

  • So in the bird,

    肺部不會動,

  • air passes through the lung, but the lung does not expand or contract.

    它的材質就像是密實的海綿,

  • The lung is immobilized,

    它沒有彈性,

  • it has the texture of a dense sponge

    且被胸廓從上方和側邊 固定在一個位置,

  • and it's inflexible and locked into place on the top and sides by the ribcage

    底部則是被一片水平的薄膜固定。

  • and on the bottom by a horizontal membrane.

    接著,它會單方向通氣,

  • It is then unidirectionally ventilated

    方式是透過支氣管樹分枝出來的

  • by a series of flexible, bag-like structures

    一連串彈性袋狀結構,

  • that branch off of the bronchial tree,

    這些結構在肺部外面,叫做氣囊。

  • beyond the lung itself,

    這整個非常精緻的機構,

  • and these are called air sacs.

    被一組交叉的肋骨固定住,

  • Now, this entire extremely delicate setup is locked into place

    這些肋骨全都沿著胸腔頂部排列。

  • by a series of forked ribs

    在許多鳥類物種當中,

  • all along the thoracic ceiling.

    肺部和氣囊會產生出延伸物,

  • Also, in many species of birds,

    它們會入侵到骨骼組織——

  • extensions arise from the lung

    通常是脊椎,有時是肋骨——

  • and the air sacs,

    它們會把呼吸系統固定好。

  • they invade the skeletal tissues --

    這就叫做「脊椎氣腔」。

  • usually the vertebrae, sometimes the ribs --

    交叉的肋骨和脊椎氣腔

  • and they lock the respiratory system into place.

    是我們能在化石記錄中 獵尋的兩條線索,

  • And this is called "vertebral pneumaticity."

    因為這兩項骨骼特性

  • The forked ribs and the vertebral pneumaticity

    就代表恐龍的呼吸系統區域

  • are two clues that we can hunt for in the fossil record,

    是不會動的。

  • because these two skeletal traits

    呼吸系統被固定住,

  • would indicate that regions of the respiratory system of dinosaurs

    促使血液-氣體屏障演化, 變得越來越薄,

  • are immobilized.

    也就是氧氣擴散到血液中時

  • This anchoring of the respiratory system

    要穿過的那層薄膜。

  • facilitated the evolution of the thinning of the blood-gas barrier,

    因為這層薄屏障並不堅固,

  • that thin membrane over which oxygen was diffusing into the bloodstream.

    要系統固定不動才有可能如此,

  • The immobility permits this because a thin barrier is a weak barrier,

    如果系統會主動通氣, 這片不堅固的屏障就會破裂,

  • and the weak barrier would rupture if it was actively being ventilated

    像在哺乳類的肺部一樣。

  • like a mammalian lung.

    所以,我們為何要在乎這點? 這有什麼重要的?

  • So why do we care about this?

    氧氣比較容易透過薄膜擴散,

  • Why does this even matter?

    且,

  • Oxygen more easily diffuses across a thin membrane,

    在低氧的條件下,

  • and a thin membrane is one way of enhancing respiration

    薄膜是強化呼吸的一種方式——

  • under low-oxygen conditions --

    比如三疊紀時期的條件 就是低氧的條件。

  • low-oxygen conditions like that of the Triassic period.

    所以,如果恐龍確實有這種肺部,

  • So, if dinosaurs did indeed have this type of lung,

    牠們的呼吸能力 就會比其他動物更好。

  • they'd be better equipped to breathe than all other animals,

    包括哺乳類。

  • including mammals.

    各位還記得延伸親緣包圍法嗎?

  • So do you remember the extant phylogenetic bracket method

    也就是把現代動物的解剖結構

  • where we take the anatomy of modern animals,

    應用到化石記錄上?

  • and we apply that to the fossil record?

    所以,第一條線索是 現代鳥類的交叉肋骨。

  • So, clue number one was the forked ribs of modern birds.

    我們在大多數的恐龍身上 都找到這條線索。

  • Well, we find that in pretty much the majority of dinosaurs.

    這就表示,恐龍肺部的上表面

  • So that means that the top surface of the lungs of dinosaurs

    會被固定住,

  • would be locked into place,

    就像現代鳥類一樣。

  • just like modern birds.

    第二條線索是脊椎氣腔。

  • Clue number two is vertebral pneumaticity.

    我們在蜥腳下目及獸腳亞目 恐龍身上都有找到,

  • We find this in sauropod dinosaurs and theropod dinosaurs,

    這些恐龍包括了掠食性恐龍,

  • which is the group that contains predatory dinosaurs

    並導致現代鳥類的出現。

  • and gave rise to modern birds.

    雖然我們沒有找到恐龍的 肺組織化石來當作證據,

  • And while we don't find evidence of fossilized lung tissue in dinosaurs,

    脊椎氣腔給我們證據證明

  • vertebral pneumaticity gives us evidence of what the lung was doing

    這些動物活著的時候肺部如何運作。

  • during the life of these animals.

    肺部組織或氣囊組織在入侵脊椎,

  • Lung tissue or air sac tissue was invading the vertebrae,

    掏空它們,就像現代鳥類一樣,

  • hollowing them out just like a modern bird,

    把呼吸系統區域固定住,

  • and locking regions of the respiratory system into place,

    讓它們無法動彈。

  • immobilizing them.

    交叉的肋骨

  • The forked ribs

    再加上脊椎氣腔

  • and the vertebral pneumaticity together

    可以創造出不會動的堅硬框架,

  • were creating an immobilized, rigid framework

    把呼吸系統固定好,

  • that locked the respiratory system into place

    因而能夠演化出超級薄、

  • that permitted the evolution of that superthin, superdelicate blood-gas barrier

    超級細緻的血液-氣體屏障,

  • that we see today in modern birds.

    也就是現代鳥類體內的那種。

  • Evidence of this straightjacketed lung in dinosaurs

    證明恐龍具有被束縛的肺部,

  • means that they had the capability to evolve a lung

    就意味著牠們有能力 可以讓肺部演化,

  • that would have been able to breathe

    讓他們能夠在三疊紀時代的

  • under the hypoxic, or low-oxygen, atmosphere of the Triassic period.

    低氧大氣中呼吸。

  • This rigid skeletal setup in dinosaurs would have given them

    恐龍體內這種堅硬的骨骼結構

  • a significant adaptive advantage over other animals, particularly mammals,

    讓牠們在適應上比其他動物

  • whose flexible lung couldn't have adapted

    (特別是哺乳類)有明顯優勢,

  • to the hypoxic, or low-oxygen, atmosphere of the Triassic.

    其他動物的肺部有彈性,

  • This anatomy may have been the secret weapon of dinosaurs

    無法適應三疊紀時代的低氧大氣。

  • that gave them that advantage over other animals.

    這項解剖結構可能是 恐龍的秘密武器,

  • And this gives us an excellent launchpad

    讓牠們比其他動物更有優勢。

  • to start testing the hypotheses of dinosaurian diversification.

    這也讓我們有很好的基礎,

  • This is the story of the dinosaurs' beginning,

    可以開始測試恐龍多樣化的假設。

  • and it's just the beginning of the story of our research into this subject.

    這個故事講的是恐龍的起源,

  • Thank you.

    就我們對這個主題的研究而言, 這個故事只是個開端而已。

  • (Applause)

    謝謝。

Translator: Joseph Geni Reviewer: Camille Martínez

譯者: Lilian Chiu 審譯者: Helen Chang

字幕與單字

B2 中高級 中文 恐龍 肺部 鳥類 解剖 肋骨 氣腔

The secret weapon that let dinosaurs take over the planet | Emma Schachner

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    林宜悉   發佈於 2020 年 03 月 24 日
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